WEDNESDAY, Dec. 5 (HealthDay News) -- Two real-world studies from Europe demonstrate the health damage done by automotive air pollution, especially the kind emitted by diesel engines.

An 11-year period of improving air quality in Switzerland, which started with some of the cleanest air in Europe, produced measurable benefits in lung function for adults as they aged, according to a report in the Dec. 6 issue of the New England Journal of Medicine.

"Even with small improvements in air quality, you get measurable health benefits," said Dr. Ursula Ackermann-Liebrich, a professor of public health at the University of Basel. "That is true at levels even which are quite low."

And an unusual collaborative study by American and British researchers, reported in the same issue of the journal, showed that people with asthma who walked along a street used by diesel-powered traffic experienced loss of breathing much greater than those who strolled through a traffic-free park.

"The unique feature of this study in real-world conditions was that we have demonstrated that typical urban levels of air pollution with diesel-rich powered vehicles have measurable effects," said Dr. Junfeng Zhang, chairman of environmental and occupational health at the New Jersey School of Public Health and an American member of the research team. "There have been theories or hypotheses of diesel exhaust or particle matter and also laboratory studies with animals, but this was a study in the real world with real people."

The study had 60 adults with mild or moderate asthma walk for two hours along two London locales -- busy, exhaust-filled Oxford Street or the more bucolic Hyde Park.

The Oxford Street walk produced a 5 percent to 6 percent reduction in lung function, "and asthmatics already have compromised lung function," Zhang said.

The reduction in lung function was "significantly larger" than what was measured after the Hyde Park walk and was accompanied by an increase in biomarkers of lung inflammation. The negative effect on the lung was greater than has been seen in animal studies using breathing chambers, Zhang said.

The Swiss study found a decrease in the amount of airborne fine particulate pollutants, a major feature of diesel emissions. That improvement in Swiss air quality was accompanied by a slowing in the rate of the loss of breathing function that occurs as people age, Ackerman-Liebrich said. The journal report attributed the healthful effect to "decreasing exposure to airborne particulates."

"There seems to be something more potent than other forms of air pollution in diesel exhausts," said Dr. Morton Lippman, a professor of environmental medicine at New York University. "It is something many other studies have pointed to."

The issue of diesel pollution is of growing interest because "new diesel technologies are increasingly coming on the market," Lippmann said. Diesel automobiles are much more common in Europe than in the United States but are gaining attention because of their greater fuel efficiency, he noted.

The two studies are welcome because they assess the effect of diesel emissions at relatively low levels, Lippmann said. "That remains a complex issue," he said. "Getting statistically significant information on a small average effect on a large population is not easy. There are a lot of unknowns. Most effects are associated with particles rather than gases in the mixture, but there is no data on which part of the components is particularly nasty."

More information

A national program for cleaner diesel emissions is described by the U.S. Environmental Protection Agency.

SOURCES: Ursula Ackerman-Liebrich, M.D., professor, public health, University of Basel, Switzerland; JunFeng Zhang, Ph.D., chairman, environmental and occupational health, New Jersey School of Public Health, Piscataway; Morton Lippmann, New York University, Tuxedo Park; Dec. 6, 2007, New England Journal of Medicine

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