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New Research Indicates CDC Underestimates Atrazine Exposure

(Beyond Pesticides, November 28, 2007) Researchers at the Centers for Disease Control (CDC) have determined that previous studies that assessed population-based exposure to atrazine were significantly and systematically underestimated. The CDC relies on the detection and analysis of only one of the twelve identified metabolites of atrazine measured in human urine samples to estimate exposure. However, after looking at multiple metabolites, researchers found that previous assessments missed most of the exposure. Atrazine mercapturate (AM), a metabolite of atrazine, was used as definitive evidence of direct atrazine exposure. General population data indicated that less than 5% of the population was exposed to atrazine-related chemicals. However, researchers at the CDC found that this research, which relied on AM detection, gives a low and misleading estimate of exposure to atrazine and atrazine- related metabolites.

Published in Environmental Health and Perspectives and entitled “Assessing Exposure to Atrazine and Its Metabolites Using Biomonitoring”, the small-scale study involving 24 individuals measured nine atrazine-related metabolites in urine. The sample was organized with respect to how likely the individuals were to be exposed to atrazine: (1) high exposure (turf pesticide applicators), (2) low exposure (non-occupationally exposed people in whom atrazine mercapturate was found during a prior study) and (3) environmental exposure (volunteers with no known exposure to atrazine).

Results indicated that the variation in proportion of total atrazine metabolites among persons was consistently large, suggesting that one metabolite alone could not be used to determine true atrazine exposure in humans. This means that most, if not all, metabolites of atrazine will need to be measured in order to get the most accurate picture of atrazine exposure. The researchers noted that exposure to atrazine or its metabolites appears more pervasive than previously believed.

Diaminochlorotriazine (DACT) was the most commonly measured metabolite, contributing 51% of atrazine-related metabolites in turf applicators, 28% to the low exposure group and 77% to the environmental exposure group. In contrast, AM contributed only 12%, 6% and 2% to samples from those groups, respectively.

These results are important because they demonstrate the importance of indirect environmental exposure, which for atrazine, would most likely be through food and drinking water. Most of the metabolites of atrazine, like DACT, are formed via environmental degradation.

They are detected in water and can even be bound in the tissue of plants, which may be miles away from the initial site of application. This also explains why AM, which is an indication of direct exposure, was more prevalent in turf applicators than in the other groups. The other common metabolites include: desethylatrazine (DEA), desisopropyl atrazine (DIA) and hydroxydesethylatrazine (DEA-OH). DACT and DEA appear to be the most important metabolites to measure to evaluate exposures to atrazine. The researchers emphasize that further evaluation is necessary because of the small sample size used and of other variables not considered.

Atrazinewhich as been linked to cancer, birth defects, neurotoxicity, endocrine disruption and a variety of other health effects such as increased prostate cancer, decreased sperm count and high risk of breast cancer; and has been banned by the European Union is the most widely used agricultural pesticide in the U.S. Its effect on amphibians has been well documented, and similarly serious health effects have been found in larger mammals.

It is also widely applied in the Mid-western states to control weeds in field crops, especially corn and sorghum and has been found in the drinking water supplies in the Midwest at high levels. Chronically contaminated drinking water puts humans at the risk of exposure to long-term health effects.

For more information on the safety of your drinking water contact your local health department or call EPA’s Safe Drinking Water Hotline: (800) 426-4791.

Source: Environmental Health News


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