28-04-2025
Pesticide levels found in Stanislaus County air — but far below danger limits
The California Department of Pesticide Regulation shared early findings from a seasonal air monitoring study conducted last year in Stanislaus County. The central question driving the study: Are pesticide levels in the air high enough to pose health risks?
While the three pesticides monitored were detected in some samples, all concentrations remained below health-based safety thresholds. Preliminary data showed that both short- and medium-term levels of the fumigants were very low — none exceeded DPR's regulatory limits.
'From the start, this project has been about transparency, community involvement and working together to understand what's in the air during the peak months of pesticide use,' Stanislaus County Agricultural Commissioner Linda Pinfold said in a statement. 'We're all committed to protecting the health and safety of our residents, supporting our farmworkers and ensuring the long-term sustainability of our farming operations.'
Yvan Delgaro, senior environmental scientist with the DPR's Air Program, gave a presentation Friday at the Grayson Community Center, where about 40 people gathered to hear the findings.
As part of DPR's ongoing efforts to evaluate pesticide safety, the agency collects air samples to measure pesticide levels, uses computer models to analyze the data and determines whether action is needed to reduce potential health risks from exposure.
If a risk is found, DPR can recommend measures including limiting how much pesticide can be used, who can apply it, how and when it's applied — such as during certain weather conditions — and how close applications can be to homes, schools, or the size of the treated area. These rules are enforced by county agricultural commissioners.
DPR's Air Program conducted a 15-week monitoring study from Jan. 20 to May 10, 2024, testing four days a week for three specific pesticides in the air. The study period was chosen based on past pesticide application patterns.
Air monitors were placed in Grayson, the Monterey Park Tract west of Turlock, and Hughson — locations chosen due to both community interest and local pesticide use.
This marked the first time DPR conducted a multi-community air study in Stanislaus County, which was selected because of its high pesticide use between 2019 and 2021 and concerns raised by residents.
The air samples were tested for three soil fumigants: 1,3-dichloropropene (1,3-D), chloropicrin and methyl isothiocyanate (MITC). These pesticides turn into gas after being applied to soil to kill pests and can drift from the application site into the air.
All three monitoring sites showed similar detection patterns, with more frequent detection in April. The highest levels were found in Grayson that month, with 1,3-D reaching 1.5% of DPR's regulatory target — a level still well below what is considered harmful. Regulatory targets are the levels of pesticides in the air that are considered safe for everyone, with no expected health effects.
Of the three pesticides, 1,3-D was detected in 19% of samples, MITC in 34% and chloropicrin not at all.
Overall, the concentrations found were low compared to safety thresholds.
All three pesticides are classified as toxic air contaminants and restricted materials, meaning they can pose serious health risks if people are exposed to high levels. Because of these risks, a permit is required to apply them.
Each pesticide is used on different crops common in the region. 1,3-D is often applied before planting almonds and sweet potatoes, chloropicrin is used for almonds and transplanting other crops, and MITC is commonly used on tomatoes, melons and watermelons.
Exposure to these pesticides can cause a range of symptoms, including skin and nose irritation, chest pain, difficulty breathing, watery or burning eyes, coughing, headache, nausea, sore throat and excessive salivation. MITC, in particular, can lead to additional issues like numbness or tingling in the limbs, memory problems, headaches and behavioral changes.
Long-term exposure to 1,3-D has been linked to an increased risk of cancer.
DPR advises anyone who may have been exposed to a pesticide to seek immediate medical attention by calling 911 or going to the nearest hospital — and to make sure medical staff are aware that pesticide exposure is suspected.
Grayson resident John Mataka urged community members to advocate for themselves at medical appointments. He noted that symptoms can sometimes be brushed off as allergies, so it's important to ask doctors to report the exposure.
'You gotta push the doctor,' Mataka said.
New regulations on 1,3-D went into effect at the start of 2024, making this the first focused study of the pesticide under the new rules. DPR is currently working with the California Office of Environmental Health Hazard Assessment to develop additional restrictions on 1,3-D use.
The full dataset from this air monitoring study will be released in June as part of DPR's Pesticide Air Monitoring Results. A full report is expected later this year or early next year.
Residents can track local pesticide applications by visiting the Spray Days website, where they can view an interactive map and sign up for notifications.
Low-income households in disadvantaged communities may also qualify for a free home air filtration unit through the San Joaquin Valley Air Pollution Control District's Clean Air Rooms Program. To be eligible, residents must live within the district and not have previously received a unit.
To report a pesticide exposure or misuse, contact the County Agricultural Commissioner's Office. Reports can also be submitted anonymously using the CASPIR app.
Additional community presentations will be held Monday at 4:30 p.m. at the Monterey Park Tract Community Center, 7655 Foy Ave., and Tuesday at 4 p.m. at the United Samaritan Community Center in Hughson, 2314 Third St.
Snacks, interpretation and childcare activities will be provided, courtesy of Valley Improvement Projects.
'I'm grateful for the partnerships that made this study possible — they showed a strong commitment to finding balance: protecting our environment and communities while also supporting our vital agricultural industry. This is a powerful example of what we can accomplish when science, local knowledge, and community voices come together,' Pinfold stated.
