Cumulative Impacts: Investigators Present Analytic and Policy Approaches

Low-income communities, like those found in parts of West Oakland, are disproportionately impacted by environmental exposures. (Photo courtesy of California Air Resources Board)

In December 2009, COEH researchers, community advocates, health department professionals and National Research Council committee members came together in Oakland, California, for a symposium: Assessing and Addressing Cumulative Impacts in California Communities. The event was the culmination of research projects to develop methods and approaches to cumulative impacts supported by the Office of Environmental Health Hazard Assessment of the California Environmental Protection Agency (Cal/EPA).

Principal investigator and conference organizer Amy D. Kyle comments, "Much of what we do in environmental health has focused on single chemicals or agents, in terms of both research and in policy. While this has led to significant reductions in emissions of regulated pollutants, it has not protected people in communities with accumulation of multiple sources of pollution. We are trying to look at how we can do a better job with the environments that actually exist in communities."

“There is an emerging consensus that we need to look at what else is out there when making decisions, both in terms of the environment and the people. Each action can no longer be taken in a vacuum. We need a genuine community focus for environmental protection. It can be done now in ways that are meaningful, so let's get on with it.”
Amy Kyle

The project was prompted by California legislation requiring state agencies to consider the cumulative impacts of environmental and other factors that can disproportionately affect communities.  Cal/EPA has adopted a broad definition of cumulative impacts as  "exposures, public health, or environmental effects from the combined emissions and discharges in a geographic area, including environmental pollution from all sources, whether single or multi-media, routinely, accidentally, or otherwise released. Impacts will take into account sensitive populations and socio-economic factors, where applicable and to the extent data are available."

Faculty presented methods to identify high-risk communities and quantitative metrics to assess uniformity of exposures. Community advocates discussed the value of this work for neighborhoods, the need for action and the usefulness of health impact assessment strategies.

UC Berkeley Investigator Findings

Rachel Morello-Frosch highlighted key findings from the evidence base supporting work on cumulative impacts, pointing out the depth and significance of disparities in environmental exposures and in health status, the importance of considering particular susceptibilities, and how social vulnerability can amplify effects of environmental exposure. 

Measurement and Inequalities

Morello-Frosch discussed methods to identify areas with higher burdens of contamination and vulnerability developed with Manual Pastor of the University of Southern California (USC) and James Sadd of Occidental College. The method uses metrics of environmental exposure, demographic factors, and vulnerability factors that are scored to allow for comparison and applied on a geographic basis to identify areas with higher combined impact. Postdoctoral scholar Bill Jesdale demonstrated different ways of considering inequality in environmental exposures.

Michael Jerrett talked about quantitative methods to assess cumulative inequalities in environmental exposure by race/ethnicity and socioeconomic factors. Postdoctoral scholar Jason Su presented an index based on these concepts, then provided a quantitative assessment of inequality in exposures within Los Angeles (see related article in this issue.)

Policy Contexts

Kyle explored how concepts of cumulative impact were reflected in current environmental policies and how they might be addressed more broadly. For example, the California Environmental Quality Act (CEQA) requires environmental review for certain projects and requires consideration of cumulative impacts. Her case studies developed with graduate students Beth Altshuler, Miriam Zuk, and Tina Yuen suggest that CEQA does not necessarily protect communities for two mains reasons. One is that projects may proceed when there were "overriding considerations" of economic or social benefits, so there is no absolute limit to impact. Second is that methods used to characterize both environmental and cumulative impacts are limited and may not reflect current scientific knowledge.

Community Perspectives

Kyle's comments were supported by community advocates who have long articulated a need to move beyond the single chemical approach to environmental management. Bill Gallegos from Communities for a Better Environment (CBE) applauded the value of the screening and mapping methods developed by Morello-Frosch. CBE advocates for resource investment in highly impacted areas for successful remediation and future opportunities.

Joe Lyou from the California Environmental Rights Alliance discussed the range of environmental and other stressors that some communities face.  He highlighted the challenge in getting the research and policy communities to focus on what seem like obvious needs and inequalities and called for actions to adopt usable, practical approaches to making a difference now in affected areas.

Rajiv Bhatia from the San Francisco Department of Public Health discussed tools used to assess a wider array of health-related environmental and social factors through health impact assessment (HIA). This method expands traditional approaches to reveal health and social justice implications of projects or improvements to urban infrastructure.

Building on the National Discussion–NRC Panel Contributions

Professor Jonathan Levy from Harvard University emphasized the importance of improving the technical quality of measurement methods, their value to users and adaptability to demands–while acknowledging the complexity of this approach. He further discussed the report, "Science and Decisions," which strongly recommended the US EPA upgrade and reform its methods for assessing environmental health risks.

Gary Ginsberg from the State of Connecticut discussed background exposure of populations to environmental contaminants and how this is generally not considered when dose-response relationships are adapted during risk assessment procedures. The NRC panel highlights the significance of these findings.

The symposium concluded with comments from a panel of public health and environmental health leaders, chaired by COEH director John Balmes. He comments that "the panelists agreed governmental agencies should consider the cumulative impacts of multiple environmental factors when making regulatory policy decisions. There was less agreement about how cumulative impacts should be integrating into the decision-making process."


In March 2010, Morello-Frosch and Kyle served on the scientific advisory panel for the US EPA national meeting on the science of disproportionate impacts.

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