Current Status
South Coast AQMD is conducting additional air monitoring and investigating potential sources of hexavalent chromium emissions in the industrialized areas of Paramount following elevated hexavalent chromium readings identified through the City’s ongoing air monitoring network.
South Coast AQMD re-initiated air monitoring on September 26, 2026, to supplement ongoing monitoring conducted by the City of Paramount and provide more detailed information in selected areas. South Coast AQMD is also conducting facility inspections, reviewing source testing and permitting information, and evaluating potential sources of emissions.
This is an active investigation. New information will be posted on this website as it becomes available.
Investigation at a Glance
Compliance, Enforcement & Permitting
South Coast AQMD is conducting on-site inspections, reviewing compliance and permitting activities and conducting emissions source testing at metalworking facilities in Paramount. This is an active and ongoing investigation.
More information on past actions can be found on the Compliance, Enforcement & Permitting tab.
Air Monitoring
South Coast AQMD re-initiated air monitoring efforts to support ongoing compliance, enforcement, and permitting activities. Air monitors are located near the Aerocraft and ProCast facilities and additional locations were selected to collect data upwind and downwind of metal processing facilities in the general area, as well as within the adjacent community. The purpose of these air monitoring efforts are to help pinpoint potential sources of hexavalent chromium.
Scheduled Sampling: Hexavalent chromium samples are collected every three days. Each monitor collects an air sample continuously over a 24-hour period. The samples are then delivered for expedited laboratory analysis. Data is available approximately one week after collection. Results and information about monitoring locations will be posted as they become available.
Air Monitoring Sites
Note: Sites are numbered by lab sample number as indicated on the CDC, pending final naming.
Paramount Hexavalent Chromium Monitoring Results (ng/m3)
| Sample Date |
Site #7A |
Site #8A |
Site #14A |
Site #16A |
Site #18A |
Site #39A |
Site #40 |
Site #41A |
| Sat, Sep 26, 2026 |
0.21 |
0.14 |
0.30 |
0.10 |
0.19 |
0.09 |
0.15 |
0.29 |
| Tue, Sep 29, 2026 |
0.22 |
0.67 |
0.24 |
0.18 |
0.03 |
0.23 |
0.26 |
0.18 |
| Fri, Oct 2, 2026 |
0.63 |
0.80 |
0.23 |
0.12 |
0.67 |
0.29 |
0.30 |
0.20 |
| Mon, Oct 5, 2026 |
0.36 |
0.20 |
0.16 |
0.08 |
1.05 |
0.30 |
0.84 |
0.20 |
| Thu, Oct 8, 2026 |
0.74 |
2.33 |
0.22 |
0.10 |
0.57 |
0.32 |
0.31 |
0.17 |
| Sun, Oct 11, 2026 |
invalid |
0.18 |
0.18 |
0.15 |
0.18 |
0.15 |
0.14 |
invalid |
| Wed, Oct 14, 2026 |
0.64 |
0.99 |
0.10 |
0.07 |
1.17 |
0.25 |
0.75 |
0.77 |
| Sat, Oct 17, 2026 |
0.13 |
0.65 |
0.11 |
0.09 |
1.99 |
0.08 |
0.11 |
0.18 |
| Tue, Oct 20, 2026 |
0.41 |
0.91 |
0.26 |
0.19 |
0.33 |
0.42 |
invalid |
0.58 |
| Notes: Invalid means sample collected was invalid due to a variety of reasons such as loss of power, equipment malfunction, etc. |
More information on South Coast AQMD’s current and past air monitoring efforts in the City of Paramount can be found on the Air Monitoring & Data tab.
AB 2588 / Air Toxics Program
The AB 2588, Air Toxics Hot Spots program, evaluates toxic air contaminant emissions and potential health risks from existing facilities. AB 2588, which is implemented through South Coast AQMD’s Rule 1402, requires facilities with potential offsite health impacts to quantify their toxic emissions with an Air Toxics Inventory Report (ATIR), which may include source testing of emission sources. If the approved ATIR indicates offsite health impacts, facilities are required to submit a health risk assessment (HRA) to estimate the health risk at the residential and work locations. If the HRA exceeds certain thresholds, facilities may be required to conduct public notification and implement risk reduction measures.
Six facilities in the City of Paramount are currently subject to Rule 1402 and developing ATIRs and conducting source tests as part of the AB2588 process: Carlton Forge, Mattco Forge, Fenico Precision Casting, Weber Metals, Press Forge, and ProCast Industries. Further actions will be determined based results from the ATIRs.
Aerocraft, Anaplex, and Lubeco completed ATIRs, Health Risk Assessments, and risk reduction as part of the AB 2588 program several years ago. More information can be found on the AB 2588 tab.
Background
Hexavalent chromium is a toxic air contaminant and a known human carcinogen.
South Coast AQMD began monitoring air quality in Paramount in 2013 in response to community concerns about metallic odors. Elevated levels of toxic metals identified during subsequent monitoring led to expanded air monitoring, facility investigations, enforcement actions, rule development, and other efforts to identify and reduce sources of emissions.
Extensive monitoring and enforcement efforts beginning in 2016 resulted in substantial reductions in ambient hexavalent chromium levels. South Coast AQMD’s current work builds on those efforts and focuses on evaluating recent monitoring results and potential sources of emissions.
Learn More About the History of the Investigation
Air Quality Complaints
Please contact us at 1-800-CUT-SMOG or file a complaint online if you have information that can assist us in the investigation of sources of hexavalent chromium in the area. If desired, the information can be provided anonymously.
More Information
For more information, please contact the South Coast AQMD Public Advisor at publicadvisor@aqmd.gov.
Looking for older reports or other historical records? Visit the Background, Archives & Other Resources tab.