In the immediate aftermath of the 2015 Aliso Canyon gas blowout – the largest natural gas leak in U.S. history – residents in the San Fernando Valley demanded to know exactly what toxins or other chemicals they had been exposed to and what that would mean for their health.
For those residents, it’s been a long and hard fought battle to get answers.
Last month, just weeks shy of the 10th anniversary of the catastrophic event at the Southern California Gas Co.-owned facility, a team of UCLA researchers who had been tapped by Los Angeles County to conduct a health study finally published their first set of findings in a science journal.
Their conclusion: pregnant women living near the Aliso Canyon underground natural gas storage facility during the blowout were more likely to give birth to low-weight babies.
“In the years since the blowout, people in the community have wondered about whether — and how — the blowout might have affected their health,” Kimberly Paul, an investigator on the UCLA Aliso Canyon Disaster Health Research Study team and the lead author of the study, said recently.
“Our results provide evidence that the increase in low–birth-weight babies can be attributed to the gas leak,” she added.
Low birth weight has been linked to developmental and behavioral disorders including autism and attention-deficit/hyperactivity disorder. It also increases one’s risk of developing hypertension, diabetes or coronary artery disease as an adult.
That a study has come out suggesting a link between health problems and the gas leak is not surprising to people who lived through the Aliso Canyon blowout.
Over the course of nearly four months, between Oct. 23, 2015 and Feb. 11, 2016, an estimated 109,000 metric tons of methane escaped into the air due to a well leak at the Aliso Canyon underground gas storage facility.
Residents reported headaches, bloody noses, vomiting and rashes. Some claim they’ve continued to suffer health effects in the years since.
The latest findings
The recent published study concerning low birth weight found that women in their third trimester of pregnancy who lived near the site had a nearly 50% higher-than-expected chance of giving birth to a low-weight baby – that is, a newborn weighing less than 5.5 pounds.
Combing through more than a million county birth records from October 2010 to October 2019, researchers focused on 666 births among women living within 6.2 miles of an “impact zone” downwind of the Aliso Canyon facility who were exposed to the gas blowout for at least a month during their final trimester. Of the 666 cases, 64 (or 9.6%) involved babies born with low birth weight.
Before the 2015 blowout, 6.6% of women living within the impact zone gave birth to low-weight babies. In other words, the likelihood of having a baby with low birth weight increased 45.5% during the blowout.
In comparison, 6.8% of women in the rest of L.A. County who lived outside the impact zone during the blowout gave birth to babies with low birth weight – a 41.2% lower incident rate.
When the health study team excluded babies born prematurely and only considered those born after 37 or more weeks of gestation – a category known as “term low birth weight” – researchers again saw a spike in low birth weight, both among those whose mothers lived within the Aliso Canyon impact zone and those further away.
Before the blowout, 2.6% of babies within the impact zone had term low birth weight versus 2.7% throughout the rest of L.A. County. During the blowout, the rate increased to 4.5% among babies in the impact zone.
The UCLA health study team initially shared its findings in early 2024, but the results were considered preliminary at the time. Since then, its study has been peer reviewed.
Patty Glueck, who lives in Porter Ranch, a neighborhood adjacent to the Aliso Canyon facility, called the findings “alarming.”
“This was an important finding that came out because it does show that the facility is harmful to the population near it,” said Glueck, who co-founded the Aliso Moms Alliance, a group that seeks to inform communities about the potential health impacts of living near the Aliso Canyon site.
SoCalGas, meanwhile, maintains there are no longterm health risks stemming from the 2015 incident.
“Independent regulatory agencies concluded that the Aliso Canyon gas leak did not pose longterm health risks to the public,” the utility company said in a statement. “This determination was based on extensive data collected during and after the 2015–2016 incident. Some of the agencies that reviewed this data were Los Angeles County Department of Public Health, California Office of Environmental Health Hazard Assessment, California Air Resources Board, and South Coast Air Quality Management District, among others.”
In 2018, for example, the California Office of Environmental Health Hazard Assessment reported that “because the potential exposures to well-control substances would have been short-term and at low concentrations, long-term health impacts would not be expected to occur from the well-control materials.”
Future studies
But residents remain skeptical of such earlier assessments and have continuously pushed for further investigations.
That’s where the UCLA health study comes in.
The probe into low birth weights is only the start of a broader health study, said Michael Jerrett, a principal investigator with the UCLA research team and an environmental health sciences professor at the university.
Using results from the birth outcomes study, the health study team plans to cross-reference it with a statewide registry on children diagnosed with autism at age 4 or 5 for a deeper dive.
And soon, Jerrett said, his team will survey about 2,400 people, a quarter of whom will be selected to take part in physical examinations. Researchers will look at lung function and review neurological and physical exams, plus urine and blood samples, to look for possible traces of benzene, a chemical which causes cancer.
