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 Offspring of expectant mothers who lived near farms that applied the
heaviest concentrations of pesticides were most at risk, the
research showed. Mothers who lived in close proximity to
agricultural operations using the highest percentage of pesticides -
the top 1 percent - had an 11 percent increased probability of
preterm delivery and a 20 percent increased probability of having a
low birth-weight baby.
For most women, living near farms growing fruits, nuts and
vegetables failed to increase the possibility of low birth weight
and preterm delivery, the research found. But an examination of the
areas exposed to the heaviest concentrations of pesticides applied
showed magnified fetal vulnerability.
“There is a smaller subset that seems to be bearing the burden,”
said lead author Ashley Larsen, a professor at the Bren School of
Environmental Science and Management at the University of
California, Santa Barbara.
“Hopefully we can pinpoint how to reduce these very high levels,”
she said in a phone interview.
Larsen and her team coupled birth certificate records for more than
500,000 San Joaquin Valley births between 1997 and 2011 with
pesticide-use data to examine how exposure by trimester and
pesticide concentration might influence birth weight and gestational
length.
The San Joaquin Valley is California’s most productive agricultural
region.
The new study found that women exposed to the top 25 percent of
pesticide loads in the San Joaquin Valley had babies with no
detectable effect. But those in the top 5 percent of exposures had
increases in the range of 5 to 9 percent in adverse outcomes,
according to the report in the journal Nature Communications.
Larsen said she would like to see educators and policymakers work
with farmers to reduce extreme pesticide concentrations.
But Robert Gunier of the Center for Environmental Research and
Children’s Health in Berkeley, California, said he doubted such a
change would reduce adverse birth outcomes.
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Although he agreed that reducing pesticide use in the highest use
areas could eliminate adverse birth outcomes, he said in an email:
“Unfortunately, combining all pesticides in the analysis obscures
the relationships with specific pesticides or pesticide mixtures,
preventing concrete policy changes.”
“I would bet that if a law was passed to limit pesticide use in high
pesticide-use areas, the reduction would be for the most heavily
used and often least toxic pesticides, and this would not eliminate
adverse birth outcomes related to agricultural pesticide use,” he
said.
Gunier, an environmental health researcher, was not involved with
the new study.
Future studies should evaluate pesticide mixtures to identify
substances of concern, he said.
Prior research on the effects of pesticides on birth outcomes has
been inconclusive, the study’s authors write.
But the relationship between pesticides and premature birth and low
birth weight has been observed in previous studies, Gunier said.
In 2013, he was involved in a study that found that exposure to
methyl bromide, a fungicide used in cultivating strawberries, during
the second trimester was associated with markers of restricted fetal
growth.
SOURCE: http://go.nature.com/2iJEEcX Nature Communications, online
August 29, 2017.
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