How can we measure health risks from oil and gas wells near housing?

The Challenge: The risk of living near oil and gas wells in California was unknown

When David J.X. González considers the places that have most shaped his life, he remembers an 18-mile stretch of sand dunes bordering his hometown of Nipomo, on California’s Central Coast.

In the 1990s, the vast Guadalupe-Nipomo Dunes Complex was his playground—a place where he could run down steep hills before collapsing into the soft, sandy earth. People fished offshore, hikers watched for hawks, and beachcombers scouted for the threatened western snowy plover.

It was also the site of a decades-long oil spill that nearly destroyed an ecosystem. In contrast to the 1989 Exxon Valdez spill, which became known around the world, the slow-motion disaster at the Guadalupe-Nipomo Dunes—dubbed “The Silent Spill”—received significantly less attention.

But it was one of the largest oil spills in U.S. history; in which pipelines owned by Union Oil Company of California leaked some 12 million gallons of diluent, a product similar to kerosene that helps crude oil flow. The spill leached benzene and other volatile organic compounds into sand dunes and groundwater, contaminated surface wetlands, and poisoned the marshes and estuaries inhabited by rare birds and amphibians.

The aftermath of this disaster—which the polluter didn’t start cleaning until 1994, five years after the spill—showed Gonzalez the importance of regulating the oil and gas industry. It also made him wonder about the safety of the more than 240,000 oil and gas wells throughout California, mostly in Kern and Los Angeles counties.

Many of these wells were initially developed far from housing tracts, but as the population grew, the distance became much shorter, and millions of people were exposed to the steady release of toxic chemicals and smoke.

Who lived there, and what health problems did they face? How close was too close for houses or schools? Were environmental hazards concentrated in places where low-income people, and people of color, lived? And what effect do California’s worsening wildfires add to the toxic mix? Gonzalez was surprised by the lack of research, which made it impossible to quantify the problem, or to take steps to fix it.

As he pursued his education, leading up to a PhD in environment and resources from Stanford University, Gonzalez worked with his mentors to fill the gaps. By collaborating with communities, Gonzalez has been able to quantify harms and provide evidence for more protective policies.

In 2023, he became an assistant professor of environmental health science at UC Berkeley School of Public Health, and launched the EQUIS Lab, which conducts research that expands scientific understanding of how our changing environment impacts health and contributes to health disparities, addressing questions relevant to policymakers and impacted communities. It has been a busy—and fruitful—three years.

“We’re counting harm,” Gonzalez said. “We are counting the people that have been harmed by different practices and pollution from certain industries that have created the world that we live in today. I want to transition to a place where we’re counting benefits.”

The response: A comprehensive study leads to a new state law

It’s not easy to pinpoint the cause of an individual case of asthma, or of one premature birth. But Gonzalez thinks that knowledge can be reciprocal—that communities with direct experiences should shape the research, which can ultimately help improve lives.

“My theory of change,” Gonzalez said, “is that we can work alongside communities and back up their knowledge with peer-reviewed science and bring that evidence to regulators and policymakers.”

He put this theory into practice in a multi-year study of air quality and the experiences of people living near oil wells in the San Joaquin Valley. Gonzalez, then still at Stanford, and his team of researchers concluded that living close to oil wells was linked to preterm birth—the largest cause of infant and neonatal mortality worldwide.

The researchers obtained data on approximately 1 million daily observations from 314 monitors in the EPA Air Quality System from 2006–2019. The researchers included daily concentrations of five routinely monitored ambient air pollutants: Fine particle pollution (PM2.5), carbon monoxide, nitrogen dioxide, ozone, and volatile organic compounds. They found elevated concentrations of air pollutants as far as 2.5 miles downwind of wells.

They observed an association between preterm birth and exposure to oil and gas well sites. In a secondary analysis, the researchers also found evidence of higher concentrations of ambient air pollutants at air monitoring sites in proximity to drilling sites compared with unexposed monitors. More than 2.5 million Californians live within 3,200 feet of an oil or gas well. In a separate study, Gonzalez’s team also found that Black and Latinx Californians face the highest exposure to oil and gas wells.

Findings from the study became part of the base of evidence in a 2024 report to the state, which advocacy groups and lawmakers used to craft legislation about setback requirements for new oil and gas developments.

State lawmakers discussed Gonzalez’s research on the floor of the Senate before they passed SB 1137, the 2022 law that established buffer zones in neighborhoods with oil and gas wells.

This law—which was delayed until 2024 while the industry fought it—bans new oil and gas wells near homes, schools, and other sensitive areas such as hospitals. It also requires operators of existing wells to take steps to improve their safety, such as installing leak detection equipment, testing water and controlling dust and other pollutants.

“Having the scientific basis to support the policy was really important,” Gonzalez said.

He gives primary credit to the advocates who lobbied for the bill, especially VISION, a statewide coalition to end neighborhood drilling.

In his fall 2026 course on environmental health equity, he encourages students to investigate their surroundings and ask questions about pollution in the places they call home. He notes that those who can help find actionable solutions to a problem are often those who have lived experience with it.

“For some people, this is something they read about,” Gonzalez said. “For others, this is something they live.”