How much pesticide exposure in the air is acceptable?

There is a peaceful beauty to the thousands of acres of agricultural fields that define the Pajaro and Salinas valleys. And hundreds of thousands of people live, work, attend school and play in these landscapes. But these picturesque landscapes are not natural: It takes a lot of inputs, including thousands of pounds of pesticides, to make these fields thrive. Exactly how much those pesticides spill over into the bodies of the people who live, work and play in and around them has long been a contentious topic in the regulation of pesticides.

On Monday, Oct. 14, the California Department of Pesticide Regulation released a 105-page report with the results of its Air Monitoring Network for 2023. The findings are packaged as good news.

“The 2023 data found that 95 percent of all samples collected had no detectable pesticides. Twenty-one pesticides were not detected at all, and 11 were detected at very low, trace levels which indicates unlikely risk to or impact on people’s health,” DPR reports.

“Monitoring the air in communities with high pesticide use is critical to keeping California safe for everyone,” DPR Director Julie Henderson said in a statement accompanying the release of the report. “I am encouraged to see that all of the 2023 pesticide concentrations fall below our health screening levels.”

Of course, less pesticides detected in the ambient air is a good thing. But what about the 5 percent of the time, when pesticides are detected in the air – how do we account for that?

Ultimately, industrial activity, including agriculture, creates some amount of risk, and it’s up to the public, industry and regulators in a push-and-pull to determine how much risk is acceptable.

This data does not attempt to answer that question, but is a thorough a presentation of monitoring data – a critical step in understanding how much exposure people in agricultural communities have to pesticides.

DPR’s air monitoring network began in 2011, and continues today in four communities. Sites in North Monterey County (at Ohlone Elementary School, in Royal Oaks – defined more generally by DPR as Watsonville), Oxnard, Santa Maria and Shafter were selected by DPR officials among a list of 1,228 communities, ranked based on pesticide use, demographic data (with a focus on children and seniors) and people living in proximity to farms, among other factors. Last year, they monitored for 40 chemicals – 35 pesticides and five breakdown products.

At the North Monterey County site, only four chemicals came back with quantifiable detections (fumigants methyl bromide, methyl isothiocyanate or MITC, chloropicrin and 1,3-dichloropropene). Of the 50 samples, 1,3-D was detected 26 percent of the time, chloropicrin 21.6 percent of the time, methyl bromide 18 percent of the time and MITC 14.3 percent of the time.

“No chemical exceeded its acute, sub-chronic, or chronic screening level or regulatory target in 2023, meaning that pesticide concentrations found in the air are unlikely to be harmful to human health,” DPR reports of the overall findings at all four locations.

According to the U.S. Environmental Protection Agency, high concentrations of methyl bromide can cause central nervous system failures, respiratory failures and can harm the lungs, eyes and skin. Due to the damage it does to the ozone layer, methyl bromide has been largely phased out of use, thanks to the Montreal Protocol, signed back in 1987.

Although it is no longer manufactured in the U.S. and has been mostly phased out, it’s still allowed for “critical uses,” including agriculture – if “lack of methyl bromide availability would result in a significant market disruption.”

If the public wants to know why, 37 years later, there is still methyl bromide detected in the air at Ohlone Elementary School, there are some upcoming opportunities to learn more.

DPR officials will present on the air monitoring report at 10am on Friday, Oct. 25 at the department’s Pesticide Registration and Evaluation Committee meeting via Zoom. A virtual community meeting for Watsonville, Santa Maria, Oxnard and Shafter follows at 6pm on Dec. 12.

SARA RUBIN is the Weekly’s editor. Reach her at sara@montereycountynow.com