Myriam Merad

Implementation of Local Committee in thé vicînity of industrial Seveso sites, France

As a resuit of thé Toulouse catastrophe of thé 21st September 2001, a new law on thé Prévention of Technological and Natural Risks has introduced thé création of "Local Committees for Information and Concerted Actions". The aim of thé Local Committees is to promote debates on technological risks among thé stakeholders and increase transparency in thé decision-making process related to risks resulting in particular from "Seveso" industrial sites.

Introduction

The Toulouse accident on September 21,2001 has revealed thé inadequacy of a number of practices in major accidentai risks prévention process in France. The factory of thé company "Grande Paroisse" which produced ammonic (1150 t/j), nitric acid (820 t/j), urea (12000 t/j) and ammonium nitrate was located near thé center of Toulouse and distributed on nearly 70 ha of ground. This factory knew an explosion on thé level of its storage section of "downgraded ammonium nitrates" (MEDD, 2001). This explosion, which caused more than 30 deaths and thousands of wounded in a radius of 500 meters and more than 26 000 résidences damaged on a radius of 3 kilometers (MEDD, 2004), marked a turning in thé French régulation with thé promulgation of thé law n° 2003-699 of July 30,2003 relating to thé "prévention of technological and natural risks, and damages compensation". This law revealed:

1. Insufficient information of thé public and a need for a stronger implication of thé public in décision relating to thé risks (chapter I of thé law);

2. Situations where thé proximity of very urbanized zones can worsen thé conséquences of major accidents on risky industrial sites (chapter D);

3. A need to consider thé employées (as well as subcontractor employées) of risky factories and make them contribute to thé risk management in thé companies (chapter HT); 4. A need for more adéquate and more effective Systems for victims compensation (chapter TV).

In order to take measures concerning thé lack of information and dialogue between thé actors involved in thé risk prévention process, but also in thé décisions related to thé urbanization around industrial sites presenting a high level of risk, thé law of July 30,2003 in France proposes:

• in its article 2 1 thé Prefect sets up a structure called "Local Committee of Information and Dialogue" (CLIC) for any basin comprising Seveso High Threshold sites. This structure is equipped with means by thé State; • in its article 5 1 , thé CLIC is associated to thé élaboration of thé Technological Risks Prévention Plans (PPRT); in its article 21, thé CLIC must be informed of thé technical information coming from thé Safety Studies (EDD) to know: probability of occurrence as well as thé damages of accidentai evens. The CLIC is at thé same time addressee of "technical" information concerning risks and also an active actor in décisions related to urbanization control around thé high threshold Seveso sites. This paper focuses on thé link between thé CLIC dialogue structure and thé PPRT urbanization control process.

In this paper we will first présent thé CLIC structure as well as différent other dialogue and information structures. We will then présent thé urbanization control process around thé Seveso High Threshold sites within thé framework of thé Technological Risks Prévention Plans (PPRT) and stress on révolution introduced by thé CLIC in thé way risks acceptability is considered in thé décisions related to thé prévention of thé major technological risks. Thé rôle of thé dialogue and information are presented in a third part. This part insists primarily on thé new shape of actor whom thé dialogue introduces. To finish, this paper will présent a set of méthodologies aiming at avoiding and resolving possible conflicts between actors during thé dialog process.

A new dialogue structure in major industrial risks prévention process in France

The will to provide spaces of exchange and meeting between various local actors having jointly concerns and an interest for thé questions relating to thé industrial environment is revealed in France through thé existence of various place or structures: public investigations, local committees, Permanent Secrétariats for thé Prévention of Industrial Pollution (SPPPI).

Thèse various forms of structuring thé space of exchange intervene at différent rimes during décisionmaking process. Our interest goes on thé place of thèse spaces of dialogue within thé framework of thé control of thé urbanization around Industrial site.

LI Spaces of information and dialogue présent before thé installation of the CLIC

The CLIC structure, introduced by thé n° 2003-699 of July 30, 2003, cornes to redraw and officiaily recognize thé place of the coordination and dialogue between thé actors involved in thé industrial risks prévention process and more specially in thé urbanization control process around thé industrial sites.

The public investigation

The public investigation is a procédure established before thé administrative décisions that can impact freedoms and basic rights. To this end, this procédure consists in informing and collecting thé appraisals, suggestions and proposais of the public before thé decision-making 2 .

Governed by thé law Bouchardeau n° 83-630 of July 12, 1983 relating to thé "democratization of the public investigations and thé environmental protection", thé public investigation is a procédure initiated by thé Prefect and control by an investigating police chief or a board of inquiry (if thé file is sensitive) indicated by thé Président of the Administrative Court.

The investigating police chief (or a board of inquiry) has, starting from a departmental list of aptitude: o To inform. He places at thé disposai of thé public thé files and documents relating to thé investigation at thé beginning of the procédure. o To organize. He can ask for additional information, décide lonely or in thé présence of thé petitioners of the organization of the public meetings; he can solicit thé administrative judge on the realization of an expertise dependent upon the petitioner. o To follow-up. He is in-charge of collecting all the observations and remarks and of writing a report addressed to the various administrative authorities.

! Article 1 of the law n° 83-630 du July 12,1983 relative to « démocratisation des enquêtes publiques :

It is to be spécifiée that this type of investigation excludes from its field of application work carried out in order to prevent a "serious and immédiate danger" Within thé framework of thé urbanization control around thé Seveso sites, it is thé CLEE structure that captures our attention because of its proximity with thé new CLIC structure. Indeed, this nonofficial structure créâtes on thé initiative of industrial, aims at establishing a confidence relation between two principal actors: thé industrialist and thé local résident This confidence relation is based on a réduction of thé lack of information and knowledge between thé "local résident" and thé "industrialist" that posses a technical expertise conceming his company. However, thé rôle of thé CLIE in thé décision remains vague. This is reflected by thé following points:

o The recourse to thé expertise. o Give information to thé public (citizen).

The CLIC must meet at least once per year. It can call upon recognized experts to carry out a third expertise. The majority of collèges must approve thé recourse to thé expertise. In fact thé MEDD finances its opération. The formulation of thé final opinion of thé CLIC is done in a concertative process than approved by thé majority. Thus, if thé opinions and thé décisions are approved by half of thé members présent or represented, thé voice of thé président is dominating. This mie, specified within thé framework of article 5 of thé decree, leaves a large range to interprétation on (i) thé representativeness (per a number of collège or a many people in thé collèges) and (ii) thé distinction between thé concept "of opinion" which represent a lighting or a recommendation for thé action and thé concept of "décision" which implies to take thé responsibility for thé action. This last point can appear problematic when thé CLIC has to corne to a conclusion about thé proposai for a Régulation of thé PPRT. Another characteristic of this CLIC structure is that thé number of people présent, within thé CLIC meeting, is open if thé président considers thé people Hkely to bring lightings to thé debates. This various information conceming thé CLIC structure shows that this last one can face a paradox as for its relation with thé State. Indeed, in one hand a désignation and a right of veto to thé balance if an equilibrium happened between thé collèges and in an other hand thé potentiality of being autonomous of thé industrialist means (e.g.

thé CLIE).

In what follows, is presented thé new procédure used for urbanization control around thé industrial site Seveso high threshold in France. This one takes thé form of Technological Risks Prévention Plans (PPRT) and is thé continuity of thé "vulnerability" approach applied by thé French administration within thé framework of thé natural hazard.

2 A "vulnerability" approach for urbanization control around thé Seveso high threshold sites

Introduced by thé law of July 30,2003, thé Technological Risks Prévention Plan (PPRT) is a procédure that aims at preventing thé risks related to thé présence of a Seveso high threshold industrial site. For that purpose, thé PPRT consists in taking thé following measures:

• the reduction of the risk to the source (action on the risk);

• the control of the future urbanization;

• the reinforcement and/or the protection of the building;

• the control of the use of public spaces;

• the action on the land: expropriation, renunciation, pre-emption.

In order to account for specificities of thé industrial activity, thé French Ministry of environment and Sustainable Development (MEDD) has set up an expérimental process. Indeed, by taking support on its two commissions, which are respectively thé "hazard group" and thé " stakes group " thé MEDD set up a methodology for thé application of thé PPRT and by testing this methodology on eight voluntary industrial site.

Thèse methodological developments were confronted to différent industrial practical cases according to (Table 2):

(i) various natures of production and various levels of complexity;

(ii) various levels of seniority of régional présence;

(iii) various levels of local and régional sensitivity and various modes of risks govemance. The table below présents thé eight industrial site selected to test thé expérimental methodology. The eight expérimenté (Table 2) made it possible to identify a certain number of difficulties related to thé application of thé expérimental methodology PPRT. In 2005 and beyond that, this observation will make it possible to bring thé necessary adjustments to thé PPRT methodology in thé perspective of thé promulgation of thé application decree of PPRT4 and thé drafting of a methodological guide (PPRT).

2,1 The PPRT methodology

The PPRT is a methodology Connecting thé three actors that are thé State, thé Community, and thé Owner. The PPRT will allow, following thé signature of a fiaancing convention to thé trio "Préfecture, local communities and thé owners", to choose thé proportioned measures to reduce thé risk (vulnerability) around thé industrial site. For that purpose, thé PPRT methodology follows thé following phases: A technical phase. This phase under thé piloting of thé DRIRE and thé DDE must lead to an évaluation of thé risks and an analysis of thé vulnerability and an identification of measures of risks réduction. For that purpose, this phase is based on two parts carried out in parallel: (i) thé characterization of thé hazard, by thé owner and under thé supervision of thé DRIRE, starting rrom élément corning from thé Safety Studies (EDD) and (ii) thé characterization of thé stakes, by thé DDE while being based on thé local communities, starting from data relating to thé stakes. The choice of thèse measures dépends on thé crossing of thé hazard map and thé vulnerability of stakes map and dépend on: thé nature and lever of thé hazard to which a stake is exposed.

Eight levels of hazards are define according to the level of cumulated probability and thé level of intensity: TF+, TF, F+, F, M+, M, Fai+ and Fai, Moreover, according to thé level and thé nature of thé hazard, some measures are considered as inescapable, to define or subject to crédits. The zones concerned by thèse measures are defined as follows:

• zones where measures are inescapable: (e.g. land measurements within thé framework of thé highest risk);

• thé problematic zones where various types of measures can be considered and for which additional investigations are necessary. For thèse zones, thé réduction of thé vulnerability must be thé subject of a study;

• thé zones where generic measures can placed without spécifie vulnerability studies.

