Shaky Science Plagues New Clean Air Laws

Diesel operators must reduce their emissions, but have a little more flexibility in doing so thanks to some changes to the state's clean air laws.

The reason for the change: The California Clean Air Board made a "major miscalculation" regarding the pollution generated by diesel. After the admission, diesel operators requested lenience, and the board granted their request. That will save polluters from spending billions on costly retrofits, but could in turn increase asthma rates.

The miscalculating is in part due to reduced usage of heavy machinery. The economic slowdown has put the breaks on many construction projects, and stemmed hauling operations. That bad news for the economy is good news for air quality, and it meant that emission estimates, calculated several years ago, were not borne out by reality.

The regulations affect big rigs, buses, and construction equipment. New measures will give operators more time to retrofit their dirty engines, and offer credit for retrofits that have already been performed. Trucks will not have to immediately install particulate filters.

Questions still remain regarding the effects of diesel emissions and the changed regulations. Schools near polluting factories and ports have complained of high asthma rates.

But the Air Board's credibility has come under fire recently, not only for the most recent miscalculation but also because a staffer was caught falsifying data on diesel pollution.