Dursban Poisoning in school


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Autumn 2002 - CEC.org - Calculated risks - How safe is safe enough for pesticides? By John Whalen.

Soon after six-year-old Michael Eash began first grade at Montgomery Elementary School in North Wales, Pennsylvania, he seemed to be ill more often than not. A baffling array of symptoms--headaches, fever, diarrhea, leg pain--plagued him throughout the fall of 1992 and into the spring of 1993. So much so that his mother, Connie, began to worry that something was seriously wrong. But once school let out for the summer, Michael shook off his ailments and the concerns about his health faded away.

His symptoms returned shortly after school started again in the fall. And this time Michael wasn't alone: sixteen of his classmates came down with the same mystery malaise, all on the same day. A toxicologist and former drug researcher, Connie Eash grew suspicious of an environmental trigger and paid a visit to her son's school. The answer hit her in the face as soon as she arrived. Permeating the air was the sharp chemical smell of Dursban, a pesticide that, at the time, was routinely sprayed in and around the school buildings. Blood tests later confirmed her hunch; Michael was suffering from acute pesticide poisoning.

Despite hundreds of documented Dursban poisonings each year--many of them children like Michael, with underdeveloped natural defenses against neurotoxic chemicals--the product would remain one of the most widely available insecticides in North America for another seven years. Dursban was literally a household name, used in everything from pet collars to indoor roach sprays to lawn treatments. In June 2000, the US Environmental Protection Agency finally banned most uses of the chemical in residences and commercial buildings (golf courses and some agricultural settings were exempted). At about the same time, Canada's Pest Management Regulatory Agency also began phasing out Dursban from homes. It has just been approved, though, for urban residential use in Mexico. According to Leonor Cedillo Becerril, director of risk assessment for the General Directorate of Environmental Health at the Health Secretariat, Mexican authorities had not been aware of the pesticide's history. "Now that we are getting information about Dursban," she says, "we are going to consider what to do with it."

The EPA took Dursban off the market only after amassing dozens of studies showing that chlorpyrifos, the active ingredient in the pesticide, could be toxic to humans, especially children. Among the accumulated findings was evidence that chlorpyrifos can affect the central nervous system and red blood cells of animals and humans; that it can cause developmental and reproductive damage in lab animals; that it interacts with household dust to intensify its effect on the nervous system; that it lingers on carpets, pillows, and stuffed animals; and that young animals are five times more susceptible to the chemical than adult animals.

In one sampling of American children, more than 90 percent of the study group had chlorpyrifos present in their urine.

The tortuous process of calculating the risks of a pesticide--or any potential environmental or health hazard--to help determine how to regulate it is known as "risk assessment." Since the early 1970s, laws in the United States and Canada have required that new pesticides go through the process before they can be approved for commercial sale. Mexico has no formal procedure, and it is limited to cases where there is particular suspicion or an obvious emergency. "Until now, we have not had enough human resources to apply risk assessment as part of all the procedures in which it should be applied," says Cedillo.

In general, pesticide manufacturers start the risk-assessment process by providing regulatory agencies with data from studies done for them by independent labs. This typically includes animal experiments, cell cultures, field tests, and other information. Regulators then weigh these findings against the published scientific literature, including toxicological and epidemiological studies.

Though the process involves a series of exacting scientific procedures, it is far from precise. For one thing, manufacturers have frequently been accused of presenting evidence in ways that reflect favorably on their products. In the case of Dursban, for instance, the EPA fined manufacturer DowElanco US$732,000 in 1995 after learning that it had failed to report more than 300 lawsuits and assorted other claims of poisoning. While Dursban came onto the market before risk assessment was part of the registration process, such information would likely have triggered sooner re-examination of the pesticide.

"We don't know everything about anything," says Lynn Goldman, an epidemiologist and pediatrician who ran the EPA's Office of Prevention, Pesticides, and Toxic Substances in the nineties. "And so there is this residual uncertainty."

The ability to accurately assess chemical hazards has become more critical than ever. According to EPA statistics, pesticide use in the US alone has grown by 50 percent over the past three decades. Domestic sales hover around 2.2 billion pounds a year--that's eight pounds for every man, woman, and child. And there are more than 21,000 different pesticides on the US market, containing some 875 active ingredients. For many of these chemicals, the effect on people is simply not known.

