Erica Weir's otherwise excellent public health article on the risks of methylmercury was flawed by misinformation on the clinical management of patients with methylmercury poisoning.1 The information provided appears to be based on the characteristics of elemental and inorganic mercury, not methylmercury.
The half-life of methylmercury in blood is relatively long (approximately 44 days) and the concentrations in newly formed hair are about 250 times higher than in blood.2 Once concentrated in hair, the level of methylmercury remains unchanged; measurements in consecutive hair segments are thus useful indicators of past exposure (depending on the length of the hair). Measurements in hair correlate with the total body burden. Indeed, measurements in the mother's hair corresponding with the last month of pregnancy are proportional to the methylmercury levels in autopsy brain samples from infants who have died within a few weeks of birth. It is not useful to measure urine levels because methylmercury is not excreted by the kidneys. Likewise, chelation has no place in the treatment of acute or chronic methylmercury poisoning; there is no specific treatment.
Signature
John Ruedy
Clinical pharmacologist Halifax, NS
References
- 1.Weir E. Methylmercury exposure: fishing for answers. CMAJ 2001;165(2):205-6. [PMC free article] [PubMed]
- 2.Clarkson TW. The toxicology of mercury. Crit Rev Clin Lab Sci 1997;34(3):369-403. [DOI] [PubMed]