South Coast AQMD has completed the most extensive hexavalent chromium air monitoring program ever conducted in the South Coast Air Basin. Routine monitoring has since been transitioned to the City of Paramount, which continues to operate its air monitoring network. South Coast AQMD remains actively involved through targeted investigations, special sampling, and enforcement actions when needed.
South Coast AQMD re-initiated air measurements in the industrialized area of Paramount on September 26, 2026. This monitoring supplements ongoing monitoring conducted by the City of Paramount and provides additional information in selected areas.
Current Air Monitoring
One air monitor was located near the Aerocraft and Procast facilities and is at a similar location where the City of Paramount also operates an air sampler. Additional air monitoring locations were selected to collect data upwind and downwind of metal processing facilities in the general area, as well as within the adjacent community to help identify potential sources of hexavalent chromium.
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. |
South Coast AQMD's current monitoring activities are designed to:
- Measure ambient levels of hexavalent chromium and other pollutants;
- Evaluate areas where additional information may be needed;
- Support investigations of potential emission sources;
- Assess trends in air quality over time; and
- Provide information to support compliance, enforcement, permitting, and other regulatory activities.
2025 Air Monitoring Efforts
- A mobile monitoring survey on September 30, 2025, around the facilities and nearby neighborhoods. Mobile surveys collect short-duration (less than 5 minutes) samples to help identify potential air pollution “hot spots.” The survey targeted metals such as chromium, nickel, titanium, vanadium, arsenic, and lead. Data was found to be within typical background levels.
- Technical on-site evaluations at the facilities to identify any potential sources of hexavalent chromium within facility operations.
2016-2021 Air Monitoring Campaign
Between 2016 and 2021, South Coast AQMD conducted an extensive air monitoring campaign to pinpoint sources of hexavalent chromium and other toxic metals. Air filter sample measurements were paused in December 2020 due to increased COVID-19 concerns. However, monitoring for multi-metals near Kindred Hospital continued.
Paramount Emissions Investigation Fact Sheet – April 2021: English (PDF) | Español (PDF)
Monthly Average Results of Hexavalent Chromium Near Facilities
Air monitoring results show substantial reduction of hexavalent chromium levels in late 2016/early 2017 at Aerocraft (site #8) and Anaplex (sites #14/#15). Overall, levels of hexavalent chromium have been consistently lower over the past few years at these sites.
Toxic Metals with Long-Term Health Levels
Continuous multi-metals screening measurements are used to complement regular air monitoring to get a better understanding of emissions from nearby facilities. This, along with our monitoring data, was used to provide a more complete picture in the Paramount area. This type of sampling has been used for four years at the Kindred Hospital. Toxic metals with long-term health thresholds (see below) are within typical (background) levels and well under long-term health-based exposure levels established by the Office of Environmental Health Hazard Assessment or the U.S. Environmental Protection Agency.
In October 2018, air monitoring results showed reduced levels of hexavalent chromium, resulting in South Coast AQMD updating its air monitoring efforts in Paramount to focus on conducting studies to evaluate other potential sources of hexavalent chromium and also monitoring other areas of the Basin that may have higher potential for air toxics exposure.
Older studies, individual site reports and other related technical documents remain available in the Archives and Other Resources page.