A phase of discussion. This phase, implyiBg thé Préfecture, thé DDE, thé DRIRE, thé owners, thé local communities, thé CLIC and associations, consists in reacting on thé results of thé technical phase of thé PPRT in order to propose a "project of lawfiil zoning and an associated payment". This consists in identifying thé zones and thé sectors of prohibition or lawM régulations. Let us note that thé zones of risk open to thé dialogue are thé zones TF, F, M and Fai. A lawful phase. This phase must lead to thé publication of a "préfectoral decree of approval of thé PPRT". This decree is established after "public investigation" into thé project of PPRT and thé collection of thé formai opinions of thé associated parts. The description of methodological step PPRT shows that thé dialogue, of thé various actors implied and/or concerned with thé préventive measures, intervenes only when thé technical aspects are suggested. Thus, it is necessary to make sure that thé actors involve in thé dialogue process understand thé technical dimensions (probability, kinetics, intensity and vulnerability) before they contribute to thé development of thé lawful project of zoning. Moreover, thé outcome of thé PPRT highlights a certain nimber of problems at thé dialogue phase: thé responsibility for thé CLIC and thèse collèges of actors, thé economical as sociological stakes which implies thé choice of a risks prévention measure on thé zone scale near thé industrial site.

The expérience feedback on PPRT experiments during thé year 2004 and thé consultation of a certain number of actors implied in process PPRT reveals thé présence of thé following difficulties:

A]. Technical contents of exercise PPRT.

• Identification of thé perimeter of study of thé PPRT

• Distinction between EDD and lawful PPRT.

• Cohérence with thé EDD.

• Identification of thé scénarios for thé PPRT.

• Information of thé criteria "probability", "intensity" and "kinetics" suggested.

• Intégration of uncertainty, thé methods of calculation and thé exits

• Hierarchization of thé scénarios of accident.

• Identification of a level of acceptability.

• Lawful zoning of thé PPRT.

• Relation between old zoning and new zoning.

• Identification of thé three zones relating to thé three thresholds of effect.

B]. Organisation of thé meetings of technical work and thé dialogue and briefîngs.

• Order and coordination between thé meetings of thé technical groups "group risk" and "vulnerability group".

• Regularity of thé technical meetings

• Regularity of thé briefings

• Finality and limits of thé conciliation meetings.

• Meetings practical modalities.

• Forai and finality of thé dialogue.

• Local Function of thé Committee of Information and Dialogue (CLIC).

C]. Practical and lawful methods in accordance with thé publication of a PPRT.

• Financings of expropriation, thé renunciation and pre-emption

• Rôle and responsibility for thé fascinating parts with thé PPRT.

• Cohérence with thé existing and prospected urbanism.

The différent difficulties listed above shows thé importance of thé technical dimension in thé framing of thé coordination between thé actors involved in thé PPRT process. This shows that thé development of an acceptability of thé risks, by thé various actors of thé dialogue, must and is managed differently within thé framework from thé PPRT.

The risks acceptability: more than one mathematical dimension

Very often treated in thé framework of thé EDD, thé concept of " risk acceptability " is assimilated to a thé "level of criticality". There is however a distinction between thèse two concepts. The level of criticality is an évaluation of thé scénario of accident starting from thé crossing of its probability (or its frequency) and of its gravity. The level of acceptability represents thé choice of thé industrialist a priori. A structure of criticality grid (e.g. Numbers levels) is suggested, thé level of acceptability should be, as for him, a local concept to fix by thé industrialist and not main road. The grid of criticality or acceptability, used within thé framework of thé EDD, makes it possible to estimate a level of criticality, for thé whole scénarios, on thé basis of two axis: probability and thé gravity of thé conséquences following thé occurrence of a scénario of accident (Figure 1). The criticality grid makes it possible, amongst other things, to show thé impact of thé barriers (in prévention or protection) installations on thé réduction of thé risk taking into account thé level of acceptability frxed a priori by thé industrialist. Thé PPRT do not hâve as a finality to carry out a quotation of acceptability. This aspect falls within thé compétence of thé EDD. The PPRT will define a approval of zones submitted to public constraint and annexed to Local Plan of Urbanization (PLU). Thèse zones are delimited on thé basis of information provided by thé crossing, after dialogue, of information coming from thé hazard map and thé vulnerability map. Thus, thé grid used within thé framework of thé PPRT is a grid making it possible to distinguish, starting from thé crossing of thé hazard and thé vulnerability of thé stakes, of zones (expropriation, pre-emption and renunciation) opened with thé dialogue (Figure 2). Thé way in which thé acceptability is treated within thé framework of thé PPRT must be clearly clarirîed. The probability does not summarize by its self thé risk acceptability. By distinction to thé EDD where thé acceptability is fîxed a priori by thé industrialist by using thé support offered by thé criticality grid (or of acceptability), thé acceptability within thé framework of thé PPRT does not dépend any more of thé only industrialist. The probability cnterion, in complément of thé two other criteria, which are thé kinetics and thé intensity of thé scénario of accident, is used to produce thé hazard map. This map does not aim at defining zones of acceptability, but rather at identifying zones subjected to différent levels of request. Thèse zones are named: zones of very strong hazard, extrême hazard, means hazard and weak hazard. It is with thé crossing, with thé resuit of thé technical part of thé PPRT, of thé hazard map and thé vulnerability map that thé concept of acceptability appears. At thé différence of thé EDD, acceptability is carried by thé dialogue process within thé "Local Committee of Information and Dialogue" (CLIC). While being based on thé proposais of thé technical groups, this committee has thé rôle of making go up thé stakes and thé local constraints to take into account before thé publication of lawful zoning.

3 The dialogue and thé information process : thé CLIC and thé PPRT

The presented PPRT methodology shows that thé information as well as thé dialogue will not be entirely carried by committee CLIC. This shows us thé need for specifying thé range of thèse two concepts: thé dialogue and thé range of thé consensus. The glossary establishes by thé working group Dguhc-MAD/CERTU/CETE (2001) defines thèse two concepts as follows:

o "thé dialogue is a policy of consultation of thé people concerned with a décision before this one is taken. The dialogue consists in confronting thé proposais of thé building owner within thé criticism of thé interested actors (inhabitants, associations...). The petitioner commits himself listening to thé opinions and thé suggestions of thé consulted people, with if required modifying his project to take account of their counter-proposals, to even give up it completely "(Dguhc-MAD/CERTU/CETE, 2001).

o "a consensus is an agreement between several people which implies thé concept of assent. The terni also indicates thé agreement, even nonexplicit, of a strong majority of thé public opinion "(Dguhc-MAD/CERTU/CETE, 2001).

How thé dialogue must it be organized? How to arrive at a consensus within thé framework of dialogue CLIC structure?

The dialogue and briefîngs organization

It is necessary to distinguish various forms of making in relation and thus of organization of privileged working places named "meetings" between thé risks prévention actors. To this end, it is adapted to distinguish various forms of meetings: briefings; technical meetings; conciliation meetings. Thèse three types of meetings must answer thé "général following requirements":

• thé "Master of meeting" must be clearly identified. This one is thé regulator of meeting. It must appoint a secretary of meeting for thé drafting of thé report;

• necessary information to thé good course of thé meeting must be placed at thé disposai of thé fascinating parts a number suffïcient days before thé occurrence of thé meeting;

• a glossary and a communication supports must be placed at disposai;

• thé object, thé fmality as well as thé place of thé meeting in thé realization of thé PPRT must be clearly clarified;

• thé "rules of game" of thé meeting as well as thé rôle of each participant must be clarified at thé beginning of each meeting;

• thé fmancing of thé meetings must be clearly specified before thé organization of each meeting

• a recall of thé conclusions of thé previous meetings must be carried out at thé beginning of each meeting;

• a synthesis of thé "outstanding facts" must be presented at thé end of each meeting;

• thé calendar of thé other meetings must be stated at thé end of each meeting;

• thé questions having not obtained satisfactory answers during thé meeting must be treated at thé beginning of thé next meeting.

In addition to thèse général requirements, requirements spécifie to typologies of meetings indicated above of which necessary:

• Technical meetings. Thèse meetings arise in two forms:

• Individual meetings of the hazard group and thé vulnerability of the stakes group. From their nature, those owe meeting of thé technicians holding a knowledge and an expertise on thé studied object. Thèse meetings must be limited to a reduced group (max. 10 people). The regulator of meeting must be ensured of thé good compréhension of thé methodology of work.

• Meetings gathering thé two technical groups at thé same Urne. Thèse meetings aim at coordinating work of thé hazard groups and vulnerability of thé stakes group from thé point of view of a dialogue or briefmg.

• Briefings. Those are characterized by thé présence, on thé same place, people "having taken part" in thé development of the technical conclusions of the PPRT and people concerned with thé technical conclusions (e.g. local councillors, association, etc). The purpose of thèse meetings is to bring a visibility on unfolding of work of thé technical groups and their practical perspectives. Thèse meetings must remain open to ail people concerned. Thèse meetings must take place with each projection of the technical conclusions. The communication around expérimentation PPRT but also after this one will hâve to be done on:

• Proposing a glossary.

• Training on thé use of PPRT approach.

• Framing of thé supports of communication adapted to thé various profiles of PPRT stakeholders.

When thé dialogue arrives at a not-consensus between thé actors, it is necessary to hâve recourse to a third part. Thus, when thé consensus is not "natural", thé article L 515-8 of thé code of thé environment précise that thé CLIC can call upon an expert. The sub-chapter below introduced a distinction between three types of actors whose mission is to support and/or to act on thé consensus.

The expert, thé mediator and the fadlitator

In order to take care of thé correct opération of thé dialogue, two types of measures can be taken within thé framework of thé PPRT:

o Measures known as intem with thé dialogue. Those would consist in introducing or making carry by an actor of thé dialogue thé rôle of "mediator" or "facilitator".

o Measures known as external with thé dialogue. Those consist in calling upon an "expert".

The mediator, thé facilitator or thé expert hâve in common thé fact of intervening within thé framework of a neutral approach. In what follows, thé rôle as well as thé techniques used by thèse various profiles belonging to thé same category of actor "says intermediate" are presented.

