Mixed messages in the air

"He's not going to get there if they water down these regulations," said Kathryn Phillips, an advocate with the nonprofit group Environmental Defense.

Schwarzenegger says he's just trying to be realistic.

"We have to have the ramp-up time and look at always what technology is available and how we can meet a certain goal," the governor said in a recent interview. "It is walking a fine line."

Fumes from heavy diesel construction equipment are linked to tens of thousands of cases of asthma and 1,100 deaths annually, state studies show. Scientists and economists say staying in compliance with the federal Clean Air Act would cost the industry more than $3 billion over the next two decades. Construction companies say it could be at least three times that amount.

"We don't believe the technology is evolving fast enough" to do what the new state regulations would require, said Mike Lewis of the Construction Industry Air Quality Coalition, a trade group. "We're not arguing with the goal. But you are asking us to replace 85% of our equipment by 2020. We don't believe there is enough money in the industry to do this."

Construction companies and builders have buried regulators with letters and e-mails saying the regulations would put them out of business.

Officials at the Air Resources Board, a state entity that enforces environmental laws, say the costs are manageable for a multibillion-dollar industry whose business is about to boom because of a surge in public works spending.

They also say a delay could cost the state $1.2 billion in lost federal transportation funding.

The 112,000 tractors, excavators, backhoes and other construction vehicles that regulators are targeting are the second-largest source of diesel pollution, after trucks and buses, in California. The rules drafted by the Air Resources Board would require construction firms, over the course of several years, to replace their dirtiest equipment or retrofit the machines with devices that capture soot.

Doing so, state scientists say, would avoid hundreds of deaths each year and thousands of cases of asthma. Such a move would cut smog and curb the release of greenhouse gases.

It also would arguably heed the governor's call to spur the economy with tough environmental rules that create a need for new technologies -- technologies that could be developed by the state's budding "clean tech" industry.