Frequently Asked Questions

Aliso Canyon Disaster Background

The Aliso Canyon Disaster was a gas well blowout that occurred over the course of 4 months from October 23, 2015, to February 11, 2016, at the Aliso Canyon underground gas storage facility which is owned and operated by the Southern California Gas Company (SoCal Gas), a subsidiary of Sempra Energy. The underground gas storage facility is situated in the Aliso Canyon oil field in the Santa Susana Mountains in Los Angeles County, California, north of the Porter Ranch neighborhood of the City of Los Angeles. The blowout was the largest in United States history and released an estimated total of 109,000 metric tons of methane into the atmosphere.

As a result of the blowout, people in neighboring communities experienced "rotten egg" odors, oily mists, and acute health symptoms, including eye, nose, and throat irritation, headaches, and respiratory symptoms. The Los Angeles County Department of Public Health (Public Health) received thousands of health reports from residents in nearby communities and directed the temporary relocation of over 8,000 households and two local schools. Many residents reported ongoing health symptoms after returning home from temporary relocation and expressed concerns about potential long-term health effects.

Health Study Information

On August 8, 2018, California Attorney General Xavier Becerra, along with the California Air Resources Board, Los Angeles City Attorney Mike Feuer, and the County of Los Angeles secured a $119.5 million settlement with SoCal Gas over the Disaster. As part of this settlement, $25 Million was secured for a long-term health study.

The Aliso Canyon Disaster Health Research Study (Health Study) will be a scientifically-based, multi-faceted and objective investigation of the potential short- and long-term health impacts of the Aliso Canyon gas well blowout and gas storage facility operations on people living in the surrounding communities.

A health study is a scientific inquiry designed to address a specific research objective related to health. Health studies can take many forms depending upon the research objective and setting. However, by definition, a health study should involve a rigorous, systematic, and objective process of exploration and measurement.

The information gleaned from health studies can be helpful in many ways. In the context of an environmental disaster, health studies can help shed light on whether exposures to chemicals or toxins from the disaster may have contributed to illness among people who were near the disaster. Health studies can also help determine if stress and emotional trauma associated with a disaster contributed to adverse physical and mental health impacts. More broadly, health studies can produce information that may be used to inform policies, programs, and other strategies to create safer environmental conditions and prevent future disasters.

Aliso Canyon Settlement and Health Study funds

On August 8, 2018, California Attorney General Xavier Becerra, along with the California Air Resources Board, Los Angeles City Attorney Mike Feuer, and the County of Los Angeles secured a $119.5 million settlement with the Southern California Gas Company over the Aliso Canyon Disaster. As part of this settlement, $25 million was secured for a study of the long-term effects of the Aliso Canyon Disaster and exposure to gas and its constituents. For more information on the settlement, please visit the Aliso Canyon Disaster Background page.

For information about The People of the State of California v. Southern California Gas Company settlement, including information relating to supplemental environmental projects (SEP's) being implemented as part of the settlement, please view the breakdown of the settlement linked here .

As part of The People of the State of California v. Southern California Gas Company's Consent Decree (Appendix D) approved by the Los Angeles Superior Court on February 25, 2019 [Full Details of the Settlement are avilable here ], a Community Air Monitoring Fund will be utilized to develop a real-time air monitoring network and a symptom and incident reporting system in Porter Ranch and potentially other nearby communities . This initiative is being led by the Aliso Fund Committee. The Aliso Fund Committee is composed of one representative each from the Attorney General, Los Angeles City Attorney, and the Los Angeles County Counsel. Several public meetings have been held about enhanced air monitoring networks. For more information, visit the South Coast Air Quality Management District (SCAQMD) website

Public Health's goal is to allocate as much of the settlement funding as feasible to the Health Study research contract and has therefore been providing in-kind support during the initial development phases of the Health Study. Up to this point in time, the focus has been on identifying health concerns and research priorities through community engagement and establishing the groundwork required to launch the Health Study. For example, settlement funds supported the development and implementation of the Community Opinion Survey which provided valuable insights on the experiences, concerns, and priorities of residents from communities near the Aliso Canyon underground gas storage facility, many of whom were directly impacted by the Aliso Canyon gas well blowout. Additionally, settlement funds supported the collection and testing of Samples of Waste Materials from the Aliso Canyon Blowout and Well-Control Attempts Importantly, settlement funds have supported the establishment of a Scientific Oversight Committee (SOC), a group of scientific subject matter experts mandated by the settlement agreement, and the SOC's development of key components of a Request For Proposals (RFP) for health research services.

