A new report prepared for Phoenix area governments says diesel engines are the main cause of the metropolitan area's pollution problems.

The head of the Arizona House Environment Committee says she may incorporate the report's findings into legislation - even if it means taking on the powerful trucking industry and the business community that increasingly relies on trucking.
Dave Berry, vice president of Phoenix-based Swift Transportation and a member of the technical committee that is overseeing the Brown Cloud study, opposes requiring cleaner diesel fuel in the state. He would rather see a national diesel fuel standard, rather than requiring truckers to have to deal with a patchwork of different state regulations and fuel standards.
The Brown Cloud study was started three years ago in response to growing concern about visible pollution in the Phoenix area. The report identifies particulate matter that is 2.5 micrometers or smaller as the main ingredient of the urban haze, which is 50% dirtier than it was five years ago. The carbon particles in the exhaust of both gasoline and diesel engines absorb and scatter light, creating the Brown Cloud.