14 June 2004 00:01 [Source: ICB Americas]
Even at significantly higher levels than recommended by California’s leading health assessment agency, per-chlorate in drinking water seems to pose no additional risks to healthy people, University of California at Irvine (UCI) researchers said last week.
UCI’s Urban Water Research Cen-ter (UWRC) says the current public health goal of 6 parts per billion established earlier this year by state regulators is “well reasoned” and is consistent with a value set only on health considerations.
However, the researchers say their findings show that exposure to perchlorate at levels below 100 parts per billion would still protect the public health. Their report is being provided to the California Department of Health Services and other policymakers as they wrestle with setting a statewide standard for perchlorate in drinking water.
Perchlorate, a byproduct of rocket fuel manufacturing that was discharged as waste into groundwater supplies from defense sites, is a chemical that interferes with the normal function of the thyroid gland.
Impaired thyroid function in expectant mothers may affect the fetus and newborn. Treatment of rats with other chemicals that result in chronic lowering of thyroid hormones has been shown to produce thyroid gland tumors. “Clearly more research should be conducted related to exposure to perchlorate, particularly with pregnant women and other susceptible individuals,” says Ronald Shank, a UCI professor and chair of community and environmental medicine.
“But we found no evidence in the current studies that demonstrate a difference in health effects in healthy individuals between low levels of perchlorate, such as the 6 ppb [parts per billion] public health goal, and a level 10 times higher,” he adds.
Perchlorate has been found throughout California in approximately 350 wells in 89 water systems; 90 percent of these are located in Southern Cali-fornia. Los Angeles, Orange, San Bernadino and Riverside counties report 40 to 89 percent of the water systems tested contain perchlorate levels greater than 6 ppb.
The UWRC convened a committee of scholars in consultation with state health officials, environmental health scientists, toxicologists, engineers and economists to determine the nature and the effect of different standard levels on human health, California’s water supplies, the types of treatment available, and the cost of compliance. The committee’s charge was to examine the information available on all aspects of the contaminant and determine what is in the best interests of the state, its people and its water supply.
According to Betty Olson, interim director of the UWRC, the processes involved in standard setting are often difficult, requiring the weighing of health concerns against cost of treatment and availability of water.
The committee looked at the same information that will be considered by state health officials, including the distribution and concentration of perchlorate in California’s water supplies; the capacity to accurately, and at reasonable cost, measure percholorate in drinking water; the public health goal; the cost, as known to date, to treat contaminated supplies; the contribution from food; and the benefit of treating water to remove perchlorate achieved at different levels.
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