Residents return to Porter Ranch gas leak site

Mixed Emotions in Porter Ranch
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Story highlights

  • Porter Ranch residents are returning home four months after a gas leak began
  • The methane leak was the second largest in the United States
  • The leak lasted 112 days before being permanently capped on February 18

(CNN)Four months after natural gas began leaking from a storage facility, residents of Porter Ranch, California, are returning home. Among them, 8-year-old Taylor Lee, who got a chance to ride his new bike, a Christmas present.

"It's really fast! I like it!" said Taylor. He and his family have been living in a hotel provided by Southern California Gas since the methane leak began.
Natural gas began leaking from the well at Southern California Gas' Aliso Canyon storage facility on October 23 of last year. The leak lasted 112 days before being permanently capped on February 18.
    A new study in the journal Science confirms that the methane gas leak was not only the largest in California's history, but also the second largest in the nation. According to Dr. Steven Conley, lead author of the study, as much as 60 metric tons of methane, a greenhouse gas, was spewing from the leak each hour.
    "If you stuck a balloon over the leak, it would fill up the Rose Bowl," said Conley.
    The leak displaced nearly 2,290 households, requiring families to move into temporary housing and hotels provided by Southern California Gas. Residents such as Taylor experienced nosebleeds attributed to gas exposure. Other residents complained of nausea, headaches, and eye and throat irritation.
    "Some of these symptoms are what you would expect from mercaptan exposure," said Dr. Michael Jerrett, chairman of the Environmental Health Science department at the UCLA Fielding School of Public Health. The odorant mercaptan is added to natural gas to give it the signature rotten egg smell, to help people identify the colorless and otherwise odorless gas.
    Southern California Gas said the leak is not an imminent health risk. "The well is located in an isolated, mountain area more than a mile away from, and more than 1,200 feet higher than, the closest home or public area. Scientists agree natural gas is not toxic and that its odorant is harmless at the minute levels at which it is added to natural gas," the gas provider said.
    Within two weeks of the leak being reported, Conley began flying over the well site and had no idea how much methane was spewing from the site. On his initial flight, he thought something might be wrong with his instruments. "In the air, we never see levels at this level, more than a mile away," said Conley.
    "I kept tapping the display to see if it would change," he said.
    Recent flight recordings have found levels to be close to normal for a safe atmosphere.
    Jarrett of UCLA has also been tracking volatile organic compounds and said levels of most of the air toxins are very low now, compared to what is expected in the Los Angeles basin in general. "That may be because a large part of the population was absent in that period," Jarrett said.
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    Natural gas also contains the compound benzene, which is considered a carcinogen by the World Health Organization. When asked about long-term exposure to benzene, Jarrett said there was little research out there that looked at the compound at these levels. Most of the research has looked at long-term exposure in industrial settings, with higher benzene concentrations.
    "It seems unlikely, when looking at a lifetime of exposure, that this would result in major increases in cancer risk. But we don't know that with certainty. And that's because of a gap in the science," said Jarrett.
    "We don't understand the implications of this type of (benzene) exposure on pregnant mothers, children (and) the elderly, who have shown to be more susceptible to air pollution," he said.