The study by the Institute of Medicine of the National Academies found no direct relation between such hazardous materials and the so-called Gulf War Syndrome that affected a number of veterans of the conflict.

However, data from studies of occupational and environmental exposures to air pollution, vehicle exhaust and other combustion products led the committee that wrote the report to conclude that exposure to such substances is associated with an increased risk of lung cancer.

"This provides sufficient evidence that exposure to combustion products during the Gulf War could be associated with lung cancer in some veterans," committee chairman Lynn Goldman said in a statement.

"It should be emphasized that smoking is the major culprit for lung cancer, accounting for 80 percent of all cases, according to the American Cancer Society," Goldman added.

The substances studied by the committee included fuels for military vehicles, propellents in Scud missiles, and those given off by combustion sources such as oil-well fires, exhausts and tent heaters.

Of the approximately 800 studies reviewed in detail for the report, most involved individuals who were exposed to these agents in occupational settings over long periods of time.

Few of the studies actually involved veterans who may have been exposed while serving in the Persian Gulf.

The most common symptoms experienced by Gulf War veterans include headaches, depression, weakness, muscular pain and breathing problems.

Some 100,000 of the 700,000 US soldiers who took part in the campaign to oust Iraq from Kuwait in 1991 have complained of experiencing at least one of the symptoms. British, French and Canadian troops were also affected.

The Institute of Medicine advises the US government on health policy.

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