Editing Persistent organic pollutant

{{redirect|POPs||Pops (disambiguation)}}
{{Short description|Organic compounds that are resistant to environmental degradation}}
{{Pollution sidebar|Air}}

'''Persistent organic pollutants''' ('''POPs''') are [[organic compounds]] that are resistant to degradation through [[chemical decomposition|chemical]], [[biodegradation|biological]], and [[photolysis|photolytic]] processes.<ref name="ritter">{{cite web|title=Persistent organic pollutants|author=Ritter L|author2=Solomon KR|author3=Forget J|author4=Stemeroff M|author5=O'Leary C.|url=http://www.chem.unep.ch/pops/ritter/en/ritteren.pdf|publisher=[[United Nations Environment Programme]]|access-date=2007-09-16|url-status=dead|archive-url=https://web.archive.org/web/20070926101350/http://www.chem.unep.ch/pops/ritter/en/ritteren.pdf|archive-date=2007-09-26}}</ref> They are toxic and adversely affect human health and the environment around the world.<ref name="ritter" /> Because they can be transported [[air pollution|by wind]] and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released.

The effect of POPs on human and environmental health was discussed, with intention to eliminate or severely restrict their production, by the international community at the [[Stockholm Convention on Persistent Organic Pollutants]] in 2001.

Most POPs are [[pesticide]]s or [[insecticide]]s, and some are also [[solvent]]s, [[pharmaceutical]]s, and industrial chemicals.<ref name="ritter" /> Although some POPs arise naturally (e.g. from volcanoes), most are man-made.<ref name="El-Shahawi, M.S. 2010">{{cite journal |last1=El-Shahawi |first1=M.S. |last2=Hamza |first2=A. |last3=Bashammakh |first3=A.S. |last4=Al-Saggaf |first4=W.T. |title=An overview on the accumulation, distribution, transformations, toxicity and analytical methods for the monitoring of persistent organic pollutants |journal=Talanta |date=15 March 2010 |volume=80 |issue=5 |pages=1587–1597 |doi=10.1016/j.talanta.2009.09.055 |pmid=20152382}}</ref> The "dirty dozen" POPs identified by the Stockholm Convention include [[aldrin]], [[chlordane]], [[dieldrin]], [[endrin]], [[heptachlor]], [[Hexachlorobenzene|HCB]], [[mirex]], [[toxaphene]], [[Polychlorinated biphenyl|PCBs]], [[DDT]], [[Dioxins and dioxin-like compounds|dioxins]], and [[polychlorinated dibenzofurans]]. However, there have since been many new POPs added (e.g. [[PFOS]]).

==Consequences of persistence==
POPs typically are halogenated organic compounds (see lists below) and as such exhibit high [[Lipophilicity|lipid solubility]].  For this reason, they [[bioaccumulation|bioaccumulate]] in [[Adipose tissue|fatty tissues]].<ref>{{Cite journal |last1=Leonards |first1=P. E. G. |last2=Broekhuizen |first2=S. |last3=de Voogt |first3=P. |last4=Van Straalen |first4=N. M. |last5=Brinkman |first5=U. A.Th. |last6=Cofino |first6=W. P. |last7=van Hattum |first7=B. |date=1998-11-01 |title=Studies of Bioaccumulation and Biotransformation of PCBs in Mustelids Based on Concentration and Congener Patterns in Predators and Preys |url=https://doi.org/10.1007/s002449900428 |journal=Archives of Environmental Contamination and Toxicology |language=en |volume=35 |issue=4 |pages=654–665 |doi=10.1007/s002449900428 |pmid=9776784 |bibcode=1998ArECT..35..654L |issn=1432-0703|url-access=subscription }}</ref><ref>{{Cite journal |last1=Elliott |first1=Kyle Hamish |last2=Cesh |first2=Lillian S. |last3=Dooley |first3=Jessica A. |last4=Letcher |first4=Robert J. |last5=Elliott |first5=John E. |date=2009-06-01 |title=PCBs and DDE, but not PBDEs, increase with trophic level and marine input in nestling bald eagles |url=https://www.sciencedirect.com/science/article/pii/S0048969709002058 |journal=Science of the Total Environment |series=Thematic Issue - BioMicroWorld Conference |volume=407 |issue=12 |pages=3867–3875 |doi=10.1016/j.scitotenv.2009.02.027 |pmid=19339036 |bibcode=2009ScTEn.407.3867E |issn=0048-9697|url-access=subscription }}</ref><ref>{{Cite journal |last1=Gobas |first1=Frank A.P.C. |last2=Arnot |first2=Jon A. |date=2010-05-14 |title=Food web bioaccumulation model for polychlorinated biphenyls in San Francisco Bay, California, USA |url=https://setac.onlinelibrary.wiley.com/doi/10.1002/etc.164 |journal=Environmental Toxicology and Chemistry |language=en |volume=29 |issue=6 |pages=1385–1395 |doi=10.1002/etc.164 |pmid=20821583 |bibcode=2010EnvTC..29.1385G |issn=0730-7268|url-access=subscription }}</ref><ref>{{Cite journal |last1=Huang |first1=Andrew C. |last2=Nelson |first2=Cait |last3=Elliott |first3=John E. |last4=Guertin |first4=Daniel A. |last5=Ritland |first5=Carol |last6=Drouillard |first6=Ken |last7=Cheng |first7=Kimberly M. |last8=Schwantje |first8=Helen M. |date=2018-07-01 |title=River otters (Lontra canadensis) "trapped" in a coastal environment contaminated with persistent organic pollutants: Demographic and physiological consequences |journal=Environmental Pollution |volume=238 |pages=306–316 |doi=10.1016/j.envpol.2018.03.035 |pmid=29573713 |bibcode=2018EPoll.238..306H |issn=0269-7491|doi-access=free }}</ref> [[Halogenated]] compounds also exhibit great [[Chemical stability|stability]] reflecting the nonreactivity of C-Cl bonds toward [[hydrolysis]] and [[Photodissociation|photolytic degradation]]. The stability and lipophilicity of organic compounds often correlates with their halogen content, thus polyhalogenated organic compounds are of particular concern.<ref name="ritter" /> They exert their negative effects on the environment through two processes: long range transport, which allows them to travel far from their source, and bioaccumulation, which reconcentrates these chemical compounds to potentially dangerous levels.<ref name="Walker, C.H. 2001">Walker, C.H., "Organic Pollutants: An Ecotoxicological Perspective" (2001).</ref> Compounds that make up POPs are also classed as [[Persistent, bioaccumulative and toxic substances|PBTs]] (persistent, bioaccumulative and toxic) or TOMPs (toxic organic micro pollutants).<ref>{{Cite web|date=2013-08-20|title=Persistent, Bioaccumulative and Toxic Chemicals (PBTs)|url=https://saferchemicals.org/get-the-facts/toxic-chemicals/persistent-bioaccumulative-and-toxic-chemicals-pbts/|access-date=2022-02-01|website=Safer Chemicals Healthy Families|language=en-US}}</ref>

