Scientific Panel's Report on Water Pollutant at Odds with EPA Findings
A water pollutant also found in some produce and milk is not as dangerous as the U.S. Environmental Protection Agency determined in a preliminary risk assessment two years ago, a panel of scientists announced Monday.
The National Academy of Sciences concluded that daily perchlorate intake at levels 20 times higher than those posed by the EPA is safe even for sensitive populations, such as fetuses and pregnant women.
The Natural Resources Defense Council, an environmental group, denounced the panel's report and claimed the White House, Pentagon and defense industry strong-armed scientists to downplay the chemical's hazards.
Academy officials brushed off the defense council's accusations as unfounded and said the recommendations were based on the best scientific research available, including some funded by perchlorate-linked businesses.
"We looked at all the data we could get ahold of and evaluated the data on its own merits, not on sources of funding," said Dr. Richard B. Johnston Jr., who chaired the 16-member National Academy of Sciences committee.
Perchlorate is a salt used in rocket fuel, fireworks, flares and other products. It has contaminated 20 wells in the Rialto-Colton groundwater basin, and a plume inching south from a former military munitions storage area threatens to pollute more.
At certain levels, the chemical can impair thyroid functioning, which plays an important role in fetal and newborn brain development.
In 2002, EPA researchers came up with figures that put the recommended safe perchlorate level in drinking water at 1 part per billion, or ppb. One ppb is equivalent to half a teaspoon of perchlorate in an Olympic-size swimming pool.
The academy came up with what's known as a reference dose after examining the research, but the panel did not recommend a water standard.
The panel concluded that even sensitive individuals could consume up to 0.0007 milligram of perchlorate per kilogram of body weight with no effect. The EPA's reference dose is 0.00003 milligram per kilogram of body weight.
The two numbers differ partly because the EPA examined animal exposure studies the academy deemed unreliable, and the federal agency also applied a safety factor that was 30 times higher than what the panel used.
Even so, the EPA did not consider perchlorate exposure from sources other than water, such as milk and lettuce, and health officials will have to factor that in before developing a water standard, said Dr. Gina Solomon, a senior scientists for the defense council.
"Depending on what they assume, they are going to come up with some very different numbers," she said.
The academy report could prompt the California Department of Environmental Health Hazard Assessment to lower the state's 6 ppb public health goal for perchlorate, but it will likely cause federal regulators to inch their recommended level higher, Solomon said.
Allan Hirsch, spokesman for Environmental Health Hazard Assessment, said the public health goal may need some fine-tuning after the academy recommendations are considered.
"It's too early to say whether we would change it or whether it would be up or down," he said.
The public health goal is not an enforceable drinking water standard, but it is a step toward state regulation.
Water providers are encouraged not to serve water that exceeds the goal. Locally, water providers have refused to serve water with even detectable amounts of perchlorate.
Besides the reference dose, the academy also concluded that perchlorate exposure is unlikely to cause thyroid tumors.
The panel also advised pregnant women exposed to the chemical to take iodine pills since perchlorate impairs the thyroid's ability to uptake the element. Solomon scoffed at that suggestion.
"That's like putting a pregnant woman in a room full of smokers and asking her to wear a gas mask," she said.
Source: Knight Ridder/Tribune Business News