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Chlorofluorocarbon

Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propane.

The most common example is dichlorodifluoromethane (R-12). R-12 is also commonly called Freon and was used as a refrigerant. Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), gaseous fire suppression systems, and solvents. As a result of CFCs contributing to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs) including R-410A,R-134a and R-1234yf.

Structure, properties and production
As in simpler alkanes, carbon in the CFCs bond with tetrahedral symmetry. Because the fluorine and chlorine atoms differ greatly in size and effective charge from hydrogen and from each other, the methane-derived CFCs deviate from perfect tetrahedral symmetry.

The physical properties of CFCs and HCFCs are tunable by changes in the number and identity of the halogen atoms. In general, they are volatile but less so than their parent alkanes. The decreased volatility is attributed to the molecular polarity induced by the halides, which induces intermolecular interactions. Thus, methane boils at −161 °C whereas the fluoromethanes boil between −51.7 (CF2H2) and −128 °C (CF4). The CFCs have still higher boiling points because the chloride is even more polarizable than fluoride. Because of their polarity, the CFCs are useful solvents, and their boiling points make them suitable as refrigerants. The CFCs are far less flammable than methane, in part because they contain fewer C-H bonds and in part because, in the case of the chlorides and bromides, the released halides quench the free radicals that sustain flames.

The densities of CFCs are higher than their corresponding alkanes. In general, the density of these compounds correlates with the number of chlorides.

CFCs and HCFCs are usually produced by halogen exchange starting from chlorinated methanes and ethanes. Illustrative is the synthesis of chlorodifluoromethane from chloroform:
 * HCCl3 + 2 HF → HCF2Cl + 2 HCl

Brominated derivatives are generated by free-radical reactions of hydrochlorofluorocarbons, replacing C-H bonds with C-Br bonds. The production of the anesthetic 2-bromo-2-chloro-1,1,1-trifluoroethane ("halothane") is illustrative:
 * CF3CH2Cl + Br2 → CF3CHBrCl + HBr

Applications
CFCs and HCFCs are used in various applications because of their low toxicity, reactivity and flammability. Every permutation of fluorine, chlorine and hydrogen based on methane and ethane has been examined and most have been commercialized. Furthermore, many examples are known for higher numbers of carbon as well as related compounds containing bromine. Uses include refrigerants, blowing agents, aerosol propellants in medicinal applications, and degreasing solvents.

Billions of kilograms of chlorodifluoromethane are produced annually as a precursor to tetrafluoroethylene, the monomer that is converted into Teflon.

Classes of compounds and Numbering System

 * Chlorofluorocarbons (CFCs): when derived from methane and ethane these compounds have the formulae CClmF4−m and C2ClmF6−m, where m is nonzero.
 * Hydro-chlorofluorocarbons (HCFCs): when derived from methane and ethane these compounds have the formula CClmFnH4−m−n and C2ClxFyH6−x−y, where m, n, x, and y are nonzero.
 * and bromofluorocarbons have formulae similar to the CFCs and HCFCs but also include bromine.
 * Hydrofluorocarbons (HFCs): when derived from methane, ethane, propane, and butane, these compounds have the respective formulae CFmH4−m, C2FmH6−m, C3FmH8−m, and C4FmH10−m, where m is nonzero.

Numbering system
A special numbering system is to be used for fluorinated alkanes, prefixed with Freon-, R-, CFC- and HCFC-, where the rightmost value indicates the number of fluorine atoms, the next value to the left is the number of hydrogen atoms plus 1, and the next value to the left is the number of carbon atoms less one (zeroes are not stated), and the remaining atoms are chlorine.

Freon-12, for example, indicates a methane derivative (only two numbers) containing two fluorine atoms (the second 2) and no hydrogen (1-1=0). It is therefore CCl2F2.

Another equation that can be applied to get the correct molecular formula of the CFC/R/Freon class compounds is to take the numbering and add 90 to it. The resulting value will give the number of carbons as the first numeral, the second numeral gives the number of hydrogen atoms, and the third numeral gives the number of fluorine atoms. The rest of the unaccounted carbon bonds are occupied by chlorine atoms. The value of this equation is always a three figure number. An easy example is that of CFC-12, which gives: 90+12=102 -> 1 carbon, 0 hydrogens, 2 fluorine atoms, and hence 2 chlorine atoms resulting in CCl2F2. The main advantage of this method of deducing the molecular composition in comparison with the method described in the paragraph above is that it gives the number of carbon atoms of the molecule.

Freons containing bromine are signified by four numbers. Isomers, which are common for ethane and propane derivatives, are indicated by letters following the numbers:

Reactions
The reaction of the CFCs which is responsible for the depletion of ozone, is the photo-induced scission of a C-Cl bond:
 * CCl3F → CCl2F. + Cl.

The chlorine atom, written often as Cl., behaves very differently from the chlorine molecule (Cl2). The radical Cl. is long-lived in the upper atmosphere, where it catalyzes the conversion of ozone into O2. Ozone absorbs UV-B radiation, so its depletion allows more of this high energy radiation to reach the Earth's surface. Bromine atoms are even more efficient catalysts; hence brominated CFCs are also regulated.

Impact as greenhouse gases
CFCs were phased out via the Montreal Protocol due to their part in ozone depletion.

The atmospheric impacts of CFCs are not limited to their role as ozone-depleting chemicals. Infrared absorption bands prevent heat at that wavelength from escaping Earth's atmosphere. CFCs have their strongest absorption bands from C-F and C-Cl bonds in the spectral region of 7.8–15.3 μm —referred to as the "atmospheric window" due to the relative transparency of the atmosphere within this region.

The strength of CFC absorption bands and the unique susceptibility of the atmosphere at wavelengths where CFCs (indeed all covalent fluorine compounds) absorb radiation creates a "super" greenhouse effect from CFCs and other unreactive fluorine-containing gases such as perfluorocarbons, HFCs, HCFCs, bromofluorocarbons, SF6, and NF3. This "atmospheric window" absorption is intensified by the low concentration of each individual CFC. Because CO2 is close to saturation with high concentrations and few infrared absorption bands, the radiation budget and hence the greenhouse effect has low sensitivity to changes in CO2 concentration; the increase in temperature is roughly logarithmic. Conversely, the low concentration of CFCs allow their effects to increase linearly with mass, so that chlorofluorocarbons are greenhouse gases with a much higher potential to enhance the greenhouse effect than CO2.

Groups are actively disposing of legacy CFCs to reduce their impact on the atmosphere.

According to NASA in 2018, the hole in the ozone layer has begun to recover as a result of CFC bans. However, research released in 2019 reports an alarming increase in CFCs, pointing to unregulated use in China.

History
Prior to, and during the 1920s, refrigerators used toxic gases as refrigerants, including ammonia, sulphur dioxide, and chloromethane. Later in the 1920s after a series of fatal accidents involving the leaking of chloromethane from refrigerators, a major collaborative effort began between American corporations Frigidaire, General Motors, and DuPont to develop a safer, non-toxic alternative. Thomas Midgley Jr. of General Motors is credited for synthesizing the first chlorofluorocarbons. The Frigidaire corporation was issued the first patent, number 1,886,339, for the formula for CFCs on December 31, 1928. In a demonstration for the American Chemical Society, Midgley flamboyantly demonstrated all these properties by inhaling a breath of the gas and using it to blow out a candle in 1930.

By 1930, General Motors and Du Pont formed the Kinetic Chemical Company to produce Freon, and by 1935, over 8 million refrigerators utilizing R-12 were sold by Frigidaire and its competitors. In 1932, Carrier began using R-11 in the worlds first self-contained home air conditioning unit known as the "atmospheric cabinet". As a result of CFCs being largely non-toxic, they quickly became the coolant of choice in large air-conditioning systems. Public health codes in cities were revised to designate chlorofluorocarbons as the only gases that could be used as refrigerants in public buildings.

Growth in CFCs continued over the following decades leading to peak annual sales of over 1 billion USD with greater than 1 million metric tonnes being produced annually. It wasn't until 1974 that it was first discovered by two University of California chemists, Professor F. Sherwood Rowland and Dr. Mario Molina, that the use of chlorofluorocarbons were causing a significant depletion in atmospheric ozone concentrations. This initiated the environmental effort which eventually resulted in the enactment of the Montreal Protocol.

