Uncertainties in the Reference Dose for Methlymercury

The Scientific Paper:

Michael L. Dourson, Andrea E. Wullenweber, and Kenneth A. Poirier. NeuroToxicology Vol. 22. pp. 677-689. 2001.

Review This Scientific Paper’s Abstract:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db
=PubMed&list_uids=11770889&dopt=Abstract

The Purpose of this Study:
This scientific paper critically examines the National Academy of Sciences (NAS) and the National Research Council report on the toxicological effects of methylmercury plus the recently published Environmental Protection Agency (EPA) reference dose (RfD) for methylmercury. This paper also examines the evaluations conducted by other agencies and organizations, plus it summarizes existing research needs.

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

• This peer-reviewed, scientific paper was published in 2001.
• These scientists did a chapter-by-chapter review of the findings of the NAS report “Toxicological Effects of Methylmercury” to compare the report’s findings with data from other statistical analyses.
• The EPA methylmercury reference dose contains much uncertainty. Other regulatory agencies such as the Food and Drug Administration (FDA) use less uncertainty in calculating risk from methylmercury from eating fish.
• In particular, these scientists carefully looked at the selection of uncertainty factors that were used in this NAS report. These scientists also questioned and investigated why the NAS decided to multiply the final methylmercury reference dose by 10-fold in order to establish a large margin of added caution.
• The NAS report confirmed the current EPA methylmercury reference dose is based on using the benchmark dose lower level (BMDL) of 12 parts per million (ppm) of mercury in maternal hair. The mercury BMDL is derived from the findings of The Faroe Islands Study.
• The NAS Committee on Toxicological Effects of Methylmercury was not charged with calculating a methylmercury reference dose. This committee did provide guidance to EPA on the developing of their methylmercury reference dose (RfD).
• Reference dose estimates are not precise because there are so many uncertainty factors used in calculating reference dose levels. As a result, the reference dose level has a range of likely values of approximately 10-fold.

A Bottom Line:
To improve the precision of the current EPA methylmercury reference dose, these scientists identified the following research needs: 1) determine the critical effect for methylmercury; 2) analyze the impact of mixed chemical exposures; 3) evaluate continuous versus peak exposures to methylmercury; and 4) refine the uncertainty factors used in determining the EPA methylmercury reference dose.

These scientists identify the need for new research on PCBs exposure in the womb like that known to have occurred to infants in The Faroe Islands Study. PCBs are dangerous chemical pollutants.

Find This Scientific Paper for Your Review:
Uncertainties in the Reference Dose for Methlymercury. NeuroToxicology Vol. 22. pp. 677-689. 2001.