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Researchers in France report that women exposed to detectable levels of the herbicide atrazine during pregnancy are more likely to give birth to smaller babies. Prior human and animal studies report similar results. This study is important because it focused on pregnant women. It also takes another step in determining whether atrazine exposure during pregnancy affects infant development. To do this, the researchers addressed the criticisms of prior studies and considered other chemical exposures that might contribute to the effects seen in the infants at birth.


Atrazine is an herbicide used to kill weeds that grow among agricultural crops. It is mainly used on corn, sorghum and sugarcane fields. Although the European Union banned its use in 2001, the United States and 70 other countries still use atrazine.

Atrazine is one of the most used herbicides in the United States. Every year, farmers apply more than 70 million pounds to crops before and after planting. It is most commonly used in Midwestern states such as Illinois, Indiana, Iowa and Nebraska.

People are directly exposed to atrazine when they make and use the herbicide. Exposure also occurs through contaminated soil and dust in the air. The biggest source for people, though, is drinking water. Rain and wind can carry the herbicide off the fields to contaminate surface and ground water used for drinking water.

The U.S. Enviornmental Protection Agency (EPA) sets the lifetime exposure limit at three parts per billion.

Some previous human studies from the United States and France suggest that atrazine might increase the risk of low birth weight, early birth or birth defects (Munger et al. 1997; Ochoa-Acuña et al. 2009; Villanueva et al. 2005). Animal studies concur with these findings.

In addition, animals exposed to high levels of atrazine have liver, kidney and heart problems. Lower levels can affect prostate and mammary glands in rat studies. Some studies have found that the herbicide can disrupt the endocrine system in frogs and lead to males with female sex organs (Hayes et al. 2002).

The EPA is again evaluating the herbicide's human health effects to determine if its use should be restricted. This is the third reassessment of the chemical in about 20 years. Atrazine was deemed safe in the two previous evaluations. In the current round, the science advisory panel will decide whether to keep regulations as they are or further restrict the herbicide's use on crops. The decision is expected later this year after the board's final meeting this summer.

What did researchers do?

The researchers measured levels of atrazine and 11 of its metabolites in the urine of 579 pregnant women. Each supplied one urine sample for the study.

Atrazine levels were compared to the newborn's weight, length and head circumference, as gathered from medical records. The authors also asked pediatrician's about the presence of genital malformations among the male infants.

Women were classified as directly exposed if atrazine or one of its four metabolites were measured in their urine. They were considered unexposed if none of the compounds were measured.

In addition, four other types of herbicides were measured in the women's urine.

The women, who were part of a larger study conducted between 2002 and 2006 in the Brittany region of France, also completed a questionnaire about family social and demographic characteristics, diet and lifestyle. During analysis, the authors took these factors into account as well as exposure to other herbicides used on corn crops in their regions, including simazine, alachlor, metolachlor and acetochlor.

What did they find?

The risk of growth restriction was 50 percent higher among babies born to women with detectable atrazine levels in their urine. On average, these babies weighed 154 grams less than babies born to mothers without atrazine exposure. This relationship was present even after the authors accounted for other factors, including exposure to other pesticides.

The researchers found a small (40 percent) increase in the risk of genital malformations among exposed infants. This finding was based on five infants - a relatively small number - with atrazine exposure and genital malformations. The researchers did not find an increased risk of other congential malformations among women with detectable atrazine levels.

Almost 6 percent of women had measureable levels of atrazine in their urine and 27 percent had detectable levels of atrazine or one of its metabolites. Surprisingly the authors found that women who provided urine after atrazine was banned still had measureable levels of atrazine and its metabolites in their urine.

Only eight of these women reported doing farm work during pregnancy. Atrazine was detected in the urine of women who lived in rural and urban areas. This suggests that pregnant women can be exposed to atrazine even when they don't live near or work on farms.

What does it mean?

Exposure to low levels of the herbizide atrazine during pregnancy is linked to having smaller babies. Babies born to women who had measureable levels of atrazine and its metabolites in their urine during pregnancy were lighter, shorter and had smaller heads than babies born to women who were not exposed.

The is the first study to directly examine levels of atrazine in the urine of pregnant women and link these levels to infant health outcomes. The study is important and different from prior similar studies because the researchers took into account the women's other pesticide exposures.

These results are consistent with previous human and animal studies and raise some concern for pregnant women living in places where atrazine is still used.

These results also suggest that pregnant women - in rural and urban settings - could still be exposed to atrazine even after it is banned. This might be due to people illegally using atrazine or because atrazine persists in the environment - mainly in surface and drinking water. In the area of France where the study was done, atrazine had been banned for years but was still found at measurable levels in the water.

The potential link between atrazine exposure and male genital anomalies needs to be replicated in other studies, but the finding is consistent with some prior animal studies.


Atrazine reregistration. U.S. Environmental Protection Agency.

Atrazine science reevaluation: Potential health impacts. U.S. Environmental Protection Agency.

Atrazine ToxFAQs. Agency for Toxic Substances and Disease Registry.

European Union on atrazine. Living on Earth. World Media Foundation. April 21, 2006.

Hayes, TB, A Collins, M Lee, M Mendoza, N Noriega, AA Stuart, and A Vonk. 2002. Hermaphroditic, demasculinized frogs following exposure to the herbicide, atrazine, at ecologically relevant doses. Proceedings of the National Academy of Sciences 99(8):5476-5480.

Munger, R, P Isacson, S Hu, T Burns, J Hanson, CF Lynch, K Cherryholmes, P Van Dorpe, WJ Hausler. 1997. Intrauterine growth retardation in Iowa communities with herbicide-contaminated drinking water supplies. Environmental Health Perspectives 105:308-314.

Ochoa-Acuña, H, J Frankenberger, L Hahn and C Carbajo. 2009. Drinking-water herbicide exposure in Indiana and prevalence of small-for-gestational-age and preterm delivery.
Environmental Health Perspectives 117:1619-1624.

Villanueva, CM, G Durand, MB Coutté, C Chevrier and S Cordier. 2005. Atrazine in municipal drinking water and risk of low birth weight, preterm delivery, and small-for-gestational-age status. Occupational and Environmental Medicine 62:400-405.