Drinking water arsenic: The Millard County, Utah mortality study

The EPA risk assessment for drinking water arsenic is based on skin cancer and wide-ranging exposures of between 10 and 1,820 mu g/L drinking water arsenic from studies conducted in Taiwan in the 1960s. This investigation in a cohort of 4,058 residents from Millard County, Utah, represents one of the larger studies in a U.S, population. Exposure was based on drinking water arsenic concentrations performed by the Utah Health Laboratory using EFA approved test methods. Median arsenic concentrations in drinking water ranged from 14 mu g/L to 166 mu g/L. The cohort was established based on historic membership records of the Church of Jesus Christ of Latter-Day Saints (LDS). Current vital status was determined by the LDS. Death certificates of the deceased were collected and reviewed for cause of death. Cause of death was coded using the International Cause of Death (ICD) version 9 coding rubric. Results from the standard mortality ratio (SMR) analysis include statistically significant associations for hypertensive heart disease (SMR=2.20), nephritis and nephrosis (SMR=1.72), and prostate cancer (SMR=1.45) among males, and hypertensive heart disease (SMR=1.73) and all other heart disease including pulmonary heart disease and diseases of the pericardium (SMR=1.43) among females. These results indicate that cancer and other health effects may be important at low exposure levels of less than 200 mu g/L. A Cox proportional hazards analysis using an exposure matrix to include the number of years in residence and the median arsenic level for the town of residence is underway.