Does Methylmercury Have a Role in Developmental Disabilities in Children?

Purpose:

These scientists review the data available in 2000 that associates methylmercury exposure with bad effects on human development. They also list some of the unanswered questions in methylmercury research.

Bottom Line:

These two scientists believe in 2000 that methylmercury exposure does not have a role in developmental disabilities in children.

Important issues that these two scientist believe need resolving:

• How should methylmercury levels be measured?
• Do short periods of exposure to high methylmercury levels (peak methylmercury exposures) or does the average exposure to methylmercury levels (over time) more accurately indicate human brain methylmercury exposure?
• Should the thing that scientists look for in recent high-level and chronic methylmercury exposures be different?
• Do dietary exposure top-of-the-low doses of methylmercury differ from high methylmercury dose exposure?
• What is the importance of methylmercury exposures at different ages?
• How should scientific studies deal with simultaneous methylmercury exposures?
• Are animal and human methylmercury exposures comparable?
• How important is effect modification?
• How should child development be evaluated?
• What are the problems in conducting statistical analyses?

Abstract:

Methylmercury (MeHg) is a potent neurotoxin that in high exposures can cause mental retardation, cerebral palsy, and seizures. The developing brain appears particularly sensitive to MeHg. Exposure levels in pregnant experimental animals that do not result in detectable signs or symptoms in the mother can adversely affect the offspring's development. Studies of human poisonings suggest this may also occur in humans. Human exposure to MeHg is primarily dietary through the consumption of fish: MeHg is present in all fresh and saltwater fish. Populations that depend on fish as a major source of dietary protein may achieve MeHg exposure levels hypothesized to adversely affect brain development. Increasing mercury levels in the environment have heightened concerns about dietary exposure and a possible role for MeHg in developmental disabilities. Follow-up studies of an outbreak of MeHg poisoning in Iraq revealed a dose-response relationship for prenatal MeHg exposure. That relationship suggested that prenatal exposure as low as 10 ppm (measured in maternal hair growing during pregnancy) could adversely affect fetal brain development. However, using the same end points as were used in the Iraq study, no associations have been reported in fish-eating populations. Using a more extensive range of developmental end points, some studies of populations consuming seafood have reported associations with prenatal MeHg exposure, whereas others have found none. This paper reviews the data presently available associating MeHg exposure with development and poses some of the unanswered questions in this field.

Find This Paper for Your Review:

Does methylmercury Have a Role in Developmental Disabilities in Children? Environmental Health Perspectives Supplements Vol. 108, No. S3. pp. 413-420. 2000.