There is no question that the air is polluted by diesel exhaust, emitted by many trucks, buses, trains, ships and construction and farm machines. That issue is now before the state Air Resources Board, which on July 30 is scheduled to consider an April report of a state-funded advisory panel that concludes diesel exhaust poses a serious cancer danger. The report followed nine years of study and rancorous debate. The air board should formally endorse it and declare diesel a toxic air contaminant under state law. But if politics, not science, carries the day, the board probably will put off that important decision, and cleaning up our air will be further delayed.
Diesel exhaust contains many compounds.
State and federal regulations control some of those, like benzene and arsenic. Others, like phenol, napthalene and styrene, are controlled in factories but not in vehicle exhaust. A 1983 state law requires the air board to identify toxic air contaminants and then devise a strategy to protect Californians from them. Benzene was the first of the 19 compounds so far labeled as toxic air contaminants under this unique law. Adding diesel fumes to that list seems warranted.