Commercial development and use in fire extinguishing
During World War II, various chloroalkanes were in standard use in military aircraft, although these early halons suffered from excessive toxicity. Nevertheless, after the war they slowly became more common in civil aviation as well. In the 1960s, fluoroalkanes and bromofluoroalkanes became available and were quickly recognized as being highly effective fire-fighting materials. Much early research with Halon 1301 was conducted under the auspices of the US Armed Forces, while Halon 1211 was, initially, mainly developed in the UK. By the late 1960s they were standard in many applications where water and dry-powder extinguishers posed a threat of damage to the protected property, including computer rooms, telecommunications switches, laboratories, museums and art collections. Beginning with warships, in the 1970s, bromofluoroalkanes also progressively came to be associated with rapid knockdown of severe fires in confined spaces with minimal risk to personnel.

By the early 1980s, bromofluoroalkanes were in common use on aircraft, ships, and large vehicles as well as in computer facilities and galleries. However, concern was beginning to be expressed about the impact of chloroalkanes and bromoalkanes on the ozone layer. The Vienna Convention for the Protection of the Ozone Layer did not cover bromofluoroalkanes under the same restrictions, instead, the consumption of bromofluoroalkanes was frozen at 1986 levels. This is due to the fact that emergency discharge of extinguishing systems was thought to be too small in volume to produce a significant impact, and too important to human safety for restriction.

Regulation
Since the late 1970s, the use of CFCs has been heavily regulated because of their destructive effects on the ozone layer. After the development of his electron capture detector, James Lovelock was the first to detect the widespread presence of CFCs in the air, finding a mole fraction of 60 ppt of CFC-11 over Ireland. In a self-funded research expedition ending in 1973, Lovelock went on to measure CFC-11 in both the Arctic and Antarctic, finding the presence of the gas in each of 50 air samples collected, and concluding that CFCs are not hazardous to the environment. The experiment did however provide the first useful data on the presence of CFCs in the atmosphere. The damage caused by CFCs was discovered by Sherry Rowland and Mario Molina who, after hearing a lecture on the subject of Lovelock's work, embarked on research resulting in the first publication suggesting the connection in 1974. It turns out that one of CFCs' most attractive features—their low reactivity—is key to their most destructive effects. CFCs' lack of reactivity gives them a lifespan that can exceed 100 years, giving them time to diffuse into the upper stratosphere. Once in the stratosphere, the sun's ultraviolet radiation is strong enough to cause the homolytic cleavage of the C-Cl bond. In 1976, under the Toxic Substances Control Act, the EPA banned commercial manufacturing and use of CFCs and aerosol propellants. This was later superseded in the 1990 amendments to the Clean Air Act to address stratospheric ozone depletion.

By 1987, in response to a dramatic seasonal depletion of the ozone layer over Antarctica, diplomats in Montreal forged a treaty, the Montreal Protocol, which called for drastic reductions in the production of CFCs. On 2 March 1989, 12 European Community nations agreed to ban the production of all CFCs by the end of the century. In 1990, diplomats met in London and voted to significantly strengthen the Montreal Protocol by calling for a complete elimination of CFCs by 2000. By 2010, CFCs should have been completely eliminated from developing countries as well. Because the only CFCs available to countries adhering to the treaty is from recycling, their prices have increased considerably. A worldwide end to production should also terminate the smuggling of this material. However, there are current CFC smuggling issues, as recognized by the United Nations Environmental Programme (UNEP) in a 2006 report titled "Illegal Trade in Ozone Depleting Substances". UNEP estimates that between 16,000–38,000 tonnes of CFCs passed through the black market in the mid-1990s. The report estimated between 7,000 and 14,000 tonnes of CFCs are smuggled annually into developing countries. Asian countries are those with the most smuggling; as of 2007, China, India and South Korea were found to account for around 70% of global CFC production, South Korea later to ban CFC production in 2010. Possible reasons for continued CFC smuggling were also examined: the report noted that many of the refrigeration systems that were designed  to be operated utilizing the banned CFC products have long lifespans and continue to operate. The cost of replacing the equipment of these items is sometimes cheaper than outfitting them with a more ozone-friendly appliance. Additionally, CFC smuggling is not considered a significant issue, so the perceived penalties for smuggling are low. In 2018 public attention was drawn to the issue, that at an unknown place in east Asia an estimated amount of 13,000 metric tons annually of CFCs have been produced since about 2012 in violation of the protocol. While the eventual phaseout of CFCs is likely, efforts are being taken to stem these current non-compliance problems.

By the time of the Montreal Protocol, it was realised that deliberate and accidental discharges during system tests and maintenance accounted for substantially larger volumes than emergency discharges, and consequently halons were brought into the treaty, albeit with many exceptions.

Regulatory gap
While the production and consumption of CFCs are regulated under the Montreal Protocol, emissions from existing banks of CFCs are not regulated under the agreement. In 2002, there were an estimated 5,791 kilotons of CFCs in existing products such as refrigerators, air conditioners, aerosol cans and others. Approximately one-third of these CFCs are projected to be emitted over the next decade if action is not taken, posing a threat to both the ozone layer and the climate. A proportion of these CFCs can be safely captured and destroyed by means of high temperature, controlled incineration which destroys the CFC molecule.

Regulation and DuPont
In 1978 the United States banned the use of CFCs such as Freon in aerosol cans, the beginning of a long series of regulatory actions against their use. The critical DuPont manufacturing patent for Freon ("Process for Fluorinating Halohydrocarbons", U.S. Patent #3258500) was set to expire in 1979. In conjunction with other industrial peers DuPont formed a lobbying group, the "Alliance for Responsible CFC Policy", to combat regulations of ozone-depleting compounds. In 1986 DuPont, with new patents in hand, reversed its previous stance and publicly condemned CFCs. DuPont representatives appeared before the Montreal Protocol urging that CFCs be banned worldwide and stated that their new HCFCs would meet the worldwide demand for refrigerants.

Phasing-out of CFCs
Use of certain chloroalkanes as solvents for large scale application, such as dry cleaning, have been phased out, for example, by the IPPC directive on greenhouse gases in 1994 and by the volatile organic compounds (VOC) directive of the EU in 1997. Permitted chlorofluoroalkane uses are medicinal only.

Bromofluoroalkanes have been largely phased out and the possession of equipment for their use is prohibited in some countries like the Netherlands and Belgium, from 1 January 2004, based on the Montreal Protocol and guidelines of the European Union.

Production of new stocks ceased in most (probably all) countries in 1994. However many countries still require aircraft to be fitted with halon fire suppression systems because no safe and completely satisfactory alternative has been discovered for this application. There are also a few other, highly specialized uses. These programs recycle halon through "halon banks" coordinated by the Halon Recycling Corporation to ensure that discharge to the atmosphere occurs only in a genuine emergency and to conserve remaining stocks.

The interim replacements for CFCs are hydrochlorofluorocarbons (HCFCs), which deplete stratospheric ozone, but to a much lesser extent than CFCs. Ultimately, hydrofluorocarbons (HFCs) will replace HCFCs. Unlike CFCs and HCFCs, HFCs have an ozone depletion potential (ODP) of 0. DuPont began producing hydrofluorocarbons as alternatives to Freon in the 1980s. These included Suva refrigerants and Dymel propellants. Natural refrigerants are climate friendly solutions that are enjoying increasing support from large companies and governments interested in reducing global warming emissions from refrigeration and air conditioning.

Phasing-out of HFCs and HCFCs
Hydrofluorocarbons are included in the Kyoto Protocol and are regulated under the Kigali Amendment to the Montreal Protocol due to their very high Global Warming Potential (GWP) and the recognition of halocarbon contributions to climate change.

On September 21, 2007, approximately 200 countries agreed to accelerate the elimination of hydrochlorofluorocarbons entirely by 2020 in a United Nations-sponsored Montreal summit. Developing nations were given until 2030. Many nations, such as the United States and China, who had previously resisted such efforts, agreed with the accelerated phase out schedule. India successfully achieved the complete phase out of HCFC-141 b in 2020.

It was reported that levels of HCFCs in the atmosphere had started to fall in 2021 due to their phase out under the Montreal Protocol.

Properly collecting, controlling, and destroying CFCs and HCFCs
While new production of these refrigerants has been banned, large volumes still exist in older systems and have been said to pose an immediate threat to our environment. Preventing the release of these harmful refrigerants has been ranked as one of the single most effective actions we can take to mitigate catastrophic climate change.

Development of alternatives for CFCs
Work on alternatives for chlorofluorocarbons in refrigerants began in the late 1970s after the first warnings of damage to stratospheric ozone were published.

