SAN DIEGO, Calif. (Jan. 31, 2000) — Several truck, bus and construction industry groups have filed suit against the California Air Resources Board, charging that the agency manipulated data to support the conclusion it wanted to make — that diesel exhaust causes cancer.

The lawsuit, filed by California Trucking Association, the American Trucking Associations, the California Bus Association, and construction industry groups, said that CARB used old railroad worker diesel exhaust exposure studies to come up with a “unit risk” for lung cancer. Using that information, CARB and its Scientific Review Panel calculated that 450 out of every million state residents could get lunch cancer if they were continuously exposed for 70 years to 1 microgram of diesel exhaust particulate matter per cubic meter of air.

Because diesel engines and fuels continue to get cleaner, the lawsuit says, it is not fair to target diesel exhaust as a whole as a toxic air contaminant.

The suit claims that CARB’s Office of Environmental Health Hazard Assessment Both the Health Effects Institute and U.S. EPA’s Clean Air Scientific Advisory Committee have publicly stated that the railroad studies don’t support the diesel toxicity listing.

“CARB’s diesel TAC listing was an arbitrary political decision based neither on the ‘best available scientific evidence’ nor on ‘sound scientific knowledge,'” the lawsuit says.