When diesel fuel burns in an engine, the resulting exhaust is made up of vapors, soot and gases, which may contain thousands of different chemical substances. Soot consists of extremely small particles that can be inhaled deep into the lungs. The particles carry cancer-causing substances known as polycyclic aromatic hydrocarbons. Gases in diesel exhaust, such as nitrous oxide, nitrogen dioxide, formaldehyde, benzene, sulfur dioxide, hydrogen sulfide, carbon dioxide, and carbon monoxide can also create health problems. Emissions currently include over 40 substances that are listed by the U.S. Environmental Protection Agency as hazardous air pollutants (HAPs). The EPA, the World Health Organization, the Department of Health and Human Services, and the National Institute of Environmental Health Sciences have all identified diesel exhaust as a likely carcinogen (cancer-causing agent). In the State of California, under Proposition 65, diesel emission is listed as a carcinogenic chemical.

People are continuously exposed to the dangers of inhaling diesel emissions. High exposure areas include walking on sidewalks, along bus routes, cycling near diesel trucks or buses, and driving a vehicle behind a diesel bus or truck. Even being a passenger in a diesel bus or truck results in exposure to diesel pollution. In Jan. 2001, the California Air Resources Board announced that a person riding inside a diesel bus may be exposed to four times more toxic diesel exhaust than someone standing or riding beside it. People who spend considerate time in a high exposure areas are particularly affected. Emissions also contribute to the general degradation of air quality. Pennsylvania has the seventh highest emission of diesel pollution nationwide. In the Philadelphia region, road congestion and major fleets of public transit buses, school buses, delivery trucks and long haul trucks create a significant diesel air quality problem. A report by a national association of air pollution control officials found that diesel exhaust is responsible for more than 3,000 cancers in the Philadelphia metropolitan area over a lifetime.

Health Risks

While diesel emissions pose a serious health risk for all, some groups of people are especially susceptible to the dangers:

  • People with respiratory and cardiovascular problems: Asthmatics are especially affected because the tiny particles disrupt their already constricted breathing. Persons with preexisting emphysema and heart disease are also more susceptible to the effects of diesel pollution.
  • The elderly are particularly affected as their immune systems are compromised or weakened.
  • Workers in high exposure areas: Including bridge, tunnel and loading dock workers, auto mechanics, toll booth collectors, truck and forklift drivers, and people who work in areas where these vehicles are used, stored and maintained. Studies have suggested that these workers are more likely to develop chronic respiratory symptoms, bronchitis and reduced lung capacity.
  • Children: High danger of exposure from constant school bus use. Also, the respiratory system of children work at four times the rate of an adult, making them particularly susceptible.

According to the American Federation State County Municipal Employees (AFSCME), exposure to diesel exhaust contributes to the following health conditions:

  • The incidence and severity of asthma attacks, chronic bronchitis, emphysema, coughing, wheezing and phlegm formation
  • Irritation of the eyes, nose and mouth
  • Long-term effects: According to the National Institute for Occupational Safety and Health, exposure to elevated diesel pollution increases the risk of developing lung cancer.
Additional Information

In addition to reducing the health risks associated with diesel exhaust, the American Lung Association affirms that the reduction of fine particles and toxic emission from diesel engines will decrease:

  • Lost school days for children and workdays for parents
  • Large amounts of particles which are precursors to ozone
  • Hospital admissions for respiratory and heart diseases
  • 8,300 premature deaths annually

U.S. EPA Region III recently completed an analysis of the health and economic impacts of particulate matter in the Philadelphia area. A summary of its findings can be found HERE while the PowerPoint presentation given to the PDD Working Group is HERE (.ppt - 14.7 MB). UPDATE 12/7/04 - U.S. EPA has issued a disclaimer concerning its findings on the impact of PM from diesel exhaust in Philadelphia. Read the disclaimer HERE.