Applying large amounts of pesticides to farm fields can have negative effects on babies born to mothers living nearby, according to new research.

The data-crunching published inNature Communicationslooked at the farm-heavy San Joaquin Valley in California, where a variety of pesticides get applied to dozens of different crops including fruits, vegetables and nuts.

Researchers matched birth records for more than a half-million babies born between 1997-2011 to pesticide application rates for a one-square-mile region including the mother鈥檚 address.

Most babies were fine. In fact, researchers had to look at the five percent exposed to the highest amount of pesticides to find meaningful impacts, and it was the top one percent--those presumably exposed to the most pesticides--that showed lower birth weights, shorter gestation lengths and adverse birth outcomes.

鈥淲e see these important effects, but just for a small subset of the population living in this agriculturally dominated region,鈥� says study author Ashley Larsen, an assistant professor in theBren School of Environmental Science & Managementat the University of California, Santa Barbara. 鈥淲e鈥檙e working on trying to understand what鈥檚 behind these hotspots of pesticide use and when they occur.鈥�

Larsen and her colleagues drew upon California鈥檚 database of pesticide application, which correlates the amount of pesticide active ingredients applied to a specific geographic area. Larsen says California regulations are unique in requiring this degree of public information on pesticide use.

Still, this research is not able to pinpoint any individual problem chemical. The study looks only at aggregate active ingredients. In California, insecticides and fungicides are very widely used, while herbicides are less dominant.

In the Midwest, herbicides are the dominant pesticide used on row crops such as corn and soybeans. Still, Alan Kolok, director of the Nebraska Watershed Network, says there are some lessons for the Midwest.

鈥淥verall, the population is safe,鈥� Kolok says. 鈥淭he risk of pesticides, even in the San Joaquin Valley to the Californians, is not really an issue for 95 percent of the population. However, there is a tail of the population, 5 percent or 1 percent or 1/10 of 1 percent, those individuals that are getting really high loads of chemical in their local environments, that are experiencing adverse impacts.鈥�

Kolok says there is no way to directly compare the exposure that group faced to any region or population in the Midwest. But people concerned about pesticide exposure here can still learn from the results.

鈥淭he takehome message for out here is, when would there be periods in Iowa and Nebraska when you, you personally, might fall into that tail?鈥� he asked, referring to the sliver of the population adversely affected. 鈥淎nd one time might be spring, as opposed to winter or summer or fall, because that鈥檚 when herbicides in Iowa and Nebraska are applied.鈥�

He says pregnant women living close to farm fields in the Midwest might decide to limit their exposure to the spring application of pesticides.

Kolok and Larsen both say the results from the California study could also help agriculture and public health officials design ways to mitigate the risk in the regions where the largest exposures occur.

鈥淭he real shining ray of hope is this isn鈥檛 Rachel Carson withSilent Springand DDT,鈥� Kolok says, referring to the 1962 book widely credited with raising alarm bells about the risks of pesticide use, 鈥渨here birds are falling out of the sky and bald eagles are on the verge of extinction.鈥�

Rather, Kolok sees this study saying almost the opposite.

鈥淥ur environment is comparatively clean,鈥� he says, 鈥渢he only issue is not that we鈥檙e all contaminated with pesticides. The issue is that there are spots that are contaminated.鈥�

That鈥檚 a manageable-sized problem to approach, he says.

鈥淵ou can identify really significant sources [of exposure], and by identifying those significant sources and taking steps to remediate them, you could actually have a noticeable, significant impact on the health of a small percentage of the public,鈥� Kolok says.

In the Midwest today, though, Kolok says such fine-resolution data on pesticide application is not available.

Larsen says she鈥檚 hopeful the study will lead to proactive efforts to reduce risk.

鈥淧articularly where we have this pesticide-use data,鈥� she says, 鈥渢hat policy makers, or (medical) practitioners even, could interact with individuals who are at the highest risk at prenatal care visits or something of the sort.鈥�

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