How a new system of drones and low-cost sensors can protect communities from air pollution

Clouds settle low in the sky as dusk sets in across Pajaro Valley. Fields of strawberries stretch out as far as the eye can see, catching the last amber rays of the day. In the distance, the twin stacks of Moss Landing Power Plant sit among factories pushing plumes of smoke into the air.

On the exterior wall of a house in Castroville, a newly installed sensor glows green with an important message: It’s safe to go outside. For Maribel Martínez, a farmworker and mother living here, the information is crucial. Two of her children have asthma, and knowing when the air is hazardous to breathe is important for protecting their health.

“I always tell them to check the monitor before going out,” she said. “They know that if the monitor is red, we don’t go outside. We close the doors and shut the windows.”

Martínez’s sensor is one of several recently installed to monitor air pollution in Pajaro Valley by scientists at UC Santa Cruz. The work is part of a larger research project using drone flights and new monitoring technologies to better understand when and where farmworkers are most severely exposed to air pollution.

Farmworkers like Martinez are grappling with extreme heat, pesticide exposure, and air pollution. To avoid the hottest hours of the day, they start early, getting out to the fields at dawn when it is cooler. But avoiding overheating in the face of rising temperatures is also exposing farmworkers to higher levels of air pollution.

“The folks contributing the least to climate change are the ones bearing the most of the brunt,” said UC Santa Cruz professor Javier González-Rocha.

Communities in Pajaro Valley face pollutants including microscopic particles called PM2.5 and ground level ozone. PM2.5, which comes from sources like wildfire smoke and vehicle exhausts, can penetrate deep into the lungs and enter the bloodstream, triggering asthma and worsening heart disease.

Ground level ozone forms as a result of interactions between vehicle and industrial emissions and volatile organic compounds, chemicals in the air that come from a variety of sources, including pesticides. It can damage airways when inhaled.

Using drones to measure levels of pollution at different altitudes, Javier González-Rocha found a concerning pattern. During the dawn and dusk, prime work times for farmworkers avoiding heat, cooler temperatures allow clouds of pollutants to drift downwards. The result: Pollution levels at ground level are higher.

“Starting work earlier is an imperfect solution. It’s removing the worker from one risk, but it’s exposing them to another,” said González-Rocha, who’s leading a project at UCSC to close air monitoring gaps directly south of Santa Cruz.

Back in Castroville, he points over to a high school in the distance where students are playing soccer. A sinking haze of pollution can just be made out in the glare from the stadium lights.

For González-Rocha, the work has personal significance. The son of immigrant farmworkers, he grew up playing in the fields of Pajaro Valley while his parents labored. This upbringing inspired him to use his Ph.D. in aerospace engineering to research and improve air pollution monitoring for farmworker communities.

Sensors installed by the UCSC team, like the one at Martinez’s house, help residents know when pollution levels are high. But before González-Rocha and his colleagues started installing them, there was a large monitoring gap in the Pajaro Valley, compared to neighboring wealthier cities like Santa Cruz and Monterey.

To address that gap, González-Rocha partnered with Adrian Ayala, a local community advocate and former board president of the North Monterey Unified School District, to reach families in the valley and offer sensor installation. They set up a meeting with community members to explain how the sensors worked and why measuring pollution mattered.

Their efforts were met with hesitancy from some families — installing sensors required Ayala to enter homes for installation, and some families had privacy concerns around providing data to the sensors.

But slowly and surely, community members came around. Ayala reassured families that no personal information would be collected and that the air monitors would help detect pollution in the area. Since April, he has installed seven sensors around the region with plans for more.

Ayala stressed the importance of not just providing sensors, but educating families about how to use them.

“The goal is to also train them so that this project doesn’t end here. They learn, and from here on out, they can start installing sensors,” he said.

But difficulties still exist. The monitors installed so far are PurpleAir sensors, a proprietary brand that requires Wi-Fi and a power source to work.

“A lot of people here don’t have Wi-Fi,” Martínez said. “I was close to discontinuing my internet. It’s very expensive.” Without connection to Wi-Fi, PurpleAir monitors can’t transmit data.

So González-Rocha and a team of undergraduate students at UCSC are developing new, low-cost sensors that don’t need Wi-Fi to work.

The new sensors use long-range radio to send their recorded data to a central receiver node. Once that node, the only part of the system that needs Wi-Fi, receives the data, it can transmit the data back to the team.

The sensors also come equipped with solar panels, meaning they don’t need to be plugged in and can be placed anywhere, such as in the middle of a field. González-Rocha and Ayala hope to start installing the versatile, low-cost monitors in the coming year.

“The question was how do we come up with a solution that places the user at the center, because if we create a fancy tool but it’s not compatible with the user, then we’ve failed,” González-Rocha said.

To help communities better understand air pollution and access data, Javier’s team has partnered with Regeneración, a nonprofit promoting community climate action in Pajaro Valley. The nonprofit has run focus groups and listening sessions to better understand what challenges residents have in understanding air pollution data.

This outreach is crucial, said Eloy Ortiz, special projects manager at Regeneración. “A lot of these folks are in survival mode,” he said. “They’re thinking about how to get the rent paid, how to get food on the table. They’re not necessarily thinking about air quality.”

For Martínez, the work is already having an impact, giving her and her sons peace of mind. “For us, it’s important because there’s a lot we don’t know,” she said. “But now we’re talking about air quality, and we’re looking after our health a bit more.”