More than 100,000 metric tons of methane and ethane gas escaped into the atmosphere from the Aliso Canyon gas well between October 2015 and February 2016. The well is owned by Southern California Gas Company and located in the Santa Susana Mountains near the Porter Ranch community in the San Fernando Valley. The event is known as the Aliso Canyon Natural Gas Disaster and was the largest uncontrolled release from a single underground gas storage facility in US history.

More than 130,400 people lived within five miles of the disaster. Nearly 12,300 (23%) were under age 19 and 18% were 65 or older. Thousands of people were evacuated, businesses shut down, and school children were relocated to several miles away. Residents in the area experienced many health symptoms during and after the disaster, raising concerns about health impacts for people living and working near the gas well blowout.

The Aliso Canyon Disaster Health Research Study will assess short- and long-term effects of the disaster and routine emissions on the health of communities living and working in proximity to the blowout. It is a five-year study that began in December 2022 and will end October 2027.