Los Angeles County officials have ordered an expanded air monitoring plan to better measure the potential health risks associated with the Porter Ranch gas leak.
The new plan directs the South Coast Air Quality Management District to oversee round-the-clock air testing of the massive Southern California Gas company leak in the Aliso Canyon storage facility that began Oct. 23.
The expanded monitoring began Jan. 12. Up until then, air samples were collected ten times a day for ten minutes at a time. The Los Angeles County Department of Public Health says its review of those samples has so far shown no serious health threat.
"However, the data is very limited," says Angelo Bellomo, the Department's deputy director for health protection. The 24-hour testing will help level off the "peaks and valleys" in the data from the ten-minute tests and will provide more accurate levels that can be compared to state safety standards, he says.
As part of the expanded monitoring, "we’re going to be looking for a greater number of chemicals" that may pose long-term health risks, such as radon, adds Bellomo.
The preliminary data the gas company and the Air Quality Management District have provided to public health officials have so far shown levels of the carcinogen benzene at .08 to 5.6 parts per billion (ppb), according to a Jan. 19 letter from the public health department to the Los Angeles County Board of Supervisors.
The California Office of Environmental Health Hazards Assessment says a person exposed to benzene for one hour at levels of 8 ppb or greater may suffer acute health effects, including drowsiness, rapid or irregular heart beats, headaches, unconsciousness and, at high enough levels, death.
Long-term (months or years) exposure to benzene at levels of 1 ppb can result in an elevated risk of blood and bone marrow cancers, particularly leukemia, according to the state agency.
Health officials have also found levels of the explosive gas methane, to be at "well-below the lower explosive limit," according to the letter to the supervisors.
Data collected in the new expanded tests will be posted on the Department of Public Health website at least weekly, beginning Jan. 22, officials say.
Some Porter Ranch residents and others who live near the leak have reported experiencing nausea, headaches and nose bleeds since gas first started spewing from a ruptured well last fall.
Those experiencing such symptoms are advised to contact the L.A. County Department of Public Health, which is also also urging residents to keep pets indoors when the odor from the additive in the natural gas is present.