New Methods Detect “Hotspots” of Cumulative Exposures in California Communities

Photo: Town of Bolinas
Photo Credit: Town of Bolinas photo courtesy of Wikipedia

Outdoor levels of particulate matter air pollution in Richmond are among the highest in California. The city is a busy hub of truck, rail, and marine transportation and home to Chevron Richmond, one of the major refineries in the United States. Yet it is the cumulative exposure to multiple stressors in this community such as noise, crime, and poverty, and their potential to amplify the health effects of specific exposures like air pollution, that now concerns scientists and policymakers.

The Northern California Household Exposure Study, conducted by UC Berkeley professor Rachel Morello-Frosch with colleagues at Brown University, Silent Spring Institute, and Communities for a Better environment, compared environmental exposures in a fence-line community bordering the Chevron Richmond refinery with a group of Bay Area homes located in rural Bolinas, California, where the air is cleaner.

She found measurements of indoor air pollution in Richmond were higher overall than in Bolinas. Higher levels of vanadium and nickel were also indicative of heavy oil combustion and shipping. In nearly half of the Richmond homes, measurements of particulate matter less than or equal to 2.5 microns in diameter (PM2.5) exceeded California’s annual ambient air quality standard.1 Her findings provide new evidence that indoor air quality is an indicator of the cumulative impact of outdoor emissions from industry and traffic in heavily impacted neighborhoods.2

Photo: Richmond community with refinery tanks in the background Richmond community with refinery tanks in the background

New analytic methods and technologies are making it possible to accurately pinpoint cumulative exposure “hot spots” like those in Richmond where populations are disproportionally affected by multiple pollutants and other psychological and social stressors with the potential to affect health.

Currently, the California Environmental Protection Agency (Cal/EPA) is strengthening its ability to screen the environmental health of California communities with an innovative tool under review by multiple stakeholders and the general public.

“This tool is part of a larger plan that started in 2004 with the Cal/EPA Environmental Justice Action Plan,” explains Arsenio Mataka, assistant secretary for Environmental Justice and Tribal Affairs at Cal/EPA.

“Under that plan an environmental justice advisory committee – as well the Secretary and several of the heads of boards and departments – put forth a recommendation to evaluate and assess cumulative impacts. We charged the Office of Environmental Health Hazard Assessment (OEHHA) to put together a working group consisting of industry, business, environmental justice groups, and academics. In 2010, OEHHA released its report with a methodology to assess cumulative impacts for the State of California.”

The final version of the environmental health screening tool, termed CalEnvironScreen, is expected to be an important aid to Cal/EPA planning and decision-making. Potentially, it could inform decisions related to economic development to support communities heavily impacted by cumulative environmental pollution.

Photo: Training residents how to use the air samplers Training residents how to use the air samplers

“We know these tools are not a substitute for environmental assessments,” says Mataka, “but they are a way to prioritize funding, clean-ups, and enforcement.”

“From a policy perspective, we have limited resources,” adds Mataka. “A tool like this not only could fulfill our environmental justice mandate, but it could also help us focus our time and attention on those areas of the state that appear to be in the greatest need.”

Morello-Frosch notes that, in the past, environmental justice communities have been identified when they mobilize to bring attention to their issues. “The problem is that there may be communities that have significant environmental health challenges or pollution sources with localized impacts, but the community itself doesn’t have the capacity to engage in the regulatory process.” Cumulative impact screening could remove this burden of proof.3

Mataka believes it is important to find those communities that may be suffering equally to some of the more historic environmental justice communities. “We have programs for education and outreach to build capacity in these communities to bring them to the level of others that have had resources and attention,” says Mataka.

With funding from OEHHA and the California Air Resources Board, Morello-Frosch and COEH co-investigators Amy Kyle and Michael Jerrett, along with research scientist Jason Su, were the first to publish a tool to summarize racial-ethnic and socioeconomic inequalities in cumulative environmental hazards, which they tested in Los Angeles County, one of the most ethnically diverse and polluted metropolitan areas in the United States.4

Photos: Long Beach Port and Los Angeles Long Beach Port photo courtesy of WPPilot and Los Angeles photo courtesy of Joe Mabel

They measured poverty and racial-ethnic composition to summarize social inequality at the census tract-level. To show unequal levels of pollution, they used measurements of nitrogen dioxide (NO2), PM2.5, and estimates of cancer risk associated with diesel exhaust from the Environmental Protection Agency’s National-Scale Air Toxics Assessment (NATA) model.

The greatest environmental inequities were seen for diesel particulate matter cancer risk, followed by NO2 then PM2.5. Notably, the study showed that cumulative hazard inequalities were greater than for any single pollutant. The highest levels of cumulative impacts were found in downtown L.A. followed by the Long Beach port area.5

Environmental justice tools sharpen the focus on inequalities across regions. But in the wake of the Northern California Household Exposure Study, Morello-Frosch discovered community members in Richmond wanted to dig much deeper to assess local health and neighborhood issues.

With funding from the Avon Foundation, she worked with a student to help Communities for a Better Environment launch an environmental health survey that fully integrated local residents into the research process. Participants developed and implemented a questionnaire based on community-identified concerns in four neighborhoods likely impacted by mobile and stationary sources of pollution.6 They surveyed a total of 198 people, who provided data on 722 residents including 282 children.

The Richmond Health Survey, published in the October issue of Health, Education and Behavior, found that although residents thought their neighborhoods were good places to live, they were concerned about local stressors such as the prevalence of asthma among long-time residents and among children, where it is double the national average.7

Since the survey’s release, it has been widely used an outreach and organizational tool. For instance, residents presented their findings to the County’s Hazardous Materials Commission. “I think the timing of the Richmond survey has provided good impetus to fold in questions and concerns that communities identified into the process of updating the General Plan,” says Morello-Frosch.

The key to making these screening tools work from a policy point of view, according to Morello-Frosch, is to develop an approach that is scientifically valid, but also transparent. “Ultimately, if community stakeholders trust the method, you are more likely to have better outcomes in terms of elucidating potential solutions to the concerns of environmental justice communities.”

Rachel Morello-Frosch is co-director of UC Berkeley’s Doctor of Public Health program and a professor jointly appointed in the College of Natural Resources and the School of Public Health.

More information about the draft Cal/EPA tool is available online at

1,2Brody JG, Morello-Frosch R, Zota A, Brown P, Pérez C, Rudel RA. Linking exposure assessment science with policy objectives for environmental justice and breast cancer advocacy: the northern California household exposure study. Am J Public Health. 2009 Nov;99 Suppl 3:S600-9.
3Morello-Frosch R, Zuk M, Jerrett M, Shamasunder B, Kyle AD. Understanding the cumulative impacts of inequalities in environmental health: implications for policy. Health Aff. 2011 May;30(5):879-87.
4US Census Bureau
5Su JG, Morello-Frosch R, Jesdale BM, Kyle AD, Shamasunder B, Jerrett M. An index for assessing demographic inequalities in cumulative environmental hazards with application to Los Angeles, California. Environ Sci Technol. 2009;43(20):7626-34.
6,7Cohen A, Lopez A, Malloy N, Morello-Frosch R. Our environment, our health: a community-based participatory environmental health survey in Richmond, California. Health Educ Behav. 2012 Apr;39(2):198-209.

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