An Assessment of the Cord Blood: Maternal Blood Methylmercury Ratio: Implications for Risk Assessment

The Scientific Paper:

Alan H. Stern and Andrew E. Smith. Environmental Health Perspectives (EHP). Vol. 111, No.12. pp 1465- 1470. 2003.

Review This Scientific Paper’s Abstract:
http://ehp.niehs.nih.gov/members/2004/7417/7417.html

The Purpose of this Study:
These scientists conducted a statistical review to look again at the then current 2003 Environmental Protection Agency (EPA) methylmercury reference dose in seafood. These scientists also revisited areas of uncertainty in how the EPA did its calculations in reaching their methylmercury reference dose.

Some Background, Methods, Results, Caveats, and Other Select Points:

• This peer-reviewed, scientific paper was published in 2003.
• This scientific paper is primarily a discussion of statistics.
• These scientists report that the ratio of methylmercury or methylmercury-derived mercury in umbilical cord blood compared to the mother’s blood at the time of her infant’s birth is greater than the value used in EPA methylmercury assessments.
• Although methylmercury from fish consumption is the largest source of mercury in the blood of mothers and infants, their blood also contains inorganic mercury from iron in the diet and from certain types of dental fillings in the mother’s teeth. Because different mothers have different numbers of certain types of dental fillings, the effect of the mercury from these certain types of dental fillings on the umbilical cord blood / maternal blood ratio is unknown.
• These scientists believe that the statistics used by the EPA regarding dose levels contain two areas of significant uncertainty: 1) the dose level does not directly account for the positive influence of the ratio of umbilical cord blood to maternal blood mercury concentrations; and 2) it does not resolve uncertainty regarding the most likely mercury estimates for pregnancy and third trimester-specific likely mercury estimates.
• When calculating their revised methylmercury reference dose (RfD), the EPA used certain statistics to convert fetal umbilical cord blood mercury levels to an estimated amount of mercury the mother ate. These scientists looked at other scientific studies with data on the umbilical cord blood / maternal blood mercury ratio. They also reviewed 10 other studies to estimate the variability around the EPA methylmercury reference dose.

A Bottom Line:
These two scientists believe that the EPA methylmercury reference dose is too conservative.

Whether the information generated in this scientific paper warrants a revision to the EPA methylmercury reference dose will depend on the outcome of a comprehensive re-analysis of all of the statistics used by these scientists.

Find This Scientific Paper for Your Review:
An Assessment of the Cord Blood: Maternal Blood Methylmercury Ratio: Implications for Risk Assessment. Environmental Health Perspectives (EHP). Vol. 111, No.12. pp 1465- 1470. 2003.