The hydrochlorofluorocarbons (HCFCs) are less stable in the lower atmosphere, enabling them to break down before reaching the ozone layer. Nevertheless, a significant fraction of the HCFCs do break down in the stratosphere and they have contributed to more chlorine buildup there than originally predicted. Later alternatives lacking the chlorine, the hydrofluorocarbons (HFCs) have an even shorter lifetimes in the lower atmosphere. One of these compounds, HFC-134a, were used in place of CFC-12 in automobile air conditioners. Hydrocarbon refrigerants (a propane/isobutane blend) were also used extensively in mobile air conditioning systems in Australia, the US and many other countries, as they had excellent thermodynamic properties and performed particularly well in high ambient temperatures. 1,1-Dichloro-1-fluoroethane (HCFC-141b) has replaced HFC-134a, due to its low ODP and GWP values. And according to the Montreal Protocol, HCFC-141b is supposed to be phased out completely and replaced with zero ODP substances such as cyclopentane, HFOs, and HFC-345a before January 2020.

Among the natural refrigerants (along with ammonia and carbon dioxide), hydrocarbons have negligible environmental impacts and are also used worldwide in domestic and commercial refrigeration applications, and are becoming available in new split system air conditioners. Various other solvents and methods have replaced the use of CFCs in laboratory analytics.

In Metered-dose inhalers (MDI), a non-ozone effecting substitute was developed as a propellant, known as "hydrofluoroalkane."

Development of Hydrofluoroolefins as alternatives to CFCs and HCFCs
The development of Hydrofluoroolefins (HFOs) as replacements for Hydrochlorofluorocarbons and Hydrofluorocarbons began after the Kigali amendment to the Montreal Protocol in 2016, which called for the phase out of high global warming potential (GWP) refrigerants and to replace them with other refrigerants with a lower GWP, closer to that of carbon dioxide. HFOs have an ozone depletion potential of 0.0, compared to the 1.0 of principal CFC-11, and a low GWP which make them environmentally safer alternatives to CFCs, HCFCs and HFCs.

Hydrofluoroolefins serve as functional replacements for applications where high GWP hydrofluorocarbons were once used. In April 2022, the EPA signed a pre-published final rule Listing of HFO-1234yf under the Significant New Alternatives Policy (SNAP) Program for Motor Vehicle Air Conditioning in Nonroad Vehicles and Servicing Fittings for Small Refrigerant Cans. This ruling allows HFO-1234yf to take over in applications where ozone depleting CFCs such as R-12, and high GWP HFCs such as R-134a were once used. The phaseout and replacement of CFCs and HFCs in the automotive industry will ultimately reduce the release of these gases to atmosphere and in turn have a positive contribution to the mitigation of climate change.

Tracer of ocean circulation
Since the time history of CFC concentrations in the atmosphere is relatively well known, they have provided an important constraint on ocean circulation. CFCs dissolve in seawater at the ocean surface and are subsequently transported into the ocean interior. Because CFCs are inert, their concentration in the ocean interior reflects simply the convolution of their atmospheric time evolution and ocean circulation and mixing.

CFC and SF6 tracer-derived age of ocean water
Chlorofluorocarbons (CFCs) are anthropogenic compounds that have been released into the atmosphere since the 1930s in various applications such as in air-conditioning, refrigeration, blowing agents in foams, insulations and packing materials, propellants in aerosol cans, and as solvents. The entry of CFCs into the ocean makes them extremely useful as transient tracers to estimate rates and pathways of ocean circulation and mixing processes. However, due to production restrictions of CFCs in the 1980s, atmospheric concentrations of CFC-11 and CFC-12 has stopped increasing, and the CFC-11 to CFC-12 ratio in the atmosphere have been steadily decreasing, making water dating of water masses more problematic. Incidentally, production and release of sulfur hexafluoride (SF6) have rapidly increased in the atmosphere since the 1970s. Similar to CFCs, SF6 is also an inert gas and is not affected by oceanic chemical or biological activities. Thus, using CFCs in concert with SF6 as a tracer resolves the water dating issues due to decreased CFC concentrations.

Using CFCs or SF6 as a tracer of ocean circulation allows for the derivation of rates for ocean processes due to the time-dependent source function. The elapsed time since a subsurface water mass was last in contact with the atmosphere is the tracer-derived age. Estimates of age can be derived based on the partial pressure of an individual compound and the ratio of the partial pressure of CFCs to each other (or SF6).

Partial pressure and ratio dating techniques
The age of a water parcel can be estimated by the CFC partial pressure (pCFC) age or SF6 partial pressure (pSF6) age. The pCFC age of a water sample is defined as:

 * $$pCFC = \frac{[CFC]}{F(T,S)}$$

where [CFC] is the measured CFC concentration (pmol kg−1) and F is the solubility of CFC gas in seawater as a function of temperature and salinity. The CFC partial pressure is expressed in units of 10–12 atmospheres or parts-per-trillion (ppt). The solubility measurements of CFC-11 and CFC-12 have been previously measured by Warner and Weiss Additionally, the solubility measurement of CFC-113 was measured by Bu and Warner and SF6 by Wanninkhof et al. and Bullister et al. Theses authors mentioned above have expressed the solubility (F) at a total pressure of 1 atm as:
 * $$\ln F = a_1 + a_2\left(\frac{100}{T}\right) + a_3\ln\left(\frac{T}{100}\right) + a_4\left(\frac{T}{100}\right)^2 + S\left[b_1 + b_2\left(\frac{T}{100}\right) + b_3\left(\frac{T}{100}\right)^2\right]$$

where F = solubility expressed in either mol l−1 or mol kg−1 atm−1, T = absolute temperature, S = salinity in parts per thousand (ppt), a1, a2, a3, b1, b2, and b3 are constants to be determined from the least squares fit to the solubility measurements. This equation is derived from the integrated Van 't Hoff equation and the logarithmic Setchenow salinity dependence.

It can be noted that the solubility of CFCs increase with decreasing temperature at approximately 1% per degree Celsius.

Once the partial pressure of the CFC (or SF6) is derived, it is then compared to the atmospheric time histories for CFC-11, CFC-12, or SF6 in which the pCFC directly corresponds to the year with the same. The difference between the corresponding date and the collection date of the seawater sample is the average age for the water parcel. The age of a parcel of water can also be calculated using the ratio of two CFC partial pressures or the ratio of the SF6 partial pressure to a CFC partial pressure.

Safety
According to their material safety data sheets, CFCs and HCFCs are colorless, volatile, non-toxic liquids and gases with a faintly sweet ethereal odor. Overexposure at concentrations of 11% or more may cause dizziness, loss of concentration, central nervous system depression or cardiac arrhythmia. Vapors displace air and can cause asphyxiation in confined spaces. Dermal absorption of chlorofluorocarbons is possible, but low. Where the pulmonary uptake of inhaled chlorofluorocarbons occurs quickly with peak blood concentrations occurring in as little as 15 seconds with steady concentrations evening out after 20 minutes. Absorption of orally ingested chlorofluorocarbons is 35 to 48 times lower compared to inhalation. Although non-flammable, their combustion products include hydrofluoric acid and related species. Normal occupational exposure is rated at 0.07% and does not pose any serious health risks.

title: Chlorofluorocarbon


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Dew

Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening due to condensation.

As the exposed surface cools by radiating its heat, atmospheric moisture condenses at a rate greater than that at which it can evaporate, resulting in the formation of water droplets.

When temperatures are low enough, dew takes the form of ice, called frost.

Because dew is related to the temperature of surfaces, in late summer it forms most easily on surfaces that are not warmed by conducted heat from deep ground, such as grass, leaves, railings, car roofs, and bridges.

Formation
Water vapor will condense into droplets depending on the temperature. The temperature at which droplets form is called the dew point. When surface temperature drops, eventually reaching the dew point, atmospheric water vapor condenses to form small droplets on the surface. This process distinguishes dew from those hydrometeors (meteorological occurrences of water), which form directly in air that has cooled to its dew point (typically around condensation nuclei), such as fog or clouds. The thermodynamic principles of formation, however, are the same. Dew is commonly formed during select times of the day. Nights, early mornings, and early evenings are all times during which dew is likely to be found.

Occurrence
Adequate cooling of the surface typically takes place when it loses more energy by infrared radiation than it receives as solar radiation from the Sun, which is especially the case on clear nights. Poor thermal conductivity restricts the replacement of such losses from deeper ground layers, which are typically warmer at night. Preferred objects of dew formation are thus poor conducting or well isolated from the ground, and non-metallic, while shiny metal coated surfaces are poor infrared radiators. Preferred weather conditions include the absence of clouds and little water vapor in the higher atmosphere to minimize greenhouse effects and sufficient humidity of the air near the ground. Typical dew nights are classically considered calm, because the wind transports (nocturnally) warmer air from higher levels to the cold surface. However, if the atmosphere is the major source of moisture (this type is called dewfall), a certain amount of ventilation is needed to replace the vapor that is already condensed. The highest optimum wind speeds could be found on arid islands. Wind always seems adverse, however, if the wet soil beneath is the major source of vapor (in which case dew is said to form by distillation).

