Pesticides May Be Linked to Slightly Smaller Babies, Shorter Pregnancies

THURSDAY, April 5 (HealthDay News) — Exposure to a type of
pesticide commonly used on crops eaten by U.S. consumers is linked to
shorter pregnancies and smaller babies, new research says.

The pesticides are known as organophosphates, which kill insects by
disrupting their brains and nervous systems. Originally developed as nerve
poisons during World War II, they can disrupt human nervous systems as
well, according to the U.S. Environmental Protection Agency.

The effects seen in the study were relatively small. Pregnancies for
women exposed to higher levels of organophosphates had babies that were,
on average, 1/3 pound lighter than women exposed to lower levels of the
pesticides, and their pregnancies were about three to four days
shorter.

Spread out over millions of babies, however, lighter babies and shorter
pregnancies could have serious health consequences, said senior study
author Dr. Bruce Lanphear, a clinician scientist at the Child Family
Research Institute at BC Children’s Hospital in Vancouver, British
Columbia.

“When we see a [1/3 pound] reduction in birth weight, we have to start
to take notice,” Lanphear said. “For an individual kid, it’s maybe not a
big deal, but for a population it can be. If you shift the whole
population down [1/3 pound], it can lead to dramatic increases in kids who
are very small. What we see is subtle shifts that, across a whole
population, could have dramatic effects on the premature rate.”

Prior research also has found that exposure to higher levels of
organophosphates during pregnancy is associated with lower IQs and more
behavior problems in children.

The study is published in the April 5 online edition of the journal
Environmental Health Perspectives.

Use of organophosphates has declined in recent years, but it remains
the most commonly used insecticide, said Lanphear, who is also a professor
at Simon Fraser University in British Columbia. Prior research has shown
that more than 90 percent of pregnant women and children have measurable
levels of organophosphate pesticides in their body.

The study included more than 300 pregnant women in the Cincinnati area,
including whites and blacks living in urban, suburban and rural areas and
representing the full spectrum of socioeconomic status. Twice during
pregnancy, women had their urine tested for organophosphate metabolites,
or chemicals that result when the pesticides are broken down.

Researchers also tested for or asked about other factors that could
influence the health of a pregnancy and fetus, including smoking or
exposure to secondhand smoke, race, poverty and maternal depression.

Women whose exposure was in the 85th percentile, meaning they had the
most exposure, had smaller babies and shorter pregnancies on average than
those in the 15th percentile. Women in the 85th percentile showed evidence
of exposure that was 10 times the rate of exposure for women in the
15th.

The reduction in pregnancy length was statistically significant only in
white women, while reduction in birth weight was significant only for
black women.

The study couldn’t pinpoint the main source of pesticide exposure, but
previous research has singled out diet and home pesticide use as leading
sources in non-agricultural settings, the authors said.

Commenting on the study, experts voiced mixed opinions.

“This is an important study, part of the ever-accumulating body of
evidence that pesticides are hazardous to human health, even at low
doses,” said Dr. Kenneth Spaeth, director of the Occupational and
Environmental Medicine Center at North Shore-LIJ Health System in New Hyde
Park, N.Y. “We tend to think that the kinds of low-level exposures we get
on a regular basis are not harmful, but studies like this help show there
is harm, and we need to be much more mindful and rethink how we regulate
and understand how these pesticides affect us.”

It’s known that pesticides reach the fetus, “because we find traces of
pesticides in umbilical cord blood,” Spaeth said. “Pesticides can also
accumulate in breast milk, so you get a double whammy for infants who can
be exposed in the womb, and then after birth.”

Dr. Michael Katz, interim medical director for the March of Dimes,
cautioned against drawing firm conclusions from the study. Although it was
carefully designed and conducted, he said, researchers found an
association between pesticide exposure and shorter pregnancies and lower
birth weights, but they don’t show that the pesticides caused the fetal
effects.

That would require a randomized controlled trial, which is unlikely to
ever be done because ethical constraints prevent scientists from
deliberately exposing kids to pesticides.

In addition, the differences in birth weight and pregnancy length were
minor and fall within what are normal variations, Katz added.

“The differences were very small, and there are things that can be
statistically significant but aren’t biologically significant,” he
said.

Researchers can’t explain why they saw racial differences in the effect
on fetuses. Prior research, however, has shown racial differences in how
people metabolize toxins, while blacks and whites may be exposed to
different organophosphates, experts said.

More information

The U.S. National Institute of Environmental Health Sciences
has more on pesticides.

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