ALBUQUERQUE, N.M. – A U.S. Environmental Protection Agency (EPA) report meant to show a link between diesel fumes and various health problems has once again been rejected by a panel of independent scientists.

It’s now making another return to the drawing board, after a decade of draft versions by the government’s environmental watchdog.

“The EPA gets a validation and assessment of their own staff’s interpretation of scientific reports,” explains Allen Schaeffer, vice-president of environmental affairs for the American Trucking Associations. “They are as independent as possible.

“In this case, the group decided to reject the document and send it back to the agency. It’s the second time it’s done that in two years.”

The EPA has been trying to develop a health assessment of diesel exhaust since 1990, says Joe Mauderly of the Lovelace Respiratory Research Institute, chairman of the independent Clean Air Science Advisory Committee. But his group will release a report by the end of this month showing that some of the EPA’s assumptions are still flawed.

“By the end of the meeting (in early December) there were enough things the committee was not comfortable with,” he says.

In part it comes down to a question of calculations. The EPA is making some of its assumptions by drawing on tests done on animals. But in extrapolating the information to show an effect on humans, it draws on the same figures and assumptions that show a possible link to allergic reactions to determine an exposure that would lead to more serious “lung pathology” such as fibrosis and lung inflamation, Mauderly says.

And while the EPA says it needs more time to find a level of exposure that would lead to a cancer risk (it’s dropped estimates that appeared in previous drafts), the text of the document still refers to a cancer risk that is “highly likely” at certain exposure levels.

“If you’re not comfortable that you can calculate a number, how can you be confident enough to say ‘highly likely’?” Mauderly asks. “The committee said, ‘We don’t think you’re that confident’.”

This is also the only specific fuel that the EPA has decided to target. The U.S. Clean Air Act has instead cited specific air pollutants that come after a fuel is used, such as ozone, NOx, carbon monoxide and particulate matter.

Referring to how the health affects of gasoline, power plants and wood smoke aren’t being studied, he admits, “there is a political aspect” to looking at diesel fuel.

For Bill Craig, who lives north of Toronto, the health effects of long-term exposure to diesel exhaust is more than political. He’s had to give up the trucking career he loved because of severe allergic reactions that have developed.

“For years, I sat on that loader and it didn’t bother me,” he says, referring to the logging operation he worked.

For about a decade, between 1978 and 1988, he didn’t show any problems when hauling logs out of the bush. But then his voice began to deepen after working on the job; and then his throat started to become sore. His breathing eventually became labored on the job, and he began to feel pain in his right lung, which had been damaged when he was working as a firefighter in the mid-’70s.

That may make his lungs more sensitive to the fumes, the former owner/operator admits. But he loved the job so much that he switched to cabs that would better filter and re-circulate the air inside, and he used a respirator when working around the truck.

“My eyes would just pain all night long,” he says. “Immediately, my throat swells up. I’m talking 30 seconds.”

He’s had to sell his truck, and even his beloved motorcycle, because he can’t stand fumes on the highway.

“I enjoy trucking,” he says.

He just doesn’t have the choice to continue. n