The processes of dew formation do not restrict its occurrence to the night and the outdoors. They are also working when eyeglasses get steamy in a warm, wet room or in industrial processes. However, the term condensation is preferred in these cases.

Measurement
A classical device for dew measurement is the drosometer. A small (artificial) condenser surface is suspended from an arm attached to a pointer or a pen that records the weight changes of the condenser on a drum. Besides being very wind sensitive, however, this, like all artificial surface devices, only provides a measure of the meteorological potential for dew formation. The actual amount of dew in a specific place is strongly dependent on surface properties. For its measurement, plants, leaves, or whole soil columns are placed on a balance with their surface at the same height and in the same surroundings as would occur naturally, thus providing a small lysimeter. Further methods include estimation by means of comparing the droplets to standardized photographs or volumetric measurement of the amount of water wiped from the surface. Some of these methods include guttation, while others only measure dewfall and/or distillation.

Significance
Due to its dependence on radiation balance, dew amounts can reach a theoretical maximum of about 0.8 mm per night; measured values, however, rarely exceed 0.5 mm. In most climates of the world, the annual average is too small to compete with rain. In regions with considerable dry seasons, adapted plants like lichen or pine seedlings benefit from dew. Large-scale, natural irrigation without rainfall, such as in the Atacama and Namib deserts, however, is mostly attributed to fog water. In the Negev Desert in Israel, dew has been found to account for almost half of the water found in three dominant desert species: Salsola inermis, Artemisia sieberi and Haloxylon scoparium.

Another effect of dew is its hydration of fungal substrates and the mycelia of species such as pleated inkcaps, often found on lawns, and Phytophthora infestans which causes blight on potato plants.

Historic
The book On the Universe (De Mundo) (composed before 250 BC or between 350 and 200 BC) stated: "Dew is moisture minute in composition falling from a clear sky; ice is water congealed in a condensed form from a clear sky; hoar-frost is congealed dew, and 'dew-frost' is dew which is half congealed".

In Greek mythology, Ersa is the goddess and personification of dew. Also, according to the myth, the dew in the morning was created when Eos (Ersa's aunt), goddess of the dawn, cried for her son's death, although later he received immortality.

Dew, known in Hebrew as טל (tal), is significant in the Jewish religion for agricultural and theological purposes. On the first day of Passover, the Chazan, dressed in a white kittel, leads a service in which he prays for dew between that point and Sukkot. During the rainy season between December and Passover there are also additions in the Amidah for blessed dew to come together with rain. There are many midrashim that refer to dew as being the tool for ultimate resurrection. "Dewy" or "my father is the morning dew" are approximate etymologies of the Hebrew given name, Avital.

In the Biblical Torah or Old Testament, dew is used symbolically in : "My doctrine shall drop as the rain, my speech shall distill as the dew, as the small rain upon the tender herb, and as the showers upon the grass."

In the Catholic Mass in the Western Rite, whenever the Second Eucharistic Prayer is used, the priest prays over bread and wine, to God the Father; ‘Make holy, therefore, these gifts, we pray, by sending down your Spirit upon them like the dewfall, so that they may become for us the Body and  Blood of our Lord Jesus Christ.’ The idea that the Holy Spirit enters the world and our lives in a quiet, undramatic way, ‘like the dewfall’,  has great appeal for many Christians.

Artificial harvesting
The harvesting of dew potentially allows water availability in areas where supporting weather conditions, such as rain, are lacking. Several man-made devices such as antique big stone piles in Ukraine, medieval dew ponds in Southern England, and volcanic stone covers on the fields of Lanzarote have been thought to be dew-catching devices, but could be shown to work on other principles. At present, the International Organization for Dew Utilization (OPUR) is working on effective, foil-based condensers for regions where rain or fog cannot cover water needs throughout the year.

Large-scale dew harvesting systems have been made by the Indian Institute of Management Ahmedabad (IIMA) with the participation of OPUR in the coastal, semiarid region of Kutch .These condensers can harvest more than 200 liters (on average) of dew water per night for about 90 nights in the October-to-May dew season. The IIMA research laboratory has shown that dew can serve as a supplementary source of water in coastal arid areas.

A large-scale dew harvesting scheme envisages circulating cold sea water in EPDM collectors near the seashore. These condense dew and fog to supply clean drinking water. Other, more recent, studies display possible roof integration for dew harvesting devices.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Dew


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Dew point

The dew point of a given body of air is the temperature to which it must be cooled to become saturated with water vapor. This temperature depends on the pressure and water content of the air. When the air is cooled below the dew point, its moisture capacity is reduced and airborne water vapor will condense to form liquid water known as dew. When this occurs through the air's contact with a colder surface, dew will form on that surface.

The dew point is affected by the air's humidity. The more moisture the air contains, the higher its dew point.

When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed via deposition rather than condensation. In liquids, the analog to the dew point is the cloud point.

Humidity
If all the other factors influencing humidity remain constant, at ground level the relative humidity rises as the temperature falls; this is because less vapor is needed to saturate the air. In normal conditions, the dew point temperature will not be greater than the air temperature, since relative humidity typically does not exceed 100%.

In technical terms, the dew point is the temperature at which the water vapor in a sample of air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates. At temperatures below the dew point, the rate of condensation will be greater than that of evaporation, forming more liquid water. The condensed water is called dew when it forms on a solid surface, or frost if it freezes. In the air, the condensed water is called either fog or a cloud, depending on its altitude when it forms. If the temperature is below the dew point, and no dew or fog forms, the vapor is called supersaturated. This can happen if there are not enough particles in the air to act as condensation nuclei.

The dew point depends on how much water vapor the air contains. If the air is very dry and has few water molecules, the dew point is low and surfaces must be much cooler than the air for condensation to occur. If the air is very humid and contains many water molecules, the dew point is high and condensation can occur on surfaces that are only a few degrees cooler than the air.

A high relative humidity implies that the dew point is close to the current air temperature. A relative humidity of 100% indicates the dew point is equal to the current temperature and that the air is maximally saturated with water. When the moisture content remains constant and temperature increases, relative humidity decreases, but the dew point remains constant.

General aviation pilots use dew point data to calculate the likelihood of carburetor icing and fog, and to estimate the height of a cumuliform cloud base.

Increasing the barometric pressure raises the dew point. This means that, if the pressure increases, the mass of water vapor per volume unit of air must be reduced in order to maintain the same dew point. For example, consider New York City (33 ft elevation) and Denver (5280 ft elevation ). Because Denver is at a higher elevation than New York, it will tend to have a lower barometric pressure. This means that if the dew point and temperature in both cities are the same, the amount of water vapor in the air will be greater in Denver.

Relationship to human comfort
When the air temperature is high, the human body uses the evaporation of perspiration to cool down, with the cooling effect directly related to how fast the perspiration evaporates. The rate at which perspiration can evaporate depends on how much moisture is in the air and how much moisture the air can hold. If the air is already saturated with moisture (humid), perspiration will not evaporate. The body's thermoregulation will produce perspiration in an effort to keep the body at its normal temperature even when the rate at which it is producing sweat exceeds the evaporation rate, so one can become coated with sweat on humid days even without generating additional body heat (such as by exercising).

As the air surrounding one's body is warmed by body heat, it will rise and be replaced with other air. If air is moved away from one's body with a natural breeze or a fan, sweat will evaporate faster, making perspiration more effective at cooling the body, thereby increasing comfort. By contrast, comfort decreases as unevaporated perspiration increases.

A wet bulb thermometer also uses evaporative cooling, so it provides a good measure for use in evaluating comfort level.

Discomfort also exists when the dew point is very low (below around -5 °C). The drier air can cause skin to crack and become irritated more easily. It will also dry out the airways. The US Occupational Safety and Health Administration recommends indoor air be maintained at 20 - 24.5 C with a 20–60% relative humidity, equivalent to a dew point of approximately 4.0 to 16.5 C (by Simple Rule calculation below).

Lower dew points, less than 10 °C, correlate with lower ambient temperatures and cause the body to require less cooling. A lower dew point can go along with a high temperature only at extremely low relative humidity, allowing for relatively effective cooling.

People inhabiting tropical and subtropical climates acclimatize somewhat to higher dew points. Thus, a resident of Singapore or Miami, for example, might have a higher threshold for discomfort than a resident of a temperate climate like London or Chicago. People accustomed to temperate climates often begin to feel uncomfortable when the dew point gets above 15 C, while others might find dew points up to 18 C comfortable. Most inhabitants of temperate areas will consider dew points above 21 °C oppressive and tropical-like, while inhabitants of hot and humid areas may not find this uncomfortable. Thermal comfort depends not just on physical environmental factors, but also on psychological factors.