Information on the allocation of Health Study funds has been shared with Community Advisory Group (CAG) and community members. For more information, follow the link provided below.

Continued CAG Meeting 18: Health Study Budget Summary Slides

Key Roles and Responsibilities

Independent third-party researchers will conduct the Health Study. An open and competitive Request for Proposals (RFP) process, administered by Public Health, is being used to solicit and review research proposals from independent third-party researchers. It's anticipated that the research team will be selected and announced in the Fall of 2022.

In accordance with the settlement with SoCal Gas, Public Health responsible for:

  • Administering the funds dedicated to the Health Study
  • Establishing and facilitating a Scientific Oversight Committee (SOC)
  • Coordinating an open and competitive process to solicit independent third-party researchers to conduct the Health Study
  • Providing administrative support for the development and implementation of a Health Study conducted by independent researchers

In addition to the responsibilities outlined in the settlement, leading up to the release of the RFP, Public Health conducted extensive community outreach and gathered community feedback on the Aliso Canyon Disaster and the forthcoming Health Study. This feedback has been instrumental to the developmental stages of the Health Study's goals and priorities and of the upcoming RFP.

The Scientific Oversight Committee (SOC) is a scientific advisory group that was mandated as part of the settlement agreement with SoCal Gas. The SOC plays a critical role in the development and advancement of the Health Study. The SOC's key responsibilities include:

  • Deciding the Health Study's goals, and priorities
  • Reviewing and evaluating research progress
  • Providing scientific advice to Public Health and the researchers

Comprised of independent experts and public agency representatives, the SOC lends expertise in the following areas: Epidemiology, Clinical Psychology, Medicine, Disaster Behavioral Health, Toxicology, Community-Based Research, Exposure Assessment, Environmental Science, Air Monitoring, and Air Modeling. At the end of the Health Study's third year, the SOC will independently analyze the Health Study's progress and determine if the Health Study should continue. Afterwards, the SOC will evaluate the Health Study's progress on an annual basis.

The communities impacted by the Aliso Canyon Disaster are the key focus of the Health Study. There are many important questions to answer about how the blowout may have affected the physical, mental, and emotional health of those residing and/or working near Aliso Canyon. Feedback from impacted community members, the Community Advisory Group (CAG) and other community stakeholders supported the identification of research questions, goals, and priorities for the Health Study. Community engagement has and will take various forms throughout the planning and implementation of the Health Study, including providing input on the development of the Health Study and participating in various public events and opportunities. The community's key roles have included:

  • Identifying the questions, issues, and concerns that are most important to the community
  • Informing the scope of the Health Study

Health Study Process

To be considered for funding, applicants must propose research that is responsive to the Health Study's Goals and Priorities reflected throughout the Request for Proposals (RFP). It is expected that a variety of study designs and research methods will be proposed. Proposals will be systematically reviewed to identify those with the greatest potential to evaluate the health impacts of exposure to the Aliso Canyon Disaster on the populations in the areas surrounding the Southern California Gas Company's (SoCal Gas) Aliso Canyon underground gas storage facility.

Feedback from the Scientific Oversight Committee (SOC) and the Community Advisory Group (CAG) guided the decision to solicit independent third-party research services by administering a Request for Proposals (RFP). The RFP process provides an open invitation to interested researchers and research organizations to apply for the funding opportunity and will maximize the likelihood of securing researchers who have the necessary experience and expertise to implement a scientifically-based Health Study.

Interested independent third-party researchers must submit a proposal and meet the minimum mandatory qualifications listed in the Request for Proposals (RFP) to be considered. The solicitation process is not limited to a pre-approved list of contractors. The RFP includes specifics about the research opportunity, including work requirements and funding. Submitted proposals will be evaluated and scored by an evaluation committee consisting of subject matter experts based on several factors such as qualifications, experience, proposed budget, and proposed work plan.

The Los Angeles County Department of Public Health (Public Health) released the Request For Proposals (RFP) in January of 2022. Selected researchers can start implementing their research plans after they have been awarded a contract, which is expected to occur by the Fall of 2022.

The length of the research will depend on several factors including, but not limited to:

  • The type of research proposed by the research team who is awarded a contract
  • The time needed for researchers to collect and analyze the research specific data and to interpret the findings
  • The Scientific Oversight Committee's (SOC) evaluation of research progress and determination of whether the research should continue after the Health Study's third year and each following year

It is anticipated that the research will take 2 or more years.

