AR, TE Arbuckle and P-H Chyou. 2003. Risk factors for female
infertility in an agricultural region. Epidemiology
et al. report a strong association between using herbicides
and infertility in women. In their study population, women who were
infertile were 27 times more likely to have mixed or applied herbicides
in the two years prior to attempting conception than women who were
fertile. Other factors, including smoking and exposure to passive
smoke, steady weight gain during adult life, and consuming alcoholic
beverages were also associated with infertility.
did they do? Greenlee et al. conducted a retrospective
case-control study examining the association between infertility
in women and different risk factors.
recruited infertile women to the study via electronic records of
women seeking infertility treatment. Their diagnoses included endometriosis,
anovulation, pituitary-hypothalamic dysfunctions, etc. Couples whose
sterility was a result of any form of male infertility or surgival
intervention, e.g., hysterectomy or vasectomy, were excluded from
controls were pregnant women from the same population. From the
same age range, control women were seeking prenatal care during
their first pregnancy, and had conceived in fewer than 12 months
of trying. Any controls who reported ever having difficulty conceiving
or maintaining a pregnancy, or whose male partner had a questionable
history of infertility were also excluded.
were then matched to cases on the bases of age and date of clinical
determine exposure histories, cases and controls were interviewed
about their activities for the 2 years prior to attempting to become
pregnant. The questionnaire included questions on demographics,
occupation, exposures, pesticide use, residency on a farm, tobacco
and alcohol use, etc.
did they find? A total of 1,791 potential cases were screened
for the study, along with 822 potential controls. After recruitment
and screening, 322 cases and 322 matched controls participated in
the study. Cases and controls were well matched for most variables,
including age, household income, smoking status, body mass index,
age at menarche, and number of sexual partners in lifetime.
differed somewhat in schooling (cases more likely to be a high school
graduate; but not more likely to have schooling beyond high school).
Cases were somewhat more likely to have exposure to passive smoke,
to consume alcohol, and to have steadily gained weight. The odds-ratios
for these variables were mostly under 2, with the odds-ratio of
infertility rising to 6.7 for women who consumed at least 7 alcoholic
drinks per week.
several associations that Greenlee et al. examined between
infertility and exposure to agricultural chemicals, two stood out:
infertile women were almost 27 times more likely to have mixed or
applied herbicides (but not insecticides) than fertile women, and
3.3 times more likely to have used fungicides. Both these odds-ratios
reflect adjustments for maternal level of education, passive smoke
exposure and other variables. Perhaps paradoxically, living on a
farm, ranch or in a rural home reduced the likelihood of infertility.
the 27-fold increase in risk of infertility associated with having
mixed or applied herbicides was very strong, the number of case
women who fell in this category, 21, was relatively small. Hence
the 95% confidence limits for the estimate of the odds-ratio was
quite broad, from 1.9 to 348.
does it mean? These findings are consistent with a host
of previous studies, involving both epidemiological research and
laboratory experiments, that have found associations between infertility
and agricultural chemicals. The laboratory experiments with animals
and cell lines are unambiguous: an array of compounds working through
multiple pathways affecting a variety of specific endpoints can
suppress fertility in exposed animals. In people, elevated risk
of poor sperm quality in Missouri men with relatively high urinary
levels of alachlor, atrazine and diazinon, reported recently by
Swan et al.
in 2003, is the most powerful example to date.
collective weight of evidence is very strong, especially in light
of the animal experiments. Taken together, they indicate that fertility
of American women and men is being undermined by today's use of
agricultural chemicals. Greenlee et al.'s data in this
study suggest that precautionary measures to avoid impairing a woman's
fertility should include avoiding working with herbicides and fungicides
for at least two years prior to attempting to conceive. Swan's results,
on the other hand, indicate that sufficient exposure to impair fertility
can take place even without working directly with pesticides, and
thus that broader measures to reduce exposures will be necessary.