EPA Study of Diesel Health Effects Targets Past, Not Present or Future

Published January 1, 2003

Chronic exposure to emissions from older diesel technology is linked to increased rates of lung cancer, the U.S. Environmental Protection Agency reported on September 3.

Proponents of alternative energy sources praised the report as a call to action for tougher emission standards for cars and trucks and development of renewable energy sources. However, industry sources and pro-growth environmentalists pointed out the study addressed obsolete technology and failed to quantify the asserted link between diesel emissions and health effects.

EPA’s 651-page diesel health assessment report was based on a series of occupational health studies and animal exposure tests of older diesel technology. The report concluded that although uncertainties exist, “it is reasonable to presume that the hazard extends to environmental exposure levels as well.” Such exposure would have to be long-term, according to EPA, to cause respiratory problems such as lung cancer.

“Overall, the evidence for a potential cancer hazard to humans resulting from chronic inhalation exposure to [diesel emissions] is persuasive,” stated the report.

But Dr. William Bunn, vice president and chief medical officer for International Truck and Engine Corporation, told Environment & Climate News, “The EPA report actually concludes that the true risk from diesel exposure could be zero, given the great uncertainties in the scientific data.

“Based on recommendations by the agency’s independent Clean Air Scientific Advisory Committee,” continued Bunn, “the health assessment report recognizes the great scientific uncertainty in the diesel health effects database and concludes that no quantitative determination of the level of risk can be justified at this time.

“This is an unusual and important finding,” Bunn concluded, “because numerical measures of risk are considered essential to conclude that a substance poses a serious public health concern.”

Focus on Old Technology

The Diesel Technology Forum also questioned the EPA report’s relevancy to public health today. “The Environmental Protection Agency’s new report on diesel emissions is an appraisal of past diesel technology, drawing on data collected before the Clean Air Act–primarily during the 1950s, ’60s and ’70s–rather than an assessment of today’s clean diesel technology,” said the Forum.

The Washington Post observed that newer generations of diesel engines will be safer than today’s. “The study, involving tests on occupational exposure and on animals, focused on diesel engines manufactured before the mid-1990s, when the government began pressing for tougher emission standards,” reported the Post. “With new engine and fuel technology expected to produce significantly cleaner engine exhaust by 2007, experts project a 90 percent reduction, from today’s levels, in health-threatening exhaust particles from on-road vehicles.”

“The agency expects significant environmental and public health benefits as the environmental performance of diesel engines and diesel fuel improves,” acknowledged Paul Gilman of the EPA Office of Research and Development.

Greener Future

“While the report focused on the past, the future is clean diesel: Diesel trucks and buses built today are more than eight times cleaner than just a dozen years ago,” said Allen Schaeffer, executive director of the Diesel Technology Forum. “Thanks to state-of-the-art engine designs, cleaner-burning fuels, and effective emissions-control systems, diesel technology has progressed by quantum leaps over the past 30 years–and will continue to improve its emissions performance in the future.”

Schaeffer noted that with cleaner fuels, emissions treatment systems, and advanced engine technology, diesel trucks and buses are approaching the environmental performance levels of alternative fuels. A recent test by the California Air Resources Board found a clean diesel bus running on low sulfur fuel and equipped with the latest emissions-control technology outperformed a natural-gas-powered bus on eight of 11 emissions tests.

“The health assessment also concludes–based largely on studies of workers in jobs with prolonged exposure to diesel exhaust 30 to 50 years ago–that diesel exhaust is ‘likely’ to be carcinogenic to humans,” the Technology Forum added in its public statement. “However, after exhaustive research, EPA found insufficient scientific evidence to quantify a relationship between diesel exhaust exposure and lung cancer. The report does note that its findings are based on exposures to engines which did not meet today’s high emission standards, and which occurred in the workplace settings of another era.”

“Working behind the scenes, diesel technology has become an irreplaceable part of the U.S. economy and our quality of life,” said Schaeffer. Two-thirds of all farm equipment runs on diesel, and diesel-powered trucks, trains, boats, and barges move 94 percent of the nation’s goods–more than 18 million tons of freight each day. “For many applications, there is no alternative to diesel. That’s why manufacturers and fuel refiners are working overtime to continue reducing emissions from this vital technology,” he concluded.

James M. Taylor is managing editor of Environment & Climate News.

For more information …

More information on EPA’s September 3 diesel health assessment is available on the Internet at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060. An executive summary and the complete text of the 669-page report are available through PolicyBot. Point your Web browser to http://www.heartland.org, click on the PolicyBot icon, and search for documents #10899 (front matter and executive summary, 30pp.) and #10900 (full text, 669pp., 9.2mb).