Health Study Goals and Priorities

The overarching goal of the Health Study is to contribute to the understanding of the potential short- and long-term physical, mental, behavioral, social, and community health impacts of exposure to the Aliso Canyon Disaster. Specifically, the Health Study will:

  • Evaluate relationships between exposures to airborne chemicals and other potential toxicants during and/or following the disaster and adverse health impacts to the community, which could include, but is not limited to, physical and mental health;
  • Assess the impact stressors related to the Aliso Canyon Disaster on the quality of life, well-being and functioning of residents in the impacted communities during and following the disaster, and;
  • Evaluate outcomes among vulnerable populations, such as children and older adults, in the impacted communities.

The Health Study priorities include specific health, quality of life and wellbeing outcomes, populations, and exposures of concern to the community and raised by the Scientific Oversight Committee (SOC). For example, health outcomes of concern to the community include chronic health outcomes (such as cancers and respiratory conditions), as well as acute symptoms and intermediate-term outcomes (such as adverse birth outcomes).

The Health Study Goals and Priorities comprise one of several available resources for independent, third-party researchers to learn about the concerns and priorities of communities surrounding the Aliso Canyon gas storage facility. Researchers who apply for Health Study funding must propose study designs and research methods that are scientifically based, responsive to the RFP, and address the Health Study Goals and Priorities.

A wealth of feedback from community members collected during and since the Aliso Canyon blowout disaster and from the Community Advisory Group (CAG) was used by the Scientific Oversight Committee (SOC) to guide the development of the draft Goals and Priorities for the Health Study. The draft Goals and Priorities were made available for public comment on the Health Study website for 6 weeks. Members of the public submitted comments via an online feedback form or by email. In addition to providing general feedback, community members were encouraged to identify the issues that are of greatest concern and/or interest to them.

All of the feedback received was shared with the SOC to refine the Goals and Priorities and to further guide their development of the Request for Proposals (RFP) for the Health Study.

Existing Data on Potential Exposures and Health Outcomes

A wealth of existing data and information related to the Aliso Canyon blowout (Disaster) and gas storage facility operations exists and may be used by independent third-party researchers to conduct the forthcoming Health Study. The Health Study's Scientific Oversight Committee (SOC) believes that the wealth of existing data and information can support robust analyses to evaluate potential impacts to health, quality of life and well-being among residents of communities impacted by the Aliso Canyon Disaster.

Numerous parties - including regulatory agencies, academic institutions, and companies - have taken measurements within the facility and the surrounding communities and continue to collect relevant data and information. The existing data and information include but are not limited to hazardous materials and wastes inventory reports, sampling and analysis data, air monitoring data, and incident reports, among others.

Of note, samples have been collected directly from the gas storage reservoir and from bins that were storing soils and materials from the blowout and well-control operations. The samples were tested for an extensive array of oil and gas chemicals and the results provide information on the chemicals that were stored in the reservoir and released during the blowout and well-control attempts (results available in Sampling and Analysis Report ). Additionally, SoCalGas is required to regularly submit chemical inventories as part of the Unified Program overseen by the California Environmental Protection Agency (CalEPA). More information on this program is available on the California Environmental Reporting System website. Environmental samples that were, and continue to be, collected within the Aliso Canyon facility and surrounding communities provide information on the chemicals to which residents may have been exposed.

The Attorney General, Los Angeles City Attorney, and County all agreed to settle the litigation against the Southern California Gas Company (SoCal Gas) and resolve all disputes in the lawsuits, and therefore, the County is not going to issue a subpoena seeking information from SoCal Gas. Los Angeles County and Public Health, guided by the Health Study's Scientific Oversight Committee (SOC), will continue to compile additional information related to the blowout and operations at the Aliso Canyon gas storage facility.

To view a summary of the existing secondary data sources on potential chemical exposures and health outcomes, please visit the Health Study Research & Data page.

Please visit the Health Study Research & Data page for a summary of existing secondary data sources on potential chemical exposures, including, but not limited to, environmental reports, sampling and assessment results, and air monitoring results, and health effects reported through survey. The purpose of the summary is to serve as an inventory of data and information that may inform research to be conducted as part of the Health Study. Among other pertinent information, the summary includes information on air sampling conducted within the Aliso Canyon gas storage facility and the surrounding communities spanning from the time of the blowout to the present day, and other environmental data and data sources including soil and water sampling collected within the Aliso Canyon facility and surrounding communities. Another source of information noted in the summary are hazardous materials and wastes inventories that SoCalGas is required to submit to the California Environmental Reporting System (CERS) on an annual basis.

