Motor Vehicle Pollution, Social Justice and Public Health

Motor Vehicle Pollution, Social Justice and Public Health

David Sittenfeld, Jon Levy, Sam Lipson, Joanne Nicklas, and Wig Zamore

A growing body of scientific evidence suggests that that chronic exposure to motor vehicle pollution can trigger health problems such as asthma and cardiovascular disease. These associations constitute a major public health concern and also present issues of environmental justice, since many of the population living near major roadways are from low-income or minority groups.. A number of community and academic partners are working with the Museum of Science both to engage the public in discussions around this important issue and to undertake community-based research that will help to address uncertainties in the science.

Heath Effects from Particulate Pollution

The EPA’s website states:

“Particle pollution, also called particulate matter or PM, is a complex mixture of extremely small particles and liquid droplets in the air. When breathed in, these particles can reach the deepest regions of the lungs. Exposure to particle pollution is linked to a variety of significant health problems, ranging from aggravated asthma to premature death in people with heart and lung disease.”

The EPA, which has regulated PM from motor vehicles since the implementation of the Clean Air Act in 1970, currently regulates two types of particulate pollution: “inhalable coarse particles” (particle size is between 2.5 and 10 microns) and “fine particles” or PM2.5,(2.5 microns and smaller). The most recent revisions were in 2006 under the National Ambient Air Quality Standards (NAAQS), and reduced the allowed daily standard for PM2.5 from 65 micrograms per cubic meter (µg/m3) to 35 µg/m3. This standard is scheduled to take place beginning in 2015, although a delay until 2020 is currently being considered.

Emerging research in public health is now demonstrating that a third category of much smaller particulate matter, known as ultrafine particulates (UFP), are also correlated with adverse cardiac and respiratory health effects. Health effects from UFP emissions may be more serious than emissions from either of the two categories described above. UFP includes particles that are smaller than 0.1 µm (100 nanometers) and are currently unregulated by EPA. A sizable fraction of diesel emissions are these types of ultrafine particles. UFP emissions are the shortest-lived and the most difficult to detect, but new research techniques are demonstrating that they are emitted in huge quantities on and close to major roadways.

UFP emissions carry several unique health concerns because of their reduced particle size. First, the smaller size allows for a greatly increased number of particles in a given area, so concentrations near roadways of these UFP emissions can be much higher than with larger particulate emissions. Second, the smaller size and increased surface area of these ultrafine particles means that they have the potential to translocate more easily to other areas of the body through the lung, and also that they demonstrate increased bioactivity and oxidative stress. Finally, although these particles can be relatively short-lived in the air, our lungs have difficulty transporting them out of the body, and so they have been shown to bioaccumulate more than the larger particle sizes (Oberdorster, 2005).

Much of the work in this area has been done by Günter Oberdörster, Director of the University of Rochester’s Ultrafine Particle Center. In summarizing his laboratory investigations of the adverse health effects from ultrafine particulates, Dr. Oberdörster writes:

“Numerous epidemiological studies have shown that acute adverse health effects are associated with exposures to ambient airborne particles…We hypothesize that ultrafine particles (particle size below 0.1 µm) are one potential source causing these effects. Such particles occur in fumes generated by heating and combustion processes and are also normal constituents of the ambient aerosol, specifically in urban areas generated from numerous sources (e.g., car exhaust, heating)…Our studies with laboratory-generated ultrafine particles have shown that these particles have a significantly greater potency to induce inflammatory lung injury than larger-sized particles with the same chemical composition.” (Oberdörster, 2009).

Both physical proximity to major roadways and traffic density have been shown to correlate with higher UFP and PM2.5 levels. In addition, these densities have been strongly correlated with increases in the cardiac and respiratory conditions referenced above.

Some of the most significant work in this area is being done by Michael Jerrett at the University of Southern California, who found a 44% greater lung cancer mortality in communities whose centers lie within 500 meters of a major highway intersection (Jerrett, 2005). In a study released last year, Jerrett also shows a strong correlation between roadway traffic density and decreased circulatory function (Jarrett, 2009). Michael Riedeker from the University of North Carolina demonstrated in a 2004 study that heart function decreased with increasing PM concentration on roadways in a group of otherwise healthy police officers (Riedeker, 2004). In addition, a number of relevant studies have been conducted using unionized long-haul truck drivers as subjects, correcting for smoking and other risk factors, and mortality rates from lung cancer and ischemic heart disease have been consistently higher in populations that were exposed to higher and more frequent motor vehicle emissions (Laden, 2007).

There is significant and growing evidence that these emissions can exacerbate and/or trigger a number of chronic conditions such as asthma. Researchers at the University of Southern California published a review paper in 2008, summarizing a number of recent findings in the peer-reviewed literature, concluding that:

“There is consistent evidence that living near traffic sources is associated with asthma occurrence and exacerbations…stronger associations with traffic were found among long-term residents.” (Salam, 2008)

Air quality and health inequities

The health effects associated with traffic pollution are not uniform upon all demographic populations. According to the Environmental Protection Agency,

“Often, urban environments have high levels of outdoor pollution and poor housing conditions, which frequently are associated with increased levels of indoor pollution. Disproportionate numbers of people of color and people from low income households live in these areas, and thus may be exposed to higher than average levels of air pollution, both indoors and outside. These exposures, along with other factors such as inadequate health care, may explain why roughly two of three times as many African Americans as Caucasians die from asthma.” (EPA, 2009)

The chronic condition of asthma can be used as a case study in considering the inequalities and environmental justice issues connected to the health effects of traffic pollution from major roadways. Asthma is just one potential health concern, but is one for which large datasets are readily available with associated demographic information.