=== Long-range transport ===
{{See also|Global distillation}}
POPs enter the [[gas]] phase under certain environmental temperatures and [[Volatility (chemistry)|volatilize]] from [[soil]]s, [[vegetation]], and [[bodies of water]] into the [[atmosphere]], resisting breakdown reactions in the air, to travel long distances before being re-deposited.<ref name="Kelly, B.C. 2007">{{cite journal |last1=Kelly |first1=Barry C. |last2=Ikonomou |first2=Michael G. |last3=Blair |first3=Joel D. |last4=Morin |first4=Anne E. |last5=Gobas |first5=Frank A. P. C. |title=Food Web–Specific Biomagnification of Persistent Organic Pollutants |journal=Science |date=13 July 2007 |volume=317 |issue=5835 |pages=236–239 |doi=10.1126/science.1138275 |pmid=17626882 |bibcode=2007Sci...317..236K |s2cid=52835862 }}</ref> This results in accumulation of POPs in areas far from where they were used or emitted, specifically environments where POPs have never been introduced such as [[Antarctica]], and the [[Arctic Circle]].<ref>{{cite journal | author1 = Beyer A.| author2=Mackay D.| author3=Matthies M.| author4=Wania F.| author5=Webster E. | year = 2000 | title = Assessing Long-Range Transport Potential of Persistent Organic Pollutants | journal = Environmental Science & Technology | volume = 34 | issue = 4| pages = 699–703 | doi = 10.1021/es990207w | bibcode = 2000EnST...34..699B }}</ref> POPs can be present as vapors in the atmosphere or bound to the surface of solid [[particulates|particles]] ([[aerosol]]s). A determining factor for the long-range transport is the fraction of a POP that is adsorbed on aerosols. In adsorbed form it is – as opposed to the gas phase – protected from photo-oxidation, i.e. direct [[photolysis]] as well as oxidation by [[OH radical]]s or ozone.<ref>{{Cite journal|last1=Koester|first1=Carolyn J.|last2=Hites|first2=Ronald A.|date=March 1992|title=Photodegradation of polychlorinated dioxins and dibenzofurans adsorbed to fly ash|journal=Environmental Science & Technology|language=en|volume=26|issue=3|pages=502–507|doi=10.1021/es00027a008|bibcode=1992EnST...26..502K|issn=0013-936X}}</ref><ref>{{Cite journal|last1=Raff|first1=Jonathan D.|last2=Hites|first2=Ronald A.|date=October 2007|title=Deposition versus Photochemical Removal of PBDEs from Lake Superior Air|journal=Environmental Science & Technology|language=en|volume=41|issue=19|pages=6725–6731|doi=10.1021/es070789e|pmid=17969687|bibcode=2007EnST...41.6725R|issn=0013-936X}}</ref>

POPs have low solubility in water but are easily captured by solid particles, and are soluble in organic fluids ([[oil]]s, [[fat]]s, and [[liquid fuel]]s). POPs are not easily degraded in the environment due to their stability and low [[Chemical decomposition|decomposition]] rates. Due to this capacity for long-range transport, POP environmental contamination is extensive, even in areas where POPs have never been used, and will remain in these environments years after restrictions implemented due to their resistance to degradation.<ref name="ritter" /><ref name="Wania, F. 1996">{{cite journal | author = Wania F., Mackay D. | year = 1996 | title = Tracking the Distribution of Persistent Organic Pollutants | journal = Environmental Science & Technology | volume = 30 | issue = 9| pages = 390A–396A | doi = 10.1021/es962399q | pmid = 21649427 }}</ref><ref>{{cite thesis|last=Astoviza|first=Malena J.|title=Evaluación de la distribución de contaminantes orgánicos persistentes (COPs) en aire en la zona de la cuenca del Plata mediante muestreadores pasivos artificiales|date=15 April 2014|pages=160|publisher=Universidad Nacional de La Plata |doi=10.35537/10915/34729 |language=es|url=http://sedici.unlp.edu.ar/handle/10915/34729|access-date=16 April 2014|type=Tesis |doi-access=free}}</ref>

