PARAMOUNT, CA — Air quality regulators have launched a new investigation into elevated levels of a cancer-causing chemical in Paramount, renewing scrutiny of industrial facilities near Long Beach following years of efforts to reduce toxic emissions.
The South Coast Air Quality Management District announced Wednesday, Oct. 28, that it had resumed monitoring for hexavalent chromium, a known human carcinogen, after elevated concentrations were detected by the city's air monitoring network.
In response to questions from Patch, the agency confirmed that two monitoring sites near Madison Street and Minnesota Avenue had recorded concentrations substantially above typical background levels. Between Sept. 26 and Oct. 20, readings at the two locations ranged from 0.08 to 2.33 nanograms per cubic meter, according to Connie Villanueva, a senior public affairs specialist with South Coast AQMD.
By comparison, the typical background range at the agency's nearest regional monitoring station in Compton extends up to 0.16 nanograms per cubic meter. The highest Paramount reading, recorded Oct. 8, was approximately 14.6 times that upper background value. Although many readings remained within background levels, the elevated concentrations have prompted renewed inspections and emissions testing at nearby metalworking facilities, according to the agency's published monitoring results.
Despite Paramount's proximity to North Long Beach, regulators say the latest findings do not indicate that elevated pollution is likely to spread into the neighboring community under typical wind conditions.
"North Long Beach is in the predominant upwind direction of Paramount so pollution observed in Paramount is not anticipated to typically be transported to North Long Beach," Villanueva told Patch.
The agency has not collected new hexavalent chromium samples specifically in North Long Beach during the current investigation and has no immediate plans to expand monitoring there. However, previous measurements collected in Long Beach, Signal Hill and Compton through South Coast AQMD's Multiple Air Toxics Exposure Study V showed typical background concentrations, Villanueva said.
Current monitoring suggests elevated levels extend several blocks around industrial facilities in Paramount. During an earlier investigation, concentrations were found to decrease fivefold approximately 500 feet downwind of the facilities examined.
The latest findings have revived concerns in a city that has faced years of scrutiny over industrial emissions. South Coast AQMD began investigating air quality complaints in Paramount in 2013, with extensive monitoring and enforcement efforts beginning in 2016 after elevated concentrations of toxic metals were detected.
Those efforts led to substantial reductions in hexavalent chromium levels, although the city continued operating its own monitoring network. In October 2025, the agency issued notices of violation to two metal casting businesses: Pro Cast Industries, at 15555 Minnesota Ave., and Fenico LLC, at 7805 Madison St.
The violations included operating equipment without required permits, failing to conduct mandatory emissions testing and inadequate cleaning around chromium alloy melting operations. Those citations predate the latest monitoring campaign, and regulators have not established which facilities are responsible for the current elevated readings.
Villanueva said concentrations detected during the original 2016 investigation were substantially higher than those recorded recently, but investigators are continuing to evaluate potential industrial sources.
Hexavalent chromium, also known as chromium-6, is a toxic air contaminant associated with an increased risk of cancer following long-term exposure. However, South Coast AQMD cautioned that the current monitoring results cannot establish the health risks facing individual residents or workers.
"Our current air monitoring efforts are not designed to establish risks to human health," Villanueva said. "They are being used to identify potential sources and reduce emissions as appropriate."
Determining those risks would require additional information about the sources of emissions and the extent of exposure over time. South Coast AQMD is working with the City of Paramount and the Los Angeles County Department of Public Health to review the data and better understand potential exposure among workers and nearby residents.
The agency resumed its own monitoring Sept. 26, collecting 24-hour samples every three days at selected locations near industrial facilities and surrounding neighborhoods. Investigators are also reviewing permits, conducting facility inspections and evaluating possible sources of emissions.
Additional findings will be published on South Coast AQMD's Paramount investigation webpage as the investigation continues.
Residents can report suspected air quality problems by calling 1-800-CUT-SMOG (1-800-288-7664) or visiting South Coast AQMD's website.
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