Effects of Genetic Polymorphisms on Mercury Neurotoxicity in the MDA cohort

Mercury is a potent neurotoxin of concern to both the general public and occupationally exposed workers (e.g. dentists). Recent studies suggest that several genes mediating the metabolism and neurotoxicity of mercury are polymorphic in humans. This work hypothesizes that single nucleotide polymorphisms (SNPs) in these genes underlie inter-individual differences in mercury susceptibility related to peripheral neuropathy. A cohort of approximately 200 dental professionals will be recruited during the 153rd Michigan Dental Association (MDA) Annual Convention in Lansing, MI on April 23-25, 2009. Samples of urine (inorganic mercury), hair (organic mercury) and saliva will be collected. DNA genotyping will be performed using the saliva. Questionnaires will be administrated for dietary fish consumption and confounders. Nerve conduction tests will be performed on each subject. Subjects with pre-existing conditions (diabetes, neuropathy, cardiovascular diseases, etc) will be excluded from the analysis. Linear regression models will be used to explore associations among changes in peripheral nerve latency and amplitude, hair and urine mercury concentrations, genetic polymorphisms, dietary fish consumption, and personal and occupational mercury amalgam exposures. Using National Health and Nutrition Examination Survey (NHANES) data, the study will also try to determine the threshold in urine mercury levels of the general public that may be at risk of developing peripheral neuropathy. All linear regression models will be adjusted for sex, BMI, age, teeth-grinding and gum-chewing. The outcome of this work is expected to significantly enhance our ability to assess the human health risks of mercury to both the general public and to occupationally exposed workers.