The mediator and thé facilitator

This actor "says intermediate" must take care of thé disappearance of thé situations of misunderstanding or incompréhension between thé actors to imply in thé dialogue while taking care to establish a proximity with thé whole of thé actors, by presenting a good control of thé situation of negotiation and to thus hâve about it an adapted strategy or tactic [START_REF] Grima | La médiation dans les relations professionnelles françaises : une relation à trois ?. Gérer et comprendre[END_REF]. François [START_REF] Grima | La médiation dans les relations professionnelles françaises : une relation à trois ?. Gérer et comprendre[END_REF] distinguishes four styles of mediators:

Distancied compréhension

Empathie compréhension

Positive anticipation on thé capacity of thé parts to be agreed

Facilitator. Médiation like a technique.

Traîner. Médiation as thé research of equity.

Négative anticipation on thé capacîty of thé parts to be agreed

Articulator. Médiation like givegiving.

Third negotiator. Médiation like research of justice.

The facilitator is defined like an organizer of debate aiming at helping thé actors of thé dialogue to go towards a satisfactory agreement. The characteristic of thé facilitator is to avoid thé situations of overflow. Within thé framework of thé PPRT, this rôle can be carried by thé président of thé CLIC. This last represented by thé Prefect or a designated person.

The tramer présents a contractual vision of thé social relations and must hold a good level of expertise in thé légal fleld. [START_REF] Grima | La médiation dans les relations professionnelles françaises : une relation à trois ?. Gérer et comprendre[END_REF] defines it as "an organizer of a harmonious social debate, not being able to tolerate agreements calling it into question". Within thé framework of thé PPRT, this rôle must be played by an actor holding a double compétence: control of thé technical significance of thé aspects (risk, stakes) as well as thé control of thé lawful aspects as well as thé control of thé légal aspects direefly related on thé PPRT and indirectly to thé obligations and constraints of thé various actors of thé dialogue.

The rôle of thé articulator exceeds thé rôle of thé facilitator in his animation of thé debates. Indeed, this one is in thé search of resuit (production of agreement) while weighing on thé negotiation without intervening there directly. The third negotiator holds a protocolar and formai position. It controls thé negotiation while being based on a conclusive step aiming at showing thé superiority of a proposai of an actor on thé others. Within thé framework of thé PPRT, this rôle can be becupied by thé expert appointed by thé CLIC.

If thé first both form of médiation can be presented some are thé situations of dialogue, thé two last take place only in thé event of conflict. The argued negotiation then becomes necessary. By negotiation one understands "a séries of talks, exchanges of views, steps which one undertakes to manage an agreement or to conclude a business. It supposes that there exists from thé différent points of view and a will to find an agreement "(Dguhc-MAD/CERTU/CETE, 2001).

The expert

The various consulted dictionaries define thé expert by his experiment in his fleld of compétence and thé quality of its know-how; thé dictionary Hachette (1997) spécifies that thé expert is that "Which acquired a great skill by thé practice". Thus, thé expert is appointed through his official or professional statute and not starting from his compétences; he says thé "people named by authority of justice, or chosen by thé interested parts, to examine, estimate certain things, and to submit a report of it" (Dictionary of thé French Academy, 1835). The expert is also "that which cornes afterwards, to say truth" (Philippe Fritsch (2000) in Decrop, 1997 andDecrop and[START_REF] Decrop G | Prévenir les risques : de quoi les experts sont-ils responsables ?[END_REF]. Three types of experts are distinguished according to thé situation of expertise:

• The professional expert. One fînds a proof of their légal existence, in France, in thé form of corporation created by thé King in 1690. At that time thé expertise was carried out with an aim of thé collection of thé royal tax and with an aim of estimating thé goods of late (Decrop andGalland, 1998).

• The légal expert. It auxiliary of justice named by thé authority or is indicated by thé interested parties "to examine and estimate certain things, and to submit of it a report" [START_REF] Decrop G | Prévenir les risques : de quoi les experts sont-ils responsables ?[END_REF]).

• The scientific expert. It represents thé new type of expert who draws his legitimacy from thé scientist. It is called with thé rescue in public décision, not to evaluate thé past, but to anticipate thé future and to deliver its opinion. It is with max [START_REF] Weber | Le savant et le politique[END_REF] that one owes thé first theorization of thé expert whom it then defines as a bond between "thé scientist" and thé "policy" and is with thé "spécifie" service of thé latter.

Because it is thé assemblage point between thé scientist and thé policy, thé expertise must, not to be confused in its practice with those, to delimit its sphères of responsibility and its limits for compétence. Indeed, thé expertise stops where thé policy (décision) begins: thé expert is adecision-making aid, thé public décision maker intégrâtes various contextual dimensions of thé study of risk to establish thé best solutions and to communicate his décisions with thé public [START_REF] Decrop | De l'expertise scientifique au risque négocié : Le cas du risque en montagne[END_REF]Godard and AÏ, 2002). Thus, thé expert has thé rôle of clarifying thé décision of an institution and of placing at his disposai his experiment and his capacities of analysis. It is to thé final décision maker (institution) that thus returns thé responsibility of take into account thé various disciplinary fields of thé technical expertise (légal, économie, etc.) and to integrate them in thé décision. Bovy and of Erik Laes (2002) define thé scientific rôle of expert in thé following way:

• thé compétence of opinion. The expert answers a request for decision-making aid, it advises but does not suggest; it engages in thé decision-making process but is not carrying thé latter.

• a rôle of référée. The scientific expert is not référée except if "it is asked to him" to act in this direction; consequently thé scientific expert merges with thé légal expert;

• a rôle of negotiator. This rôle is not asserted in terni of communication of thé results to thé public but within thé framework of thé work of collective expertise; thé negotiation is done on thé objectives, it is thus not a finality but a condition of good practice of thé collective expertise;

• thé communication. It has as a rôle to explain to thé agent (thé applicant of thé study) thé contents of thé established facts. The communication of thé expert is there to explain and not convince.

Work on thé rules of intervention of thé expert is rare not to say non-existent. In Decrop (1997), [START_REF] Godard | Traité des nouveaux risques[END_REF] and [START_REF] Bovy | Comment le centre belge d'Etude de l'énergie nucléaire gère la culture de l'Expert ? Colloque européen sur la sûreté de fonctionnement[END_REF] thé intervention of thé expert is distinguished according to thé formai framework from its désignation and that abstract from its récognition. From a formai point of view, thé expert is by contract dépendent with thé décision maker while holding autonomy of intervention, independence and scientific freedom in order to conclude his mission. It is to thé expert that returns thé rôle to identify thé priority problems, to define his framework and its working conditions in manner autonomous without being subjected to a hierarchical constraint of thé seeker organization of thé study under penalty of lack of objectivity of thé returned conclusions.

In thé framework of probîems PPRT, thé expert intervenes when thé dialogue arrives at a node of blocking at thé level of thé concertative structure which is thé CLIC. The decree of February The various tactics aiming at using thé three stratégies presented in Table 4 (reflexive, substantives and contextual) concern thé qualitative steps of organization of thé negotiations for going towards a consensus. When thé médiation arrives at a situation of not-consensus and where thé qualitative steps cornes up against their limits, of thé steps operational based on quantitative approaches can be employed. In what follows, an illustration of thé two types of operational approaches of avoidance or going towards a résolution of conflict are presented.

Qualitative approaches

The implementation of thé Technological Risks Prévention Plans (PPRT) is typically a complex problems where a significant number of actors participate (directly or not) during thé "concertative (dialogue) phase. The Soft-OR 6 approaches are developed for thèse typologies of problems.

In what follows, a Soft-OR method is presented. This method is SODA (in [START_REF] Hjortso | Enhancing public participation in natural resource management using soft OR-an application of stratégie option development and analysis in tactical forest planning[END_REF].

Conflictual situations are inhérent to processes where various groups of actors having différent values, perceptions, objectives, constraints and rôles in thé dialogue but also in thé élaboration of thé final décision. In order to understand and be a support to solve thèse various conflict situations, we can refer to thé work developed by [START_REF] Ackoff | Redesigning thé future[END_REF] and [START_REF] Eden | Using Cognitive mapping[END_REF]. The SODA method makes it possible to identify and structure thé concerns "known as being subjective" of thé actors in order to make them discuss and share by thé group; and then to go towards a consensus.

The SODA method is based on thé eight following steps [START_REF] Eden | Stratégie thinking with computers[END_REF]):

1. Initial individual interviews and development of cognitive maps.

2. Feedback interviews aiming at validating thé initial cognitive maps.

3. An analysis with an aim of identifying key solutions.

4. Formai research and experts interviews.

5. Refînement of thé solutions.

6. Workshop to work on thé conscience and thé sensitizing of thé actors.

7. Workshop to identify orientations.

8. Workshop to elaborate a set of actions.

Among, thèse eight steps, two times are of primary importance. First, thé step consists in interviewing thé group of actor in order to understanding and let émerge thé various solutions and options where they wish to tend. Using an interaction process between thé involved actors and thé facilitator, this approach help to highlight thé expectation as well as thé solutions that allow changing thé way thé group of actors has initially perceived thé situations of conflict.

This makes it possible to elaborate what is known as a cognitive cartography. Various stratégies can help to highlight, capture and collect thé individual structure of thé trio: value/objective/aspiration. The guiding principle of thé step of mapping support on thé postdate that thé individual continuously has a représentation of thé world through "a System is built" made up of a fînished number of topic and répétitive concepts (built). The cognitive map is represented by a network of concepts (nodes) bound by chains of argumentation. It makes it possible to break insulation individual perceptions of thé conséquences and thé explanations associated with thé concepts. In a sensé, this map is a support to thé communication.

In thé second time, thé facilitator analyzes thé various cartographies (by actor) with an aim of highlightîng common points. The maps are gathered and incorporated in a représentation aiming at providing a global vision of thé représentation, by thé group of actors, of thé problem. This makes it possible to emphasize various explanations, conséquences, dilemmas, options as well as thé even négative positive visions of thé effects of thé options.

This type of approach can be easily to be set up as of thé launching of process PPRT. It will make it possible to act upstream and avoid, even to argue and act on, thé possible conflict situations at thé time of thé dialogue.

This approach is only one example of a set of other qualitative approaches that can be used. Among those, thé ones based on understanding and acting on thé group dynamics (Mucchielli, 2002).

