By Eric Pianin
Washington Post Staff Writer
Wednesday, September 4, 2002; Page A02 Washington Post
The Environmental Protection Agency concluded yesterday that long-term exposure to exhaust from diesel engines likely causes lung cancer in humans and triggers a variety of other lung and respiratory illnesses.
The study, the culmination of decades of research, highlights the health problems posed by the complex mix of gases and fine particles emitted by heavy-duty diesel engines operating on the nation's highways, farms and construction sites.
"Overall, the evidence for a potential cancer hazard to humans resulting from chronic inhalation exposure to [diesel emissions] is persuasive," the report states.
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. 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 fuels improves," said Paul Gilman of EPA's Office of Research and Development.
Although the EPA's final assessment echoes preliminary agency findings and other documents from various world health organizations and studies in California, it provides added urgency to efforts by the EPA and others to tighten diesel emission standards under the Clean Air Act.
A federal appeals court in May unanimously upheld a Clinton administration regulation requiring a speedy and dramatic reduction in pollution from large trucks and buses. That rule -- strongly contested by truck manufacturers and diesel fuel refiners because of the associated costs -- would cut emissions of particulate matter by 90 percent and nitrogen oxides by 95 percent, beginning in 2007.
The Bush administration has largely taken a strong stand in support of the tougher emissions standards. Last month, the White House and EPA rejected a plea from House Speaker J. Dennis Hastert (R-Ill.) and other lawmakers to postpone the new anti-pollution standards for long-haul diesel trucks. The standards will provide stiff penalties for engine manufacturers that don't meet an October deadline for compliance under a consent decree.
The administration has also announced it will increase efforts to regulate emissions from off-road diesel-driven machinery and equipment, such as farm equipment and earth movers. A study by state air pollution control officials found that more than 8,500 premature deaths are caused annually by extraordinarily high levels of air pollution from such machinery.
Some environmental groups have voiced concern that EPA and White House officials might attempt to dilute the effectiveness of the Clinton rules governing on-road diesel trucks and buses. That's because administration officials have said they would consider incentives to encourage engine makers and refineries to change engine designs and switch to low-sulfur diesel fuel for off-road vehicles by 2006, in return for a reduction in the emission standards for trucks and buses.
One approach under consideration is to set an emissions cap for on-road and off-road vehicles and machinery, and then create a market-based system to allow companies to buy and trade credits for off-road and on-road emissions.
"Children riding buses back to school today need stronger protections against the health impacts of diesel exhaust, but the Bush administration is considering rolling back clean air standards for diesel buses and trucks," said Emily Figdor, clean air advocate for the U.S. Public Interest Research Group. "Until recently, the Bush administration appeared committed to ushering in the next generation of diesel vehicles."
EPA spokesman Joe Martyak disputed assertions that the administration was backing away from its commitment to reducing health-threatening diesel emissions.
"We're already sensitive to the importance of this issue, which is why we are moving along on the diesel issue, on-road and off-road, with an aggressive schedule," he said. "We've been well aware of the health implications and impact of [diesel engine particulate matter] and this report affirms some of those concerns."
The EPA's 651-page diesel health assessment report cited occupational health studies and tests on animals showing diesel emissions to be a carcinogen, or cancer-causing substance. While there remain uncertainties, the report said, "it is reasonable to presume that the hazard extends to environmental exposure levels" as well.
"The overall evidence for potential human health effects of diesel exhausts is persuasive," the report added.
© 2002 The Washington Post Company