A Paramount metal-finishing plant was forced to suspend some operations Thursday after violating limits on a potent cancer-causing air pollutant.
Aerocraft Heat Treating Co., Inc. shut down operations that had the potential to emit Chromium 6 after levels of the pollutant outside the facility exceeded a specified threshold.
The company had agreed to the limit and other restrictions last month in an order with the South Coast Air Quality Management District.
Aerocraft is one of two metal finishers targeted by air quality regulators after the discovery last fall of extremely high levels of Chromium 6 in the southeast Los Angeles County community.
"While it is not certain that Aerocraft is responsible for these emissions, the curtailment is being taken out of an abundance of caution," Greg Stonick, the company's general manager said in a statement.
It is the first curtailment required of Aerocraft since the air district's hearing board adopted an abatement order for the plant on Dec. 16.
Air district executive officer Wayne Nastri said in a statement that "the order is working just as intended by preventing the facility from emitting potentially harmful levels of this toxic compound."
Aerocraft will not be allowed to resume operations until monitoring data shows Chromium 6 levels drop below the limit it agreed to, Nastri said.
A South Coast air district monitor downwind of Aerocraft detected an average Chromium 6 level of 1.67 nanograms per cubic meter from Jan. 7 to Jan. 13, putting it above the limit of 1 nanogram per cubic meter.
That limit is designed to reduce health risks to residents in surrounding homes, which sit within a few hundred feet from the facilities.
Chromium 6, also called hexavalent chromium, is a potent human carcinogen associated with lung cancer over years or decades of exposure.
The other Paramount firm identified by regulators as contributing to high levels of Chromium 6, Anaplex Corp., agreed to a similar order earlier this month but has not exceeded the same threshold, according to the air district.
The air district began monitoring for metal pollution in Paramount in 2013 following community complaints of harsh metallic odors. New air monitors deployed in October found Chromium 6 levels near Anaplex and Aerocraft at more than 350 times acceptable levels.
Since that discovery, residents and elected officials have pressed authorities to move quickly to address the pollution problems in the city of 55,000. Paramount has more than 80 metal-related businesses, some of them interspersed with homes and schools.
After the high pollution levels were detected, Aerocraft voluntarily ceased operations to clean the facility and isolate potential problems.
The City of Paramount is "very concerned" that elevated hexavalent chromium levels continue to be emitted, spokesman Chris Callard said.
"We find it extremely disappointing that, after all the effort to come to an agreement, Aerocraft couldn't go more than 60 days before falling short of the terms," Callard said in a statement.
Stonick said the company "is continuing to conduct a thorough investigation into possible sources of hexavalent chromium."