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 concentration is considered a good measure of recent arsenic exposure and is commonly used to monitor exposure in environmental and occupational settings. However, measurements reflect exposure only in the last few days. To cover longer time periods exposure can be estimated using arsenic intake data, calculated by combining measures of environmental arsenic and inhalation/ingestion rates. We compared these different exposure assessment approaches in a population chronically exposed to arsenic in drinking water in northern Chile. The study group consisted of 232 people, some drinking water low in arsenic (15 micrograms/l) and others drinking water with high arsenic concentrations (up to 670 micrograms/l). First 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 micronuclei assay. Eight different indices of exposure were generated, six based on urinary arsenic (microgram As/l urine; microgram As/g creatinine; microgram InAs/l urine; microgram MMA/l urine; microgram DMA/l urine; microgram As/h, excreted), and two on fluid intake data (microgram As/day, ingested; microgram As/l fluid ingested-day). The relationship between the different exposure indices was explored using correlation analysis. In men, exposure indices were also related to a biomarker of effect, bladder cell micronuclei. While creatinine-adjusted urinary arsenic concentrations had the strongest correlations with the two intake estimates (r = 0.76, r = 0.81), unadjusted urinary arsenic showed the strongest relationship with bladder cell 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 studies.