Dew point weather records

 * Highest dew point temperature: A dew point of 35 °C — while the temperature was 42 °C — was observed at Dhahran, Saudi Arabia, at 3:00 p.m. on 8 July 2003.

Measurement
Devices called hygrometers are used to measure dew point over a wide range of temperatures. These devices consist of a polished metal mirror which is cooled as air is passed over it. The dew point is revealed by observing the loss of clarity in the reflection cast by the mirror. Manual devices of this sort can be used to calibrate other types of humidity sensors, and automatic sensors may be used in a control loop with a humidifier or dehumidifier to control the dew point of the air in a building or in a smaller space for a manufacturing process.

Calculating the dew point

A well-known empirical approximation used to calculate the dew point, Td, given just the actual ("dry bulb") air temperature, T (in degrees Celsius) and relative humidity (in percent), RH, is the Magnus formula: $$\begin{align} \gamma(T,\mathrm{RH})&=\ln\left(\frac\mathrm{RH}{100}\right)+\frac{bT}{c+T};\\[8pt] T_\mathrm{d}&= \frac{c\gamma(T,\mathrm{RH})}{b-\gamma(T,\mathrm{RH})};\end{align} $$ where b = 17.625 and c = 243.04°C. The values of b and c were selected by minimizing the maximum deviation over the range -40°C to +50°C.

The more complete formulation and origin of this approximation involves the interrelated saturated water vapor pressure (in units of millibars, also called hectopascals) at T, Ps(T), and the actual vapor pressure (also in units of millibars), Pa(T), which can be either found with RH or approximated with the barometric pressure (in millibars), BPmbar, and "wet-bulb" temperature, Tw is (unless declared otherwise, all temperatures are expressed in degrees Celsius): $$ \begin{align} P_\mathrm{s}(T)& = \frac{100}\mathrm{RH}P_\mathrm{a}(T) = ae^{\frac{bT}{c+T}};\\[8pt] P_\mathrm{a}(T) & = \frac\mathrm{RH}{100}P_\mathrm{s}(T)=ae^{\gamma(T,\mathrm{RH})}\\ &\approx P_\mathrm{s}(T_\mathrm{w}) - BP_\mathrm{mbar} 0.00066 \left(1 + 0.00115T_\mathrm{w} \right)\left(T-T_\mathrm{w}\right);\\[8pt] T_\mathrm{d} & = \frac{c\ln\frac{P_\mathrm{a}(T)}{a}}{b-\ln\frac{P_\mathrm{a}(T)}{a}}; \end{align}$$

For greater accuracy, Ps(T) (and therefore γ(T, RH)) can be enhanced, using part of the Bögel modification, also known as the Arden Buck equation, which adds a fourth constant d: $$\begin{align}P_\mathrm{s,m}(T)&=ae^{\left(b-\frac{T}{d}\right)\left(\frac{T}{c+T}\right)};\\[8pt] \gamma_\mathrm{m}(T,\mathrm{RH})&=\ln\left(\frac\mathrm{RH}{100}e^{\left(b-\frac{T}{d}\right)\left(\frac{T}{c+T}\right)}\right);\\[8pt] T_{d} & = \frac{c\ln\frac{P_\mathrm{a}(T)}{a}}{b-\ln\frac{P_\mathrm{a}(T)}{a}} = \frac{c\ln\left(\frac\mathrm{RH}{100}\frac{P_\mathrm{s,m}(T)}{a}\right)}{b-\ln\left(\frac\mathrm{RH}{100}\frac{P_\mathrm{s,m}(T)}{a}\right)} = \frac{c\gamma_m(T,\mathrm{RH})}{b-\gamma_m(T,\mathrm{RH})}; \end{align}$$ where
 * a = 6.1121 mbar, b = 18.678, c = 257.14 °C, d = 234.5 °C.

There are several different constant sets in use. The ones used in NOAA's presentation are taken from a 1980 paper by David Bolton in the Monthly Weather Review: These valuations provide a maximum error of 0.1%, for −30 °C ≤ T ≤ 35°C and 1% < RH < 100%. Also noteworthy is the Sonntag1990, Another common set of values originates from the 1974 Psychrometry and Psychrometric Charts. Also, in the Journal of Applied Meteorology and Climatology, Arden Buck presents several different valuation sets, with different maximum errors for different temperature ranges. Two particular sets provide a range of −40 °C to +50 °C between the two, with even lower maximum error within the indicated range than all the sets above:
 * a = 6.112 mbar, b = 17.67, c = 243.5 °C.
 * a = 6.112 mbar, b = 17.62, c = 243.12 °C; for −45 °C ≤ T ≤ 60 °C (error ±0.35 °C).
 * a = 6.105 mbar, b = 17.27, c = 237.7 °C; for 0 °C ≤ T ≤ 60 °C (error ±0.4 °C).
 * a = 6.1121 mbar, b = 17.368, c = 238.88 °C; for 0 °C ≤ T ≤ 50 °C (error ≤ 0.05%).
 * a = 6.1121 mbar, b = 17.966, c = 247.15 °C; for −40 °C ≤ T ≤ 0 °C (error ≤ 0.06%).

Simple approximation
There is also a very simple approximation that allows conversion between the dew point, temperature, and relative humidity. This approach is accurate to within about ±1 °C as long as the relative humidity is above 50%: $$\begin{align} T_\mathrm{d} &\approx T-\frac{100-\mathrm{RH}}{5}; \\[5pt] \mathrm{RH} &\approx 100-5(T-T_\mathrm{d}); \end{align}$$

This can be expressed as a simple rule of thumb: For every 1 °C difference in the dew point and dry bulb temperatures, the relative humidity decreases by 5%, starting with RH = 100% when the dew point equals the dry bulb temperature.

The derivation of this approach, a discussion of its accuracy, comparisons to other approximations, and more information on the history and applications of the dew point, can be found in an article published in the Bulletin of the American Meteorological Society.

For temperatures in degrees Fahrenheit, these approximations work out to $$\begin{align} T_\mathrm{d,^\circ F} &\approx T_\mathrm{{}^\circ F}-\tfrac{9}{25}\left(100-\mathrm{RH}\right);\\[5pt] \mathrm{RH} &\approx 100-\tfrac{25}{9}\left(T_\mathrm{{}^\circ F}-T_\mathrm{d,^\circ F}\right); \end{align}$$

For example, a relative humidity of 100% means dew point is the same as air temp. For 90% RH, dew point is 3 °F lower than air temperature. For every 10 percent lower, dew point drops 3 °F.

Frost point
The frost point is similar to the dew point in that it is the temperature to which a given parcel of humid air must be cooled, at constant atmospheric pressure, for water vapor to be deposited on a surface as ice crystals without undergoing the liquid phase (compare with sublimation). The frost point for a given parcel of air is always higher than the dew point, as breaking the stronger bonding between water molecules on the surface of ice compared to the surface of (supercooled) liquid water requires a higher temperature.

title: Dew point


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Talk:Telomere

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Histone Modifications in Telomeres
I removed this section from the main wikipedia page because it is likely only of interest to specialists (maybe just the author shilling their own work?) and the article is already too sprawling and hard to read.

The telomeres of human cells have been found to have a unique histone modification pattern, with the most enriched modifications being H2BK5me1 and H3K3me3 and the least enriched modifications being H3K36me3 and H3K9me3

title: Talk:Telomere


text:
Cockfight

Cockfighting is a blood sport involving domesticated roosters as the combatants. The first documented use of the word gamecock, denoting use of the cock as to a "game", a sport, pastime or entertainment, was recorded in 1634, after the term "cock of the game" used by George Wilson, in the earliest known book on the sport of cockfighting in The Commendation of Cocks and Cock Fighting in 1607. But it was during Magellan's voyage of discovery of the Philippines in 1521 when modern cockfighting was first witnessed and documented for Westerners by the Italian Antonio Pigafetta, Magellan's chronicler, in the Kingdom of Taytay.

The gamecocks (not to be confused with game birds), are specially bred and conditioned for increased stamina and strength. Male and female chickens of such a breed are referred to as gamefowl. Cocks possess congenital aggression toward all males of the same species. Wagers are often made on the outcome of the match, held in a ring called a cockpit.

Cockfighting is a blood sport due in some part to the physical trauma the cocks inflict on each other, which is sometimes increased by attaching metal spurs to the cocks' natural spurs. While not all fights are to the death, the cocks may endure significant physical trauma. In some areas around the world, cockfighting is still practiced as a mainstream event; in some countries it is regulated by law, or forbidden outright.

