ADDITIONS TO THE MEDICAL GEOLOGIST’S TOOLBOX: APPLICATION OF SENSITIVE BIOLOGICAL ENDPOINTS TO ASSESS HUMAN EXPOSURE AND POTENTIAL HEALTH EFFECTS AT LOW ENVIRONMENTAL CONTAMINANT CONCENTRATIONS

Measurements of biomarkers of internal exposure and DNA damage can provide important information to supplement traditional exposure measurements and comprehensive questionnaires in epidemiological studies where concentrations of geogenic carcinogens are very low. For example, such information is particularly important for ongoing studies of the potential health effects related to cumulative exposure to arsenic in drinking water at levels below the current Maximum Contaminant Level of 10 μg/L. Although more costly than traditional techniques, such methods can be readily applied in population-based case-control studies. This talk will describe the complementary uses of 1) direct measurements of current concentrations of arsenic in drinking water in exposed populations, 2) use of databases provided by water utilities, government agencies, and environmental groups to assess historical exposures to arsenic from drinking water before diagnosis of health effects, 3) measurements of total and speciated arsenic concentrations in urine, toenails and hair to estimate short and long-term internal exposures, 4) use of the COMET assay, a functional DNA repair evaluation technique, to examine inhibition of DNA repair mechanisms and overall DNA damage in target tissues, and 5) characterization of single nucleotide polymorphisms (SNPs) for common DNA repair genes. The complementary roles played by these assessment methods are illustrated by a recent study of the relationship between cutaneous melanoma and potential synergistic effects of exposure to UV radiation from sunlight and ingestion of arsenic in drinking water in a New Mexico non-Hispanic white population. The comparison of the results of this population-based study to those of an in vitro study of the effects of inorganic arsenic and UV radiation on DNA repair in keratinocyte cell cultures will also be discussed.