UCSC researcher aims to fill gaps in Pajaro Valley air monitoring data, help farmworkers deal with pollution health impacts

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A researcher from UC Santa Cruz is working to identify and fill air monitoring data gaps in the Pajaro Valley to better inform residents, especially farmworkers and their employers, about how to better protect themselves during peak exposure to air pollutants. 

Some key findings include a higher concentration of air pollutants during the early morning hours, the impact of prescribed burns happening north of the valley and air quality at times reaching unhealthy levels.  

For the past year and a half, Javier González-Rocha, an assistant professor of mathematics at UCSC, and his team have been continuously monitoring the air quality in the Pajaro Valley after realizing the area had no air monitors, while areas north of Watsonville had dozens. 

His team so far has installed 35 air monitors in homes and apartments across the region, going as far as Castroville in Monterey County, to understand where air pollution is more concentrated. González-Rocha is partnering with Watsonville-based environmental justice organization Regeneración to help share his research with the community throughout the process. 

González-Rocha, a Watsonville native, said that he’s always been conscious about how the air quality in the region might be affecting farmworkers. 

“They are exposed to pesticides, they’re exposed to dust and exposed to vehicle exhaust,” he said. “All of these things are really compounding on farm workers.”

His team examined data from the California Office of Environmental Health Hazard Assessment, which demonstrated the significant pollution exposures in the region, much of which has to do with pesticides – not surprising since agriculture is the biggest economic driver in the Pajaro Valley and Watsonville. 

South County communities rank among the most polluted in the region, according to the CalEnviroScreen, a state database used to identify communities that are affected by pollution. 

“North of Watsonville things tend to be better. But as you go towards Pajaro, things tend to get worse,” González-Rocha said. 

One of the major findings from González-Rocha’s research is that concentrations of pollutants – such as vehicle emissions, dust and pesticides – are higher in the early morning, just before sunrise. The reasons for this have to do with the “mechanics of the atmosphere” and the geography of the region, he said. 

“Pajaro Valley, it’s a valley, right? So, at nighttime as the air cools, the air wants to flow to its lowest point and things end up funneling down to the valley,” González-Rocha said. 

Throughout the day, pollutants are dispersed constantly in the atmosphere because the air is warmer, said González-Rocha. In the evening and early morning, though, the ground and air begin to cool and trap pollutants closer to the air people breathe. 

González-Rocha told Lookout that after sharing his team’s findings with the farmworker community at a session led by Regeneración, people were able to connect the dots with their own experiences. 

PESTICIDES IN THE PAJARO VALLEY: Read Lookout’s news and Community Voices opinion coverage here

“A lot of farmworkers were saying, ‘Ah, that makes sense why you hear people cough in the morning,’” he said. “They’re able to connect what we’re seeing in the data with things that they experience.” 

Studies have shown that pesticide exposure can be linked to significant respiratory issues, such as chronic bronchitis, asthma and wheezing. 

This type of data also presents an opportunity to improve coordination between land managers – people who are in charge of prescribed burns – and farm owners, González-Rocha said. 

His team gathered data following a prescribed burn at Wilder Ranch State Park on Oct. 6, and noticed immediate impacts in the Pajaro Valley. González-Rocha told Lookout that the morning after the burn, the peak for air pollution was around 9 a.m.

Farmworkers typically enter the fields around 6 a.m., said González-Rocha. One way employers could improve the conditions for their employees, he said, is to offer personal protective equipment (PPE), like masks instead of bandanas, to use in the morning. He also suggested shifting the harvesting periods so work can start later in the day. 

“Where we saw the spike, it was an event that lasted two to three hours,” González-Rocha said. “It’s not something that would have impacted the air quality for the entire day. But, if there would have been some coordination to start work a bit later, we could have prevented people from breathing that spike in air quality.” 

The highest air quality index levels recorded last November and December exceeded “acceptable” levels by at least 14 points, said González-Rocha. The air quality index (AQI) is a way to measure outdoor air quality and health, with anything above 100 AQI considered unhealthy. During that two-month period, the highest AQI was 114. 

Changes in air quality are not limited to pesticides or vehicle emissions, said González-Rocha; air quality is also affected by warmer temperatures. In March, when most of the county was experiencing a heat wave, the air quality index levels were also elevated in South County, but not to levels that were considered unhealthy, like in late 2025. 

While the pollution levels can be harmless for someone who primarily works indoors, farmworkers, he said, are exposed to the environment while doing exhaustive work daily.

The next step, González-Rocha said, is figuring out how to present the data in a way that’s understandable to the community, so residents can make decisions about how to stay healthy. 

He and the team at Regeneración have been sharing this information with the community through meetings, but González-Rocha said a clearly designed data dashboard could help people better understand the situation. 

But, to do that, there are two things to take into account, said 2, special projects manager for Regeneración. 

“We don’t want to just create something else. We don’t want to give information to people and have something else to worry about,” Ortiz said. 

The organization also needs to consider making the data available in Mixtec for the region’s growing Indigenous population, he said. Regeneración met with members of that community to get a sense of what they would need to be included in a future dashboard showing the pollution data. 

Ortiz told Lookout he hopes that by making this information readily available to the farmworking community, people will be able to make informed decisions, such as whether to use masks as opposed to bandanas. While data is not everything, González-Rocha said, it does have a role in shaping the conversation. 

“Enabling agency, that’s really what it is,” González-Rocha said. “One of the hopes is that even if we don’t get a solution, we can highlight new information that can get us to think about what our shared responsibility is, even as consumers.” 

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