“[T]he Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) are advising women who may become pregnant, pregnant women, nursing mothers, and young children to avoid . . . eat[ing] Shark, Swordfish, King Mackerel, or Tilefish because they contain high levels of mercury.”

http://www.epa.gov/waterscience/fish/advice/

Basically, feeding the hungry means feeding them meat that’s high in mercury. Methylmercury is an organic form of mercury that behaves as a bioaccumulative environmental toxicant. Methylmercury is highly toxic, since it is easily absorbed, and it is considered a neurotoxin. Methylmercury undergoes biomagnification along the food chain. As a result, seafood consumption is the main way methylmercury is taken up by humans.

From http://www.metapress.com/content/m110264028861m60/

The concentrations of methylmercury (MeHg) in 124 samples of muscle taken from nine species of common sharks of varying sizes and locations along the Florida coast were determined. Muscle MeHg levels averaged 0.88 µg/g (wet sample basis) and ranged from 0.06 to 2.87 µg/g, with 33.1% of the samples exceeding the U.S. Food and Drug Administration’s 1 µg/g action level. Differences were found in MeHg concentration by species but not by sex. A positive correlation between MeHg levels and shark size was found such that most sharks larger than approximately 200 cm total length contained MeHg concentrations exceeding the 1 µg/g action level. Fetal sharks contained consistently lower MeHg levels than their mothers. Sharks collected off southern regions of the state contained significantly higher MeHg concentrations than those off the northeast coast. The human health concerns for consumers of Florida shark meat are discussed in relation to these findings.

Notes, resources and references:

Mercury in Aquatic Ecosystems, http://toxics.usgs.gov/investigations/mercury.html (last visited on May 26, 2009).

Methylmercury Poisoning, http://organizedwisdom.com/Methylmercury_Poisoning (last visited on May 26, 2009).

Definition of Methylmercury, http://www.medterms.com/script/main/art.asp?articlekey=31628 (last visited on May 26, 2009).

Methylmercury Contamination in Fish and Shellfish, http://www.csa.com/discoveryguides/mercury/review.pdf (last visited on May 26, 2009).

Human Health, http://www.epa.gov/hg/health.htm (last visited on May 26, 2009).

Impacts of Metals on Aquatic Ecosystems and Human Health, http://www.infomine.com/publications/docs/Mining.com/Apr2008c.pdf (last visited on May 26, 2009).

Glossary, http://www.scienzagiovane.unibo.it/english/pollution/glossary-pollution.html (last visited on May 26, 2009).