Mercury is a persistent and naturally occurring metal that has provoked substantial concern because methyl mercury (an organic form) accumulates in fish and can cause subtle neurological deficiencies in children who have been exposed to it in the womb.
Accordingly, the U.S. Food and Drug Administration is under pressure to reduce its permissible level of mercury in fish sold in the United States.3 To address concern about mercury, several senators and President George W. Bush have proposed new legislation to cut emissions of pollutants from power plants, which are the biggest anthropogenic source of mercury in the United States.
However, these different parties disagree about how mercury should be regulated. The controversy is likely to grow through December 2004, which is the deadline for the U.S. Environmental Protection Agency (EPA) to regulate emissions following the maximum achievable control technology (MACT) provisions of the Clean Air Act. This proposed regulation has faced some opposition because it is relatively costly.
In general, established U.S. regulatory policy suggests that regulatory decisions to manage risks should carefully assess the costs of controls and the resulting improvements to human health and the environment. However, attempts to implement this policy in the case of mercury are complicated by significant scientific uncertainty about the role of natural and anthropogenic sources of environmental mercury, how mercury is transported through the environment and where it eventually rests, the processes that produce methylmercury, the effects of methylmercury on ecosystems, and the nature and scope of mercury-related risks to human health.