Examination of dietary methylmercury exposure in the Casa Pia study of theHealth Effects of Dental Amalgams in Children

This study examined methylmercury concentrations in blood of children parti cipating in the Casa Pia Study of the Health Effects of Dental Amalgams in Children over a 1-yr period and related them to their,diets in terms of fis h and other seafood consumption. One hundred and fifty children between the ages of 8 and 10 yr who were residents of the Casa Pia School System of Li sbon, Portugal, participated. Parents or caregivers completed a food freque ncy questionnaire designed specifically for this study at baseline. Childre n provided urinary and blood samples for mercury determinations at baseline and at 1 yr following placement of dental tooth fillings. Mercury levels i n fish samples from children's diets were also obtained. Mercury determinat ions in urine, blood, and fish were performed using cold vapor atomic fluor escence spectroscopy. The mean value of baseline methylmercury concentratio ns in blood increased as the report of seafood consumption increased, altho ugh not statistically significantly. However, blood methylmercury and total mercury concentrations were significantly lower at 1-yr follow-up than at baseline. Sixty-one percent of parents/caregivers reported that their child ren consumed fish on a weekly basis. The fish offered at a sample of the sc hools contained low levels of methylmercury (range 13.9-23.6 ng/g). Thus, c hildren participating in the Casa Pia dental amalgam study are exposed to l ow dietary levels of methylmercury by way of fish consumption, and this fin ding was reflected in the low mean blood methylmercury concentrations obser ved. The present findings indicate that dietary methylmercury is not a sign ificant source of mercury exposure and is not likely to confound the associ ation of dental amalgam mercury with potential health effects in the presen t study.