Health concerns grow over major weed killer
Charles Duhigg
San Diego Union-Tribune
08/23/2009
For decades, farmers, lawn care workers and professional green thumbs have relied on the popular weed killer atrazine to protect their crops, golf courses and manicured lawns.
But atrazine often washes into water supplies and has become among the most common contaminants in American reservoirs and other sources of drinking water.
Now, new research suggests that atrazine may be dangerous at lower concentrations than previously thought. Recent studies suggest that, even at concentrations meeting current federal standards, the chemical may be associated with birth defects, low birth weights and menstrual problems.
Laboratory experiments suggest that when animals are exposed to brief doses of atrazine before birth, they may become more vulnerable to cancer later.
An investigation by The New York Times has found that in some towns, atrazine concentrations in drinking water have jumped, sometimes for longer than a month. The reports produced by local water systems for residents often fail to reflect those higher concentrations.
Officials at the Environmental Protection Agency say Americans are not exposed to unsafe levels of atrazine. They say that current regulations are adequate to protect human health, and that the doses of atrazine coming through people's taps are safe — even when concentrations jump.
Some scientists and health advocates disagree. They argue that the recent studies offer enough concerns that the government should begin re-examining its regulations. They also say that local water systems — which have primary responsibility for the safety of drinking water — should be forced to monitor atrazine more frequently, in order to detect short-term increases and warn people when they occur.
The EPA has not cautioned pregnant women about the potential risks of atrazine so that they can consider using inexpensive home filtration systems. Though the agency is aware of new research suggesting risks, it will not formally review those studies until next year at the earliest. Federal scientists who have worked on atrazine say the agency has largely shifted its focus to other compounds.
Interviews with local water officials indicate that many of them are unaware that atrazine concentrations have sometimes jumped sharply in their communities. Other officials are concerned. Forty-three water systems in six states — Illinois, Indiana, Iowa, Kansas, Mississippi and Ohio — recently sued atrazine's manufacturers to force them to pay for removing the chemical from drinking water.
Representatives of the EPA and Syngenta, the company that manufactures most of the atrazine sold, say that current federal standards are based on hundreds of studies showing Americans are safe. In a written statement, the EPA said that it applied large safety buffers in regulating atrazine and continued to monitor emerging science.
“The exposure that the agency allows under its atrazine drinking water regulations is at least 300 to 1,000 times lower than the level where the agency saw health effects in the most sensitive animal species tested,” the statement said. New studies, while raising important issues, do not “suggest a revision to EPA's current regulatory approach, which has been built on the review and consideration of hundreds of studies, including animal toxicity and human epidemiological studies dealing with atrazine,” the agency said.
Syngenta said the lawsuits were baseless.
The head of another government agency voiced apprehension.
“I'm very concerned about the general population's exposure to atrazine,” said Dr. Linda Birnbaum, director of the National Institute of Environmental Health Sciences, a division of the Department of Health and Human Services. “We don't really know what these chemicals do to fetuses or prepubescent children.
“At a minimum, pregnant women should have access to accurate information about what's in their drinking water.”
Recent studies suggest that when adults and fetuses are exposed to even small doses of atrazine, like those allowed under law, they may suffer serious health effects. In particular, some scientists worry that atrazine may be safe during many periods of life but dangerous during brief windows of development, such as when a fetus is growing and pregnant women are told to drink lots of water.
“There are short, critical times — like when a fetus' brain is developing — when chemicals can have disastrous impacts, even in very small concentrations,” said Deborah Cory-Slechta, a professor at the University of Rochester in New York who has studied atrazine's effects on the brain and serves on the EPA's science advisory board. “The way the EPA tests chemicals can vastly underestimate risks.
“There's still a huge amount we don't know about atrazine.”
In recent years, five epidemiological studies published in peer-reviewed journals have found evidence suggesting that small amounts of atrazine in drinking water, including levels considered safe by federal standards, may be associated with birth defects — including skull and facial malformations and misshapen limbs — as well as low birth weights in newborns and premature births. Defects and premature births are leading causes of infant deaths.
Some of those studies suggest that as atrazine concentrations rise, the incidence of birth defects grows. One study — by researchers at Purdue University, published in the journal Environmental Health Perspectives — suggests that concentrations as small as 0.1 parts per billion may be associated with low birth weights.
Atrazine is just one example of what critics say are regulatory weaknesses in the protections of America's drinking water. Health and environmental advocates argue that the laws safeguarding drinking water and policing toxins are insufficient, and that the EPA is often too slow in evaluating emerging risks, not cautious enough and too unwilling to warn the public when health concerns arise.
In January, a Government Accountability Office report said that the EPA's system for assessing toxic chemicals was broken, and that the agency often failed to gather adequate information on whether chemicals posed health risks.
Forty percent of the nation's community water systems violated the Safe Drinking Water Act at least once last year, according to the Times analysis of EPA data, and dozens of chemicals have been detected at unsafe levels in drinking water.
Atrazine, which is sold under various brand names including AAtrex, is most commonly used on corn in farming states. It can also be found on lawns, gardens, parks and golf courses. Sometimes, the only way to avoid atrazine during summer months, when concentrations tend to rise as cropland is sprayed, is by forgoing tap water and relying on bottled water or using a home filtration system.
