Diesel fumes hit asthmatics with one-two punch

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Diesel fumes hit asthmatics with one-two punch

By E. J. Mundell

NEW ORLEANS, Apr 22 (Reuters Health) - As many asthmatics know, a blast of

diesel exhaust can trigger bouts of wheezing, coughing and other asthma

symptoms. Now researchers say they have figured out why these fumes are so

tough on those afflicted with the illness.

According to researcher Dr. Fred D. Finkelman of the University of Cincinnati

in Ohio, the fine particles in diesel exhaust hit the human immune system

with a double whammy, upping the production of an immune protein that

triggers asthma attacks while suppressing a second protein that might

otherwise bring symptoms to a halt.

The findings " add to the evidence that it would be best to reduce diesel

exhaust particle emissions, " Finkelman said in an interview with Reuters

Health. He presented his findings here Monday at the annual Experimental

Biology 2002 conference.

Numerous studies have found that individuals living in urban areas or near

busy highways are at much higher risk for asthma and other allergies compared

with those living in less congested locales. While most experts have

suspected diesel fumes as the prime culprit, until now the exact mechanism by

which truck exhaust aggravates the immune system has remained unclear.

In their study, Finkelman and his colleagues injected small amounts of diesel

exhaust particles into the bloodstreams of mice. The investigators found

that, after injection, the mice secreted abnormally high levels of

interleukin-6 (IL-6), an immune system protein " released by cells of the

immune system in response to substances such as bacteria and viruses that the

immune system perceives as dangerous. " In the asthmatic lung, this response

can go overboard, triggering airway constriction, coughing and congestion.

Luckily, the immune system has a kind of countering mechanism, a protein

called interferon-gamma. When released in large quantities, interferon-gamma

works to put the brakes on runaway immune responses.

However, the Cincinnati researchers found that, in mice, diesel exhaust

appears to dampen interferon-gamma production--giving IL-6 free reign to

trigger asthmatic symptoms.

With diesel fumes being such an obvious health hazard, reducing emissions

would seem to be a 'no-brainer' from the viewpoint of public health. But the

issue " is not that simple, " Finkelman cautioned.

" Compared to gasoline engines, diesel engines are more fuel efficient and

emit less greenhouse gases per mile traveled, " he said. And getting consumers

to pay for cleaner air while doing without some of the gas-guzzling luxuries

they've come to love has proven to be a tough sell. In the end, Finkelman

said, " society has to balance efforts to decrease pollutants that have

harmful medical effects with the costs of these efforts. "

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