The nail as a noninvasive indicator of methylmercury exposures and mercury/selenium molar ratios in brain, kidney, and livers of Long-Evans rats.

Animal studies indicate that the toxic effects of methylmercury (MeHg) exposures increase when selenium (Se) status is low. Toxicity is directly proportional to Hg/Se molar ratios in critical tissues such as brain and increase dramatically as molar ratios exceed 1:1. In this study, we examined the nail as a biomonitor of Hg/Se molar ratios in kidney, liver, and brain tissues of weanling male Long-Evans rats fed controlled diets containing varying amounts of Se and MeHg. Linear regression analyses indicate that the natural log transform of the Hg/Se ratio in the nails is strongly related to the Hg/Se molar ratio in kidney, liver, and brain (p < 0.01 in all cases). The nail appears to be a reliably accurate noninvasive biomonitor of the Hg/Se molar ratio in tissues and should, therefore, be considered for use in human studies.