=== Bioaccumulation ===
[[Bioaccumulation]] of POPs is typically associated with the compounds high lipid solubility and ability to accumulate in the [[adipose tissue|fatty tissues]] of living organisms including human tissues for long periods of time.<ref name="Wania, F. 1996"/><ref name="Vallack, H.W. 1998">{{cite journal |last1=Vallack |first1=Harry W. |last2=Bakker |first2=Dick J. |last3=Brandt |first3=Ingvar |last4=Broström-Lundén |first4=Eva |last5=Brouwer |first5=Abraham |last6=Bull |first6=Keith R. |last7=Gough |first7=Clair |last8=Guardans |first8=Ramon |last9=Holoubek |first9=Ivan |last10=Jansson |first10=Bo |last11=Koch |first11=Rainer |last12=Kuylenstierna |first12=Johan |last13=Lecloux |first13=André |last14=Mackay |first14=Donald |last15=McCutcheon |first15=Patrick |last16=Mocarelli |first16=Paolo |last17=Taalman |first17=Rob D.F. |title=Controlling persistent organic pollutants–what next? |journal=Environmental Toxicology and Pharmacology |date=November 1998 |volume=6 |issue=3 |pages=143–175 |doi=10.1016/S1382-6689(98)00036-2| pmid = 21781891|bibcode=1998EnvTP...6..143V }}</ref> Persistent chemicals tend to have higher concentrations and are eliminated more slowly. Dietary accumulation or bioaccumulation is another hallmark characteristic of POPs, as POPs move up the food chain, they increase in concentration as they are processed and metabolized in certain tissues of organisms. The natural capacity for animals [[Human gastrointestinal tract|gastrointestinal tract]] to concentrate ingested chemicals, along with poorly [[Metabolism|metabolized]] and [[hydrophobic]] nature of POPs, makes such compounds highly susceptible to bioaccumulation.<ref>{{cite journal |last1=Yu |first1=George W. |last2=Laseter |first2=John |last3=Mylander |first3=Charles |title=Persistent Organic Pollutants in Serum and Several Different Fat Compartments in Humans |journal=Journal of Environmental and Public Health |date=2011 |volume=2011 |page=417980 |doi=10.1155/2011/417980 |pmid= 21647350 |pmc=3103883 |doi-access=free}}</ref> Thus POPs not only persist in the environment, but also as they are taken in by animals they bioaccumulate, increasing their concentration and toxicity in the environment.<ref name="Kelly, B.C. 2007"/><ref>{{cite journal |last1=Lohmann |first1=Rainer |last2=Breivik |first2=Knut |last3=Dachs |first3=Jordi |last4=Muir |first4=Derek |title=Global fate of POPs: Current and future research directions |journal=Environmental Pollution |date=November 2007 |volume=150 |issue=1 |pages=150–165 |doi=10.1016/j.envpol.2007.06.051 |pmid=17698265|bibcode=2007EPoll.150..150L }}</ref> This increase in concentration is called biomagnification, which is where organisms higher up in the food chain have a greater accumulation of POPs.<ref>{{Cite web|last=US EPA|first=OITA|date=2014-04-02|title=Persistent Organic Pollutants: A Global Issue, A Global Response|url=https://www.epa.gov/international-cooperation/persistent-organic-pollutants-global-issue-global-response|access-date=2022-02-01|website=www.epa.gov|language=en}}</ref> Bioaccumulation and long-range transport are the reason why POPs can accumulate in organisms like whales, even in remote areas like Antarctica.<ref>{{Cite journal|last1=Remili|first1=Anaïs|last2=Gallego|first2=Pierre|last3=Pinzone|first3=Marianna|last4=Castro|first4=Cristina|last5=Jauniaux|first5=Thierry|last6=Garigliany|first6=Mutien-Marie|last7=Malarvannan|first7=Govindan|last8=Covaci|first8=Adrian|last9=Das|first9=Krishna|date=2020-12-01|title=Humpback whales (Megaptera novaeangliae) breeding off Mozambique and Ecuador show geographic variation of persistent organic pollutants and isotopic niches|url=http://www.sciencedirect.com/science/article/pii/S0269749120362631|journal=Environmental Pollution|language=en|volume=267|pages=115575|doi=10.1016/j.envpol.2020.115575|pmid=33254700|bibcode=2020EPoll.26715575R |hdl=10067/1744230151162165141 |s2cid=225008427 |issn=0269-7491|hdl-access=free}}</ref>

== Stockholm Convention on Persistent Organic Pollutants ==
[[File:Map of Stockholm Convention on Persistent Organic Pollutants.svg|thumb|275px|State parties to the Stockholm Convention on Persistent Organic Pollutants]]
{{Main|Stockholm Convention on Persistent Organic Pollutants}}

The Stockholm Convention was adopted and put into practice by the [[United Nations Environment Programme]] (UNEP) on May 22, 2001. The UNEP decided that POP regulation needed to be addressed globally for the future. The purpose statement of the agreement is "to protect human health and the environment from persistent organic pollutants." As of 2024, there are 185 countries plus the European Union have ratified the Stockholm Convention.<ref name="UNTC">United Nations Treaty Collection: [https://treaties.un.org/Pages/ViewDetails.aspx?src=IND&mtdsg_no=XXVII-15&chapter=27&clang=_en CHAPTER XXVII – ENVIRONMENT – 15. Stockholm Convention on Persistent Organic Pollutants]</ref> The convention and its participants have recognized the potential human and environmental toxicity of POPs. They recognize that POPs have the potential for long-range transport and bioaccumulation and biomagnification. The convention seeks to study and then judge whether or not a number of chemicals that have been developed with advances in technology and science can be categorized as POPs. The initial meeting in 2001 made a preliminary list, termed the "dirty dozen", of chemicals that are classified as POPs.<ref name=":0" /> As of 2024, the [[United States]] has signed the Stockholm Convention but has not ratified it. There are a handful of other countries that have not ratified the convention but most countries in the world have ratified the convention.<ref name="UNTC" />

