Los Angeles County health officials are calling for an independent study into the short- and long-term health effects on residents near the San Fernando Valley’s Aliso Canyon, which in 2015 was the site of the largest natural gas blowout in U.S. history.

The county Department of Public Health’s request for proposals, announced Tuesday, seeks third-party researchers to lead the Aliso Canyon Disaster Health Research Study, officials said.

“We are committed to selecting an independent research group with the broad but also highly specialized expertise needed to shed further light on the health impacts of this catastrophic environmental disaster,” said Dr. Paul Simon, the department’s chief science officer.

The announcement was a long time coming for residents of the surrounding Porter Ranch community, which was most affected by the massive October 2015 leak from Southern California Gas Co.’s Aliso Canyon natural gas storage facility in the Santa Susana Mountains. The leak lasted 111 days and released more than 109,000 metric tons of methane — a potent greenhouse gas — and other chemicals into the area.

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