Stanislaus County ranked top priority for state pesticide air monitoring
The California Department of Pesticide Regulation is expanding its air monitoring network, and Stanislaus County is a priority site.
The air monitoring network provides DPR with important data, allowing for long-term assessment of potential pesticide exposures in agricultural communities with high pesticide use. Monitors test for 40 analytes, including fumigants, organophosphates, herbicides, fungicides and insecticides.
DPR will be adding four new monitors.
Stanislaus County was ranked as second on the priority list, following Tulare County. Imperial, Siskiyou and San Joaquin counties were also on the list.
Eight places in Stanislaus County were among the final list of communities identified as being located in either high-fumigant or high-organophosphate use areas.
The Bret Harte, Bystrom, Denair, Hickman, Parklawn, Rouse and Modesto Airport neighborhoods are in areas of high fumigant use. Westley is an area of both high fumigant and high organophosphate use.
DPR started with 1,611 communities in California and narrowed the list down based on areas with high fumigant and organophosphate use. It excluded counties that already have an air monitoring network and focused on communities near schools.
DPR also considered counties with high Population Characteristic scores, as calculated by the Office of Environmental Health Hazard Assessment.
The higher the PC percentile, the more susceptible a population may be to pollutant exposure. The airport district in Stanislaus County had the highest PC percentile — at 98.88.
DPR held a virtual meeting on Tuesday, with 25 attendees, to discuss the proposal and how it identifies priority locations.
“Air monitoring is not just a technical topic. It touches on issues that people care deeply about, including public health, transparency and trust,” said DPR’s deputy director of the monitoring and mitigation division, Madison Le. “This expansion represents a major step forward.”
Currently, there are five monitoring network sites in Ventura County, Santa Barbara County, Kern County, Monterey County and Merced County, plus a station specifically to monitor the pesticide 1,3-Dichloropropene in Fresno County. Data has been monitored at these sites for over a decade.
“That kind of long-term data collection is invaluable. There are few places across the country or the world with that kind of long-term data set,” said Aniela Burant, senior environmental scientist at DPR.
In 2024, a DPR launched a seasonal study in Stanislaus County using mobile monitoring stations in the Monterey Park Tract, Grayson and Hughson for 15 weeks. The results of the study found that the three pesticides monitored were detected in some samples, but all concentrations remained below health-based safety thresholds.
DPR received additional funding from the Legislature to permanently expand its air monitoring efforts in 2024. This includes four new monitoring stations, a mobile monitoring platform and the conversion of the 1,3-D monitoring station in Fresno County to a full air monitoring network station.
The target date for the expansions is the end of 2027, according to DPR.
DPR is asking the public for feedback on its order of the ranking of the counties, any other counties that should be considered and any factors it should consider. It is also asking for the public to rank the communities with the most desirable location for monitoring, meaning it is “accessible to sampling personnel on weekdays and weekends, have electrical outlets and are secure from appointment loss or tampering.”
The location must also be on a school property or directly adjacent to a school property.
The public comment period ends on May 11. Feedback can be submitted online in English or Spanish at tinyurl.com/dprcomment.
This story was originally published April 15, 2026 at 1:58 PM.