=== Compounds on the Stockholm Convention list ===
{{cite-section|date=July 2024}}
In May 1995, the UNEP Governing Council investigated POPs.<ref name="thedirtydozen">{{cite web|title=The Dirty Dozen|url=http://www.unido.org/fileadmin/import/29239_popspresentation.swf|publisher=United Nations Industrial Development Organization|access-date=27 March 2014|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304055652/http://www.unido.org/fileadmin/import/29239_popspresentation.swf|url-status=dead}}</ref> Initially the Convention recognized only twelve POPs for their adverse effects on human health and the environment, placing a global ban on these particularly harmful and toxic compounds and requiring its parties to take measures to eliminate or reduce the release of POPs in the environment.<ref name="El-Shahawi, M.S. 2010"/><ref name=":0">{{cite web|url=http://chm.pops.int/Portals/0/Repository/convention_text/UNEP-POPS-COP-CONVTEXT-FULL.English.PDF| title=STOCKHOLM CONVENTION ON PERSISTENT ORGANIC POLLUTANTS| pages=1–43| access-date=27 March 2014}}</ref><ref>{{Cite web |title=Website of the Stockholm Convention |url=http://chm.pops.int/}}</ref>

# '''[[Aldrin]]''', an insecticide used in soils to kill [[termite]]s, [[grasshopper]]s, [[Western corn rootworm]], and others, is also known to kill birds, fish, and humans. Humans are primarily exposed to aldrin through dairy products and animal meats.
# '''[[Chlordane]]''', an insecticide used to control termites and on a range of agricultural crops, is known to be lethal in various species of birds, including mallard ducks, bobwhite quail, and pink shrimp; it is a chemical that remains in the soil with a reported [[half-life]] of one year. Chlordane has been postulated to affect the human immune system and is classified as a possible human [[carcinogen]]. Chlordane air pollution is believed the primary route of human exposure.
# '''[[Dieldrin]]''', a pesticide used to control termites, textile pests, insect-borne diseases and insects living in agricultural soils. In soil and insects, aldrin can be oxidized, resulting in rapid conversion to dieldrin. Dieldrin's half-life is approximately five years. Dieldrin is highly toxic to fish and other aquatic animals, particularly frogs, whose embryos can develop spinal deformities after exposure to low levels. Dieldrin has been linked to [[Parkinson's disease]], [[breast cancer]], and classified as immunotoxic, neurotoxic, with [[Endocrine disruptor|endocrine disrupting]] capacity. Dieldrin residues have been found in air, water, soil, fish, birds, and mammals. Human exposure to dieldrin primarily derives from food.
# '''[[Endrin]]''', an insecticide sprayed on the leaves of crops, and used to control rodents. Animals can metabolize endrin, so fatty tissue accumulation is not an issue, however the chemical has a long half-life in soil for up to 12 years. Endrin is highly toxic to aquatic animals and humans as a [[neurotoxin]]. Human exposure results primarily through food.
# '''[[Heptachlor]]''', a [[pesticide]] primarily used to kill soil insects and termites, along with cotton insects, grasshoppers, other crop pests, and malaria-carrying mosquitoes. Heptachlor, even at very low doses has been associated with the decline of several wild bird populations – [[Canada goose|Canada geese]] and [[American kestrel]]s. In laboratory tests have shown high-dose heptachlor as lethal, with adverse behavioral changes and reduced reproductive success at low-doses, and is classified as a possible human carcinogen. Human exposure primarily results from food.
# '''[[Hexachlorobenzene]] (HCB''') was first introduced in 1945–59 to treat seeds because it can kill [[Fungicide|fungi]] on food crops. HCB-treated seed grain consumption is associated with photosensitive skin lesions, [[colic]], debilitation, and a [[Metabolic syndrome|metabolic disorder]] called porphyria turcica, which can be lethal. Mothers who pass HCB to their infants through the placenta and breast milk had limited reproductive success including infant death. Human exposure is primarily from food.
# '''[[Mirex]]''', an insecticide used against ants and termites or as a [[flame retardant]] in plastics, rubber, and electrical goods. Mirex is one of the most stable and persistent pesticides, with a half-life of up to 10 years.  Mirex is toxic to several plant, fish and [[crustacean]] species, with suggested carcinogenic capacity in humans. Humans are exposed primarily through animal meat, fish, and wild game.
# '''[[Toxaphene]]''', an insecticide used on cotton, cereal, grain, fruits, nuts, and vegetables, as well as for tick and mite control in livestock. Widespread toxaphene use in the US and chemical persistence, with a half-life of up to 12 years in soil, results in residual toxaphene in the environment. Toxaphene is highly toxic to fish, inducing dramatic weight loss and reduced egg viability. Human exposure primarily results from food. While human toxicity to direct toxaphene exposure is low, the compound is classified as a possible human carcinogen.
# '''[[Polychlorinated biphenyls]]''' (PCBs), used as [[Heat-transfer oil|heat exchange fluids]], in [[transformer|electrical transformers]], and [[capacitor]]s, and as additives in paint, carbonless copy paper, and plastics. Persistence varies with degree of [[halogenation]], an estimated half-life of 10 years. PCBs are toxic to fish at high doses, and associated with spawning failure at low doses. Human exposure occurs through food, and is associated with reproductive failure and immune suppression. Immediate effects of PCB exposure include pigmentation of nails and [[mucous membranes]] and swelling of the eyelids, along with fatigue, nausea, and vomiting. Effects are [[Transgenerational epigenetics|transgenerational]], as the chemical can persist in a mother's body for up to 7 years, resulting in developmental delays and behavioral problems in her children. Food contamination has led to large scale PCB exposure.
# [[DDT|'''Dichlorodiphenyltrichloroethane''']] (DDT) is probably the most infamous POP. It was widely used as insecticide during WWII to protect against malaria and typhus. After the war, DDT was used as an agricultural insecticide. In 1962, the American biologist [[Rachel Carson]] published ''[[Silent Spring]]'', describing the impact of DDT spraying on the US environment and human health. DDT's persistence in the soil for up to 10–15 years after application has resulted in widespread and persistent DDT residues throughout the world including the arctic, even though it has been banned or severely restricted in most of the world. DDT is toxic to many organisms including birds where it is detrimental to reproduction due to eggshell thinning. DDT can be detected in foods from all over the world and food-borne DDT remains the greatest source of human exposure. Short-term acute effects of DDT on humans are limited, however long-term exposure has been associated with chronic health effects including increased risk of cancer and diabetes, reduced reproductive success, and neurological disease.
# '''[[Dioxins]]''' are unintentional by-products of high-temperature processes, such as incomplete combustion and pesticide production. Dioxins are typically emitted from the burning of hospital waste, municipal waste, and [[hazardous waste]], along with automobile emissions, peat, coal, and wood. Dioxins have been associated with several adverse effects in humans, including immune and enzyme disorders, [[chloracne]], and are classified as a possible human carcinogen. In laboratory studies of dioxin effects an increase in birth defects and stillbirths, and lethal exposure have been associated with the substances. Food, particularly from animals, is the principal source of human exposure to dioxins. Dioxins were present in [[Agent Orange]], which was used by the United States in chemical warfare against Vietnam and caused devastating multi-generational effects in both Vietnamese and American civilians.
# '''[[Polychlorinated dibenzofurans]]''' are by-products of high-temperature processes, such as incomplete [[combustion]] after [[Incineration|waste incineration]] or in automobiles, pesticide production, and [[polychlorinated biphenyl]] production. Structurally similar to dioxins, the two compounds share toxic effects. Furans persist in the environment and classified as possible human carcinogens. Human exposure to furans primarily results from food, particularly animal products.

