U.S. EPA Links Diesel Exhaust to Lung Cancer

By Cat Lazaroff

WASHINGTON, DC, September 4, 2002 (ENS) - Breathing exhaust fumes from diesel engines may raise a person's risk of developing lung cancer, the U.S. Environmental Protection Agency has concluded. The agency's new report provides new ammunition for supporters of stricter emissions regulations for on and off road diesel engines, environmental groups said.

While noting that there are still uncertainties about the long term effects of exposure to diesel exhaust, the report by the Environmental Protection Agency's (EPA) National Center for Environmental Assessment warns that chronic inhalation of the fumes at levels now present in many urban environments "is likely to pose a lung cancer hazard to humans, as well as damage the lung in other ways depending on exposure."

This assessment examined information regarding the possible health hazards associated with exposure to diesel engine exhaust, which is a mixture of gases and fine particles or soot. Besides recognizing a likely long term cancer risk, the report also found that short term exposures can cause irritation and inflammation in the lungs, and may worsen existing allergies and asthma symptoms.


Exhaust from diesel trucks and buses has now been linked to respiratory illnesses and even cancer. (Two photos courtesy EPA)
The assessment's health hazard conclusions are based on exposure to exhaust from diesel engines built prior to the mid-1990s, but the EPA says they apply to most engines now in use, which include many older engines. Diesel engines are now used in large trucks, buses, trains and ships, and in farm and construction equipment.

The EPA predicts that the use of the fuel will rise "due to the superior performance characteristics" of engines burning diesel.

Early in 2001, the EPA issued landmark standards to clean up dirty diesel trucks and buses, comparable to the advent of the catalytic converter on cars several decades ago. When the standards take full effect in 2007, they are expected to reduce emissions from trucks and buses by more than 90 percent, the equivalent of taking 13 million of the nation's 14 million trucks and buses off the roads.

"The Agency expects significant environmental and public health benefits as the environmental performance of diesel engines and diesel fuels improves," the EPA notes.

The Bush administration has backed the standards since taking office, and has defended them in court against industry challenges. Last month, the EPA rejected requests by some diesel engine manufacturers to postpone the new standards, allowing penalties against manufacturers who fail to meet the new standards to be penalized beginning as early as October 2002.


Diesel burning trucks and buses produce millions of tons of nitrogen oxides, sulfur dioxides, carbon monoxide and soot.
But the Bush administration has also proposed loosening some of the restrictions of the new diesel rules, by allowing the diesel engine industry to meet some of the requirements by trading pollution credits, rather than by developing cleaner engines.

"Until recently, the Bush administration appeared committed to ushering in the next generation of diesel vehicles," said Emily Figdor, clean air advocate at the U.S. Public Interest Research Group (PIRG). "In June, however, the administration announced that they might allow diesel engine companies to trade emission reduction credits rather than produce cleaner trucks and buses."

As part of a plan to reduce pollution from diesel powered construction and farm equipment, the administration is considering developing an emissions trading program between the truck and the non-road engine sectors. This could enable companies to avoid the tough emission reductions required for trucks and buses, and compromise the clean up of non-road diesel engines, which release more soot each year than all of the cars, trucks and buses on the roads combined.

"In order to reduce the public's exposure to harmful diesel emissions, the Bush administration should honor its commitment to fully implement clean air standards for diesel trucks and buses and should pass equivalent standards for diesel construction and farm equipment," said Figdor.


Los Angeles covered in smog. Diesel vehicles are among the prime sources of the pollution that leads to smog. (Photo courtesy Aliothnet)
The EPA released its final diesel health assessment on Tuesday, as many students headed back to school aboard diesel powered buses. Previous research by environmental groups and the state of California has pointed to diesel exhaust, particularly from buses, as a major health threat to children.

Many state and local agencies, often with federal help, are working to retrofit some of the nation's 442,000 school buses with emissions traps, or replace them with cleaner, natural gas fueled models.

In addition to concluding that diesel fumes likely cause lung cancer, the EPA found that diesel exhaust triggers asthma and other respiratory effects, calling the fumes "a chronic respiratory hazard to humans." Based on animal testing and studies of people in jobs with high exposures, the fumes were shown to be carcinogenic, or cancer causing.

The agency did not attempt to quantify the cancer risk from exposure to diesel emissions, though the report notes that the risk is likely to be higher for people who regularly work with or around diesel engines. But even everyday exposure to background levels of diesel fumes probably puts people at risk, the EPA said.


Diesel ship engines are major pollution sources in port cities. (Photo by Carlye Calvin, courtesy University Corporation for Atmospheric Research)
"Overall, the evidence for a potential cancer hazard to humans resulting from chronic inhalation exposure to [diesel engine emissions] is persuasive," the 651 page report concludes.

The impacts of diesel exhaust vary from place to place. In some heavily traveled urban areas, diesel exhaust may account for as much as 25 percent of the airborne microscopic soot, the report notes.

Diesel soot can worsen cardiovascular and respiratory conditions and lead to premature death. Other potentially toxic components of diesel exhaust include carbon monoxide, nitrogen compounds, sulfur compounds, and various hydrocarbons.

Besides the 2007 diesel rules affecting large truck and bus engines, the EPA last year proposed strict new emissions standards for several types of nonroad engines, including snowmobiles, all terrain vehicles, yachts and other sources.

And in May 2002, the EPA proposed to change an existing voluntary standard for new ship engines into a federal mandate - a move that environmental groups criticized as doing little to reduce emissions from ships in U.S. ports.