"One of the problems with risk assessment is that it is very theoretical," says Richard J. Jackson, director of the National Center of Environmental Health at the US Centers for Disease Control and Prevention. "You calculate what people are being exposed to, you look at what happens to animals, and then you calculate how that might be converted to what would happen in people." When the process is applied to the physical sciences--estimating the safety of a bridge, for example--the findings are as straightforward as the physics on which they are based. "But biology is so much messier," Jackson says. "The variety of human beings is so much greater than either what happens in physics or what happens in test animals, that risk assessment has somewhat limited use in real-world calculations."

Once a pesticide goes on the market, the burden of scientific proof required to take it off is very high. Too high, critics say, especially when children are the ones at risk. "We had plenty of evidence on the dangers of chlorpyrifos, much earlier than when they finally phased it out," says Sandra Steingraber, a biologist and author of Living Downstream: An Ecologist Looks at Cancer and the Environment. "It should have been phased out a long time before."

Given that difficulty, the question of fine-tuning risk assessment to protect children has become a matter of intense debate. The push to take children's health into separate account actually began in the 1980s, when it first became clear that children exposed to lead and PCBs suffered different and often more intense effects than adults. Public health experts noticed that the impact of toxic substances on developing children could be subtle, could occur over long periods of time, and could vary by the stage of development the child was in when exposed.

In 1993, the US National Research Council (NRC) published a landmark study, Pesticides in the Diets of Infants and Children, confirming the earlier observations. The NRC concluded that children were more vulnerable to the effects of pesticides than adults, and that the EPA was not doing enough to protect them. Because of their physiological immaturity and increased exposure to pesticides, the report noted, children demanded special consideration in risk assessments.

Those findings led to a number of sweeping reforms in the United States. Most notable was the Food Quality Protection Act (FQPA) of 1996, which instituted more stringent requirements for risk assessment, including up to a ten-fold safety margin to take into account children's higher sensitivity and the lack of hard data on developmental effects. The new law also ordered the EPA to re-evaluate allowable pesticide levels on foods. Hundreds of pesticides that pre-dated risk assessment were suddenly under scrutiny. Included in the FQPA was a "worst first" provision that required the agency to start with pesticides posing "the greatest risk to public health." Dursban was tagged for assessment.

Canada's Pest Management Regulatory Agency embraced the objectives of the FQPA requirements, although some contend that the guidelines relating to children are vague and tough to enforce. In a May 1999 audit report, Canada's then-Commissioner of the Environment and Sustainable Development, Brian Emmett, found that the federal government had not lived up to its promises. "The need to re-evaluate pesticides has been formally recognized by the federal government for over thirteen years, and we expected that it would have developed a program to do so," he wrote. "We found Canada's track record to be one of inaction and unfulfilled commitments."

A new bill is pending in Parliament to address many of these complaints. Introduced by Health Minister Ann McLellan in March, the bill would amend Canada's Pest Control Products Act to include such improvements as a ten-fold safety margin for pesticides used around homes or schools, risk assessments that take into account aggregate exposures and the cumulative effects of similar chemicals, and mandatory re-evaluations for pesticides every fifteen years. Government enforcement powers would also be more clearly defined and strengthened.

In extending extra protections to children, policy makers have tacitly acknowledged that risk assessment is an inexact science, and that its inherent imprecision requires an extra level of precaution. In other words, it is better to err on the side of caution when the stakes are so high. But there is ongoing debate over how much precaution is warranted and when it becomes overkill. Where is the line? Can any pesticide be 100 percent safe? What about the risks of insect infestation? Chemical manufacturers, eager to keep their products on the shelves, argue that "sound science" requires more facts and less extrapolation of safety margins in the absence of hard evidence.

Proponents of the so-called precautionary principle, on the other hand, reply that high-minded calls for "sound science" in a process that can never fully analyze incredibly complex environmental and health interactions are disingenuous. "We're still in a situation where what we don't know dwarfs what we do know," says Kathleen Cooper, a researcher at the Canadian Environmental Law Association. "That becomes the argument for precaution, and for a lower standard of scientific proof. If you insist on full scientific certainty before you set protective standards, then you'll never set standards."

