Hot Spots vs Clusters: Environmental Right to Know in Santa Ana

This image shows the thresholds set for both cancer and non-cancer risk posed by Toxic Release Facilities in the South Coast Air Quality Management District. The AQMD uses these thresholds to determine "Hot Spots," which require a thorough public health assessment and mitigation efforts on the part of the facility.

“Assembly Bill (AB) 2588 (Connelly), the Air Toxics 'Hot Spots' Information and Assessment Act, requires facilities that are ranked as a high priority (see Prioritization) to submit a health risk assessment (HRA) to the air pollution control and air quality management districts (district). A risk assessment, as defined under the Air Toxics 'Hot Spots' Act, includes a comprehensive analysis of the dispersion of hazardous substances into the environment, the potential for human exposure, and a quantitative assessment of both individual and population-wide health risks associated with those levels of exposure. The risk assessments submitted by the facilities are reviewed by the Office of Environmental Health Hazard Assessment (OEHHA) and approved by the district. In addition, the district may require facilities in the intermediate and low priority categories to also submit a health risk assessment."

According to this chart, South Coast AQMD sets the maximum incremental cancer risk threshold at 10 or more "chances" of cancer per 1 million residents, while a site is considered "cancer burdened" if exceeding 1 "chances" per 2 million residents (or .5 cases per 1 million). Further elaborated, this webpage specifies that an "actionable risk" is set at 25 "chances" per 1 million residents and a "significant risk" is set at 100 "chances" per 1 million residents. According to the website, "Facilities above these risk levels may be designated as a Potentially High Risk Level Facility under Rule 1402." However, it is unclear what AQMD means by "chances," or how this "facility-level" risk translates into community-level.

As shown here, CARB's facility search engine will provide emissions data on specific toxics, but this does not easily translate into an understanding of their health risks, especially any cumulative or combined risk.

Furthermore, the determination of "low risk" at the facility-level blatantly contradicts data at a more aggragated level. CalEnviroScreen's data on Toxic Release Inventories shows all of Santa Ana's census tracts as being above the 90th percentile for toxic emissions in the state. What is more, this data shows another dramatic increase in emissions for the census tracts containing these TRI clusters.

The census tract, too, may not be an adequate unit of analysis, given that these clusters often impact neighboring census tracts which do not contain TRIs themselves. For example, this census tract, which sits above a TRI cluster contains only one TRI facility, and yet it is still in the 96th percentile.