"Torrance Air" Air Quality Monitoring Project

A fenceline air monitoring system at the Torrance Refinery and multiple monitoring stations located in the nearby community


The Torrance Air Quality Monitoring Project, known as “Torrance Air,” is monitoring local air quality using a fenceline air monitoring system at the Torrance Refinery and multiple monitoring stations located in the nearby communities. The data is currently available to the public through a mobile-friendly website at  

Locations for the air quality monitoring stations were selected to best represent the City’s geography and local meteorology. These stations measure harmful air pollutants, including hydrofluoric acid (HF). Three of the stations are already up and running at:  

  • North Torrance High School (began reporting data late October 2019); 

  • Elm Avenue (began reporting data late October 2019); and 

  • West Torrance High School (began reporting data late December 2019).

A fourth air monitoring station will be installed and operated at Guenser Park (downwind of the Torrance Refinery) by South Coast AQMD as part of its Rule 1180 - Refinery Fenceline and Community Air Monitoring in early 2020.  

The fenceline air monitoring system is located on the north side of the Torrance Refinery. The system uses instruments that measure the same set of pollutants as the community monitors and will provide information on air pollution resulting from refinery operations and/or other sources nearby. That data also will be found on The refinery will add additional fenceline monitors around the complete perimeter in early 2020 to comply with Rule 1180 requirements.  

Please note: All data displayed on the “Torrance Air” website is preliminary and is subject to final quality assurance and validation. 

Benzene Investigation

South Coast AQMD is aware that data displayed on the website from the three community air monitors (see figure 1) shows levels of benzene that are above typical background ranges during certain times of the day.  South Coast AQMD takes this matter seriously and has launched an extensive investigation into potential causes for the higher readings of benzene, including:

  • Conducting investigations into other potential sources of benzene in the area through additional monitoring and nighttime surveillances;

  • Analyzing data and information from air monitors in and around the area;

  • Working with Torrance Air contractors to evaluate instruments and quality control procedures for accuracy of data reported; and

  • Comparing independent monitoring done by South Coast AQMD with preliminary data from Torrance Air monitors.

Investigations can take some time; however, South Coast AQMD is working as fast as we can. Details on our ongoing activities can be found below, and additional information will be updated to the website as it becomes available. 

 Health-Based Standards 

When evaluating air pollutants, it is important to look at both short-term and long-term exposure levels. The Office of Environmental Health Hazard Assessment (OEHHA) is responsible for establishing both short-term (acute) and long-term (chronic) health-based standards, otherwise known as Reference Exposure Levels (RELs). OEHHA also establishes risk assessment values to evaluate cancer risks.

Short-term exposure is assessed by comparing 1-hour average benzene measurements to the acute REL of 8 parts per billion (ppb). In general, the benzene readings have been below the 8 ppb health-based standard at the three community sites, with the exception of two readings. One of 8.84 ppb recorded the evening of January 3, 2020 at the North High School monitor and one of 15.24 ppb recorded in the early morning of January 16, 2020 at the West High School Monitor. Both of these readings have since been invalidated due to instrument performance issues. Exposure to benzene at levels below the short-term health standard would not be expected to cause immediate health concerns. For typical environmental levels of benzene, the main concern is the cancer risk posed by long-term exposure to benzene. There is no simple “threshold” to evaluate cancer risks, however, we can compare measured levels to the typical “background” levels of that same pollutant from our air toxics studies to assess whether and how much it may differ from typical levels.

The long-term (chronic REL) health-based standard for benzene developed by OEHHA is 1 ppb and refers to exposure occurring over a long time (e.g., typical analysis for chronic exposure uses one year of data) for health effects other than cancer. If long-term average benzene measurements are above the 1 ppb health-based standard, then the chances of experiencing certain health problems are increased. This does not mean that people would experience health problems when levels peak above the chronic standards at certain periods of time in the day. Short-term (1-hour) data should not be compared directly to the chronic REL.

Investigations and Enforcement Action 

South Coast AQMD continues to review and analyze the data from the air pollution monitors and wind stations in the area. Preliminary analysis shows that benzene concentrations reported at all three community sites are higher late at night and early in the morning.  Benzene can be released into the atmosphere from a variety of sources including vehicle exhaust, gasoline vapors, oil production, refineries, and certain chemical and manufacturing operations.

Higher concentrations of benzene in the early morning can potentially be due to increased traffic from trucks, cars and other mobile sources in the area. Late night increases in benzene levels could be due to the combined effect of meteorology and other local sources, which are still being investigated. 

South Coast AQMD continues its independent measurements at the three Torrance Air monitoring stations, which includes a mobile monitoring survey in other parts of the Torrance community such as around the West Torrance High School campus and nearby facilities. 

On January 3, 2020, South Coast AQMD received odor complaints from an area northwest of the Torrance Refinery. The odor was traced back to a tank at the refinery, and a Notice of Violation was issued for Public Nuisance (see below). This incident was determined not to have contributed to the elevated benzene level recorded the evening of January 3rd.   

In addition, on January 8, 2020, South Coast AQMD inspectors conducted an investigation at Power Run Oil, which is located on property across the street from West Torrance High School. The investigation identified a leak at a gauge hatch on a storage tank. The hatch was immediately repaired by facility operators and a Notice of Violation (see below) was issued to the facility. The facility is located adjacent to a parking lot across the street from the high school campus and is used for student and faculty parking.  

Instrument Evaluation Updated!

Overall, benzene readings from the monitor at West High have been higher than the data collected at North Torrance High School and Elm Ave. As part of our efforts to evaluate instruments and benzene levels within the Torrance Air network, South Coast AQMD has:

  • Conducted mobile monitoring to compare levels of benzene at the three monitoring sites;

  • Collected canister “grab” samples at both the West High and North High monitors for comparison;

  • Recently deployed additional stationary monitors to measure and compare benzene levels at the West High Station;

  • Collected additional samples during the late night and early morning hours at the West High station; and

  • Inspected the West High monitor calibration setup and performed minor maintenance.

Data from the mobile monitoring was generally lower than what was reported on the West High station.  Additionally, the results from both the quick grab canister samples and the stationary monitor near the West High Station showed levels of benzene to be four times lower than what was reported on the Torrance Air website.

Three late evening samples (between 11 p.m. and 5 a.m.) were collected on different days. Laboratory results for these samples also showed benzene levels were two to four times lower than average data reported from the West High Monitor during those hours.

On January 17, South Coast AQMD conducted an inspection of the West High monitor and performed some standard maintenance which resulted in levels of benzene showing more similar results to the North High and Elm Ave. monitors as well as South Coast AQMD’s stationary monitors.

Based on data and analysis from South Coast AQMD’s independent monitoring and investigation, benzene levels reported at these monitors prior to January 17th have been affected by a calibration issue. Both of the erroneous readings that were above 8 ppb have been invalidated. 

South Coast AQMD is working with the contractor responsible for the monitors to collect more additional data to better validate the performance of the West High monitor. South Coast AQMD continues to conduct independent checks on the monitors, and the contractor has upgraded parts on all three monitors and added another monitor at the West High location for comparison based on our initial observations.

Notices of Violation Issued

Torrance Refining Corporation (Exxon)
Power Run Oil, LLC

Figure 1. Map showing the locations of the “Torrance Air” community air monitoring stations

Figure 1. Map showing the locations of the “Torrance Air” community air monitoring stations

Related Interest

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