Quantitative approacesh

The quantitative approaches of negotiation and décision support are numerous. The décision trees are an example. This approach allow, using probabilities and graphical support to highlight thé most relevant option(s) carrying thé consensus of thé actors.

However, due to thé fact that:

• thé risk is by nature dépendent of several criteria (risk is combination of hazard and vulnérable stakes);

• thé choice of measures to reduce thé risk dépend on thé agreement between thé actors after a dialogue process;

• thé décision criteria must be elicited by thé various actors to accredit thé choice of préventive measure on a zone.

It was decided to présent one quantitative approach: thé multiple -criteria approach. Ail thé decision-making methods structure thé decisional contexts in three principal phases (Figure 5): o a problem structuring phase; o a running phase; o a recommendation phase.

The first phase consists in:

• describing thé context and thé decision-making process. One identifies there thé multiple actors, their Systems of values and various key-times of decision-making process;

• building thé actions, éléments on which cames thé décision;

• identifying thé décision situations (Roy and [START_REF] Bouyssou | Aide Multicritère à la Décision: Méthodes et Cas[END_REF] which consists in thinking about thé way in which thé recommendations or thé results must be presented; and identifying thé spirit in which is elaborate thé decision-making " décision problematic" (Roy, 1985; Roy and Bouyssou, 1993).

• modeling thé conséquences of thé actions and criteria in order to compare an action to an other.

Compute information reiated to decisional situation

Aggregation procédure Recommandations \ Figure 1. Multiple-criteria decision-making methodology for risk study [START_REF] Merad | Apport des méthodes d'aide multicritère à la décision pour la hiérarchisation du risque lié à la présence d'ouvrages souterrains[END_REF] This first phase will hâve a significant influence on thé way decision-making support is elaborate and will then hâve an impact on thé way conclusion and solutions are structured. Thé second phase is a more mathematical one. The phase known as "exploitation phase" consists in choosing thé most adapted " aggregation procédure " to move from a partial évaluation of a potential action (according to a criterion) to a global évaluation of an action with an aim of providing a total conclusion (recommendation) which will be used as support for thé décision. Bernard Roy (1993) proposes a four steps methodology, which allows thé mediator, facilitator or expert to déterminé his problem of décision as well as possible:

• Level I: Subject reiated to thé décision and thé spirit of thé recommendation.

• Level II: Conséquences analyses and criteria élaboration.

• Level III: Modeling thé global préférences and operational approaches for préférences aggregation.

• Level IV: Investigation procédures and framing of thé recommendations.

This last level, less mathematical, is thé so-called "recommendation phase". This one includes thé sensitivity analyses as well as robustness analysis. During this phase, it is possible to adjust thé phases of decision-making approach. if thé context requires it.

The multiple-criteria decision-making approach can help to argue and justify thé choice of a measurement on a zone where PPRT constraints must be imposed. That can be possible taking into account thé criteria which characterize thé risk, thé criteria which characterize thé stakes as well as other sets of criteria which reflect thé économie conséquences, social, légal... etc. aspects due to thé implementation of thé PPRT préventive measures.

Moreover, thèse steps make it possible to clarify thé "préférences" of thé various actors involved in dialogue process.

The two typologies of methodology presented above are not exclusive one of thé other; they are often complementary: thé qualitative approach must be used preferably before thé quantitative approach. They can be used at différent times during thé médiation or expertise procédure according to thé nature of thé problem.

Conclusions

Strongly regulated, thé dialogue in France is dépendent on thé various laws, decrees and circulars which define thé moments, thé methods and thé shapes which must cover thèse times of exchange and coordination between thé various actors of thé risks prévention process. The law of July 30,2003 is a good example. The French State gave both a place to thé local actors (e.g. Communes, association, citizens) and means for a good dialogue by introducing thé new framework of exchange "thé Local Committee of Information and Dialogue" (CLIC) and by offering to this committee a place within thé framework of thé decision-making related to urbanization control around thé High hreshtold Seveso industrial site, In spite of a fixed définition of thé CLIC structure within thé framework of thé decree of February 1, 2005, thé effective working of thé CLIC cannot be done without considering thé history and thé culture of dialogue and information established on a local scale. This observation is ail most true when it came to urbanization control problems. The expérimental process sets up in 2004 and 2005 aiming at establishing a methodology for thé Technological risks Prévention Plans of thé (PPRT) revealed thé déterminant rôle of technical information in reglementary décisions about urbanization control. This technical information guides and détermines thé nature and way thé meetings sessions and moment are between thé actors. Lets say finally that if thé dialogue is an upstream process to thé décision, it is necessary to think about thé way this moment must be organized to make it became as efficient as possible. Beyond thé organization of dialogue meetings, it is necessary to wonder about thé émergence of a new kind of actors: thé expert, thé facilitator and thé mediator. Thèse actors hâve thé ability to prevent, avoid or clarify potential conflicts that can émerge due to thé plurality of stakes and to thé complexity of thé technical aspects defining thé major industrial accidents risks. Various approaches, some times qualitative and some times quantitative, can be used considering thé relation nature between différent actors and thé group dynamic within thé CLIC structure.

  stratégie and operational orientations: to promote policies of lute against thé harmful effects and thé installation of an anti-pollution plan for thé industrialists. o A mission of orientation of thé expertise concerning thé local conditions. Within thé framework of thé control of thé urbanization around thé industrial site, thé extent of thé sphère of activity of thé SPPPI includes thé industrial basin. In thèse terms, thé SPPPI has a mission of information and centralization of thé problems common to various industrials site. Lets notice that neither thé law n°2003-699 of July 30, 2003, nor thé decree n° 2005-82 of 1 February 2005 relating to thé création of thé local committees of information and dialogue pursuant to thé article L 125-2 of thé code of thé environment, nor thé circular n° 00908 of May 15, 2001 relating to thé installation of thé interdepartmental local commissions of coordination (CLIC) clearly spécifies thé interactions of this structure of dialogue with thé new CLIC and does not recognize its official existence. 1.1.3 Local committees Existing in various forms, having various objectives, and having an official structure or not thèse local committees are multiple. One finds there thé Local Committees of Information and Safety (CLIS), thé Local Committees of Information and Monitoring for nuclear power (CLIS), thé Local Committees of Information and Exchange (CLIE) and more recently thé Local Committees of Information and Dialogue (CLIC).The table below présents thé forms and mission of thé first three structures. Tableau 1. The three shapes of local committees[START_REF] Mazri | Rapport intermédiaire de thèse « Apport des méthodologie d'aide à la décision dans la gestion des risques industriels majeurs[END_REF]

Figure 1 .

 1 Figure 1. An example of a criticality grid (Grid SRPP)

Figure 2 .

 2 Figure 2. Identificatio of thé lawfiil zones starting from level of hazard and level of vulnerability

Tableau 3 .

 3 Styles of mediators[START_REF] Grima | La médiation dans les relations professionnelles françaises : une relation à trois ?. Gérer et comprendre[END_REF]

  This structure does not hâve a légal existence. It joined together actors on a local scale such as thé State through its services (e.g. DRIRE), thé industrialists, thé local communities, associations for thé protection of environment, média, experts...) around questions having a link with thé industrial environment. There are 11 SPPPI on thé French territory. It is thé Prefect who defines thé composition and spécifies thé missions of thé SPPPI. The SPPPI of Area PACA is one of thé oldest. Placed under thé authority of thé Prefect and animated by thé Régional

		2 .
	The space of exchange is:
	(i)	opened to ail people concerned with thé décisions;
	(ii)	centered on a décision;
	(iii)	limited in thé time. Upstream of thé decision-making but downstream of thé technical
		éléments having contributed to framing thé décision.
	1.1.2 The Permanent Secrétariat for thé Prévention of Industrial Pollution (SPPPI)

Division of Industry, of Research and of Environment (DRIRE), this one was decided in 1971, and was made operational in 1972, following problem raised by thé concentration of industrial site around "Etang de Berre" région in order to ensure balance between thé économie dimensions and thé thé environmental quality. The principal missions allocated with thé SPPPI are: o A mission of information: information of thé public on pollution and thé means of reducing them. o A mission of

1.2 The Local Committee of Information and Dialogue (CLIC)

	industrial risks to coordinate each other and to be able to give their opinions concerning infoimation
	provide within thé Safety Studies and thé Technological Risk Prévention Plans.
	It was necessary to wait until February 1,2005, with thé promulgation of thé decree n° 2005-82 relating
	to thé création of thé local committees of information and dialogue pursuant to thé article L 125-2 of
	thé Code of thé environment, to see thé rôle, thé missions and thé framework of thé CLIC specified and
	fîxed.
	This committee, créâtes by Prefect of départaient decree for any Seveso high threshold site, is limited
	to 30 people. The CLIC is structured around five collèges of actors 3 including:
	o The "administration" collège:
	o Prefects, or their représentative;
	o a représentative interdepartmental services of défense and civil protection;
	o a représentative departmental services of flre and rescue;
	o a représentative services in charge of thé inspection of thé classified installations;
	o a régional or departmental représentative of thé equipment division;
	o a représentative services in charge of thé factory inspectorate, employment and
	vocational training.
	o The "local authorities" collège: deliberating assemblies of thé local and territorial communities
	or the publicly-owned establishments of the concerned inter-commune co-operation.
	o The "owners"college:
	o Management representatives.
	o If necessary, a représentative of thé authorities managers of thé works of road, railway,
	harbour infrastructure or of inland navigation or modal multi-installations located in
	the perimeter of the committee,
	o The "local résidents" collège: Représentatives of thé local associative world, résidents located
	inside the zone covered by the local committee and, if necessary, the qualified personalities.
	o The "employees" college:
	o Employee representatives proposed by the delegation of the personnel committee of
	safety, health and working conditions.
	o If necessary,
	The neutrality of thé expertise, required if a conflicts happen,
	could be called in question, this owing to thé fact that thé CLEE is at thé industrialist initiative,
	o Means. Financial means that are necessary to thé CLIE opérations dépends on thé industrialist.
	Within thé framework of thé urbanization control around thé industrial site, it is necessary to
	recognize thé responsibility for thé trio Industrialist /State/Local communities.
	By many facets, thé installation of this new structure of information and dialogue, that is represented by
	thé CLIC, has strongly change thé practices in industrial risks prévention process in France.
	Indeed, introduced through thé July 2002 circular of thé Ministry for Ecology and Sustainable
	Development (MEDD) that recommend to thé Prefects thé installation of thé "CLICs by anticipation",
	this "pilot structure" became since 2003 an opportunity for thé various actors concerned with thé major

it includes employée représentatives of each concerned

  The members of thé committee of hygiène, safety and thé working conditions and thé union delegates are replaced when their mandate of member of thé committee of hygiène, safety and thé working conditions or of union delegate ends.

establishment, at a rate of at least a staff représentative per establishment, proposed per thé délégation of thé personnel of thé committee of hygiène, safety and thé working conditions among its members or, failing this, per thé union delegates. o

The CLIC is concerned with various actions: o Give opinion. It is associated thé development of thé Technological Risks Prévention Plans (PPRT). It can give a report on thé project of plan. It gives observations on thé information memoranda provide by thé authorities and thé owner to thé citizens. o Receive information. Technical information such as on thé accidents having perceptible conséquences outside thé site, thé critical analyses, EDD, emergency and information plans concerning thé becoming of thé owner and thé opération such as extension projects or modification of thé installations.

