New England is one of three areas in the United States with the highest annual deposition of mercury, an established environmental pollutant with a variety of health effects. We measured the mercury content in toenails of 27 individuals in New Hampshire who participated as controls in a health study in 1994-95. The mean total toenail mercury concentration was 0.27 mcg/g (median 0.16; SD 0.27; range 0.04-1.15 mcg/g). The best predictor of toenail mercury levels was the mean combined fish and shellfish consumption measured using four simple questions from a validated food frequency questionnaire. Toenail total mercury content was significantly correlated with the mean average weekly consumption of finfish and shellfish (Spearman correlation coefficient 0.48, P ¼ 0.012). Multivariate models confirmed that toenail total mercury concentration was best predicted by total finfish and shellfish consumption. Keywords: mercury, fish consumption, exposure assessment, metals, epidemiology.
IntroductionMercury is an established environmental pollutant with a variety of serious health effects in humans (Risher et al., 1999). Numerous attempts have been made to identify and characterize useful biomarkers of exposure to mercury, including blood, urine, hair, fingernails and toenails, both as correlates of environmental exposures and also in relation to diseases such as coronary heart disease (e.g., Sinclair et al., 1980;MacIntosh et al., 1997;Guallar et al., 2002;Mortada et al., 2002;Yoshizawa et al., 2002). Toenail mercury concentrations are reasonably stable indicators of exposure over time (Garland et al., 1993) and toenails have the advantage over hair and fingernails of being less susceptible to external contamination. Toenail mercury content is significantly associated with fish consumption; in fact, knowledge of fish consumption alone can be sufficient to characterize mercury exposure as measured in toenails (Garland et al., 1993;MacIntosh et al., 1997).New England is one of three areas in the United States with the highest annual deposition of mercury (Rice et al., 1997). Since 1994, the New Hampshire Department of Health and Human Services has issued a fish consumption advisory because of mercury contamination (New Hampshire Department of Health and Human Services Bureau of Health Risk Assessment, 2001) and studies of wildlife have demonstrated high mercury levels in eight states in north America (Evers et al., 2003). To our knowledge, no published studies have described biomarkers of mercury exposure in New Hampshire's human population. The aims of this pilot study were to analyze mercury levels in toenails taken from individuals in New Hampshire who participated as controls in a previous health study, and to determine their correlation with three dietary measures of seafood intake.
MethodsWe analyzed toenail clippings obtained from control subjects during a case-control study conducted in 1994-95 in New Hampshire, which was reported previously (Karagas et al., 1998;Karagas et al., 2001). The original study investi...