Process
Two owners place their gamecock in the cockpit. The cocks fight until one of them dies or is critically injured. Historically, this was in a cockpit, a term which was also used in the 16th century to mean a place of entertainment or frenzied activity. William Shakespeare used the term in Henry V to specifically mean the area around the stage of a theatre. In Tudor times, the Palace of Westminster had a permanent cockpit, called the Cockpit-in-Court.

History
Cockfighting is an ancient spectator sport. There is evidence that cockfighting was a pastime in the Indus Valley civilization. The Encyclopædia Britannica (2008) holds:

"The sport was popular in ancient times in India, China, Persia, and other Eastern countries and was introduced into Ancient Greece in the time of Themistocles (c. 524–460 BC). For a long time the Romans affected to despise this 'Greek diversion', but they ended up adopting it so enthusiastically that the agricultural writer Columella (1st century AD) complained that its devotees often spent their whole patrimony in betting at the side of the pit."

Based on his analysis of a Mohenjo-daro seal, Iravatham Mahadevan speculates that the city's ancient name could have been Kukkutarma ("the city [-rma] of the cockerel [kukkuta]"). However, according to a recent study, "it is not known whether these birds made much contribution to the modern domestic fowl. Chickens from the Harappan culture of the Indus Valley (2500–2100 BC) may have been the main source of diffusion throughout the world." Also, "Within the Indus Valley, indications are that chickens were used for sport and not for food (Zeuner 1963)", cited in R.D. Crawford (1990). and that by 1000 BC they had assumed "religious significance".

In China, the first recorded cockfight took place in 517 BC.

Some additional insight into the pre-history of European and American secular cockfighting may be taken from The London Encyclopaedia:

"At first cockfighting was partly a religious and partly a political institution at Athens; and was continued for improving the seeds of valor in the minds of their youth, but was afterwards perverted both there and in the other parts of Greece to a common pastime, without any political or religious intention."

An early image of a fighting rooster has been found on a 6th-century BC seal of Jaazaniah from the biblical city of Mizpah in Benjamin, near Jerusalem. Remains of these birds have been found at other Israelite Iron Age sites, when the rooster was used as a fighting bird; they are also pictured on other seals from the period as a symbol of ferocity, such as the late-7th-century BC red jasper seal inscribed "Jehoahaz, son of the king", which likely belonged to Jehoahaz of Judah "while he was still a prince during his father's life".

The anthropologist Clifford Geertz wrote the influential essay Deep Play: Notes on the Balinese Cockfight, on the meaning of the cockfight in Balinese culture.

Regional variations
In some regional variations, the birds are equipped with either metal spurs (called gaffs) or knives, tied to the leg in the area where the bird's natural spur has been partially removed. A cockspur is a bracelet (often made of leather) with a curved, sharp spike which is attached to the leg of the bird. The spikes typically range in length from "short spurs" of just over an inch to "long spurs" almost two and a half inches long. In the highest levels of 17th century English cockfighting, the spikes were made of silver. The sharp spurs have been known to injure or even kill the bird handlers. In the naked heel variation, the bird's natural spurs are left intact and sharpened: fighting is done without gaffs or taping, particularly in India (especially in Tamil Nadu). There it is mostly fought naked heel and either three rounds of twenty minutes with a gap of again twenty minutes or four rounds of fifteen minutes each and a gap of fifteen minutes between them.

Cockfighting is common throughout Southeast Asia, where it is implicated in spreading bird flu. Cockfighting is a popular form of fertility worship in Southeast Asia.

India
The sport of cockfighting has long been outlawed in India, with the Supreme Court proclaiming the practice to be in direct violation of the Prevention of Cruelty to Animals Act 1960. According to M Ravindranath Babu Superintendent, Indian Police, it is also considered a hijack of traditional festivals to promote illegal betting and gambling. Despite this, institutional resistance to government bans on cockfighting occurs. At India's ‘Sun God’ festival in 2012, the local Bharatiya Janata Party district committee campaigned for the right to have cock-fights. This was then agreed by local police if it took place inside the temples.

Cockfights are currently common in the southern Indian states of Telangana, Andhra Pradesh, Tamil Nadu and Karnataka despite a countrywide ban imposed in 1960. It is a regional spectacle primarily taking place in January, coinciding with harvest festival celebrations. Like Jallikattu, Cock fighting (Seval Sandai) an ancient spectator sport is mentioned in Sangam literature Paṭṭiṉappālai and Tirumurukāṟṟuppaṭai.

Indonesia
Cockfighting is a very old tradition in Balinese Hinduism, the Batur Bang Inscriptions I (from the year 933) and the Batuan Inscription (dated 944 on the Balinese Caka calendar) disclose that the tabuh rah ritual has existed for centuries.

In Bali, cockfights, known as tajen or sabung ayam, are practiced in an ancient religious purification ritual to expel evil spirits. This ritual, a form of animal sacrifice, is called tabuh rah ("pouring blood"). The purpose of tabuh rah is to provide an offering (the blood of the losing chicken) to the evil spirits. Cockfighting is a religious obligation at every Balinese temple festival or religious ceremony. Cockfights without a religious purpose are considered gambling in Indonesia, although it is still largely practiced in many parts of Indonesia. Women are generally not involved in the tabuh rah process. The tabuh rah process is held on the largest pavilion in a Balinese temple complex, the wantilan.

The American anthropologist Clifford Geertz published his most famous work, Notes on the Balinese Cockfight, on the practice of cockfights in Bali. In it, he argued that the cockfight served as a pastiche or model of wider Balinese society from which judgments about other aspects of the culture could be drawn.

Philippines
Cockfighting was already flourishing in pre-colonial Philippines, as recorded by Antonio Pigafetta, the Italian diarist aboard Ferdinand Magellan's 1521 expedition.

Cockfighting, locally termed sabong, remains a popular pastime in the Philippines, where both illegal and legal cockfights occur. Legal cockfights are held in cockpits every week, whilst illegal ones, called tupada or tigbakay, are held in secluded cockpits where authorities cannot raid them. In both types, knives or gaffs are used. There are two kinds of knives used in Philippine cockfighting: single-edged blades (used in derbies) and double-edged blades; lengths of knives also vary. All knives are attached on the left leg of the bird, but depending on agreement between owners, blades can be attached on the right or even on both legs. Sabong and illegal tupada, are judged by a referee called sentensyador or koyme, whose verdict is final and not subject to any appeal. Bets are usually taken by the kristo, so named because of his outstretched hands when calling out wagers from the audience from memory.

The country has hosted several World Slasher Cup derbies, held biannually at the Smart Araneta Coliseum, Quezon City, where the world's leading game fowl breeders gather. World Slasher Cup is also known as the "Olympics of Cockfighting". The World Gamefowl Expo 2014 was held in the World Trade Center Metro Manila.

Other bird species
Male saffron finches and canaries have been used in fights on occasion.

Argentina
Article 3.8 of Law 14.346 on the Ill-Treatment and Acts of Cruelty to Animals of 1954 explicitly prohibits 'carrying out public or private acts of animal fights, fights of bulls and heifers, or parodies [thereof], in which animals are killed, wounded or harassed.'

Australia
Cockfighting, and the possession of cockfighting equipment, is illegal in Australia and punishable with prison time.

Belgium
In Belgium, cockfights have been prohibited since 1867. In 1929 all organised fights between animals were banned. In 1986 and 1991, the animal welfare act was amended by also criminalising attendance of cockfights. Offenders risk six months imprisonment and a fine of 2,000 euros. Since the 1990s, several people have been prosecuted for cockfighting.

Brazil
Cockfighting (rinha de galos) was banned in 1934 with the help of President Getúlio Vargas through Brazil's 1934 constitution, passed on 16 July. Based on the recognition of animal rights in the Constitution, a Brazilian Supreme Court ruling resulted in the ban of animal related activities that involve claimed "animal suffering such as cockfighting, and a tradition practiced in southern Brazil, known as 'Farra do Boi' (the Oxen Festival)", stating that "animals also have the right to legal protection against mistreatment and suffering".

Canada
Canada's Criminal Code includes animal cruelty legislation, which criminalize any kind of fighting or baiting of any animal. These laws have been amended and made more restrictive over time, and as of 2018 include bans on fighting, promoting, arranging and profiting from fights, as well as breeding, training and transporting of animals for the purpose of fights and keeping of arenas for the purpose of animal fights, for animals of any kind.

Chile
Chilean Law no. 20.380 on Animal Protection of 25 August 2009 explicitly exempts various forms of 'animal sports' in Article 16: 'The norms of this law will not apply to sports in which animals participate, such as rodeo, cowfights, movement to the rein and equestrian sports, which will be governed by their respective regulations.'

