US EPA

4978108 

Journal Article 

Observed mercury concentrations from and quot;baby's first haircut and quot; hair samples among infants exposed to ethyl-, methyl-, and inorganic mercury pre- and postnatally: a preliminary retrospective 

Bernard, S; Redwood, L 

2003 

1 

NeuroToxicology
ISSN: 0161-813X
EISSN: 1872-9711 

2 

English 

Increased risk of harm to children from prenatal exposures to methylmercury from maternal fish consumption and inorganic mercury from maternal dental amalgams is now recognized. Concern has also been raised over postnatal exposures to the ethylmercury-containing preservative, thimerosol, present in vaccines given to infants. Thimerosal has also been administered to pregnant women through maternal vaccinations and anti-Rho (D) immune globulins. Relative to methylmercury, little is known about ethylmercury toxicokinetics, and the literature on early infant risk to mercury has mostly focused on breast milk, without factoring in concurrent direct exposure from medical products. Published reports of hair Hg measurements of infants exclusively in the first 2 years of life who were exposed to mercury from vaccines are lacking. In this preliminary retrospective study, we report on Hg levels from and quot;baby's first haircut and quot; hair samples of 45 normally developing US children. All subjects were administered the full regimen of mercury-containing vaccines according to CDC recommendations. We attained estimates of prenatal exposures from maternal fish consumption, number of surface amalgams, and administration of thimerosal-containing anti-Rho (D) immune globulins through retrospective maternal interviews. The average Hg concentration in the baby hair was 3.63 ppm, well in excess of the 90th percentile levels of 0.2 ppm reported by NHANES among 1-5-year olds. Maternal fish consumption, number of maternal amalgams, and exposure to thimerosal from vaccines were significantly and positively correlated with infant hair Hg concentrations. Since the limited toxicokinetic data on ethylmercury suggests a hair to blood ratio of 27:1, versus 250:1 for methylmercury, we discuss the predicted infant blood Hg concentrations under various assumptions regarding the relative contribution of ethyl-, methyl-, and inorganic mercury to the observed hair Hg levels in our patient sample.