Please visit the Health Study Research and Data page and refer to the summary of existing secondary data sources on potential chemical exposures, including, but not limited to, environmental reports, sampling and assessment results, and air monitoring results, and health effects reported through survey. In the summary, there is also a list of well control materials (fluids and additives) that were used during the well control operations to stop the blowout. This information can also be found in the Office of Environmental Health Hazard Assessment (OEHHA) report on Potential Chemical Hazards Associated with the Well SS-25 Well Control Materials at the Aliso Canyon Natural Gas Storage Facility Near Porter Ranch, California . In addition, in 2020, Public Health conducted extensive testing on samples that were collected from bins that were containing materials from the well blowout and well control operations. Information on this testing is also available in the summary of existing secondary data sources and the results of the testing are available on the Health Study Research & Data webpage.

On August 4th, 2020, Public Health worked with a third-party contractor to collect samples from waste bins containing soils and waste materials from the Aliso Canyon blowout and well-control operations (e.g., fluids, oily products and drilling muds) that were under legal hold by the California Public Utilities Commission (CPUC). The samples were tested for an extensive array of oil and gas chemicals. The Lab Results were reviewed by the Health Study's Scientific Oversight Committee (SOC) and are publicly available on the Health Study Research & Data page.

Upon recommendation by the SOC, additional samples were collected on October 2, 2020 for potential future use by the Health Study researchers.

Thirty-one bins containing soil contaminated with Volatile Organic Compounds (VOCs) were transported to an approved treatment/disposal facility in 2016 in accordance with South Coast Air Quality Management District (SCAQMD) Rule 1166. Further information on the regulatory context for the removal and disposal of the 31 bins is provided below. Existing records and data related to the 31 bins, including VOC monitoring logs, waste characterization laboratory test results, and waste manifests are listed in the summary of existing secondary data sources on potential chemical exposures and health outcomes on the Health Study website.

  • SCAQMD Rule 1166 requires any person excavating or grading VOC-contaminated soils - such as those caused by a leak from storage or transfer operations, or accidental spillage - to submit, obtain approval for, and operate pursuant to site-specific mitigation plan. The rule requires that surface soil monitoring take place upon the commencement of excavation activities, as well as throughout the excavation project.
  • Upon detection of VOC-contaminated soil, which is defined as soil registering greater than 50 ppm VOC using a portable hydrocarbon analyzer, operators are required to implement mitigation plan requirements. All VOC-contaminated soil must be stockpiled separately from uncontaminated soil and removed from the site within 30 days.
  • Waste manifests show that the 31 bins were transported to an approved treatment/disposal facility. Rule 1166 does not require a person to monitor or record the VOC concentration of soil after it is excavated and properly stored in bins. More information regarding Rule 1166 can be found on the South Coast AQMD website.

More information regarding Rule 1166 can be found on the SCAQMD website.

Additional efforts that are separate from the Health Study

In response to requests from residents of communities impacted by the Aliso Canyon Disaster, on November 12, 2020, the Public Health's Radiation Management team conducted radiation surveys of Aliso Canyon waste bins containing materials from the blowout and well-control operations. Radioisotope testing results can be found on the Health Study Research & Data page.

Public Health Radiation Management surveyed for the three basic types of ionizing radiation: alpha, beta, and gamma. All three types are caused by unstable atoms, which then release radioactive particles or energy to become stable. All of these types of ionizing radiation occur in nature. When analyzing radiation survey measurements, it is common to compare the measurements to background readings found in nature, which are always around us.

In summary, all test results indicate that the alpha, beta, and gamma radiation levels measured from the Aliso Canyon waste bins sampled are very low, comparable to background levels, and the low levels of radiation encountered do not pose an immediate health risk.

For further information on radiation and everyday exposure levels, please visit the Nuclear Regulatory Commission's (NRC) Doses in Our Daily Lives and Radiation and Its Health Effects.

