Editing Methylmercury (section)

===Dietary sources===
Because methylmercury is formed in aquatic systems, and because it is not readily eliminated from organisms, it is [[biomagnification|biomagnified]] in aquatic [[food chain]]s from [[bacteria]], to [[plankton]], through [[macroinvertebrate]]s, to [[herbivorous]] [[fish]] and to [[piscivorous]] (fish-eating) fish.<ref name="wiener">reviewed in Wiener, J.G., Krabbenhoft, D.P., Heinz, G.H., and Scheuhammer, A.M., 2003, "Ecotoxicology of mercury", Chapter 16 ''in'' Hoffman, D.J., B.A. Rattner, G.A. Burton, Jr., and J. Cairns, Jr., eds., ''Handbook of Ecotoxicology'', 2nd edition.: Boca Raton, FL: CRC Press, p. 409–463.</ref><ref name=":1">{{cite journal |last1=Lavoie |first1=Raphael A. |last2=Jardine |first2=Timothy D. |last3=Chumchal |first3=Matthew M. |last4=Kidd |first4=Karen A. |last5=Campbell |first5=Linda M. |title=Biomagnification of Mercury in Aquatic Food Webs: A Worldwide Meta-Analysis |journal=Environmental Science & Technology |volume=47 |issue=23 |pages=13385–13394 |date=2013-11-13 |pmid=24151937 |issn=0013-936X |bibcode=2013EnST...4713385L |doi=10.1021/es403103t}}</ref> At each step in the food chain, the [[concentration]] of methylmercury in the organism increases. The concentration of methylmercury in the top-level aquatic [[predator]]s can reach a level a million times higher than the level in the water.<ref name="wiener" /><ref name=":1" /> This is because methylmercury has a half-life of about 72 days in aquatic organisms resulting in its [[bioaccumulation]] within these food chains. Organisms, including humans,<ref>{{cite news |last=Burros |first=Marian |title=High Mercury Levels Are Found in Tuna Sushi |url=https://www.nytimes.com/2008/01/23/dining/23sushi.html |newspaper=The New York Times |date=2008-01-23}}</ref> fish-eating birds, and fish-eating mammals such as [[otter]]s and [[cetacean]]s (i.e. [[whale]]s and [[dolphin]]s) that consume fish from the top of the aquatic food chain receive the methylmercury that has accumulated through this process, plus the toxins in their habitat.<ref name="wiener" /><ref name=":1" /> Fish and other aquatic [[species]] are the main source of human methylmercury exposure.<ref name="wiener" />

The concentration of mercury in any given fish depends on the species of fish, the age and size of the fish and the type of water body in which it is found.<ref name="wiener" /> In general, fish-eating fish such as [[shark]], [[swordfish]], [[marlin]], larger species of [[tuna]], [[walleye]], [[largemouth bass]], and [[northern pike]], have higher levels of methylmercury than herbivorous fish or smaller fish such as [[tilapia]] and [[herring]].<ref>[http://www.cfsan.fda.gov/~frf/sea-mehg.html Mercury Levels in Commercial Fish and Shellfish] {{webarchive |url=https://web.archive.org/web/20060110235714/http://www.cfsan.fda.gov/~frf/sea-mehg.html |date=2006-01-10}} Accessed March 25, 2009.</ref><ref>[http://www.epa.gov/waterscience/fish/advice/ What You Need to Know about Mercury in Fish and Shellfish] Accessed March 25, 2009.</ref> Within a given species of fish, older and larger fish have higher levels of methylmercury than smaller fish. Fish that develop in water bodies that are more [[acid]]ic also tend to have higher levels of methylmercury.<ref name="wiener" />