  Those must help to bring additional data éléments to thé technical conclusions. Carried by thé Local Committee of Infonnation and Dialogue (CLIC), thèse meetings exceed thé pure briefîng. Indeed, thé opinions of thé various collèges of actors of thé CLIC must give places to an adjustment of thé technical proposais.The framing of thé lawful map of thé PPRT must be carried out in dialogue with thé various local actors. The dialogue is based on thé technical éléments of thé PPRT. The minutes of thé various meetings of work (intermediate or not) must be carried out in a préoccupation with a transparency and a préoccupation with an information to thé various actors (e.g. thé Local Committee of Information and Dialogue CLIC). The publication of a document presenting expérimental methodology PPRT at thé various actors would hâve allowed: (i) to get along on a common vocabulary enters thé various stakeholders, (ii) to avoid methodological skews of compréhension while returning to thé référence documents. The dialogue on thé recommendations of thé technical groups (hazard and vulnerability maps) is carried by thé Local Committee of Information and Dialogue. The plenary group is informed and listened.

• Conciliation and dialogue meetings.

  1,2005 on thé Local Committees of Information and Dialogue as well as thé law of July 30,2003 does not specify thé nature of thé missions of expertise. Thus, thé expertise can arise in two forms at thé same time technical and scientific. In thé framework of problems PPRT, thé expert intervenes when thé dialogue arrives at a node of blocking at thé level of thé concertative structure which is thé CLIC. The decree of February 1, 2005 on thé Local Committees of Information and Dialogue as well as thé law of July 30, 2003 does not specify thé nature of thé missions of expertise. Thus, thé expertise can anse in two forms at thé same time technical and scientifîc: • on what brought to choose thé measure of réduction of thé risk on thé zone considered at thé time of thé dialogue. To this end, thé expertise will relate to aspects related to hazard and with vulnerability stakes; • on thé économie, social, légal... etc. conséquences of thé installation of a measure on thé considered zone. To this end, thé expertise will carry on aspects other than thé two components of thé risk taken in account within thé framework of thé PPRT to know: thé cartography of thé risk and thé cartography of thé stakes. The mediator, thé facilitator or thé expert are based on methodological steps aiming clarifying thé misunderstandings, at showing thé effectiveness or thé optimality of thé installation of a préventive measure on thé considered zone. In what follows, a certain number of operational means aiming is proposed at retuming thé dialogue within thé framework of thé most effective possible PPRT. 4 Stratégies and tactics of médiation and operational steps of negotiation In order to conclude a médiation thus an expertise in situation of support to a group, thé intermediate actor (e.g. thé mediator, thé expert) must dispose of a set qualities or approaches aiming at going towards thé consensus. To this end, thé state of thé art established by Grima (2005) concerning thé stratégies and tactics used within thé framework of thé steps of médiation hâve thé advantage of being very synthetic. This state of thé art is presented in thé table below:Tableau 4. Synthesis of thé stratégies and tactics used by thé mediator[START_REF] Grima | La médiation dans les relations professionnelles françaises : une relation à trois ?. Gérer et comprendre[END_REF]

				Strategy
		Reflexive		Substantive		Contextual
	Définition of thé stratégies	To weave bonds of confidence with thé thé médiation. parts to make accept	To act on thé bonds between thé parts and to compréhension facilitate a reciprocal	To convince thé parts of thé existence of a common interest
		o To clarify thé	o To	be	made	thé	o To reassure thé
		framework action.	spokesman	of	an	negotiators.
		o To propose a	evanced			o To ensure thé
		followed approach	o Bring back thé debate on	negotiators of an
		to go toward a	thé consensual ground.	post	consensus
		consensus.	o To direct thé debate	assistance.
		o To take thé control	towards spécifies points.	o To	assist	thé
	Mobilized tactics	of thé diary of thé parties. o To put forward thé mie of good manners.	o To framework agreement. redefine thé o To take it part, o To threaten by law.	negotiators in thé présentation of thé agreement obtained with their représentatives.
			o To argue it by thé reason.	o To underline thé cost of thé absence of
			o To	uncouple	thé	agreement.
			relations.			o To resort to thé
							intervention of an
							external third.

and border thé context of thé decisionai

	Information
	Knowledge
	Build Actor	)	I Actions
			•
		9, constraints and stakes

Article 5 de la loi

2003-699 du 30 juillet 2003 relative à la «prévention des risques technologiques et naturels, et à la réparation des dommages » : Art. L. 515-22.-« le préfet définit les modalités de la concertation relative à l'élaboration du projet de plan de prévention des risques technologiques dans les conditions prévues à l'article L. 300-2 du code de l'urbanisme. Sont notamment associés à l'élaboration du plan de prévention des risques technologiques les exploitants des installations à l'origine du risque, les communes sur le territoire desquelles le plan doit s'appliquer, les établissements publics de coopération intercommunale compétents en matière d'urbanisme et dont le périmètre d'intervention est couvert en tout ou partie par le plan ainsi que le comité local d'information et de concertation créé en application de l'article L. 125-2. »

Article

of decree of February 1,2005 concerning thé CLIC.

Thé PPRT decree will be published at thé begiiming of September 2005. s The stakes are représentée! by thé peoples, thé goods, thé activities, and cultural patrimony or thé environment exposed to a hazard.

OR : Operational Research. r o


O Bour

S Berger

C Couturier

L Riquier°

DETERMINATION OF GUIDANCE VALUES FOR CLOSED LANDFILL GAS EMISSIONS

In order to promote active landfill gas collection and treatment or natural attenuation, it is necessary to identify trigger values concerning landfill gas emissions in the preliminary stage of a risk assessment. The determination of these values is the first goal of a work which includes a large regulation review and the study of a generic inhalation exposure scenario for the most common reuse of French Municipal Solid Waste (MSW) landfill surface, namely a recreational area without residential buildings. The health risk levels of this scenario are lower than the usual levels and enable to determine trigger values for methane production rate. These results and the methane oxidation rate in the landfill cover allow for the determination of residual methane surface emission rates. The combination of these parameters with on-site specific measurements enables the promotion of natural attenuation or active landfill gas treatment.

INTRODUCTION

The French Agency for Environment and Energy Management and the French Ministry of the Environment and Sustainable Development are currently defining criteria concerning the regulation of residual emissions of Landfill Gas (LFG) from definitely closed Landfills. The determination of these criteria is to be based on risk assessment studies as well as on European and National regulation and practices related to closed Landfills for non-hazardous wastes.

Landfill gas emissions decrease after the end of landfill exploitation during the aftercare phase. The need for LFG treatment at low production levels depends on different parameters concerning the LFG source, the type and the composition of the cover, and the human receptors for LFG trace contaminants. Health risk and odour level assessment related to the landfill gas emissions represent one of the most important stage of the environmental management of landfill site with a residual organic compound fraction.

The European risk assessment and risk reduction practices are various, especially concerning risk reduction. The LFG residual risks depend mainly on the guidance values for collecting and treating landfill gas. These values also determine the type of landfill surface reuse after the exploitation phase.

A research program concerning LFG odour and risk assessment began at the end of 2003. The purpose was to build methodological guidelines for LFG risk and odour assessment. The research program consisted in two parts : completing the review of practices, and proposing guidance values especially for the case of closed landfills. These stages of the study were conducted with the collaboration of SOLAGRO and Riquier Etudes environment.

REGULATION AND GUIDELINES REVIEW

Regulations and guidelines related to residual emissions of closed landfills

In a first stage, a review of the European regulations in 12 countries has been made. This review has concerned especially the LFG collection and treatment for definitively closed landfills. The study has been carried out by consulting the regulation, and owing to the answers to an inquiry sent to 130 correspondents.

In the European countries, regulation is based on : the EU directive 1999/31/EC concerning landfilling of wastes, and the prescribed methane limit value in air (usually approx. 1% of methane).

The UK EPA has produced a series of guidelines related to the management of landfill gas. Two documents give a lot of information :

Guidance on the Management of Landfill Gas (UK EPA, 2002) ; Guidance for Monitoring Landfill Gas Surface Emissions (UK EPA, 2003). These guidelines give indications concerning the different stages of hazard identification, risk screening stage and risk assessment, methods for monitoring the surface emissions and criteria for closing and post-exploitation. In a first tier these guidelines propose to calculate the approximate gas flow and compare with the trigger values of 50 -100 m 3 (CH 4 )/h. A predicted methane flow that exceeds these values indicates that flaring, or other treatment processes, is needed. The other stages of the tiered risk assessment are a simple or complete quantitative risk assessment.

Concerning the monitoring of LFG surface emissions, prescriptions are given if measurements values obtained with an FID are greater than 100 ppmv on the landfill surface, and 1 000 ppmv above cracks, during the preliminary annual survey stage. In this case, a regular surface emission survey has to be defined and the new trigger values are 0,05 m 3 (CH 4 )/ha/h for the closed landfills surface and 5 m 3 (CH 4 )/ha/h for the temporary cover. These values are relatively low but can be reached on sites managed according to the best practices. If the flux boxes measures exceed these trigger values, corrective actions have to be implemented in order to minimize the emissions.

Prescriptions are given concerning the site odour assessment, which detail how odour monitoring should be undertaken.

