US EPA

4978221 

Journal Article 

Mercury levels in blood and brain of infant monkeys exposed to thimerosal 

Burbacher, TM; Shen, D; Liberato, N; Grant, K; Cernichiari, E; Clarkson, T 

2003 

1 

Neurotoxicology and Teratology
ISSN: 0892-0362
EISSN: 1872-9738 

3 

English 

Recently, questions have arisen about the safety of thimerosal, an ethylmercury containing preservative used in some infant vaccines. Current EPA guidelines for methylmercury exposure (primarily through fish in the diet) have been used to assess the public health risk to children receiving thimerosal-containing immunizations as infants. Depending on the exact vaccinations, schedule, and size of the infant, some children may receive ethylmercury (in the form of thimerosal) approaching or at the EPA guideline levels. The purpose of this study was to compare the distribution of total and inorganic mercury in newborn monkeys following thimerosal exposure (via injection) with newborns exposed to methylmercury (via oral gavage). Infant monkeys were exposed to thimerosal or methylmercury at birth and at 1, 2 and 3 weeks of age. Blood mercury levels were determined 2, 4 and 7 days after each exposure. Brain mercury levels were assessed 2, 4, 7 or 28 days after the last (3 week) exposure. Preliminary data indicate that the half-life of mercury in blood following thimerosal exposure is significantly lower than the half-life of mercury following methylmercury exposure. Brain levels of mercury were also significantly lower in the thimerosal group. Thus far, the data indicate that EPA guidelines for methylmercury exposure may not provide an accurate assessment of the public health risk to children receiving thimerosal-containing immunizations.