Authors
Garry, V.F., Schreinemachers, D., Harkins, M., Griffith, J.

Title
Pesticide appliers, biocides, and birth defects in rural Minnesota

Journal
Environmental Health Perspectives. 104(4):394-9. 1996.

Summary
After observing the genotoxic effects of pesticides on somatic cells (lymphocytes) in previous studies of pesticide applicators, Garry et al. speculated that similar effects could occur at the germ cell level and subsequently cause birth defects in offspring. They also hypothesized that the endocrine disrupting effects of pesticides could potentially alter the sex ratio of the offspring in pesticide applicators.

The authors obtained access to several databases in Minnesota in order to carry out this study. The state of Minnesota requires that all pesticide applicators undergo certification every 4 years to apply restricted pesticides. Using record linkage, the private pesticide applicator database (n=34 722) and a birth registry (n=210 723) were combined for the years 1989 to 1991. The Minnesota Center for Health Statistics and the Minnesota State Department of Health provided the authors access to the birth registry which contained records of all in wed-lock births and birth defect data, recorded at birth, between the selected dates. Birth defects were grouped into four major anomaly categories: circulatory/respiratory; urogenital; musculoskeletal/integumental; and central nervous system (CNS). The date of conception was determined from the date of birth and the physician’s estimate of length of gestation. Finally, a state-wide questionnaire of pesticide use and crop production, provided by the Minnesota Department of Agriculture, was utilized to stratify Minnesota into high and low pesticide use regions.

The results of this study showed that pesticide applicators had significantly more children with birth anomalies than did non-applicators (p<0.001). Specifically, pesticide applicators were more likely to have children with circulatory/respiratory (p<0.05), musculoskeletal/integumental (p<0.02), and urogental anomalies (p<0.02). They also discovered when using the forest/urban regions as a control group, the wheat/sugar beets region had an excess of CNS (OR=1.49, CI=0.9-2.4), circulatory/respiratory (OR=1.9, CI=1.4-2.6), gastrointestinal (OR=1.4, CI=0.8-2.5), urogenital (OR=2.25, CI=1.7-3.0), other birth anomalies (OR=1.32, CI=1.1-1.59), and all births with anomalies (OR=1.48, 1.31-1.66). The wheat/sugar beets/potatoes region was considered to be a high-use region based on poundage of fungicides and chlorphenoxy herbicides. Application of chlorophenoxy herbicides and nearly the entire use of fungicides occur in this region of western Minnesota with most of the application occurring in the spring. Infants conceived in the spring in areas of high fungicide and herbicide use showed a significant increase in birth defects compared to infants conceived in other seasons (OR=1.36, CI, 1.10 1.69). The authors also considered the amount and specific use of 12 herbicides by county cluster for each crop growing region. Using the data from the Minnesota Department of Agriculture, counties were defined as high or low use for each herbicide. For example, those counties that used >10 000 lbs of 2,4-D active ingredient were defined as high use regions. Areas of high use 2,4-D and MCPA (phenoxyherbicides) had an increased odds ratio for combined birth anomalies including CNS, circulatory/respiratory, urogenital and musculoskeletal (OR= OR=1.86, CI=1.7-2.1) as well as all birth defects (OR=1.51, CI=1.4-1.6) compared to regions that had low use of 2,4-D and MCPA.

The normal male: female (M:F) sex ratio is reported to be 1.04-1.07 for normal births and 1.38 for births with anomalies. In this study, the rate of male birth defects was significantly higher (p=001) in pesticide appliers than general population (33.3/1000 vs. 22.6/1000). For central nervous system, circulatory/respiratory, urogenital, and musculoskeletal/integumental anomalies the M:F ratio was 2.8 for pesticide appliers and 1.5 for the general population (p=0.05).

Due to the indirect method of exposure assessment, this study’s findings are limited. Nonetheless, the observed increase in the rate of birth defects in the offspring born to pesticide applicators and the general population residing in high-use chlorophenoxy herbicide/fungicide regions as well as, infants conceived in the spring suggest that pesticide exposure may play a role in the risk of birth defects in offspring. Although the results seem to suggest an association between exposure to pesticides and altered sex ratio, these findings should be interpreted with caution. Presently, we do not know the impact that the endocrine system has on sex ratio.