German and Austria regulation limit emissions by reducing the waste organic content. Federal German regulation especially consists in prescriptions about pre-treated wastes, e. g. the residual production of biogas (trigger values for GB21 tests : 20 and 30 Nl/kg dry materials). Some data have to be given concerning the comparison between residual emissions after pre-treatment of the waste and other practices :

• MSW landfill with a LFG good collection rate : 50 to 80 Nl/kg ; • MSW landfill with a LFG poor collection rate : > 150 Nl/kg ; • Pre-treated waste : 5,8 -9 Nl/kg. Finnish and Danish regulations also permit the use of residual LFG treatment by methane oxydation for low LFG production.

Guidelines related to LFG risks assessment

The regulation and guidelines related to LFG risks assessment have also be analyzed. The study focuses on the LFG risk assessment models and methods which could be used for closed landfills. Danish work [START_REF] Bote | Danish guidelines for investigation and risk assessment of gas producing landfills[END_REF] concerning the fires/explosion risks for houses on, or near a landfill, is available. This Danish report [START_REF] Nilausen | Metode til risikovurdering af gasproducerende lossepladser[END_REF] gives a methodological approach with the focus on the sequence of events which can lead to fires/explosion risks. Data are given concerning the methane fluxes density which can generate a methane travel by gas advection in soil (with overpressure assumptions). This methodology could be used more specifically for accidental risks.

Concerning chronic risks, a specific gas risk assessment model (GasSim, Gregory R.G. & al, 2002) can be used to provide a management tool concerning the bulk and trace gas emissions and dispersions. Several checks between GasSim, LandGem data and site data have been done and are available. Concerning the source terms, the description of the three fraction model is similar to the ADEME model often used in France. GasSim uses a gaussian plume model for the atmospheric dispersion of the emissions. For the specific use of the studied scenario, that is to say modelling of dispersion and mixing of the LFG fugitive and diffuse surface emissions on the landfill top cover, the simple air box model seems more suitable, since the on-site exposure concentrations are higher than any exposure concentrations downwind from the source.

HEALTH RISK ASSESSMENT

Definition of the conceptual exposition scheme

The construction of a conceptual exposition scheme to the LFG emissions of a closed landfill corresponds to the worst case and the most likely scenario of LFG trace contaminants inhalation exposure. Building accommodations above closed landfills with middle-aged waste (20 -30 years) surface are extremely rare, even for commercial or industrial purposes. The most frequent reuse is the development of recreational area with no residential buildings.

The worst case exposure scheme can be defined for a recreational area on the top of the landfill cover. The inhalation exposure can be assessed by taking into account the daily walkover of a child on the landfill surface. The walkover is similar to the concept used for the LFG emission preliminary survey stage. The breathable air corresponds to the mixing of residual LFG production flux with fresh air brought by wind, calculated with an air box model and a conservative wind velocity equal to 1 m/s (Figure 1).

To undertake a quantitative simplified health risks assessment for the inhalation path, a source term has to be calculated for a median size landfill site. A site with a total amount of collected waste of 100 kt in 10 years was chosen. The LFG emissions will be driven only on the top surface. In order to maximize the LFG trace contaminants concentration and to build a rather conservative scenario, a 10 meters thick deposit and a top surface of 10 000 m 2 will be taken into account.

Assumptions and health chronic risk calculation related to the exposition scheme

In the first part of the study the amount of LFG produced which has not been collected and treated with a generic approach has to be considered. The LFG emissions must be collected and treated for a period of 30 years in France after the exploitation phase. Nevertheless, it is common that the wells or another part of the collection system are not very effective. The collection rate will also be low due to mechanical constrains, biological clogging or leachate saturation of the waste in a conservative scenario.

The overpressure in the waste is also lower in the post-exploitation phase. The decrease of this overpressure will lead to LFG migration by diffusion (Figure 2). In this case, LFG can be assumed to be more difficult to collect. Fugitive LFG emissions will also be more representative than the drained LFG. Ten years after the end of the exploitation phase the LFG diffusion fluxes (estimated by the Fick's law) will be approximately at the same level as the advection fluxes for a one meter thick silty clay layer and LFG overpressure assumptions. This type of cover is representative of the composition of a median size landfill cover. In the case of predominant advective fluxes, lateral migrations and explosion/fire hazards could be the major risks if a target was in the surroundings of the landfill.

This fact can be used to consider the conservative assumptions that all the LFG produced in the landfill will be available to increase the concentrations of the LFG trace contaminants in air above the cap of the landfill 10 years after the end of the exploitation. The French model with 3 fractions (based on the IPCC and US EPA equations) was used to calculate the LFG flux.

The second set of parameters concerns the LFG trace contaminants. French guidelines for landfill health risk assessment are available [START_REF] Astee | Guide méthodologique pour l'évaluation des risques sanitaires dans les études d'impacts des installations de stockage de déchets ménagers et assimilés (ISDMA)[END_REF]. At least three compounds (benzene, 1,2-dichloroethane and H 2 S) have to be considered, and complemented if necessary. For this study, 3 complementary compounds were considered : vinyl chloride, formaldehyde and acetaldehyde.

The data of a French LFG trace contaminants concentrations review (ASTEE, 2004) was compared with other data sets of trace contaminants concentrations, and especially the median concentrations proposed for the use of GasSim by Golder Associates in 2003 and 2004 and by Komex [START_REF] Hillier | Assessment of trace components in Landfill Gas from "Typical" UK Sites[END_REF] in late 2004. For each compound, the median concentration value was corrected with a factor which divides by approximately two, the gap between the median value and the maximal value of LFG trace contaminants. This correction is justified by the weakness of the French LFG trace contaminants data set. This correction factor reaches half a magnitude order for 5 of the 6 compounds. The summary of the LFG contaminant concentrations is presented in Table 1.

In this case, chronic risks by inhalation were lower than the US EPA and ATSDR toxicological reference values. Concerning the odour assessment, the concentration levels could reach and even exceed the threshold levels. Specific measures must be taken in case of observed odour.

DETERMINATION OF GUIDANCE VALUES

Choice of criteria and values

The calculation of the landfill methane production is the most common method used for preliminary landfill desk studies. This parameter also determines a quantitative criterium.

Concerning the choice of a trigger value, the LFG collection and treatment feasability for standard equipment (50 m 3 (LFG)/h) has to be taken into account, the absence of health risks for the generic scenario studied (1 ha, 100 kt MSW, 50 m 3 LFG/h) and the site specific parameters also have to be considered. Others site specific parameters are the LFG trace contaminant concentrations and the land surface used for the deposit.

Monitoring the LFG total NMVOC and hydrogen sulfide concentrations enables to reduce significantly the health risks with minimal in situ characterization works. The correction factor used in the health assessment can also be used to determine the low LFG production with higher LFG trace contaminant concentrations, and without exceeding common health risks levels, namely approx. 10 m 3 (LFG)/h. Measuring LFG trace contaminants can also be used for the odour assessment, even if the concentrations in odour units could be more easily compared with on-site odour assessment. The landfill surface parameter was also chosen in order to estimate the surface emissions. This parameter could be linked with natural attenuation rate for covers which allow methane oxidation. An oxidation rate of 5 to 10 m 3 CH 4 /ha/h [START_REF] Stegmann | Discussion of criteria for the completion of landfill aftercare[END_REF] reduces a large fraction of the methane residual emissions 10 years after the end of the exploitation, according to the generic scenario studied. Other studies demonstrate that LFG trace contaminants can also be oxidised in landfill cover (Kjeldsen & al. (2003), Scheutz & al. (2003)).

Definition of 3 areas

A combination of the production rate and surface rate is needed for the large surface sites which could easily exceed a production rate trigger value. Three areas (Figure 3) could be defined with the trigger values which lead to active collection and treatment, natural attenuation or a screening risk assessment, prior to the use of some specific prescriptions. Other site specific criteria like LFG total NMVOC and hydrogen sulfide concentrations will be used in the simplified risk assessment in order to precise the need for an active collection.

CONCLUSIONS

The aim of the methodological works includes the determination of trigger values in order to manage low LFG production in the case of closed landfill. The combination of the proposed parameters (methane production rate, methane surface emission rate, total NMVOC and hydrogen sulphide concentrations) does not give sufficient indications for the case of old landfills with methane migration risks and presence of houses on or near landfills.

The trigger values proposed in this study could be corrected with the progress of the best available LFG treatments and with a better knowledge of the probability distribution of LFG trace contaminant concentrations. Nevertheless, due to the large concentration probability distribution, this methodological work proposes to use on-site LFG trace contaminant measurements, in order to give a better prescription for the non defined area located between common prescriptions for natural attenuation and active collection and treatment.

Figure 1 .

 1 Figure 1. Scheme of the air box model for a recreational use of the landfill top cap.

Figure 2 .

 2 Figure 2. Comparison convective/diffusive fluxes for a silty layer

Figure 3 .

 3 Figure 3. Definition of 3 areas for closed landfills

Table 1 :

 1 LFG trace contaminant concentrations used for the health risk assessment

	Compounds	Concentration mg/m 3
	Benzene	15
	1,2 dichloroethane	15
	Vinyl chloride	20
	Formaldehyde	1,6
	Acetaldehyde	18
	Hydrogen sulfide	100


O Bour

K Favereaux

M Sylvain

CASE STUDY OF SULPHUR COMPOUNDS EMISSIONS CHARACTERIZATION

In order to manage the methane and sulphur compounds emissions of a landfill area with deposits of plasterworks, a flux measurements study was conducted with a mobile laboratory, portable analysers and different chambers. The static chamber was first used in order to locate the methane hot spots. The funnel and the Total Reduced Sulphur (TRS) analyser allow the comparison between emissions of methane and hydrogen sulphide which represent the predominant sulphur compound. In a second stage, the variability of the hydrogen sulphide emissions was monitored with two dynamic chambers and a period of several days. Hydrogen sulphide emissions by cap are much lower than those predicted by the methane flux and the concentration of hydrogen sulphide in landfill gas (LFG).

INTRODUCTION

Accurate field emissions measurements of sulphur compounds such as hydrogen sulphide is a decisive step in assessing their environmental impact. The use of funnels and flux chambers is a simple method for locating and measuring emission rate under field conditions [START_REF] Savanne | Comparison of different methods for measuring landfill methane emissions[END_REF].

