RELATIONSHIP OF URINARY ARSENIC TO INTAKE ESTIMATES AND A BIOMARKER OF EFFECT, BLADDER CELL MICRONUCLEI

The purpose of this study was to investigate methods for ascertaining arsenic exposure for use in biomarker studies. Urinary arsenic concent ration is considered a good measure of recent arsenic exposure and is commonly used to monitor exposure in environmental and occupational se ttings. However, measurements reflect exposure only in the last few da ys. To cover longer time periods exposure can be estimated using arsen ic intake data, calculated by combining measures of environmental arse nic and inhalation/ingestion rates. We compared these different exposu re assessment approaches in a population chronically exposed to arseni c in drinking water in northern Chile. The study group consisted of 23 2 people, some drinking water low in arsenic (15 mu g/l) and others dr inking water with high arsenic concentrations (up to 670 mu g/l). Firs t morning urine samples and questionnaire data, including fluid intake information, were collected from all participants. Exfoliated bladder cells were collected from male participants for the bladder cell micr onuclei assay. Eight different indices of exposure were generated, six based on urinary arsenic (mu g As/l urine; mu g As/g creatinine; mu g InAs/l urine; mu g MMA/l urine; mu g DMA/l urine; mu g As/h, excreted ), and two on fluid intake data (mu g As/day, ingested; mu g As/l flui d ingested-day). The relationship between the different exposure indic es was explored using correlation analysis. In men, exposure indices w ere also related to a biomarker of effect, bladder cell micronuclei. W hile creatinine-adjusted urinary arsenic concentrations had the strong est correlations with the two intake estimates (r=0.76, r=0.81), unadj usted urinary arsenic showed the strongest relationship with bladder c ell micronuclei. These data suggest that, in the case of the bladder, unadjusted urinary arsenic concentrations better reflect the effective target organ dose compared to other exposure measures for biomarker s tudies.