Editing Selenium (section)

==Pollution==
Selenium pollution might impact some aquatic systems and may be caused by anthropogenic factors such as farming runoff and industrial processes.<ref>{{cite journal|last=Lemly|first=A. Dennis|date=2004-09-01|title=Aquatic selenium pollution is a global environmental safety issue|url=http://www.sciencedirect.com/science/article/pii/S0147651303000952|journal=Ecotoxicology and Environmental Safety|language=en|volume=59|issue=1|pages=44–56|doi=10.1016/S0147-6513(03)00095-2|pmid=15261722|bibcode=2004EcoES..59...44L |issn=0147-6513}}</ref> People who eat more fish are generally healthier than those who eat less,<ref>{{cite journal|last1=Estruch |first1=Ramon |last2=Sacanella |first2=Emilio |last3=Ros |first3=Emilio |date=4 January 2021 |title=Should we all go pesco-vegetarian? |journal=European Heart Journal |volume=42|issue=12 |pages=1144–1146 |doi=10.1093/eurheartj/ehaa1088|pmid=33393612|issn=0195-668X|doi-access=free}}</ref> which suggests no major human health concern from selenium pollution, although selenium has a potential effect on humans.<ref>{{cite journal|last1=Gribble |first1=Matthew| last2=Karimi |first2=Roxanne |last3=Feingold |first3=Beth |last4=Nyland |first4=Jennifer |last5=O'Hara |first5=Todd |last6=Gladyshev |first6=Michail |last7=Chen |first7=Celia | date=September 8, 2015 | title=Mercury, selenium and fish oils in marine food webs and implications for human health |quote=at higher doses, selenium might be toxic to a range of animals including humans |journal=Journal of the Marine Biological Association of the United Kingdom |volume=1 |issue=96 |pages=43–59 |doi=10.1017/S0025315415001356 |pmid=26834292 |pmc=4720108}}</ref>

Selenium poisoning of water systems may result whenever new [[Agricultural pollution|agricultural run-off]] courses through dry lands. This process leaches natural soluble selenium compounds (such as selenates) into the water, which may then be concentrated in wetlands as the water evaporates. Selenium pollution of waterways also occurs when selenium is leached from coal flue ash, mining and [[metal smelting]], crude oil processing, and landfill.<ref>{{cite journal |last=Lemly |first=D. |date=2004 |title=Aquatic selenium pollution is a global environmental safety issue |url=https://zenodo.org/record/1259837 |journal=Ecotoxicology and Environmental Safety |volume=59 |issue=1 |pages=44–56 |bibcode=2004EcoES..59...44L |doi=10.1016/S0147-6513(03)00095-2 |pmid=15261722}}</ref> High selenium levels in waterways were found to cause congenital disorders in oviparous species, including wetland birds<ref>{{cite book |last=Ohlendorf |first=H. M. |url=https://books.google.com/books?id=qN0I3husm50C&pg=PA477 |title=Ecotoxicology of selenium |date=2003 |publisher=Lewis Publishers |isbn=978-1-56670-546-2 |series=Handbook of ecotoxicology |location=Boca Raton |pages=466–491}}</ref> and fish.<ref>{{cite journal |last=Lemly |first=A. D. |date=1997 |title=A teratogenic deformity index for evaluating impacts of selenium on fish populations |url=https://zenodo.org/record/1229572 |journal=Ecotoxicology and Environmental Safety |volume=37 |issue=3 |pages=259–266 |bibcode=1997EcoES..37..259L |doi=10.1006/eesa.1997.1554 |pmid=9378093}}</ref> Elevated dietary [[methylmercury]] levels can amplify the harm of selenium toxicity in oviparous species.<ref>{{cite journal |last1=Penglase |first1=S. |last2=Hamre |first2=K. |last3=Ellingsen |first3=S. |date=2014 |title=Selenium and mercury have a synergistic negative effect on fish reproduction |journal=Aquatic Toxicology |volume=149 |pages=16–24 |bibcode=2014AqTox.149...16P |doi=10.1016/j.aquatox.2014.01.020 |pmid=24555955}}</ref><ref>{{cite journal |last1=Heinz |first1=G. H. |last2=Hoffman |first2=D. J. |date=1998 |title=Methylmercury chloride and selenomethionine interactions on health and reproduction in mallards |journal=Environmental Toxicology and Chemistry |volume=17 |issue=2 |pages=139–145 |doi=10.1002/etc.5620170202 |bibcode=1998EnvTC..17..139H |s2cid=95466655}}</ref>