The goal was to study the temporal and spatial emission variability in order to give information for the characterization methodology of sulphur compounds surface emission fluxes. The spatial distribution of the surface emissions was studied with a static flux chamber and a funnel, in order to do a preliminary quick survey of methane and sulphur compounds fluxes and air concentrations. The static flux chamber offers a relatively quick quantitative methane flux measurement in approximately five minutes with a Flame Ionisation Detector (FID). The funnel (an open chamber, 0.7 m diameter), which needs approximately half an hour of time diffusion stabilization in the chamber, was used in the second stage of the preliminary survey. This equipment provides a semi-quantitative measurement of the methane and sulphur compounds concentrations with the mobile laboratory TRS and FID analysers. In the second stage of the survey the daily variations of methane and sulphur compounds was monitored with two dynamic chambers and a constant flow rate, which was controlled by two flowmeters.

LOCATION AND EMISSION RATE CHARACTERIZATION

Determination of the location of the sulphur compounds emissions

A first survey of LFG hydrogen sulphide concentration in the wells of the collection system was used to delimit a specific area, approximately 2 ha (Figure 1). The LFG hydrogen sulphide concentration of that area ranged between 7 to 380 ppmv. During the exploitation of the landfill, deposits of plasterworks were noticed by the operators in this specific area.

A preliminary survey of the methane concentration above the cap was done with an FID analyser in order to identify the methane "hot spots".

The sorting of the sulphur compounds emissions

The studied area was divided into 20 points. The funnel used with TRS and FID analysers and the static chamber used with another FID analyser have measured 11 significant positive methane and H 2 S surface emissions rate. Due to the wind funnel sensibility and some LFG leakage from wells it was necessary to eliminate the influenced measurements for the interpretation. This method permitted to delete measurement points, due essentially to wind velocities peaks which have reached 6 m/s during the survey. The funnel measurement provided sufficient information in order to make a first sorting of the sulphur compounds emissions.

The comparison of methane surface emission rate measurements permitted to notice a good correlation for the two methods (funnel and static chamber), as previously reported [START_REF] Fécil | Development of a Method for the Measurement of Net Methane Emissions from MSW Landfills[END_REF]. Nevertheless, we observed no correlation between methane flux and sulphur compounds concentration in the studied area (Figure 2). The high heterogeneity of the H 2 S source term was probably linked with the heterogeneity of the plasterworks deposits in a small spatial scale.

A gas chromatograph with a flame photometric sensor was used to verify during the survey that the predominant sulphur compound was hydrogen sulphide.

HYDROGEN SULPHIDE EMISSION RATE AND TEMPORAL EMISSION VARIATION CHARACTERIZATION

Hydrogen sulphide emission rate characterization

A new selection of 10 measurement locations was made in order to focus on the central area which represents all the statistical distribution of the methane concentration measurements on the surface of the landfill.

The goal was to monitor the methane and sulphur compounds surface emission rate. Two dynamic chambers were used with a synthetic gas entry and exit line of approximately 0.4 m 3 /h.

The H 2 S fluxes were relatively low on the cap : the TRS concentration peaks in the dynamic chambers varied from 1 to 135 ppbv. In order to simplify the interpretation of the large data set of two weeks continuous concentration measures with 3 analysers on different locations, different periods were identified at each location. The sum of the periods for all the 10 points range from 2-3 hours to 5 days. The interpretation permits to notice periods with low and high variations on the sulphur fluxes emissions. The H 2 S surface flux values, which were calculated from the average TRS concentrations over a few hours periods without high winds, varied between 0,03 to 1 µl H 2 S /min/m 2 . The median H 2 S surface flux on the 43 defined measurement periods on the 10 selected points is approximately 0,15 µl H 2 S /min/m 2 . In fact, the highest hydrogen sulphide surface flux measured has reached punctually 4 µl H 2 S /min/m 2 (Figure 3).

Considering LFG with 50% methane content and a typical intermediary cover methane surface flux of 100 ml/min/m 2 , the predicted hydrogen sulphide surface flow should reach at least 1,4 µl H 2 S /min/m 2 with the assumption of no H 2 S oxidation and the minimal LFG H 2 S concentration of 7 ppmv. The contribution of the temporary clay cap for the measured odour production rate has a real significance, depending of the thickness and permeability of the cover and of uncontrolled LFG emissions [START_REF] Karnik | Landfill odour control a practitioner's experience[END_REF]. That low flow indicates that a high oxidation rate occurs in the rather thin silty clay cover (50 cm) of the intermediary cover. During the survey period (June-July 2004), the relatively high air temperature promoted the oxidation.

Figure 3. Methane concentration on the cap from the preliminary survey and low but significant hydrogen sulphide surface emission fluxes

Hydrogen sulphide temporal emission characterization

The general trend of the TRS and FID concentration versus time plots are similar for the period without high winds. We also notice the minor occurrence of periods with sulphur peaks which could not be directly explained by the simple wind directions and velocities. The only variation of the TRS concentration on some minor parts of the curves seems to indicate that we had encountered some adsorption, which was often observed with sulphur compounds [START_REF] Cossu | Methane Oxidation and Attenuation of Sulphurated Compounds in Landfill Top Cover Systems : Lab Scale Tests[END_REF]. We needed in fact to use a relatively long (up to 200 meters) air line to drive the pumped air from the supply gas to the dynamic chamber and from the dynamic chamber to the mobile laboratory. These relatively quick H 2 S concentration variations were also encountered for the dynamic chambers.

The proximity of the access road could also be a minor factor of the emissions variability. For the measured points with high methane and medium to high H 2 S dynamic chamber concentrations, the variations with stable atmospheric pressure conditions were generally explained by the high winds periods (Figure 5). With no high wind periods, the variability of H 2 S and methane emission was rather low (10% of the measured value, Figure 4). Due to the low emissions and consequently the low air velocity used in order to avoid another dilution in the dynamic chamber, the influence of the winds generally hides the H 2 S source term variability.

We also have used a Jerome Hydrogen sulphide analyzer (Model 631-X Arizona Instrument, Phoenix) with a static chamber for complementary measurements. This method allows to measure H 2 S surface fluxes from 0,3 µl /min/m 2 to 4 µl H 2 S/min/m 2 . The quick saturation of the sensor for high hydrogen sulphide concentration (higher than 300 ppb) limits the use in the confined volume of a static chamber. For low H 2 S fluxes, the use of this analyser was also limited by the landfill ground level hydrogen sulphide air concentration, which could limit the response precision in the sensor middle range (100 ppb -1 ppm). Due to the different surface areas covered with the two type of chambers used, we could not make a real correlation between the results of the two types of chambers.

A comparison between the portable analyser and the TRS was made for different LFG samples and with a calibration gas. The Jerome analyser exhibits a rather good selectivity with the measured value of 270 ppb of hydrogen sulphur for a 200 ppb hydrogen sulphur, 400 ppb dimethyl sulphide and 340 ppb methyl mercaptan calibration gas. The differences between the TRS and Jerome analyser measurements for more than 30 samples of diluted LFG were lower than 20% for all the samples. There are generally less than 10% of variability between TRS and Jerome 631-X results.

CONCLUSIONS

The methane and sulphur emissions of the landfill were studied in a two stages survey. Firstly, the survey of hydrogen sulphide concentration in the collection system and methane concentrations above the intermediary cap was used in a preliminary stage to define the studied area for the second characterization stage.

TRS measurements on the cap with funnel, flux box and dynamic chambers allow to provide an evaluation of the range of the hydrogen sulphide emissions for the studied site, namely 0.03 to 4 µl H 2 S/min/m 2 . The monitored temporal variations were linked to the influence of high wind.

Figure 1 .Figure 2 .

 12 Figure 1. Scheme of LFG hydrogen sulphide concentration locations in the landfill area

Figure 4 .Figure 5 .

 45 Figure 4. Methane and H 2 S emissions variability with high methane emission and no high wind periods.

The studied area exhibits relatively low emissions of hydrogen sulphide by the cap. The relative low surface H 2 S rate source limits efficiency of the monitoring for the study of the temporal variation of the source term. The high daily air temperature which promotes oxidation in the cover and the relative weakness of the H 2 S source could explain the low emissions. The heterogeneity of the deposits of plasterworks on the waste also provide a large variation of H 2 S in a small spatial scale. The predominant sulphur compounds was the hydrogen sulphide, also the portable Jerome 631-X analyser used for complementary measures provides results which could be compared with the measurements given by the mobile laboratory TRS analyser.


Elmountacer Billah
email: elmountacer.elabbassi@lneris.fr

René De Sèze
email: rene.de-seze@ineris.fr

THERMAL SKIN DAMAGE AND MOBILE PHONE USE

Keywords: Mobile phone (MP), Electromagnetic field (EMF), Skin température, Thermal damage

Mobile phone "cell phone" use has dramatically increased over thé last décade, but doubts remain over its safety. Epidemiological investigation of mobile phone (MP) users reported symptoms of discomfort feeling, warmth behind/around or on thé ear and heat sensation of thé cheek. Thèse symptoms may be due to thermal insulation, conduction of thé heat produced in thé phone by thé battery currents and running of thé radiofrequency (RF) electronic circuits, and electromagnetic fïeld (EMF) energy absorbed by thé user's head. Using a Luxtron 790 fiberoptic thermometer we measured thé température of thé temporal skin due to GSM 1800 MHz MP radiated power (125 mW). To perforai a sham exposure, we suppressed thé EMF exposure by switching thé RF signal from thé antenna to a 50 O load. The ambient air température was 23°C, thé relative humidity was 50 ± 10 %, thé air flow rate in thé room was 0.01 m-s' 1 (natural convection) and thé MP was held in thé normal position of use "cheek position" (CENELEC Standard 50361) for 30 minutes to reach thé thermal steady state. With a switched off MP, thé increase in skin température was statistically significant 1.88°C. When MP was switched on, thé increase was 2.93°C in réception mode, 3.29°C in émission mode without load and 3.31 °C in émission mode with load. The température différence with or without load was not significant (t n = 0.707; p = 0.489), which means that thé contribution of EMF absorption to skin heating is negligible. The highest température increases detected during thèse experiments (T S km = 37.1°C ~ core température) are in thé environmental range and are lower than those physiologically experienced by thé surface skin during hot summer days. No skin damage by thermal insuit is experienced for T skin < 44°C, whereby a pain sensation replaces thé feeling of température élévation in humans. This local skin température increase will cause thermorégulation responses. The skin blood vessels will be dilated and skin will be wet. The resuit suggests that thé heat sensations reported by thé MP users are exclusively caused by thermal insulation and heat conduction from MP associated with long calling time. No thermal skin damage can be suspected using MP in normal use.

