Maryland communities that are poor and predominantly African-American incur a disproportionate cancer risk from ambient
exposure to airborne toxins, according to researchers from the Johns Hopkins Bloomberg School of Public Health. Their study
revealed that among Maryland census tracts, the poorer the community and the higher the proportion of African-Americans, the
greater the residents' cancer risk from air toxics. Further, the researchers were able to identify the sources underlying the
inequities. Both traffic and area sources (e.g., dry cleaners and gas stations) were primarily responsible, in contrast to
point sources (e.g., power plants, heavy industry) and non-road mobile sources (e.g., construction, farm vehicles and
airplanes), which were more evenly distributed across Maryland's economic and racial strata. The study is published in the
June 2005 issue of Environmental Health Perspectives.
"The inequity in risk from air toxins shown by this study represents yet another public health strike against that segment of
Maryland's population that can least afford it," said Benjamin Apelberg, MHS, lead author of the study and a graduate student
in the Bloomberg School's Department of Epidemiology.
The researchers compared cancer risk estimates from the U.S. Environmental Protection Agency's (EPA) National Air Toxics
Assessment to the racial and socioeconomic characteristics of Maryland communities found in the 2000 U.S. Census. The EPA's
assessment of lifetime cancer risk, which is based on exposure to 29 toxic air pollutants, is based on a nationwide inventory
of sources and emissions and accounts for atmospheric transport of the pollutants, human activity patterns and the
carcinogenic potency of the air pollutants.
Apelberg and his coauthors found that census tracts in the lowest quartile of median household income were 15- to 100-fold
more likely to be at high risk of cancer from air toxins. In addition,communities with higher proportions of African-American
residents were three times more likely to be at a heightened risk. They also found that as the proportion of white residents
increased, the level of risk decreased.
Four categories of air toxins-major emissions sources; area emissions sources; on-road vehicle sources; and non-road
sources-were included in the EPA's cancer risk assessment. Vehicle emissions of air toxins from on-road automobiles had the
highest impact on cancer risk in Maryland, followed by non-road mobile sources such as construction vehicles and farm
equipment, and by area sources such as local automobile repair shops and dry cleaning facilities. Significant and consistent
disparities in risk by income and race were found for on-road vehicle emissions and area sources.
The study results suggest that low-income, African-American communities are more likely to be located near busy roadways. In
contrast, the researchers observed that cancer risk from large industrial point sources was more evenly distributed across
economic and racial strata.
"Our study is only one piece of a larger puzzle of the factors leading to health disparities. It is widely accepted that
low-income and minority communities face a disproportionate number of stressors and are more likely to have poorer health.
Long-term risk from air pollution is one of the factors that can be mitigated through sound environmental policies," said
Ronald H. White, MST, coauthor of the study and deputy director of the Bloomberg School's Risk Sciences and Public Policy
Institute.
The study authors suggest that low-income areas should be targeted for emissions-reduction policies, especially for on-road
vehicles and area sources, to help decrease the exposure of residents to air toxins.
"Public health and environmental justice needs to be a part of zoning and transportation planning. It is time to think beyond
simply building more and bigger highways as a solution to Maryland's transportations needs. Drivers need to understand that
their commuting and vehicle choices impact the health of the neighborhoods they drive through," said Timothy J. Buckley, PhD,
MHS, corresponding author of the study and an associate professor in the Bloomberg School of Public Health's Department of
Environmental Health Sciences.
"Socioeconomic and Racial Disparities in Cancer Risk from Air Toxics in Maryland" was supported by grants from the National
Institute of Environmental Health Sciences, the Johns Hopkins Center for Urban Environmental Health and the Maryland
Cigarette Restitution Fund.
Public Affairs media contacts for the Johns Hopkins Bloomberg School of Public Health: Kenna Lowe or Tim Parsons at
410-955-6878 or paffairsjhsph.edu.
Contact: Kenna L. Lowe
paffairsjhsph.edu
410-955-6878
Johns Hopkins University Bloomberg School of Public Health
jhsph.edu