The problem of cumulative impacts is not fully addressed by current regulatory and permitting practice, in part because of a reliance on traditional methods of risk assessment to decide, for example, whether a specific polluting facility can operate under existing law.
Risk is typically calculated using single stressors and is reported on a chemical-by-chemical, medium-by-medium, and source-by-source basis.
These tools all rely on secondary data maintained by government agencies as part of the regulatory and permitting process.
These stakeholders have voiced their concern and have called for additional methods to consider and include cumulative impacts in developing regulatory and enforcement priorities.
Regulatory agencies have responded to this need by embracing the National Research Council’s call for the development of “cumulative risk frameworks” within their scientific programs and enforcement activities.
EPA Cumulative Impact Tools and Application Domains.
EPA Region 9’s in-house and externally funded development and application of cumulative impacts screening-level tools, like EJSM, are part of EPA Region 9’s urban air toxics strategy, which has a major focus on mobile source air toxics.
The SVI uses US Census Tract data to determine where the socially vulnerable populations are located in EPA Region 9, but this tool does not assess the cumulative impact of environmental hazards (air pollution exposures), or their proximity, on those vulnerable populations.
The ESJM, initially funded by both CARB and US EPA, was designed to address the need for this type of analysis.These cumulative impacts tools are intended to be used by environmental and regulatory agencies for screening-level activities, such as planning and prioritization, and to assist in decision-making on such activities as permitting and determination of environmental remediation actions (i.e., “cleanup” levels).All of these cumulative impacts methods (1) define a set of indicator metrics that track different aspects of exposure, risk, and vulnerability for different geographic units in the region of study; (2) use spatial analysis techniques in a Geographic Information System (GIS) to “screen” areas to characterize their indicator profile; and (3) apply index scores to geographic locations to summarize their relative indicator profile and facilitate mapping and interpretation of the spatial patterns. A wide variety of health and exposure indicators have been used in various studies.Many neighborhoods bear the combined, or cumulative, burden of air pollution emissions from numerous industrial facilities and land uses, as well as emissions from mobile sources on high volume roads and freeways, and emissions associated with smaller facilities that either operate illegally or are not subject to regulatory oversight.This is of particular concern where the exposures affect populations that are, because of age or chronic health conditions, particularly sensitive to air pollution.Each regulatory authority only reviews those projects or facilities within its mandate and jurisdiction, with no integrated enforcement or review action across jurisdictions.