Exhausted by Diesel
How America's Dependence on Diesel Engines Threatens Our Health
Everyone is familiar with the black cloud that belches out of some diesel trucks and buses when they accelerate. This choking cloud is not only offensive, but growing evidence shows that it is also a health hazard. Diesel exhaust is a complex mixture of fine particles and toxic organic materials which come from the combustion of diesel fuel. Much of this toxic mix is contributed to our environment by mobile sources such as trucks, buses, and trains. Diesel exhaust contains hundreds of constituent chemicals, dozens of which are recognized human toxicants, carcinogens, reproductive hazards, or endocrine disruptors.1
In 1990, California identified diesel exhaust as "known to the State of California to cause cancer."2 Diesel exhaust has long been considered to be a probable human carcinogen by the National Institute of Occupational Safety and Health (NIOSH) and the International Agency for Research on Cancer (IARC).3 The U.S. Environmental Protection Agency (U.S. EPA) recently concluded in a draft report that diesel exhaust is highly likely to be a human carcinogen.4 California Environmental Protection Agency (Cal EPA) is in the process of designating diesel exhaust as a toxic air contaminant based in large part on evidence that exposure causes cancer.5,6 The state's independent panel of scientists unanimously endorsed designation of diesel exhaust as a toxic air contaminant on April 22, 1998. These agencies and independent scientists based their designations on the weight of evidence from an extensive array of scientific studies.
In addition to its load of carcinogens, diesel exhaust is also a major source of tiny sooty particles. For the same load and engine conditions, diesel engines spew out 100 times more sooty particles compared to gasoline engines.10 In the past decade there have been numerous scientific studies evaluating the relationship between airborne particle pollution and human health effects.7 Since 1988, 23 human exposure studies have evaluated acute effects of particle exposures. Almost all of these studies showed short-term impairment of respiratory function in healthy individuals and greater effects in people with asthma, especially adolescents. Eleven community health studies linked particle pollution to increased hospital admissions for respiratory diseases, chronic obstructive pulmonary diseases (COPD), pneumonia, heart disease, and death.8 Most of 38 epidemiological studies published between 1988 and 1996 found a significant association between ambient levels of particles in the air and deaths from cardiac and respiratory problems.9
Diesel vehicles are commonplace. Virtually all heavy trucks and many buses burn diesel fuel. These vehicles, together with diesel engines used in various industrial applications -- irrigation and agriculture, construction, shipping and port activities, oil drilling and mining, and railroads -- expel diesel exhaust into the air we breathe. Especially in cities, diesel exhaust is a feature of everyday life.
As we learn more about the health effects from diesel exhaust and the high levels of exposure in our communities, we must reconsider the widespread use of diesel engines. So far the U.S. EPA and state governments, including the California Air Resources Board, have accepted diesel engines as the norm, and have only tried to reduce the levels of pollution coming from those engines. We conclude in this report that, while these efforts may be of some benefit, we can and must do more. We will only achieve our goals of reducing smog and particulate pollution, and reducing the serious cancer threats posed by diesel exhaust, if our state and federal governments act aggressively to replace diesel-fueled engines with cleaner alternatives. As we discuss in this report, alternatives to diesel, such as natural gas and electric vehicles, are currently available for many applications. Many companies have successfully used alternative fuel trucks and buses, but more must be done to accelerate the transition to make these engines more available and economically viable. We strongly support state and federal government incentive programs that provide financial assistance for owners of diesel vehicles and equipment who seek to switch to cleaner alternative fuels.
The Natural Resources Defense Council (NRDC) and the Coalition for Clean Air (Coalition) have initiated a "Dump Dirty Diesel" campaign in California, which is building on NRDC's ongoing effort to phase out diesel buses in New York City and the joint efforts of NRDC and the Coalition to phase out the use of diesel buses in Los Angeles. As part of the campaign, NRDC and the Coalition have undertaken an extensive study of diesel exhaust hazards in California. Over the past year, the two organizations have worked with internationally recognized experts on diesel exhaust. These experts have analyzed the available scientific information, generated specific estimates of the cancer risk from diesel exhaust exposure, and applied these estimates to highly impacted California communities. NRDC and the Coalition have performed extensive exposure monitoring in communities located near distribution centers where diesel truck traffic is heavy.
The conclusion from this intensive study is that facilities with heavy truck traffic are exposing local communities to diesel exhaust concentrations far above the average levels in outdoor air. These affected communities, and the workers at these distribution facilities with heavy diesel truck traffic, are bearing a disproportionate burden of the health risks and are paying the price for our society's addiction to diesel engines.
Because government agencies have failed to protect the public from diesel exhaust, NRDC, the Coalition, and the Environmental Law Foundation intend to take their campaign to the courts, initiating a series of lawsuits under California's toxics initiative, Proposition 65. The public interest groups hope by this report and their litigation to push a change nationwide toward cleaner and safer trucks, buses and other vehicles. Only by forcing companies to reassess their use of diesel powered vehicles can we break our dependence on diesel and protect the health of the public.
1. For a complete list, see Krieger, et al., Proposed Identification of Diesel Exhaust as a Toxic Air Contaminant, Part A: Exposure Assessment. Technical Support Document, Public Comment And SRP Version [hereinafter referred to as ARB, Draft Diesel Exposure Assessment], February 1998, Appendix A; Health effects of diesel exhaust constituents discussed in eg. Rosenstock L, and Cullen M (eds.), Textbook of Clinical Occupational and Environmental Medicine, WB Saunders Co., Philadelphia, 1994. p. 778; Paul M (ed.), Occupational and Environmental Reproductive Hazards: A Guide for Clinicians, Williams and Wilkins, Philadelphia, 1993. pp. 234-248, 273-4; Birnbaum L, Developmental Effects of Dioxins and Related Endocrine Disrupting Chemicals, Toxicol Lett, 82/83: 743-750, 1995.
3. International Agency for Research on Cancer. Diesel and Gasoline Engine Exhausts and Some Nitroarenes. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Vol 46, Lyon, France, World Health Organization, 1989; National Institute for Occupational Safety and Health, Division of Standards Development and Technology Transfer. Current Intelligence Bulletin 50 - Carcinogenic Effects of Exposure to Diesel Exhaust, Publication No. 88-116, Cincinnati, 1988.
4. Discussed in U.S. EPA, Office of Research and Development, Health Assessment Document for Diesel Emissions, Review Draft, EPA/600/8-90/057C, February 1998. Chapter 5. [Hereinafter referred to as "U.S. EPA Health Assessment for Diesel Emissions, February 1998."]
6. U.S. EPA Health Assessment for Diesel Emissions, February 1998; Steenland K, Lung Cancer and Diesel Exhaust: a Review. Am J Ind Med, 10:177-189, 1986; Bhatia R, Lopipero P, Smith AH, Diesel Exhaust Exposure and Lung Cancer. Epidemiology, 9:84-91, 1998; Pepelko and Peirano, 1983, "Health Effects of Exposure to Diesel Engine Emissions," J. Amer. Coll. Toxicol. 2: 253-306.
7. U.S. EPA, Office of Air Quality Planning and Standards, "Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information," April 1996, ch. V, p. 12.
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