Selenium is [[bioaccumulation|bioaccumulated]] in aquatic habitats, which results in higher concentrations in organisms than the surrounding water. Organoselenium compounds can be concentrated over 200,000 times by [[zooplankton]] when water concentrations are in the 0.5 to 0.8&nbsp;μg Se/L range. Inorganic selenium bioaccumulates more readily in [[phytoplankton]] than zooplankton. Phytoplankton can concentrate inorganic selenium by a factor of 3000. Further concentration through bioaccumulation occurs along the food chain, as predators consume selenium-rich prey. It is recommended that a water concentration of 2&nbsp;μg Se/L be considered highly hazardous to sensitive fish and [[Water bird|aquatic birds]]. Selenium poisoning can be passed from parents to offspring through the egg, and selenium poisoning may persist for many generations. Reproduction of mallard ducks is impaired at dietary concentrations of 7&nbsp;μg Se/L. Many [[Benthic zone|benthic]] invertebrates can tolerate selenium concentrations up to 300&nbsp;μg/L of selenium in their diet.<ref>{{cite book| last = Lemly| first = Dennis| title = Selenium Assessment in Aquatic Ecosystems: A guide for hazard evaluation and water quality criteria| publisher = Springer| year = 1998| url = https://books.google.com/books?id=qGH37iOW7yMC&q=Selenium+Assessment+in+Aquatic+Ecosystems| isbn = 0-387-95346-9}}</ref>

Bioaccumulation of selenium in aquatic environments causes fish kills depending on the species in the affected area. There are, however, a few species that have been seen to survive these events and tolerate the increased selenium. It has also been suggested that the season could have an impact on the harmful effects of selenium on fish.<ref name="Hamilton 1–31">{{Cite journal|last=Hamilton|first=Steven J.|date=2004-06-29|title=Review of selenium toxicity in the aquatic food chain|url=http://www.sciencedirect.com/science/article/pii/S0048969704000609|journal=Science of the Total Environment|language=en|volume=326|issue=1|pages=1–31|doi=10.1016/j.scitotenv.2004.01.019|pmid=15142762|bibcode=2004ScTEn.326....1H|issn=0048-9697}}</ref> Substantial physiological changes may occur in fish with high tissue concentrations of selenium. Fish affected by selenium may experience swelling of the [[gill lamellae]], which impedes oxygen diffusion across the gills and blood flow within the gills. Respiratory capacity is further reduced due to selenium binding to [[hemoglobin]]. Other problems include degeneration of liver tissue, swelling around the heart, damaged egg follicles in ovaries, [[cataract]]s, and accumulation of fluid in the body cavity and head. Selenium often causes a malformed fish fetus which may have problems feeding or respiring; distortion of the fins or spine is also common. Adult fish may appear healthy despite their inability to produce viable offspring.{{Citation needed|date=June 2024}}

===Examples===
In [[Belews Lake]] North Carolina, 19 species of fish were eliminated from the lake due to 150–200&nbsp;μg Se/L wastewater discharged from 1974 to 1986 from a [[Duke Energy]] coal-fired power plant.<ref>{{Cite journal |last=Lemly |first=A.Dennis |date=2002–2004 |title=Symptoms and implications of selenium toxicity in fish: the Belews Lake case example |url=http://dx.doi.org/10.1016/s0166-445x(01)00264-8 |journal=Aquatic Toxicology |volume=57 |issue=1–2 |pages=39–49 |doi=10.1016/s0166-445x(01)00264-8 |pmid=11879937 |bibcode=2002AqTox..57...39L |issn=0166-445X}}</ref> At the [[Kesterson National Wildlife Refuge]] in California, thousands of fish and waterbirds were poisoned by selenium in agricultural irrigation drainage.{{Citation needed|date=June 2024}}