Garry, V.F., Schreinemachers, D., Harkins, M., Griffith, J.
Pesticide appliers, biocides, and birth defects in rural Minnesota
Environmental Health Perspectives. 104(4):394-9. 1996.
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.