This page last reviewed September 27, 2010

ARB's Community Health
Crockett: Air Monitoring Results


These data represent only a portion of the data that have been collected as part of this study. Although the air quality monitoring in Crockett ended in May 2003, not all of the data have been processed and reviewed. Therefore, no conclusions about the overall meaning of the data should be made at this time.

Monitoring details

The Crockett community in Contra Costa County was selected due to its proximity to high-risk facilities, including potential sources of dioxin and mobile source emissions. Oil refineries and major oil storage facilities are located in nearby cities. Crockett is also the location of a major food processing operation and a heavy-rail transfer facility.

In the initial phase of the study, monitoring of ambient air quality at John Swett High School in the Crockett community began in October 2001 and ended in May 2003. It should be noted that the Crockett monitoring site shut down from December 20, 2002 until February 14, 2003 due to a lack of electrical power. Approximately 70 air pollutants were monitored at the Crockett site. A table of air pollutants monitored is provided here. Criteria air pollutants were measured, some of which have health-based standards established; a standard is a level above which a pollutant is known to cause adverse health effects in humans. Toxic air pollutants were also measured. These pollutants are known or suspected to cause cancer or other serious illnesses. There is no safe level for toxic air pollutants. The data presented from John Swett High School represent 20 months of monitoring for organic gases and particulate matter. Data for the pollutants are presented here.

Criteria gaseous pollutants are routinely monitored at Concord, San Pablo, and Pittsburgh. Ambient levels of toxic air pollutants are routinely monitored at approximately twenty sites in the California air toxics monitoring network. Close to Crockett in the region is Fremont-Chapel Way, where data for the last 3 years are available for comparison. The Bay Area Air Quality Management District (BAAQMD) operates a number of toxic air pollutant monitoring sites that are closer, but much fewer pollutants are monitored.

Criteria Pollutants

Some air pollutants have health-based standards established. Information on these so-called criteria pollutants can be obtained below:

High Risk Toxic Air Pollutants

The Air Resources Board has identified the top 10 high risk toxic air pollutants and nine of them were measured in Crockett at John Swett High School. The top 10 high risk toxic air pollutants have potential health risks and cancer risks. Diesel particulate matter is a significant contributor to the potential cancer risk from air toxic pollutants in California, but diesel particulate matter was not measured at John Swett High School because a method for directly measuring this pollutant is still being developed. However, the potential cancer risk is estimated for diesel particulate matter for the entire San Francisco Bay Area air basin. As shown in a graph illustrating the cancer risk due to individual pollutants, diesel particulate matter is the highest contributor to risk from air toxic pollutants. The next highest are benzene and 1,3-butadiene. Information on the nine measured high risk pollutants can be obtained below:

Metals of interest

Due to location of refineries in the community, some metals were of particular interest in this study. Information on these metals are below:

Diesel Particulate Matter and Elemental Carbon

While diesel particulate matter contributes the most to overall risk from toxic air contaminants, it has proved very elusive to measure. We are exploring the options to estimate the impact of diesel particulate matter on public health in the community, including using elemental carbon as an estimator. However, there are technical difficulties to using elemental carbon to estimate diesel particulate matter. First, other sources of elemental carbon besides diesel particulate matter became more significant as emissions from the diesel fleet decreased as a result of improved diesel technologies. Second, there are many elemental carbon analysis methods that have evolved which give significantly different results when measuring the same particles in the air. In this study, the Air Resources Board uses one elemental carbon analysis method. Information on elemental carbon are presented below:

PAHs and Dioxins

Polycyclic aromatic hydrocarbons (PAHs) and dioxins have been identified as toxic air pollutants that may disproportionately impact infants and children. Benzo[a]pyrene is one of the six PAHs monitored in this study. Currently there are no data available for dioxins in the Crockett study area. Dioxin measurements began for the Crockett area in
December 2001 at John Swett High School and is expected to end around December 2003; the link below provides information on current activities. Information on PAHs and other compounds can be obtained below:

All data

For all available data in Microsoft Excel format:


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