Exposure to Methylmercury: Emerging Demographic and Geographic Patterns

Methylmercury exposures among humans are closely linked to consumption of fish and marine mammals. Because methylmercury is bioconcentrated in higher trophic levels of the pelagic food chain, human body burden of methylmercury reflects economic and cultural differences associated with dietary patterns. In contrast to other contaminants, methylmercury exposures are higher among more affluent individuals and populations. Cultures that traditionally favor fish consumption (e.g., those of island and Asian origin) have higher methylmercury exposures as shown by blood mercury concentrations. Unexpected areas recently identified as having higher mercury exposures include the Pacific Islands of Tahiti and Fiji and the Atlantic Ocean island of Bermuda. Within the United States coastal areas have higher mercury exposures than inland regions. Blood mercury data in the United States gathered in various states reporting programs are showing higher methylmercury exposures than estimated from the National Health and Nutrition Examination Survey. Current health-based recommendations by government agencies focus on protecting the developing fetal nervous system. Emerging data identify neurological and endocrine consequences of methylmercury exposures to adults resulting in concerns for adults' health in addition to fetal development.