Asthma is a growing problem among the general population in the US (the prevalence of asthma among Americans increased by 75% from 1990 to 2004, according to the Centers For Disease Control and Prevention); however, the disease has historically affected people of color and residents of low-income neighborhoods at far higher rates. The National Research Council reports that “Asthma mortality rates among African Americans are 2–3 times greater than among Caucasians; 5 times greater among children,” and that “Effective environmental control reduces disease severity.” (NRC, 1993)

This gap has grown rather than disappeared in recent years; the CDC reported in 2006 that the asthma death rate among non-Hispanic black children under the age of eighteen was over seven times higher than for non-Hispanic white children in the same age group for the period between 2003 and 2005, and that the disease was over three times as prevalent among Puerto Ricans of American descent of any age as for whites:

“Racial disparities remained evident in asthma prevalence through 2005… The disparity in asthma mortality between black and white children has increased in recent years. Racial disparities in childhood asthma are extensive; black and Puerto Rican children have high prevalence rates, and black children have dramatically higher mortality rates compared with white children.” (CDC, 2006)

Although the reasons and causes of asthma and other related conditions are extremely complex and may include a myriad of factors unrelated to traffic pollution, these kinds of statistics are important to consider as urban and regional planners design the landscape of the twenty-first century. The health of the underserved communities living near highways must not be neglected. Transit- and pedestrian-oriented development can help to address this pressing public health concern and simultaneously address other major societal concerns of the next several decades.

Dialogue and emerging research around Roadway Pollution

The Museum and the Cambridge Public Health Department recently held the second of a series of public forums around the issue of roadway pollution and its adverse health effects. Both programs happened as part of the Cambridge Science Festival; last year’s program ( focused upon the societal implications of possible mitigation policies, while this year’s program ( engaged participants in using Health Impact Assessment methodology to consider the well-chronicled case of the Long Beach and Los Angeles Ports. We hope to connect these kinds of public discussions with citizen science efforts to help researchers collect data and stimulate discussions in affected neighborhoods and communities.

A number of community-based research studies are under way in the Boston area to improve scientific understanding of the health impacts of motor vehicle emissions. A prominent is example is the Community Assessment of Freeway Exposure and Health (CAFEH) study by the Tufts University School of Medicine, which combines mobile sensing technologies and health assessment in neighborhoods near the I-93 corridor ( In addition, new technologies allow for novel kinds of assessment and partnerships A number of academic and community partners including the Museum of Science, the Cambridge Public Health Department, Harvard University’s Schools of Public Health and Engineering and Applied Sciences, MIT’s SENSEable City Laboratory, and the Somerville Transportation and Equity Partnership have proposed research that will combine data from a network of 100 fixed monitoring platforms on buildings and lightpoles called the CitySense network ( with information from mobile sensors on bikes, mobile phones and vehicles. This project would provide real-time data to the public about air quality in Cambridge and allow for further public discussions on the issue as the science moves forward. To learn more about these initiatives or to participate in these efforts, contact David Sittenfeld at

David Sittenfeld is Manager of the Forum program at the Museum of Science. Jon Levy is an Assistant Professor of Environmental Health at the Harvard School of Public Health. Sam Lipson is Director of Environmental Health at the Cambridge Public Health Department. Joanne Nicklas is a community public health researcher and student at Brown University. Wig Zamore is a community pollution researcher and transportation planner with the Somerville Transportation Equity Partnership and the Mystic Valley Task Force.

We thank Tim McAuley, Rex Britter, Matt Welsh, and Scot Martin for their collaboration.


The Boston Globe, April 12, 2009, “Road Hazard?”

Brauner, et. al, American Journal of Respiratory and Critical Care Medicine, “Indoor Particles Affect Vascular Function In the Aged”, 1998: vol. 177, pp. 419-425.

Brugge et al, “Near-highway pollutants in motor vehicle exhaust: A review of epidemiologic evidence of cardiac and pulmonary health risks”, Environmental Health, 2007.

Centers for Disease Control and Prevention, National Health Interview Survey, National Center for Health Statistics, 2006: “2006 Population Estimates and Prevalence Table 4-1: Current Asthma Prevalence Percents by Age, United States”, 2006, published online.

Centers for Disease Control and Prevention, National Health Interview Survey, National Center for Health Statistics, “The State of Childhood Asthma, United States, 1980–2005”, 2006, pdf on CDC website.

Environmental Protection Agency, Office of Air and Radiation, “Particle Pollution and Your Health”, 2003, pdf on website.

Environmental Protection Agency, Region 7 Air Program, “Asthma, Air Quality, and Environmental Justice”, 2009.

Jerret et al, “Spatial analysis of air pollution and mortality in Los Angeles”, Epidemiology, 16 (6): 727-736, November, 2005.

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Laden et al. Cause Specific Mortality in the Unionized U.S. Trucking Industry. Environmental Health Perspectives, April, 2007. Vol 115 (8), 1192-1196.

Oberdorster et al,“Nanotoxicology: An Emerging Discipline Evolving from Studies of Ultrafine Particles”, Environmental Health Perspectives, July 2005.

Oberdorster et al, “Translocation of inhaled ultrafine particles to the brain.”, Inhal Toxicol. 2004 Jun;16(6-7):437-45.

Pope et al, “Particulate air pollution as a predictor of mortality in a prospective study of US adults.” American Journal of Respiratory and Critical Care Medicine. 151:669-674, 1995.

Riedeker et al, “Particulate Matter Exposure in Cars Is Associated with Cardiovascular Effects in Healthy Young Men,” Am J Respir Crit Care Med ,Vol 169. pp 934–940, 2004.

Salam et. al, “Recent evidence for adverse effects of residential proximity to traffic sources on asthma”, Current Opinion in Pulmonary Medicine, 2008,
14:3–8, pp. 3-8.

Author: David Sittenfeld

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