Saldana TM, O Basso, JA Hoppin, DD Baird, C Knott, A Blair, MC Alavanja and DP Sandler. 2007. Pesticide exposure and self-reported gestational diabetes mellitus in the Agricultural Health Study. Diabetes Care. 30(3):529-34.

  

Synopsis by Dr. Sheela Sathyanarayana and Wendy Hessler

Women who reported mixing and applying agricultural pesticides during early pregnancy have a two times higher risk of developing gestational diabetes during the pregnancy. The strong association between first trimester pesticide exposure and gestational diabetes mellitus suggests that pesticide exposures may affect glucose metabolism and insulin resistance.

   Woman applying pesticides

 

 

Context: Gestational diabetes mellitus (GDM) affects approximately 4% of all pregnancies in the United States causing significant health problems during pregnancy and an increase of Type 2 diabetes (a chronic health condition) in the future. About 135,000 cases occur in the United States each year (American Diabetic Association).

GDM develops during pregnancy when cells do not normally respond to or use insulin. Insulin is the hormone responsible for turning sugars, called glucose, and starches into energy. The result is women with gestational diabetes have too much sugar circulating in their blood. The condition develops during pregnancy and goes away after the baby’s birth. However, having gestational diabetes increases a women’s risk of developing the more chronic Type II form later in life.

Doctors routinely test women for GDM during mid-pregnancy. At highest risk are those who are older than 30; are overweight; have had a large or stillborn baby in the past; have had GDM in a prior pregnancy; and are African-American, Native American, Asian, Hispanic or of Pacific Island ancestry.

Uncontrolled high blood sugar can result in complications during pregnancy and at birth. The problems can affect the baby’s health and may increase obesity and diabetes during childhood. Gestational diabetes, like Type II diabetes, is controlled through diet and exercise.

 

What did they do? Saldana et al. analyzed data collected by the Agricultural Health Study to assess the relationship between pesticide exposure during early pregnancy and diagnosis of gestational diabetes mellitus (GDM). The AHS is a large study of pesticide applicators and their spouses in Iowa and North Carolina that has tracked participants since the 1990s.

Of the thousands enrolled in the AHS, more than 11,200 women between the ages of 16 and 49 met this study’s criteria regarding pregnancies that occurred within the past 25 years. The mothers self reported pesticide use in their first trimester of pregnancy and if they were diagnosed with gestational diabetes during their most recent pregnancy.

The participants were classified according to four pesticide use categories: no exposure, indirect exposure, residential exposure (applying to house or garden) and agricultural exposure (mixing and applying pesticides to crops or repairing pesticide application farm machinery). The authors calculated the odds of reporting GDM in relation to pesticide use.

What did they find? More than half of the women – whether experiencing GDM or not – reported mixing and applying agricultural pesticides at some time in their life. Of the participants, 506 (4.5%) reported having GDM during their most recent pregnancy. Those reporting GDM were more likely to be older than 30, overweight and from North Carolina. Women who reported agricultural pesticide exposure (mixing or applying pesticides to crops or repairing pesticide application equipment) during pregnancy were more than twice as likely to report GDM (odds ratio [OR] 2.2 [95% CI 1.5–3.3]) as compared to women reporting no pesticide use in pregnancy. Specifically, four herbicides (2,4,5-T; 2,4,5-TP; atrazine; or butylate) and three insecticides (diazinon, phorate, or carbofuran) were associated with reporting GDM.

No increased risk was seen in women with indirect and residential exposure during the first trimester of pregnancy. The same held for those mixing or applying anytime in the past compared to those with no prior exposure.

 

What does it mean? Women who report mixing or applying agricultural pesticides during the first trimester of pregnancy are at a potentially higher risk for developing gestational diabetes than women who did not report handling agricultural pesticides in the first trimester of pregnancy.

Several epidemiologic studies have indicated an association between dioxin-like compounds and glucose metabolism (Remillard and Bunce 2002). Two recent studies show large increases in risk of Type II diabetes and insulin resistance in response to exposure to persistent organic pollutants at background levels. This is the first study to examine the relationship between pesticide use and GDM in pregnancy. Common risk factors for GDM are known, but it is unclear if and how environmental exposures affect risk of developing the condition.

A major weakness of this study is the self reporting of all data as opposed to actual measurements of pesticides in the women’s blood/urine. Diagnosis of GDM was also self-reported as opposed to medical records. Regardless, there is no reason to believe that there would be any inherent biases in reporting because women did not know how questionnaire data would be used.

GDM can cause significant health problems during the pregnancy period, at birth and in the future because of an increased risk for developing Type 2 diabetes, which is a long term, chronic health condition. Pesticides may affect glucose metabolism leading to GDM in pregnancy, but further research is needed to confirm the findings presented here and determine the actual mechanism by which pesticides could cause these conditions.

 


Resources:

American Diabetes Association. Gestational diabetes.

Lee, D-H, I-K Lee, K Song, M Steffes, W Toscano, BA Baker, and DR Jacobs. 2006. A strong dose-response relation between serum concentrations of persistent organic pollutants and diabetes. Results from the National Health and Examination Survey 1999–2002. Diabetes Care 29:1638-1644.

Lee, D-H, I-K Lee, , S Jin, M Steffes, and DR Jacobs. 2007. Association between serum concentrations of persistent organic pollutants and insulin resistance among nondiabetic adults. Diabetes Care 30:622-628.

Medline Plus. Diabetes and pregnancy.

National Institutes of Health. The Agricultural Health Study.

Pesticide Action Network. Pesticides database.

Remillard, RBJ and NJ Bunce. 2002. Linking dioxins to diabetes: Epidemiology and biologic plausibility. Environmental Health Perspectives 110:853-858

 

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