A five-agency task force is overseeing an investigation by the Southern California Gas Company (SoCal Gas) of a spot fire that occurred in 2019 in an area of the storage field called Catch Basin 3. It was suspected that the fire may have been fueled by storage facility gas emissions. SoCal Gas released a report to the task force on the results of the investigation which concluded that the gas emittance was determined to be a result of "natural subsurface seep" and not storage facility gas. The Report was provided to the Community Advisory Group (CAG) for their review and comment. SoCal Gas provided an update on these findings on their website. The report and data collected as part of the investigation is currently under review by the five-agency task force, consisting of representatives from the California Geologic Management Division, the California Public Utilities Commission, South Coast Air Quality Management District, Los Angeles County Fire Hazmat Department, Los Angeles County Department of Public Health, and California Air Resources Board.

Following the Aliso Canyon blowout, a community physician obtained data on CBC test results from a licensed clinical laboratory. A comparison of data from adults in the Porter Ranch zip code to data from adults in other zip codes indicated that, for many of the CBC components, blood counts were on average slightly lower in the Porter Ranch zip code than in three comparison zip codes. Based on these findings, Public Health agreed to pursue data from a larger clinical laboratory to conduct a more detailed exploratory analysis and include children. Although this exploratory analysis is separate from the Aliso Canyon Disaster Health Research Study (Health Study), the results of the exploratory analysis may inform other future research including research that is conducted as part of the Health Study. The analysis of clinical laboratory data is now complete and a report on the results titled Exploratory Analysis of Selected Blood Test Results Among Residents of Porter Ranch and Two Control Populations, 2011-2019, is available on the Health Study Research and Data page of the Health Study website.

The analysis did not find evidence of an impact of the Aliso Canyon blowout on mean values of selected blood test results among the adults and children in Porter Ranch who had blood tests conducted by Quest Diagnostics during the period of 2011 to 2019. However, the data used in the analysis had significant limitations, as described in the report. Therefore, the results by themselves are not sufficient to conclude that blood components in Porter Ranch residents were or were not affected by the blowout.

Although this exploratory analysis is separate from the Health Study, the findings may be used by the research group selected for the upcoming Health Study, or by other researchers, to inform any future research in this area.

Public Health is aware that cancer is a significant concern to residents of communities surrounding the Aliso Canyon gas storage facility. Therefore, in advance of the Health Study, Public Health connected Community Advisory Group (CAG) members with researchers at the USC Cancer Surveillance Program (CSP), the population-based cancer registry for Los Angeles County, which routinely responds to community concerns regarding cancer occurrences. The CSP collects and analyzes information on all new cancer diagnoses made among residents of the County. Through a series of conversations with the CAG members, the CSP developed an analysis plan with approved methods developed by the Centers for Disease Control and Prevention (CDC). The analysis was intended to be conducted by the CSP in advance of, and separate from, the Health Study to determine whether cancer rates in communities surrounding Aliso Canyon are higher than expected by comparing the rates to those in Los Angeles County and/or the State of California, which is a standard practice to control for factors that contribute to cancer risk. Although the CAG has not made a decision to move forward with the proposed analysis, the USC CSP remains an available resource for residents and/or communities who have concerns about cancer.

In addition, researchers who are interested in conducting the Health Study may submit proposals to study cancer through the RFP process.

Helpful Information and Resources

  • The goal of the upcoming Health Study is to contribute to the understanding of potential short-term and long-term health impacts related to the disaster.
  • It is not always possible to determine whether an environmental exposure caused long-term illness in an individual.
  • The Health Study may be able to determine that exposures from the disaster and/or gas storage facility are related to certain health outcomes. Health-related research (e.g., epidemiologic research) often aims to establish whether specified health outcomes are more common in people with specific exposures. This research may determine that an exposure is statistically associated with a specified outcome. A statistical association is a relationship between two variables, but does not establish causation. However, scientists may utilize statistical associations to draw inferences about causation.
  • It is our hope that the Health Study may help people in the community better understand how their health may have been impacted. Results of the Health Study may also help inform an individual's future medical assessments.
  • Concerns about one's health can be complicated and stressful. If you have specific concerns about your health, please consult with your healthcare provider.

LA County and other local, state, and federal agencies are working to monitor the environment and health outcomes and protect you, your health, and the environment. There are many public agencies that are responsible for making sure different laws and regulations are followed, and it can be confusing to figure out where to report a problem. Learn more about which Local Agencies to call for problems in your community. Please also check out the SoCal Gas Regulators webpage for more information.

For information and updates on the Health Study, please sign up for email updates through our Web Form. Once a research team is awarded a contract, there will be a greater understanding of what opportunities may be available for community involvement with the research. Please keep checking the website for updates.

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