=== New POPs on the Stockholm Convention list ===
Since 2001, this list has been expanded to include some [[polycyclic aromatic hydrocarbons]] (PAHs), [[brominated flame retardant]]s, and other compounds. Additions to the initial 2001 Stockholm Convention list are the following POPs:<ref>{{citation | title = Stockholm Convention on Persistent Organic Pollutants (POPs): Text and Annexes | url = https://www.pops.int/Portals/0/download.aspx?d=UNEP-POPS-COP-CONVTEXT-2023.English.pdf | publisher = Secretariat of the Stockholm Convention | date = May 2023 | access-date = 2025-01-27}}.</ref><ref name=":0" />
* [[alpha-Hexachlorocyclohexane|α-Hexachlorocyclohexane]] (α-HCH) and [[beta-Hexachlorocyclohexane|β-Hexachlorocyclohexane]] (β-HCH) are insecticides as well as by-products in the production of [[lindane]]. α-HCH and β-HCH are highly persistent in the water of colder regions. <ref>{{citation | title = Lindane, Alpha-HCH, Beta-HCH factsheet | url = https://www.pops.int/Portals/0/download.aspx?d=UNEP-POPS-NewPOPs-Factsheet-01.02.03-20200226.English.pdf | publisher = Secretariat of the Stockholm Convention | access-date = 2025-01-27}}.</ref> α-HCH and β-HCH have been linked to [[Parkinson's disease|Parkinson's]] and [[Alzheimer's disease]].{{citation needed|date=April 2015}}
* [[Chlordecone]] is primarily used as an agricultural pesticide, related to DDT and Mirex. Chlordecone is toxic to aquatic organisms, and classified as a possible human carcinogen. <ref>{{citation | title = Chlordecone ether factsheet | url = https://www.pops.int/Portals/0/download.aspx?d=UNEP-POPS-NewPOPs-Factsheet-04-20200226.English.pdf | publisher = Secretariat of the Stockholm Convention | access-date = 2025-01-27}}.</ref> Many countries have banned chlordecone sale and use, or intend to destroy stockpiles.
* [[Decabromodiphenyl ether]], a flame retardant, commonly sold as decaBDE, which is added to polymers, textiles, adhesives, coatings and more. In addition to bioaccumulation potential, the Stockholm convention identified decaBDE as affecting human endocrine, reproductive, and nervous systems.<ref>{{citation | title = Decabromodiphenyl ether factsheet | url = https://www.pops.int/Portals/0/download.aspx?d=UNEP-POPS-NewPOPs-Factsheet-05-20200313.English.pdf | publisher = Secretariat of the Stockholm Convention | access-date = 2025-01-27}}.</ref>
* [[Dechlorane plus]] is a flame retardant structurally similar to [[Mirex]]. Added to the Stockholm Convention in 2023, research into human toxicology is ongoing. <ref>{{citation | title = Dechlorane Plus: Candidate POP in Stockholm Convention | url = https://toxicslink.org/publications/factsheet/factsheets-dechlorane-plus | publisher = Toxics Link | date = July 2022 | access-date = 2025-01-27}}.</ref>
* [[Dicofol]] is a pesticide structurally similar to [[DDT]] and is highly toxic to fish, birds, aquatic invertebrates, and algae. Prolonged exposure in humans causes skin irritation.<ref>{{citation | title = Dicofol factsheet | url = https://www.pops.int/Portals/0/download.aspx?d=UNEP-POPS-NewPOPs-Factsheet-06-20200316.English.pdf | publisher = Secretariat of the Stockholm Convention | access-date = 2025-01-27}}.</ref>
* [[Hexabromodiphenyl]] is a flame retardant and possible human carcinogen.  Like the related chemicals hexaBDE, heptaBDE, and octaBDE (see below), hexabromodiphenyl is an endocrine disruptor.  <ref>{{Cite journal |last1=Kumari |first1=K. |last2=Arfin |first2=T. |date=2024 |title=Hexabromobiphenyl (HBB). |url=https://doi.org/10.1007/978-3-031-50996-4_14 |journal=Pollutants of Global Concern. Emerging Contaminants and Associated Treatment Technologies. |language=en |doi=10.1007/978-3-031-50996-4_14|url-access=subscription }}</ref>
* [[Hexabromocyclododecane]] is a flame retardant predominately used in foams and textiles that is highly toxic to aquatic organisms.  Human toxicology studies are ongoing, but it shows neuroendocrine disruption and developmental toxicity in animal studies.<ref>{{citation | title = Hexabromocyclododecane factsheet | url = https://www.pops.int/Portals/0/download.aspx?d=UNEP-POPS-NewPOPs-Factsheet-08-20200226.English.pdf | publisher = Secretariat of the Stockholm Convention | access-date = 2025-01-27}}.</ref>
* [[Hexabromodiphenyl ether]] (hexaBDE) and [[heptabromodiphenyl ether]] (heptaBDE) are main components of the flame retardant [[octabromodiphenyl ether]] (octaBDE). Commercial octaBDE is highly persistent in the environment, whose only degradation pathway is through debromination and the production of [[Bromodiphenylmethane|bromodiphenyl ethers]], which themselves can be toxic.<ref>{{citation | title = Hexabromobiphenyl ether and heptabromodiphenyl ether factsheet | url = https://www.pops.int/Portals/0/download.aspx?d=UNEP-POPS-NewPOPs-Factsheet-09-20200226.English.pdf | publisher = Secretariat of the Stockholm Convention | access-date = 2025-01-27}}.</ref>
* [[Hexachlorobutadiene]] (HCBD) is a byproduct of the production of other chlorinated compounds.  HCBD is a possible human carcinogen and causes renal damage.<ref>{{citation | title = Hexachlorobutadiene factsheet | url = https://www.pops.int/Portals/0/download.aspx?d=UNEP-POPS-NewPOPs-Factsheet-10-20200226.English.pdf | publisher = Secretariat of the Stockholm Convention | access-date = 2025-01-27}}.</ref>
* [[Lindane]] (γ-hexachlorocyclohexane), a pesticide used as a broad spectrum insecticide for seed, soil, leaf, tree and wood treatment, and against [[ectoparasite]]s in animals and humans (head lice and scabies). Lindane undergoes rapid [[biomagnification]] and is [[Immunotoxin|immunotoxic]], [[Neurotoxicity|neurotoxic]], [[carcinogenic]], linked to liver and kidney damage as well as adverse reproductive and developmental effects in various laboratory animals. Production of lindane unintentionally produces two other POPs α-HCH and β-HCH.<ref>{{Cite journal |last1=Vijgen |first1=John |last2=de Borst |first2=Bram |last3=Weber |first3=Roland |last4=Stobiecki |first4=Tomasz |last5=Forter |first5=Martin |date=2019 |title=HCH and lindane contaminated sites: European and global need for a permanent solution for a long-time neglected issue |journal=Environmental Pollution |language=en |volume=248 |pages=696–705 |doi=10.1016/j.envpol.2019.02.029|pmid=30849587 |bibcode=2019EPoll.248..696V }}</ref>
* [[Methoxychlor]] is a pesticide structurally similar to DDT.  In addition to persistence, ecological mobility, and bioaccumulation risk, it also is a human endocrine disruptor.<ref>{{citation | title = Methoxychlor factsheet | url = https://www.pops.int/Portals/0/download.aspx?d=UNEP-POPS-NewPOPs-Factsheet-19-20240726.English.pdf | publisher = Secretariat of the Stockholm Convention | access-date = 2025-01-27}}.</ref>
* [[Pentachlorobenzene]] (PeCB), is a pesticide and unintentional byproduct. PeCB has also been used in PCB products, dyestuff carriers, as a fungicide, a flame retardant, and a chemical intermediate. This compound is moderately toxic to humans, whilst being highly toxic to aquatic organisms. <ref>{{citation | title = Pentachlorobenzene factsheet | url = https://www.pops.int/Portals/0/download.aspx?d=UNEP-POPS-NewPOPs-Factsheet-11-20200226.English.pdf | publisher = Secretariat of the Stockholm Convention | access-date = 2025-01-27}}.</ref>
* [[Perfluorooctanesulfonic acid]] (PFOS) and related compounds are extremely persistent and readily [[Biomagnification|biomagnify]].  
* [[Endosulfan]]s are a group of chlorinated insecticides used to control pests on crops such coffee, cotton, rice and sorghum and soybeans, tsetse flies, ectoparasites of cattle. They are used as a [[Wood preservation|wood preservative]]. Global use and manufacturing of endosulfan has been banned under the Stockholm convention in 2011, although many countries had previously banned or introduced phase-outs of the chemical when the ban was announced. Toxic to humans and aquatic and terrestrial organisms, linked to congenital physical disorders, mental retardation, and death. Endosulfans' negative health effects are primarily liked to its endocrine disrupting capacity acting as an [[antiandrogen]].
* [[Tetrabromodiphenyl ether]] (tetraBDE) and pentabromodiphenyl ether (pentaBDE) are industrial chemicals and the main components of commercial pentabromodiphenyl ether (pentaBDE). This pair of molecules have been detected in humans in all regions of the world.

