Negative
effects of pesticide exposure on birth outcomes

Researchers unravel the negative effects of pesticide exposure on birth
outcomes, such as weight, gestation and abnormalities

Date:

August 29, 2017

Source:

University of California – Santa Barbara

Summary:

Researchers
have unraveled the negative effects of pesticide exposure on birth outcomes,
such as weight, gestation and abnormalities.

Although common opinion
holds that exposure to pesticides increases adverse birth outcomes, the
existing body of scientific evidence is ambiguous. Logistical and ethical
barriers — pesticide use data are not widely available and randomized control
trials are impossible — have gotten in the way of more accurate conclusions.

A new study by
researchers at UC Santa Barbara addresses the issue in a novel way — by
analyzing birth outcomes in California’s San Joaquin Valley.

With more than one-third
of the country’s vegetables and two-thirds of its fruits and nuts produced
there, the San Joaquin Valley, not surprisingly, is a heavy pesticide-use
region. The UCSB team investigated the effect of exposure during pregnancy in
this agriculturally dominated area and observed an increase in adverse outcomes
accompanying very high levels of pesticide exposure. Their findings appear in
the journal Nature Communications.

“For the majority of
births, there is no statistically identifiable impact of pesticide exposure on
birth outcome,” said lead author Ashley Larsen, an assistant professor in UCSB’s
Bren School of Environmental Science & Management. “Yet mothers
exposed to extreme levels of pesticides, defined here as the top 5 percent of
the pesticide exposure distribution, experienced between 5 and 9 percent
increases in the probability of adverse outcomes with an approximately 13-gram
decrease in birth weight.”

Using individual birth
certificate records for more than 500,000 single births between 1997 and 2011,
coupled with pesticide use data at a fine spatial and temporal scale, the
scientists were able to determine if residential agricultural pesticide
exposure during gestation — by trimester and by toxicity — influenced birth
weight, gestational length or birth abnormalities.

They found negative
effects of pesticide exposure for all birth outcomes — birth weight, low birth
weight, gestational length, preterm birth, birth abnormalities — but only for
mothers exposed to very high levels of pesticides — the top 5 percent of the
exposure distribution in this sample. This group was exposed to 4,200 kilograms
of pesticides applied in the 1-square-mile regions encompassing their addresses
during pregnancy.

“If we can identify
where and why these extremely high levels of use are occurring, particularly
near human settlements, policymakers and health workers can work to reduce
extreme exposures near agricultural communities via information campaigns or
farmer outreach,” Larsen explained.

Numerous chemicals are
used daily in close proximity to residential areas, making it difficult to
ascertain a specific responsible agent. As a result, in this study, the
researchers looked at the combined results from all pesticides used in the
region.

“We don’t have a
good understanding of how different chemicals interact with each other in the
environment,” Larsen said. “Additional work is needed to understand
which chemicals or combinations of chemicals are most dangerous to human
health.”

Story Source:

Materials
provided by University of
California – Santa Barbara. Original written by Julie Cohen. Note:
Content may be edited for style and length.