INTRODUCTION

The ever-rising diffusion of 'cellular' mobile phone (MP) Systems has determined an increased concern for possible users' health effects due to thé field emitted by thé handheld terminais. In fact, when a mobile phone is working, thé transmitting antenna is placed very close to thé user's head where a substantial part of thé radiated power is absorbed. Many epidemiological investigations of MP users [START_REF] Oftedal | Symptoms experienced in connection with mobile phone use[END_REF][START_REF] Sandstrôm | Mobile phone use and subjective symptoms. Comparison of symptoms experienced by users of analogue and digital mobile phones[END_REF] reported symptoms of discomfort feeling, warmth behind/around or on thé ear and heat sensation of thé cheek. Thèse symptoms may be due to changes in thé thermal exchange between thé skin and thé air due to thé contact between thé phone and thé skin (thermal insulation), conduction of thé heat produced in thé phone by thé battery currents and running of thé radiofrequency (RF) electronic circuits transmitted to thé tissue, and of a part electromagnetic field (EMF) energy absorbed by thé user's head. The head exposure to EMF présents particular problems due to thé close proximity between thé source of émission (MP antenna) and thé head of thé user. A major part between 40-50 % of MP EMF energy is absorbed by user's head [START_REF] Beraardi | Spécifie absorption rate and température increases in thé head of a cellular-phone user[END_REF] and thé absorption is highest in thé skin ~ 38.5 % [START_REF] Dimbylow | Characterisation of energy déposition in thé head from cellular phones[END_REF]. The aim of this study is to quantify thé temporal skin warming of thé MP user in thé normal position with an investigation of thé différent parameters contribution and to compare thé obtained température increases with thé thresholds for thé induction of thermal damages.

MATERIALS AND METHODS

The mobile phone used in this study was a GSM 1800 MHz Motorola mr 20 with a test card to control thé use mode of thé MP. It was used at maximal power during émission and their batteries allowed continuous émission without loss of power for thé whole duration of thé experiment The émission parameters were as following: frequency: 1800 MHz; frequency of répétition of impulses: 217 Hz; duty cycle: 1/8; peak power/average power: 1 W /125 mW. We suppressed thé EMF exposure by switching thé RF signal from thé antenna to a 50 Q load. The efficacy of thé EMF suppress was measured by thé SAM phantom thé Spécifie Absorption Rate (SAR) is negligible when using thé load [START_REF] Elabbassi | Mobile Phone Use and Temporal Skin Heat sensation[END_REF]. During experiments thé MP was: switched off; switched on in réception mode, in émission mode without load and in émission mode with load. Température was measured using a fiberoptic thermometer (Luxtron 790) with 4 SFF-5 surface température sensors which can be used in normal listening conditions. The température was measured every minute during thé experiment until thermal steady state was reached and thé data automatically recorded on a computer. The accuracy of measures was±0.1°C. The sensors were calibrated at thé beginning of each experiment in a water bath at ambient température (controlled by a mercury thermometer). For each volunteer, three sensors were used, one placed on thé temple of thé subject (skin sensor), another on thé mobile phone surface in contact with thé temple (phone sensor) and thé last measures air température (air sensor). The 'skin sensor' was placed perpendicular to thé line starting from thé tragus in alignment with thé lip edge, at thé level of thé temporo-mandibular joint, and held in position with porous adhesive tape. The 'phone sensor' was placed on thé flat surface between thé screen and thé keypad on thé middle line using adhesive tape. When thé phone was in thé normal using position, thé two sensors were both parallel and contiguous. The use of thèse two sensors allowed thé measurement of thé kinetics of thé raise in température at thé skin-telephone interface until thermal equilibrium was reached. After calibration, thé sensors were placed on thé skin and MP in their référence positions. The températures of skin and MP surface switched off at room température were measured before beginning measurement at normal using position of MP. Then mobile phone switched off was held in thé normal using position and thé variations in température recorded until température equilibrium was reached (approximately 30 minutes). The same experiment was done with switched on MP: in réception mode in émission mode without load and in émission mode with load suppressing EMF exposure. The MP was held in thé normal using position "cheek position" (CENELEC Standard 50361) to hâve thé maximal contact between thé MP surface and thé skin of thé MP user. This position may modify heat exchange between thé skin and thé ambient air and make thé MP and thé antenna close to thé head of thé MP user. Three healthy maie volunteers 25, 26 and 30 years old hâve participated for this study. For each trial 18 measurements were made to assess thé repeatability of thé measures. The mean values are given with one standard déviation (± 1 SD). The différence between expérimental conditions was computed by Student's Mests. The évalues are given with their corresponding of degrees of freedom (subscripts beneath évalues). The accepted level of significance was p < 0.05. In ail experiments, thé mean value of ambient air température (T air ) was 23.0 ± 0.8°C, thé relative humidity was 50 ± 10 %, thé air flow rate in thé room was 0.01 ras' 1 (natural convection) and thé MP was held in thé normal position of use for at least 30 minutes to reach thé thermal steady state.

RESULTS

Température measurements

Température is recorded until equilibrium was reached around 30 min after thé beginning of thé experiment. The mean value of température measurement concerns thé steady state period. The initial mean skin température (T S kjn) of volunteers at normal room température (23.0 ± 0.8°C) was 33.8 ± 0.6°C (référence). The study of thé raise in skin température due to thé physical contact with thé phone showed that thé equilibrium température at thé 'skin-phone' interface was 35.7 ± 0.2°C. This was due to thé decrease of thé skin heat loss with thé environment (Table 1). The mobile phone contact causes heat insulation of thé skin surface. The température increase is equal to + 1.88°C. The mobile phone température -as thé skin température-increases when thé MP is in contact with thé skin surface. The skin and thé phone sensor were face to face and give thé same value at thermal equilibrium at skin-phone interface. When MP was switched on, thé increase in skin température from thé initial value was 2.93°C in réception mode, 3.29°C in émission mode without load and 3.31 °C in émission mode with load.

The skin température différence between thé mobile phone switched on in émission mode with or without load expérimental condition was not significant (tn = 0.707; p = 0.489). There is no significant supplemental skin heating due to RF émission from thé MP antenna, which means that thé contribution of EMF absorption to skin heating is negligible.

Température increase at skin-phone interface and thermal equilibrium

An example of thé kinetics of thé raise in température at thé skin-telephone interface is presented in Figure 1. To reach thé skin-phone interface thermal equilibrium we must wait at least 30 min. The calling time is an important parameter for heat sensation and discomfort feeling. More important is thé time calling with MP skin contact, more is thé prevalence of warmth sensation.

Pain threshold

Studying thé bioelectromagnetic interaction from a thermal point-of-view, it is interesting to compare thé obtained température increases with thé thresholds for thé induction of thermal damages. For partial body exposure, thé limiting hazard may be local température rise, rather than excessive thermal load to thé body. Thermal injury is characterised by a rate process, such that thé threshold for injury dépends on thé duration of contact and how 'perfect' thé contact is which will be related to pressure, différences in epidermal thickness and magnitude of température rise depending on thé reactions to materials correlated well with thé thermal inertia's (thermal dose). The constitution of human cells is such that at température above around 44°C, damage can begin to occur if exposure to that température is suffîciently long. It is generally trae therefore, that if skin température in contact with solid surface is below about 43 °C, discomfort and pain sensations will be avoided and no skin damage will occur. An interesting point is that thé lowest surface température that was responsible for cutaneous burning was 44°C for an exposure of 6 h. It can be expected that if (relatively cool) blood flows at thé site of hyperthermia (thermorégulation), this would protect thé skin against burning [START_REF] Hardy | Pain sensations and Reactions[END_REF]. The threshold température increase for neurone damage is about 4.5°C (for more than 30 min) [START_REF] Guyton | Textbook of Medial Physiology[END_REF]. Experiments performed on thé eye hâve evidenced a threshold increase of 3°C-5°C in thé lens for thé induction of thé cataract [START_REF] Guy | Effect of 2450 MHZ radiation on thé rabbit eye[END_REF].

The highest température increases detected during thé présent study (T.^ = 37.1°C) is in thé environmental range and are experienced by thé surface skin during hot summer days. No skin damage by thermal insuit is experienced for Tskin < 44°C, whereby a pain sensation replaces thé feeling of température élévation in humans. No thermal skin damage can be suspected using MP in normal use.

CONCLUSION

The results show that thé heat sensations reported by thé MP users are exclusively caused by thermal insulation and heat conduction from MP associated with long calling rime. The power of EMF emitted by thé MP antenna is not sufficient to cause increase in cheek skin température when using MP. Thèse results suggest an awareness of thé symptoms, but no thermal damaging on skin is suspected.

Figure 1 :

 1 Figure 1: Skin (T skin , °C) and mobile phone température (T mp , °C) plotted against time (min), with MP switched on in réception mode (2), in émission mode without load (3) and with load (4) during one experiment. Thermal equilibrium was reached around 30 min.

Table 1 :

 1 Equilibrium mean values (± 1 SD) *n= 18' of air température (T air , °C), skin température (T skin5 °C) and mobile phone surface température (T^, °C), in thé différent expérimental conditions (référence, skin-phone interface: MP switched off, switched on in réception mode, in émission mode without load, in émission mode with load).

				Expérimental conditions
				Skin-phone interface
		Référence	Switched off	Réception	Emission	Emission + load
	T air (°C)	22.6 ± 0.7	22.9 ±0.8	23.1 ±0.7	23.2 ±0.8	23.4 ±0.7
	T skin (°C)	33.8 ±0.6	35.7 ±0.2	36.7 ±0.2	37.1 ±0.2	37.1 ±0.2
	T mp (°C)	22.8 ± 0.8	35.3 ±0.4	36.7 ±0.2	37.2 ± 0.20	37.4 ±0.2

ACKNOWLEDGEMENTS

This work was financially supported by thé régional Council of Picardy (France) and thé French Ministry of Ecology and Sustainable development (BCRD 2003, DRC 02-03).