According to Steingraber, it is inaccurate to characterize the situation as a clash between science on one side and precaution on the other. "I can't think of any successful public health measure where we waited until we had absolute proof," she says. Take the US Surgeon General's first warnings in the sixties about cigarettes and lung cancer--the ultimate proof of which didn't arrive until thirty years later, when the interaction between tobacco smoke and a specific gene was identified in 1996. Likewise, she says, public health officials acted decisively to stop the spread of cholera five decades before the bacterium behind the disease was isolated and understood. HIV policies and the bans on second-hand smoke in public places were two more public health actions that preceded definitive scientific understanding.

Although Goldman, the former EPA official, agrees that extra precaution is warranted when decisions affect the well-being of hundreds of millions of people, she points out that a preponderance of scientific proof is necessary anyway, to keep regulations from being overturned in court. Case in point: Dursban. Goldman was at the EPA in the late nineties when DowElanco voluntarily agreed to negotiate a phase-out of Dursban's home use. "In terms of the level of hard evidence we had at that point," Goldman says, "it would have been very easy for Dow to have fought an outright ban. EPA had not yet done its cumulative risk assessment, and there was not yet developmental toxicity information on the compound. So, if EPA had had to go to court to defend anything more draconian, would we have won? I can't say."

Despite the progress made in standardizing and strengthening risk assessment in the years since the passage of the FQPA, politics and self-interest are inevitably part of a process that is meant to be purely scientific and protective. "It's science, but it's loaded with guesswork," says Kathleen Cooper, of the Canadian Environmental Law Association. "When you have that kind of situation, the numbers and outcome can be manipulated. And so can the decision makers. It's a bunch of experts in white coats telling you what to do. So there's got to be transparency and accountability in the process."

Cooper and Goldman point to the crucial role that the CEC can play in improving both in the three NAFTA nations. "Transparency," says Cooper, "includes providing a forum for airing critiques of the risk-assessment process in order to improve it, and to inject more precautionary measures into the standard setting." The CEC, she suggests, could also take the lead in merging biomonitoring from all three nations into a useful North American information database--thereby bolstering the scientific knowledge set that will guide future risk assessments. "If we are going to have a commonality in trade," says Goldman, "we need to have a common language about risks."

Considering children's health
The CEC's ongoing initiative on Children's Health and the Environment in North America has stressed the importance of considering children's health in the risk-assessment process. In February, the CEC will host a trilateral workshop in Mexico to focus on that issue and to discuss approaches used in the three NAFTA nations. Representatives of the NAFTA Technical Working Group on Pesticides, whose key goals include harmonizing risk-assessment standards, are planning to attend.

A North American snapshot
Trying to do continent-wide comparisons of pesticide usage is like trying to count grains of sandóthe data keep slipping through your fingers. Each country has its own method of collecting information, as well as its own categories. In Canada, sales figures are based on self-reporting from manufacturers who choose to volunteer the information. In the United States, the EPA gathers data from many sources, including household surveys, but the resulting figures are approximations only. In Mexico, some reporting is mandatory, the rest voluntary, and responsibility is spread among a variety of agencies. All three countries lag years behind in reporting and have no current data. This obviously makes comparisons difficult and somewhat irrelevant. But as imperfect as they may be, our charts do help paint a picture of overall usage in North America.

Mexico, pesticide production
Mexico, pesticide sales
Canada, pesticide sales
US, pesticide sales
US, pesticide usage

About the contributor
John Whalen -- John Whalen is a freelance writer in Los Angeles whose work has appeared in The New Yorker, The New York Times Magazine, and Salon.com.

Related CEC resources
Children's Health and the Environment in North America

Related web resources
United States Environmental Protection Agency - The Office of Pesticide Programs -- http://www.epa.gov/pesticides/

Canada's Pest Management Regulatory Agency -- http://www.hc-sc.gc.ca/pmra-arla/english/aboutpmra/about-e.html

US Centers for Disease Control -- http://www.cdc.gov

Canadian Environmental Law Association -- http://www.cela.ca

ISSN 1609-0810

© Commission for Environmental Cooperation


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