Study finds exposure to certain toxins
can affect behavior
Women's exposure to environmental contaminants that mimic
the activity of human sex hormones during prenatal development
can affect the masculinity and femininity of their offspring,
UB researchers have found.
However, the results seem to point to a shared influence
of the parents' own gender-related behavior and exposure
to the contaminants, which can act as "endocrine disrupters,"
according to David E. Sandberg, associate professor of
psychiatry and pediatrics, and lead author on the research.
The study appeared Friday in the journal Epidemiology.
It supports the findings of an October study done in the
Netherlands, which was the first to show a relationship
between exposure to hormonally active agents in the environment
and children's gender-role behavior.
The UB study reports on gender behavior of boys and girls
born to male and female anglers and their spouses who
eat contaminated sport fish from the Great Lakes.
Their findings show that in boys, the more fish the mother
consumed, the more typically masculine the boy's behavior.
Girls with one or more older siblings also showed more
masculine behavior. In an interesting twist, results showed
that girls who were breastfed longer showed more typically
Sandberg and colleagues set out to assess the relationship
between gender behavior and exposure to toxins that have
potential to influence the action of natural estrogens
and androgens at sensitive periods of sexual differentiation
in the womb. Their study group was composed of participants
in the New York State Angler Cohort Study - men and women
from 16 counties who consumed contaminated sport fish
from Lake Ontario and its tributaries. Earlier research
with this group showed that their PCB body burden was
2-to-4 times higher than that of the general population.
The children studied, 729 boys and 672 girls between
the ages of 6 and 10, all were offspring of women in the
Angler Cohort. A parent, in most cases the mother, completed
a survey designed to assess the amount of typically masculine
or typically feminine behavior the child exhibited.
While the increase in mother's years of eating fish from
contaminated waters was associated with more masculine
behavior in boys, Sandberg said this effect doesn't appear
to be related to prenatal exposure, for several reasons.
"First, hormonally active toxins from the environment
classified as endocrine disrupters, as is the case here,
are known to interfere with androgens' masculinizing effects,
rather than promoting them," he said. "Second, if these
chemicals were acting as androgens (the masculinizing
hormone), the girls' behavior would be masculinized as
the level of contaminant exposure increased, and this
was not the case." Finally, he noted, any potential masculinizing
effect of these chemicals would be overwhelmed by the
ample androgens produced by the fetal testis.
Instead, Sandberg and colleagues theorize that the more
masculine behavior of boys whose mothers had consumed
more sport fish is the consequence of the social environment,
rather than toxic exposure.
"Our speculation is that anglers and their spouses who
consume larger quantities of sport fish may encourage
more typically masculine behavior in their sons," he said.
Sandberg went on to explain that an effect of contaminant
exposure might have been observed in the girls. "Androgens
normally transferred from the mother to the female fetus
are believed to contribute to varying degrees of normal
masculine behavior in daughters, an effect that may be
disrupted by exposure to toxins in the fish.
"We drew this conclusion from the finding that female
study participants with older sisters were more masculine
in their behavior than were first born. Because mothers
transfer large quantities of their body burden of pollutants
to their offspring during pregnancy and breast-feeding,
a later-born daughter would be exposed to relatively less
endocrine-disrupting chemicals, resulting in more masculine
behavior," he noted. "In contrast, an earlier-born daughter,
who would be exposed to more endocrine disruption in the
womb, would be more 'feminized.'"
The social environment appeared to be no less important
for the girls than for the boys, and likely was the reason
for increased feminine behavior of girls who were breastfed
longer, Sandberg said.
"We speculate that mothers who breastfeed are likely
to be more traditional in their gender-role behavior than
women who don't, and that their daughters' behaviors reflect
A biological influence of contaminated breast milk on
gender development was unlikely, Sandberg observed, because
sex hormones are thought to exert a gender-organizing
effect only prenatally.
"A major limitation of our study was that we assessed
only one side of the picture, the exposure side, which
influences the biology of the child," Sandberg said. "We
need to assess the social and family environment as well,
in an effort to tease out the relative contributions of
these two sets of factors in the development of gender
differences in behavior."
John E. Vena, John Weiner, doctoral student Gregory P.
Beeler and Mya Swanson, all of the School of Medicine
and Biomedical Sciences, and Heino F.L. Meyer-Bahlburg
of Columbia University, also contributed to the study.
The research was funded in part by the National Institute
of Environmental Health Sciences (National Institutes
of Health), the Great Lakes Protection Fund and the Agency
for Toxic Substances and Disease Registry.