== Health effects ==
{{See also|Health effects of pesticides}}
POP exposure may cause developmental defects, chronic illnesses, and death. Some are carcinogens per [[International Agency for Research on Cancer|IARC]], possibly including [[breast cancer]].<ref name="ritter"/> Many POPs are capable of [[endocrine disruption]] within the [[reproductive system]], the [[central nervous system]], or the [[immune system]].<ref>{{Cite journal |last1=Cheek |first1=A O |last2=Vonier |first2=P M |last3=Oberdörster |first3=E |last4=Burow |first4=B C |last5=McLachlan |first5=J A |date=1998-02-01 |title=Environmental signaling: a biological context for endocrine disruption. |journal=Environmental Health Perspectives |language=en |volume=106 |issue=suppl 1 |pages=5–10 |doi=10.1289/ehp.106-1533276 |issn=0091-6765 |pmc=1533276 |pmid=9539003|bibcode=1998EnvHP.106S...5C }}</ref> People and animals are exposed to POPs mostly through their diet, occupationally, or while growing in the womb.<ref name="ritter"/>  For humans not exposed to POPs through accidental or occupational means, over 90% of exposure comes from animal product foods due to bioaccumulation in fat tissues and bioaccumulate through the food chain. In general, POP serum levels increase with age and tend to be higher in females than males.<ref name="Vallack, H.W. 1998"/>