In early 2026, Jerrett anticipates getting data from the California Biobank, which keeps a record of blood samples for every baby born in the state. Researchers requested 2,600 blood samples of babies born two years before the gas blowout, during the disaster, and two years after. They plan to conduct a metabolomics analysis to further determine if a woman’s pregnancy or their babies were adversely impacted by the blowout.
In addition, Jerrett said his team has delved into other aspects of the health study, including:
- Monitoring the air for fine particulate matter in 40 homes within and outside the Aliso Canyon impact zone. Researchers are also monitoring for volatile organic compounds.
- Tracking methane levels in the air. Although methane – the main component of natural gas – isn’t toxic, when high levels of methane are detected, there tends to also be higher traces of toxic elements in the area, Jerrett said. A paper on their research has been accepted for future publication in a science journal, he said.
- Tracking emergency room visits before, during and after the blowout.
Studies take time
Although residents near Aliso Canyon are glad to finally see the study on low birth weight published, some voiced frustration that the health study team has taken this long just to get to this point.
Right after the 2015 gas blowout, residents pleaded for a health study.
By early 2017, a doctor in the Porter Ranch area, Jeffrey Nordella, reported seeing a pattern of health symptoms in some patients. He then launched his own probe into the amount of benzene — a known carcinogen — in residents’ blood, and reported finding high levels of uranium and lithium in urine and hair samples.
All the while, residents were still demanding a comprehensive public health study.
But it took several years before SoCalGas reached a settlement with the city, county and state to fund the study. And it took several more years after that to lay the groundwork for the study, which was not awarded to the UCLA team until late 2022.
By then, many who had lived near Aliso Canyon during the blowout had moved, and deep-seated mistrust had taken root in the community. Residents who remained wondered whether too much time had lapsed for any health study to capture the full impacts from the blowout. Some, already convinced the outcomes would be flawed, said they would not participate in the study.
Like others living near Aliso Canyon, Porter Ranch resident Craig Galanti is frustrated that the community’s requests for a full clinical evaluation, including a “complete blood count” (CBC) survey of all individuals who reside near the Aliso Canyon facility, has still not taken place.
“A clinical evaluation comparing residents living near petrochemical facilities, like Aliso Canyon, to those in areas without such exposure would provide the most relevant and immediate insights into the health risks we face,” Galanti, a member of a community advisory group that provided input on the health study, wrote in an email. He said the health study team “failed to prioritize this vital research.”
“Instead of focusing on the most crucial studies – a comprehensive clinical evaluation and a study of cancer occurrences in the community – UCLA has pursued less impactful research such as emergency room visits and air dispersion modeling,” he wrote. “These studies, while useful, should have been conducted early in the study’s timeline, not after significant delays.”
Although UCLA researchers plan to start the clinical assessment soon, Galanti worries it may be too late.
The UCLA study is funded through the SoCalGas settlement with the state and city and county of Los Angeles. Roughly $25 million of a nearly $120 million settlement, which a judge approved in 2019, was designated to go toward an in-depth health study.
As part of that deal, the UCLA researchers must regularly report to a scientific oversight committee established by the L.A. County Department of Public Health. The committee is made up of experts in environmental health, public health and related fields who provide guidance, review research plans and evaluate progress.
At the end of the third year of the health study, which is coming up shortly, that committee will decide if the research team is on track to meeting its goals and whether to continue funding what should be a five-year study.
Galanti is worried the committee will pull the plug on the study prematurely.
“The full scope of health impacts remains largely unexplored, and there are likely many other serious health consequences yet to be uncovered,” he said.
Jerrett said one challenge the research team has run into is a delay in getting data from the California Biobank due in part to some retirements and staff reorganization there. The UCLA team requested data more than 18 months ago and expects to get them by next February, he said.
The professor acknowledged the community’s frustration with the pace of the study but said that’s the nature of scientific inquiries. He said the research team is about 90% on track with the timeline it set for itself.
“Real science takes time,” he said, adding that collecting data and cleaning it is time-consuming.
“Do you want me to put out junk science? I could do that really fast, but if you want quality science, it’s going to take time and it has to be peer reviewed and vetted,” he said.
The fact that the health study team is taking great pains to ensure the data is reliable, and having their research peer reviewed through a rigorous process that can take more than a year, means the public can trust the findings, Jerrett said. The team is also getting regular feedback from the county’s scientific oversight committee, he said.
“I don’t think it would be in anybody’s interest to just quickly do rapid reports that aren’t fully thought out and the analyses are questionable,” he said.
The health study team holds community meetings twice a year to update the public on its work.
Its next community meeting, where results of an air-monitoring study will be presented, will take place 6 to 7:30 p.m. on Nov. 18 in the community room at The Vineyards at Porter Ranch, 20065 W. Rinaldi St., Northridge. The public may also participate remotely via Zoom.
Registration details will be posted on the UCLA Aliso Canyon Disaster Health Research Study website, at https://alisostudy.ucla.edu/community-engagement, as it gets closer to the event.