Colombia
In Colombia, cockfighting is a tradition, especially in the Caribbean region and in some areas of the Andean interior. Cockfights are held during the Festival de la Leyenda Vallenata in Valledupar. In August 2010, the Constitutional Court of Colombia rejected a lawsuit that sought to prohibit bullfighting, corralejas and cockfighting with the argument that they constitute animal abuse. In March 2019, the same court confirmed such rule, under the argument that cockfighting and bullfighting are traditions with cultural roots in some municipalities of the country. The Asociación Nacional de Criadores de Gallos de Pelea organizes an international cockfighting championship.

Cockfighting was immortalized in the novel One Hundred Years of Solitude by Gabriel García Márquez, in episodes such as the events that led to the death of Prudencio Aguilar, or the fondness for it by José Arcadio Segundo. Cockfighting was one of the main subjects of , a TV adaptation of Juan Rulfo's novel, El gallo de oro, aired in Colombia and other countries in the region during the late 90s.

Costa Rica
Cockfights have been illegal in Costa Rica since 1922. The government deems the activity as animal cruelty, public disorder and a risk for public health and is routinely repressed by the State's National Secretary for Animal Welfare. The activity is also rejected by most of the population, as 88% of Costa Ricans dislike cockfights according to recent polls of the National University. Since 2017, the activity is punishable with up to two years of prison.

Cuba
In Cuba, cockfighting is legal and popular, although gambling on matches has been banned since the 1959 Revolution. The state has opened official arenas, locally known as "galleras", including a 1,000-seat venue in Ciego de Ávila, but there are also banned underground cockfighting pits.

Cockfighting was so common following the Spanish conquest in the early 16th century that there were arenas in every urban and rural town. The first official known document about cockfighting in Cuba dates from 1737. It is a royal decree asking, to the governor of the island, a report about the inconveniences that might cause cockfights "with the people from land and sea" and asking for information about rentals of the games. The Spaniard Miguel Tacón, Lieutenant General and governor of the colony, banned cockfighting by a decree dated on October 20, 1835, limiting these spectacles only to holidays.

In 1844, a decree dictated by the Captain General of the island, Leopoldo O'Donnell, forbade to non-white people the attendance to these shows. During the second half of the 19th century, many authorizations were conceded for building arenas, until General Juan Rius Rivera, then civilian governor in Havana, prohibited cockfighting by a decree of October 31, 1899, and later the Cuban governor, General Leonard Wood, dictated the military order no. 165 prohibiting cockfights in the whole country since June 1, 1900.

In the first half of the 20th century, legality of cockfights suffered several ups and downs.

In 1909, the then-Cuban president José Miguel Gómez, with the intention to gain followers, allowed cockfights once again, and then regulations were agreed for the fights.

Up to the beginning of 1968, cockfights used to be held everywhere in the country, but with the purpose of stopping the bets, the arenas were closed and the fights forbidden by the authorities. In 1980, authorities legalized cockfights again and a state business organization was created with the participation of the private breeders, grouped in territories. Every year the state organization announces several national tournaments from January to April, makes trade shows and sells fighting cocks to clients from other Caribbean countries.

Dominican Republic
In the Dominican Republic, cockfighting is legal, but according to Dominican Today 'increasingly rejected by society' as of December 2018. There is at least one arena (gallera) in every town, whereas in bigger cities larger coliseos can be found. Important fights are broadcast on television and newspapers have dedicated pages to cockfights and the different trabas, the local name for gamefowl breeding grounds. Those dedicated to the breeding and training of fighting cocks are called galleros or traberos. The cocks are often outfitted with special spurs made from various materials (ranging from plastic to metal or even carey shell) and fights are typically to the death. Public perception of the sport is as normal as that of baseball or any other major sport.

East Timor
Cockfighting and cockfighting betting is legal on licensed venues.

France
Holding cockfights is a crime in France, but there is an exemption under subparagraph 3 of article 521–1 of the French penal code for cockfights and bullfights in locales where an uninterrupted tradition exists for them. Thus, cockfighting is allowed in the Nord-Pas de Calais region, where it takes place in a small number of towns including Raimbeaucourt, La Bistade and other villages around Lille. However, the construction of new cockfighting areas is prohibited, a law upheld by the Constitutional Council of France in 2015.

Cockfighting is also legal in some French Overseas Territories.

Germany
Cockfights have no tradition in Germany. They are illegal under increasingly stringent criminal law since 1871.

Haiti
Cockfighting is legal in Haiti. Nevins (2015) described it as 'the closest thing to a national sport in Haiti', being organised every Sunday morning in places across the country. Sharp spurs are attached to the roosters' feet to make them extra lethal, and the fight usually ends with the death of one of the animals.

Honduras
In Honduras, under Article 11 of 'Decree no. 115-2015 ─ Animal Protection and Welfare Act' that went into effect in 2016, dog and cat fights and duck races are prohibited, while 'bullfighting shows and cockfights are part of the National Folklore and as such allowed'.

India

The Supreme Court of India has banned cockfighting as a violation of the Prevention of Cruelty to Animals Act, but it remains popular, especially in the rural coast of Andhra Pradesh, with large amount of betting involved, especially around the festival of Sankranti.

Indonesia
All forms of gambling, including the gambling within secular cockfighting, were made illegal in 1981 by the Indonesian government, while the religious aspects of cockfighting within Balinese Hinduism remain protected. However, secular cockfighting remains widely popular in Bali, despite its illegal status.

Iraq
Cockfighting is illegal but widespread in Iraq. The attendees come to gamble or just for the entertainment. A rooster can cost up to $8,000, or ₹23,000.00. The most-prized birds are called Harati, which means that they are of Turkish or Indian origin, and have muscular legs and necks.

Japan
Cockfighting was introduced to Japan from China in the early 8th century and rose to popularity in the Kamakura period and the Edo period. Cockfighting endured in some Japanese regions even after being banned in 1873, during the Meiji period.

Malaysia
Animal fighting and baiting are prohibited under the Animal Welfare Act (2015).

Mexico
There are cockfight bans in the country's capital, Mexico City, and in the states of Sonora and Coahuila since September 11, 2012, and in Veracruz since November 6, 2018.

Cockfighting is tolerated in the Mexican states of Michoacán, Aguascalientes, Jalisco, Sinaloa, and Veracruz, mostly during regional fairs and other celebrations. Cockfights are performed in palenques (pits). Cockfighting remains legal in the municipality of Ixmiquilpan and throughout Mexico.

The two parties to the bird fights are traditionally distinguished by red and green, typically by wearing a scarf or badge hanging on the belt. Cockfighting may be combined with a musical show. Fairs and regional festivals of the country's municipalities are held in venues called "palenques" of roosters. These consist of a ring made of wood whose center is full of compacted earth for the best 'performance' of the roosters. In the center, a box 4 meters per side and lines that cross from center to center each side are marked with lime. Finally, the last square, measuring 40 cm on each side, is marked in the center of the arena, where the roosters are taken the third time they are released.

Netherlands
In the Netherlands, organising or attending cockfights is illegal and punishable by up to three years imprisonment, or a fine of up to 20,500 euros.

New Zealand
The act of cockfighting is illegal under the Animal Welfare Act 1999, as is the possession, training and breeding of cocks for fighting.

Pakistan
Cockfighting was a popular sport in rural Pakistan; however, "betting is illegal under the Prevention of Gambling Act 1977". Betting is illegal, but police often turn a blind eye towards it. In Sindh, people are fond of keeping fighting cock breed, known as Sindhi aseel in Pakistan. These cocks are noted being tall, heavy and good at fighting. Another popular breed is called Mianwali Aseel. In Sindh Gamblor or Khafti uses Almond and other power enhancing medicines to feed the fighter cocks.

Panama
Law 308 on the Protection of Animals was approved by the National Assembly of Panama on 15 March 2012. Article 7 of the law states: 'Dog fights, animal races, bullfights – whether of the Spanish or Portuguese style – the breeding, entry, permanence and operation in the national territory of all kinds of circus or circus show that uses trained animals of any species, are prohibited.' However, horse racing and cockfighting were exempt from the ban.

Paraguay
Organising fights between all animals, both in public and private, is prohibited in Paraguay under Law No. 4840 on Animal Protection and Welfare, promulgated on 28 January 2013. Specifically:
 * 'The use of animals in shows, fights, popular festivals and other activities that imply cruelty or mistreatment, that can cause death, suffering or make them the object of unnatural and unworthy treatments' is prohibited (Article 30).
 * 'Training domestic animals to carry out provoked fights, with the goal of holding a public or private show' is considered an 'act of mistreatment'. (Article 31)
 * 'The use of animals in shows, fights, popular festivals, and other activities that imply cruelty or mistreatment, which may cause death, suffering or make them subject to unnatural or humiliating treatment' is considered a 'very serious infraction' (Article 32), which are punishable by between 501 and 1500 minimum daily wages (jornales mínimos, Article 39), and the perpetrator may be barred from 'acquiring or possessing other animals for a period that may be up to 10 years' (Article 38).