Studies have investigated the correlation between low level exposure of POPs and various diseases. In order to assess disease risk due to POPs in a particular location, government agencies may produce a [[human health risk assessment]] which takes into account the pollutants' [[bioavailability]] and their [[dose-response relationship]]s.<ref>{{cite book |vauthors=Szabo DT, Loccisano AE |title= Dioxins and Health: Including Other Persistent Organic Pollutants and Endocrine Disruptors|chapter=POPs and Human Health Risk Assessment |volume=3rd |pages=579–618|editor-last=Schecter |editor-first=A. |publisher=John Wiley & Sons |date=March 30, 2012| doi=10.1002/9781118184141.ch19 |isbn=9781118184141}}</ref>

=== Endocrine disruption ===
The majority of POPs are known to disrupt normal functioning of the endocrine system. Low level exposure to POPs during critical [[developmental biology|developmental]] periods of fetus, newborn and child can have a lasting effect throughout their lifespan. A 2002 study<ref name="Damstra, T. 2002">{{cite journal | author = Damstra T | year = 2002 | title = Potential Effects of Certain Persistent Organic Pollutants and Endocrine Disrupting Chemicals on Health of Children | journal = Clinical Toxicology | volume = 40 | issue = 4| pages = 457–465 | doi = 10.1081/clt-120006748 | pmid = 12216998 | s2cid = 23550634 }}</ref> summarizes data on endocrine disruption and health complications from exposure to POPs during critical developmental stages in an organism's lifespan. The study aimed to answer the question whether or not chronic, low level exposure to POPs can have a health impact on the endocrine system and development of organisms from different species. The study found that exposure of POPs during a critical developmental time frame can produce a permanent changes in the organisms path of development. Exposure of POPs during non-critical developmental time frames may not lead to detectable diseases and health complications later in their life. In wildlife, the critical development time frames are [[Uterus|in utero]], [[in ovo]], and during reproductive periods. In humans, the critical development timeframe is during [[prenatal development|fetal development]].<ref name="Damstra, T. 2002"/>

=== Reproductive system ===
The same study in 2002<ref name="Damstra, T. 2002"/> with evidence of a link from POPs to [[endocrine disruptor|endocrine disruption]] also linked low dose exposure of POPs to [[reproductive health]] effects. The study stated that POP exposure can lead to negative health effects especially in the [[human male reproductive system|male reproductive system]], such as decreased [[sperm]] quality and quantity, altered sex ratio and early [[puberty]] onset. For females exposed to POPs, altered [[human female reproductive system|reproductive tissues]] and [[pregnancy]] outcomes as well as [[endometriosis]] have been reported.<ref name="El-Shahawi, M.S. 2010"/>

====Gestational weight gain and newborn head circumference====
A Greek study from 2014 investigated the link between maternal weight gain during pregnancy, their [[polychlorinated biphenyl|PCB]]-exposure level and PCB level in their newborn infants, their [[birth weight]], [[Gestational age (obstetrics)|gestational age]], and head circumference. The lower the birth weight and head circumference of the infants was, the higher POP levels during [[prenatal development]] had been, but only if mothers had either excessive or inadequate weight gain during pregnancy. No correlation between POP exposure and gestational age was found.<ref>{{cite journal|last=Vafeiadi|first=M|author2=Vrijheid M |author3=Fthenou E |author4=Chalkiadaki G |author5=Rantakokko P |author6=Kiviranta H |author7=Kyrtopoulos SA |author8=Chatzi L |author9=Kogevinas M  |title=Persistent organic pollutants exposure during pregnancy, maternal gestational weight gain, and birth outcomes in the mother-child cohort in Crete, Greece (RHEA study)|journal=Environ. Int.|year=2014|volume=64|pages=116–123|doi=10.1016/j.envint.2013.12.015|pmid=24389008|doi-access=free|bibcode=2014EnInt..64..116V}}</ref>
A 2013 [[case-control study]] conducted 2009 in Indian mothers and their offspring showed prenatal exposure of two types of [[organochlorine pesticides]] ([[Hexachlorocyclohexane|HCH]], [[DDT]] and [[Dichlorodiphenyldichloroethylene|DDE]]) impaired the growth of the [[fetus]], reduced the birth weight, length, head circumference and chest circumference.<ref>{{cite journal|last=Dewan|first=Jain V|author2=Gupta P |author3=Banerjee BD. |title=Organochlorine pesticide residues in maternal blood, cord blood, placenta, and breastmilk and their relation to birth size|journal=Chemosphere|date=February 2013|volume=90|issue=5|pages=1704–1710|doi= 10.1016/j.chemosphere.2012.09.083|pmid=23141556|bibcode=2013Chmsp..90.1704D}}</ref><ref>{{cite journal | author = Damstra T | year = 2002 | title = Potential Effects of Certain Persistent Organic Pollutants and Endocrine Disrupting Chemicals on Health of Children | journal = Clinical Toxicology | volume = 40 | issue = 4| pages = 457–465 | pmid = 12216998 | doi = 10.1081/clt-120006748 | s2cid = 23550634 }}</ref>

