Ronald Thomas looks toward the Martinez Refining Company, where a fire broke out over the weekend in Martinez, California, on Feb. 3, 2025. Thomas lives across the street from the refinery and said he had to evacuate during the fire. Ten days after the fire, Contra Costa County says a range of harmful chemicals were released, including some that pose risks for cancer and cardiovascular disease. (Gina Castro/KQED)
Ten days after a refinery fire injured six employees and prompted a shelter-in-place order for thousands of Martinez residents, Contra Costa County health officials released new details on Tuesday about toxic chemicals released during the four days it took to put the fire out.
The county said in a statement on the incident that the Martinez Refining Co., which operates the facility where the Feb. 1 fire occurred, reported that the cloud of thick black smoke that billowed over the East Bay community contained petroleum products at various stages of refinement and several other hazardous chemicals, including benzene, hydrogen sulfide, sulfur dioxide and xylene.
Health officials said some of the substances that were released can cause cancer and heart and lung disease, but they also noted that weather conditions at the time of the fire may have limited local exposure.
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County Health Director Dr. Ori Tzvieli said the wind blew most of the smoke away from populated areas.
“This could have been much worse,” Tzvieli said. “We got lucky this time. But our community shouldn’t have to rely on luck.”
Tuesday’s disclosure marks the first time health authorities have gotten a detailed look at what was in the plume that wafted over the city.
The Martinez Refinery Co., owned by PBF Energy in Martinez, California, touches residential neighborhoods on Sept. 21, 2023. (Martin do Nascimento/KQED)
Fifteen minutes after the fire started on Feb. 1, a refinery employee told the Governor’s Office of Emergency Services that a flaring incident had released more than 500 pounds of sulfur dioxide. The report also noted that it was “unknown if any other material is releasing due to the fire other than sulfur dioxide.”
Sulfur dioxide has adverse health effects on humans and animals, and high-level exposure can result in heart problems and an increased risk of death, according to studies cited by the California Air Resources Board.
The actual effects on residents, refinery workers and first responders depended on how much sulfur dioxide they were exposed to and for how long.
A day after the fire started, Contra Costa Health hazardous materials employees who were investigating reports of a sulfur smell near the refinery reported feeling dizzy and left the area.
Seventy-two hours after the start of the fire, the refinery company filed a report with the county, attributing the fire to an incident involving two workers who tried to restart an idle unit.
“While opening the equipment, hydrocarbon material started to leak,” the report said. “The two workers immediately evacuated the area, and the material subsequently caught fire.”
However, the report lacked any new information about what substances might have burned during the fire. The report also lacked chemical safety data sheets required by the California Division of Occupational Safety and Health.
County health officials responded last Wednesday with a letter to the company requesting a list of everything inside the refinery that might have burned and giving the company until Monday to respond.
“The information being requested has been deemed essential for assessing health impacts that may have occurred as a result of that incident,” the letter said.
The Martinez Refining Company in Martinez, California, on Feb. 3, 2025. (Gina Castro/KQED)
In its response, the refinery reported that the fire released several substances produced in the refining process, including naphtha and petroleum distillates.
The combustion byproducts from the fire — including benzene, hydrogen sulfide, sulfur dioxide and xylene — pose the greatest public health concern, Contra Costa Health’s statement said.
It added that the department is assessing whether there may be any long-term health effects from the chemicals, including potential impacts to soil and water.
The refinery is scheduled to provide a 30-day follow-up report in early March. The county said it would hire an outside firm to investigate how the incident happened and what steps can be taken to prevent it from happening again.
The Bay Area Air District and Contra Costa Health have each launched an investigation into the fire and have restricted access to the area where the fire burned.
Contra Costa County Fire Department firefighters outside the Martinez Refining Company as smoke billows from the refinery on Saturday in Martinez. (Courtesy of the city of Martinez)
The refinery, which operates as the Martinez Refining Co., also has an incident investigation into the fire.
“We are working urgently and thoroughly to identify the root cause(s) and take appropriate corrective actions,” an update on the company’s website reads. “Personnel continue to monitor the scene of the recent incident to assess equipment and ensure the safety of the general area.”
Nearly all of the refinery’s operating units have been shut down, but MRC warned there could be more flaring over the next several weeks as workers drain operating units.
The Martinez refinery, which is more than a century old, was owned by Shell until 2020 when it was acquired by the current owners, New Jersey’s PBF Energy. The company describes itself as “one of the largest independent petroleum refiners and suppliers of unbranded transportation fuels, heating oil, petrochemical feedstocks, lubricants and other petroleum products in the United States.”
PBF owns six refineries, including one in the Los Angeles suburb of Torrance.
The company describes its Martinez refinery as “one of the most complex refineries in the United States” in statements filed with the Securities and Exchange Commission.
The refinery has had a series of incidents that have drawn widespread criticism in the community.
On Nov. 24, 2022, the refinery released a cloud of spent catalyst that blanked the town in a powdery white substance that looked like ash.
On July 11, 2023, and Oct. 6, 2023, the refinery unintentionally released petroleum coke dust — a refining byproduct that looks like soot and is made up of particulate matter that can irritate lungs.
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