Peru
According to the Encyclopedia of Latino Culture, Peru "has probably the longest historical tradition" with cockfighting, with the practice possibly dating back to the 16th century. Cockfighting is legal and regulated by the government in Peru. Most pits (coliseos) in the country are located in Lima. Cockfighting and bullfighting are exempt from Peru's animal protection laws.

In October 2018, over 5,000 Peruvians signed a petition that called for a constitutional ban on "all cruel shows using animals" including cockfighting and bullfighting, which was accepted and taken into consideration by the Supreme Court of Peru. However, with only three of the five required judges agreeing with the petition, on 25 February 2020 the Court ruled that it could not declare the animal fighting practices unconstitutional, leaving the applicants with no further option of appeal. A week before the verdict, thousands of other people had marched through the streets of Lima in support of the animal fighting practices.

Philippines
There is no nationwide ban of cockfighting in the Philippines but since 1948, cockfighting is prohibited every Rizal Day on December 30 where violators can be fined or imprisoned due to the Republic Act No. 229. It further is supplemented by Presidential Decree No. 449 or the Anti-Cockfighting Law of 1974 which allows cockfights only on Sundays, certain holidays, and on certain other occasions, and only at licensed cockpits.

On March 14, 2020, the Department of the Interior and Local Government (DILG) announced that cockfighting is temporarily banned in the Philippines due to the prohibition of mass gatherings amid the coronavirus pandemic and community quarantines across the Philippines.

Davao City Mayor Sara Duterte banned cockfighting in Davao City since April 16, 2020, also due to the coronavirus pandemic.

The Philippines have a very deep cultural root connected to cockfighting that goes back to ancient times. It can be said that the Filipinos brought a major wave of cockfighting over to Hawaii when the Filipinos first arrived, even though it was widely condemned by locals of the area.

The popularity of cockfighting in the Philippines has extended into the digital space, with the advent of online sabong or e-sabong. This virtual iteration allows enthusiasts to participate in and bet on cockfights via internet streaming. The surge in online cockfighting has been significantly facilitated by the integration of modern technologies, particularly through online casino platforms that host these events. Payment apps like GCash have also played a crucial role, offering a convenient and secure method for placing bets and managing transactions online.

Poland
Cockfighting in Poland is banned. The law bans any animal cruelty in general, there are no specific laws for cockfighting. Likewise in many other European countries, this activity used to be popular up to the 18th century. In the Silesia area it used to be popular longer, even in the 19th century. It was usually held on the Day of Saint Gall (16 October). This activity was banned on most of the territory of Poland after the Partitions of Poland and before the country regained its independence in 1918. In western areas that were held by Germany, it was banned in 1871 by § 360 p. 13 of the Penal Code of the German Reich. In eastern areas that were held by Russia, it was banned in 1903 by § 287 of the Penal Code of Tagancev Nikolaj Stepanovič. After regaining independence these laws were still in power until new laws were passed. The first animal-cruelty law in independent Poland was passed in 1928 as a presidential decree and it was in power until 1997. It was added to the official Penalty Code in 1997 by § 35 points 1–2 in chapter 11. Currently, the penalty for the act is up to 3 years in prison or it might be up to 5 years if the cruelty is more drastic.

Romania
Cockfights are illegal in Romania under article 25.3 lit. c) of the Law 205/2004, with punishments ranging from 2 to 7 years imprisonment.

Spain
Cockfighting is banned in Spain except in two Spanish regions: the Canary Islands and Andalusia. In Andalusia, however, the activity has virtually disappeared, surviving only within a program to maintain the fighting breed "combatiente español" coordinated by the University of Córdoba. Spain's Animal Protection Law of 1991 recognizes an exception for these regions based on cultural heritage and a history of cockfighting in the region. Animal rights organizations have sought to ban the bloodsport nationwide, but have not been successful in advancing legislation through the Spanish Parliament.

Ukraine
In Ukraine, cockfights, as well as fights involving other animals (dogs, geese, etc.) are prohibited by Art. 25 of the Law of Ukraine "On the Protection of Animals from Cruelty" and Art. 299 of the Criminal Code of Ukraine. For organizing cockfights, the culprit can be sentenced to a fine of up to 850 hryvnias (ukrainan currency) or imprisonment for up to six months.

United Kingdom
Cockfighting was banned outright in England and Wales and in the British Overseas Territories with the Cruelty to Animals Act 1835. Sixty years later, in 1895, cockfighting was also banned in Scotland, where it had been relatively common in the 18th century. A reconstructed cockpit from Denbigh in North Wales may be found at St Fagans National History Museum in Cardiff and a reference exists in 1774 to a cockpit at Stanecastle in Scotland. One of the few perfect examples of a cockpit which still exist today can be found on Chislehurst common, London.

According to a 2017 report by the RSPCA, cockfighting in England and Wales was at a five-year high.

United States

, cockfighting is illegal in all 50 U.S. states, the District of Columbia, and all U.S. territories. The last state to implement a state law banning cockfighting was Louisiana; the Louisiana State Legislature voted to approve a ban in June 2007, which went into effect in August 2008.

As of 2013:
 * Cockfighting is a felony in 40 states and the District of Columbia.
 * The possession of birds for fighting is prohibited in 39 states and the District of Columbia.
 * Being a spectator at a cockfight is prohibited in 43 states and the District of Columbia.
 * The possession of cockfighting implements is prohibited in 15 states.

Additionally, the 2014 farm bill, signed into law by President Obama, contained a provision making it a federal crime to attend an animal fighting event or bring a child under the age of 16 to an animal fighting event.

The cockfighting ban was further extended by federal law to include U.S. territories—American Samoa, the Northern Mariana Islands, Guam, Puerto Rico, and the U.S. Virgin Islands—effective at the end of 2019, as signed into law in the 2018 farm bill by President Trump. In Puerto Rico, cockfighting is popular and has been considered a "national sport" since at least the 1950s. According to a National Park Service report, it generates about $100 million annually. There are some 200,000 fighting birds annually on the island. Puerto Rico's Cockfighting Commission regulates 87 clubs, but many non-government sanctioned "underground" cockfighting operations exist. On December 18, 2019, estimating that cockfighting employs 27,000 people and has a value to the economy of about $18 million, Puerto Rico passed a law attempting to keep the practice legal despite the imminent federal ban. In 2021, governor Pedro Pierluisi announced the government would support a legal effort before the U.S. Supreme Court to overturn the ban. The Supreme Court refused to hear the case, Ortiz-Diaz v. United States, in October 2021, leaving the federal ban in place.

The Animal Fighting Prohibition Enforcement Act, a federal law that made it a federal crime to transfer cockfighting implements across state or national borders and increasing the penalty for violations of federal animal fighting laws to three years in prison, became law in 2007. It passed the House of Representatives 368–39 and the Senate by unanimous consent and was signed into law by President George W. Bush.

The Animal Welfare Act was amended again in 2008 when provisions were included in the 2008 Farm Bill (P.L. 110–246). These provisions tightened prohibitions on dog and other animal fighting activities, and increased penalties for violations of the act.

Major law enforcement raids against cockfighting occurred in February 2014 in New York State (when 3,000 birds were seized and nine men were charged with felony animal-fighting in "Operation Angry Birds", the state's largest-ever cockfighting bust)   and in May 2017 in California (when the Los Angeles County Sheriff's Department seized 7,000 cockfighting birds at a ranch in Val Verde, California, one of the largest cockfighting busts in U.S. history).

Vietnam
Cockfighting is a popular folk game in Vietnam, with a long history dating back to the Lý dynasty. According to historical records, the soldiers of Lý Thường Kiệt brought this game back to Vietnam after conquering Champa. Initially, cockfighting was only held in rural and mountainous areas, where many ethnic minorities live. However, over time, the game has become increasingly popular throughout the country, from urban to rural areas.

During the feudal era, cockfighting was a popular form of entertainment for the emperor, officials, and the upper class. The emperors often held cockfights during festivals such as Tết Nguyên Đán (Vietnamese New Year), Tết Trung Thu,... to entertain their guests. Today, cockfighting is still a popular folk game in Vietnam. However, due to the influence of the market economy, cockfighting has become more professional and commercialized. Large-scale cockfighting arenas, chave been built with modern sound and lighting systems, attracting a large number of participants. Cockfighting has also become a sport that is enjoyed by many people, and is often organized in large and small tournaments throughout the country.

title: Cockfight