=== Health effects of PFAS ===
{{See also|Regulation of chemicals#Issues}}
{{Excerpt|Per- and polyfluoroalkyl substances|Health and environmental effects|paragraphs=-1}}

=== Additive and synergistic effects ===
Evaluation of the effects of POPs on health is very challenging in the laboratory setting. For example, for organisms exposed to a mixture of POPs, the effects are assumed to be [[Additive effect|additive]].<ref name="Harrad, S. 2010">ed. Harrad, S., "Persistent Organic Pollutants" (2010).</ref> Mixtures of POPs can in principle produce [[Synergy#Toxicological synergy|synergistic effects]]. With synergistic effects, the toxicity of each compound is enhanced (or depressed) by the presence of other compounds in the mixture. When put together, the effects can far exceed the approximated additive effects of the POP compound mixture.<ref name="Walker, C.H. 2001"/>

== In urban areas and indoor environments ==
Traditionally it was thought that human exposure to POPs occurred primarily through [[food]], however [[Indoor air quality|indoor pollution]] patterns that characterize certain POPs have challenged this notion. Recent studies of indoor [[dust]] and [[Atmosphere of Earth|air]] have implicated indoor environments as a major sources for human exposure via inhalation and ingestion.<ref>Walker, C.H., "Organic Pollutants: An Ecotoxicological Perspective" (2001)</ref> Furthermore, significant indoor POP pollution must be a major route of human POP exposure, considering the modern trend in spending larger proportions of life indoors. Several studies have shown that indoor (air and dust) POP levels to exceed outdoor (air and soil) POP concentrations.<ref name="Harrad, S. 2010"/>

== In rainwater ==
{{Excerpt|Per- and polyfluoroalkyl substances|Prevalence in rain, soil, water bodies, and air}}

== Control and removal in the environment ==
Current studies aimed at minimizing POPs in the environment are investigating their behavior in [[photocatalysis|photocatalytic oxidation reactions]].<ref>{{Cite journal |last1=Bertucci |first1=Simone |last2=Lova |first2=Paola |date=May 2024 |title=Exploring Solar Energy Solutions for Per- and Polyfluoroalkyl Substances Degradation: Advancements and Future Directions in Photocatalytic Processes |journal=Solar RRL |language=en |volume=8 |issue=9 |doi=10.1002/solr.202400116 |issn=2367-198X|doi-access=free }}</ref>  POPs that are found in humans and in [[aquatic ecosystem|aquatic environments]] the most are the main subjects of these experiments. [[aromatic compound|Aromatic]] and [[aliphatic compound|aliphatic]] degradation products have been identified in these reactions. [[photocatalysis|Photochemical degradation]] is negligible compared to photocatalytic degradation.<ref name="El-Shahawi, M.S. 2010"/> A method of removal of POPs from marine environments that has been explored is adsorption. It occurs when an absorbable solute comes into contact with a solid with a porous surface structure. This technique was investigated by Mohamed Nageeb Rashed of Aswan University, Egypt.<ref>Rashed, M.N. ''Organic pollutants - Monitoring, risk and treatment''. Intech. London (2013). Chapter 7 - Adsorption techniques for the removal of persistent organic pollutants from water and wastewater.</ref> Current efforts are more focused on banning the use and production of POPs worldwide rather than removal of POPs.<ref name="Vallack, H.W. 1998"/>

== See also ==
* [[Aarhus Protocol on Persistent Organic Pollutants]]
* [[Center for International Environmental Law]] (CIEL)
* [[International POPs Elimination Network]] (IPEN)
* ''[[Silent Spring]]''
* [[Environmental Persistent Pharmaceutical Pollutant]] (EPPP)
* [[Persistent, bioaccumulative and toxic substances]] (PBT)
* [[Tetraethyllead]]
* [[Triclocarban]]
* [[Triclosan]]

==References==
{{reflist|30em}}

== External links ==
* [https://apps.who.int/iris/bitstream/handle/10665/44525/9789241501101_eng.pdf?sequence=1 World Health Organization Persistent Organic Pollutants: Impact on Child Health]
* [http://www.pops.int/ Pops.int], Stockholm Convention on Persistent Organic Pollutants
* [http://www.indiaenvironmentportal.org.in/taxonomy/term/18 Resources on Persistent Organic Pollutants (POPs)]
* [https://web.archive.org/web/20070927205609/http://www.monarpop.at/ Monarpop.at], POP monitoring in the Alpine region (Europe)

{{HealthIssuesOfPlastics}}
{{pesticides}}
{{Pollution}}

{{Authority control}}

{{DEFAULTSORT:Persistent Organic Pollutant}}
[[Category:Biodegradable waste management]]
[[Category:Ecotoxicology]]
[[Category:Environmental effects of pesticides]]
[[Category:Persistent organic pollutants]]
[[Category:Pollutants]]
[[Category:Pollution]]