For the third time in less than three months, air regulators have ordered a metal-finishing facility in the South Los Angeles city of Paramount to temporarily shut down all equipment and operations with the potential to emit cancer-causing hexavalent chromium, also known as chromium 6.
The South Coast Air Quality Management District ordered Aerocraft Heat Treating Co. to suspend chromium 6 operations by midnight Friday morning because its average emissions over a week exceeded 1 nanogram per cubic meter. The AQMD takes the average of three separate air samples.
The threshold is designed to greatly reduce the cancer risk of Paramount's residents, according to air district spokesman Sam Atwood.
Aerocraft will not be able to resume chromium 6-related operations until the AQMD confirms that the average of three more samples taken over a week is below the threshold.
Last fall, the AQMD identified Aerocraft as one of two metal processing firms responsible for chromium 6 levels in Paramount that were hundreds of times higher than acceptable levels.
The company and the agency agreed to the threshold as part of an abatement order adopted by the AQMD's independent Hearing Board on Dec. 16.
The air district had previously ordered Aerocraft to shut down its chromium 6 operations from Jan. 19-27 and again from Feb. 14-21.
Anaplex Corp., the other company identified by the air district as emitting too much chromium 6, has violated the administrative order once and was ordered to suspend metal processing for about a week in early February.
The order is "working as planned," said Atwood.
As part of the abatement order, both firms are required to submit a Risk Reduction Plan to the AQMD by June 13. Based on their current operations, this will require Aerocraft and Anaplex "to install additional, permanent air pollution controls to reduce their maximum lifetime cancer risk in the community to no more than 25 in 1 million," said Atwood.
Aerocraft General Manager Greg Stonick said in a statement that the firm has already taken a number of steps to "enhance its environmental control measures," including the addition of "permanent enclosures for heat treating operations," the addition of "two new baghouses" that capture and reduce emissions, and improved "housekeeping and work practice measures designed to minimize metal dust emissions from facility operations."
The company is also considering "additional actions," he said.
Chromium 6 is a known human carcinogen. It has been associate with lung cancer when inhaled over long periods of time, typically years to decades, according to the district.