EPA releases diesel health assessment report - Industry News

Diesel Progress North American Edition, Oct, 2002

After a decade of study, the U.S. Environmental Protection Agency (EPA) has released its long-awaited diesel health assessment report. The report concludes that diesel exhaust over time can cause cancer in humans -- maybe.

The report will likely add fuel with the government's efforts to reduce truck tailpipe emissions by requiring cleaner-burning engines and diesel fuel with low sulfur content. While acknowledging uncertainties about the long-term health effects of exposure to diesel exhausts, the EPA report said studies involving both animal tests and occupational exposure suggest strong evidence of a cancer risk to humans.

"It is reasonable to presume that the hazard extends to environmental exposure levels," the report said. "The potential human health effects of diesel exhausts is persuasive, even though assumptions and uncertainties are involved."

As can be expected, response to the report broke down along party lines. The environmental lobby sees the report as justification for more and tighter controls of all types of diesel engines. Industry groups seized on the uncertainty over low term health effects.

"This will underscore that diesel exhaust is a health hazard and should be controlled," said Frank O'Donnell at the Clean Air Trust, in one of the more reasonable responses from environmentalists. O'Donnell called the report "the most in-depth health assessment to date" on diesel fumes.

However, the Diesel Technology Forum's Allen Schaeffer made a key point noting that EPA report "focused on the past." The report does acknowledge that its findings were based on emissions levels in the mid-1990s, but said the results continued to be valid because the slow turnover of truck engines has kept many of these vehicles on the road. "The future is clean diesel," Schaeffer said. "Diesel trucks and buses built today are more than eight times cleaner than just a dozen years ago."

The report estimates the level of diesel exhaust to which humans could be exposed throughout a lifetime without experiencing any adverse non-cancer health effects. "That acceptable exposure level is more than double the actual level of diesel exhaust typically found in U.S. cities," said Schaeffer.

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.

However, the Diesel Technology Forum said 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.

The report did not estimate the probability of an individual getting cancer, given a certain level of exposure to diesel exhaust. Risk assessment such as this are typically done by EPA when gauging pollution health concerns. But, the report said, "the exposure-response data are considered too uncertain" to produce a confident quantitative estimate of cancer risk to an individual."

The report does state that the "totality of evidence from human, animal and other supporting studies" suggests that diesel exhaust "is likely to be carcinogenic to humans by inhalation, and that this hazard applies to environmental exposure."

The report also said that exposure to diesel exhausts poses short-term health problems and in the long term has been shown to be a "chronic respiratory hazard to humans" and can contibute to increased asthma and other respiratory problems. Diesel exhausts account for as much as a quarter of the airborne microscopic soot in some urban areas, the report said. To access the complete Health Assessment Document for Diesel Exhaust go to: http://cfpub.epa.gov/ncea/. Under Selected Topics click on Diesel Exhaust.