Mercury compounds

Mercury, a metallic element, is a silvery liquid that vaporizes when heated into a highly toxic, odorless gas. Mercury compounds once common in pesticides and industrial processes are also toxic, causing damage to the brain and nervous system, immune system, enzyme system and genetic system.

The organic compound methylmercury, an environmental contaminant that accumulates in some fish and fish-eating wildlife, is particularly devastating to developing fetuses. The international movement to curb industrial pollution was galvanized by photojournalist W. Eugene Smith’s iconic 1971 photograph of a Japanese mother bathing her blind, deformed daughter, a casualty of a chemical company’s mercury dumping into Minamata Bay. The Minamata catastrophe devastated thousands of lives and forced the U.S., Japan and other nations to confront the mercury pollution problem. U.S. regulators barred the last of the mercury-laden pesticides in 1995. Other industrial uses remain: between 2004 and 2007, according to the U.S. Geological Survey, American industry imported more than 1 million tons of mercury.

In 1997 the Environmental Working Group’s analysis, Contamination of America's Food, concluded that fish from more than 1,660 U.S. waterways were so contaminated with mercury that they should be eaten sparingly or not at all. Soon after, the EPA confirmed that more than 1.6 million women and children could face serious health risks from mercury-contaminated food. But it took two more years for the EPA and the U.S. Food and Drug Administration to issue warnings to women to limit fish consumption during pregnancy to 12 ounces a week. The FDA failed to caution against excessive consumption of tuna. EWG challenged the agency’s advice as vague and misleading -- and unearthed internal FDA transcripts in which agency officials opined that canned tuna contained enough mercury to harm the developing brain of a baby in the womb.

In January 2004, after the FDA had repeatedly failed to give consumers clear, science-based data, EWG released an interactive Tuna Calculator to help people figure their own safe doses of tuna, based on weight. It advised women of child-bearing age and children under 5 not eat albacore tuna at all.

The mercury threat persists. In July 2005, EWG reported finding mercury in the cord blood of 10 newborn babies. These findings were echoed by EWG's Human Toxome Project, initiated in late 2006, that found methylmercury in 72 of the 73 people tested.