It may be hard to tell, but the Valley's air is getting cleaner.
The U.S. Environmental Protection Agency has proposed declaring air in Maricopa County to be within safe limits for carbon monoxide.
The proposal is a recognition that the Valley hasn't violated the federal agency's standard of an average 9 parts per million over eight hours since 1996.
State and county environmental officials said the EPA proposal, combined with a similar declaration for ozone in 2001, demonstrates the effectiveness of pollution controls on Valley businesses, vehicle exhaust emissions and special gasoline blends.
"We've been making great progress here," said Steve Owens, director of the Arizona Department of Environmental Quality. "The things we have been doing have been working and we should not deviate from the course we have been following because it is working."
The improvement won't mean any immediate change in the blend of winter gasoline required in the Valley to reduce carbon monoxide emissions. In fact, Owens said the improvement justifies the continued use of the specially formulated fuels to keep the region on track.
While largely a paperwork function, the proposed EPA rule would be a boon to Valley economic development activities, Owens said. Businesses can be confident about moving here or expanding without facing additional pollution restrictions in the near future to deal with carbon monoxide emissions.
The EPA's approval isn't guaranteed, as the public has 30 days to review the proposal and to raise objections.
Steve Brittle, spokesman for an environmental advocacy group called Don't Waste Arizona, said it's not clear yet if the public can trust the pollution reports and computer models used by the county and state to justify the EPA proposal.
"We're still looking at that," Brittle said. "Our long process of review has just started."
Carbon monoxide is an invisible, odorless gas that's deadly in large doses and causes long-term respiratory problems at lower levels. Atmospheric carbon monoxide is generated primarily from combustion engines.
Valley residents might not realize carbon monoxide levels have dropped substantially since the early 1990s because carbon monoxide cannot be seen. The more visible "brown cloud" that hovers overhead on the worst pollution days, particularly in cold months, is created largely from large dirt particles suspended in the air that become trapped close to the crowd. The Valley remains under close EPA scrutiny as a nonattainment area for those particles.
"We've still got some big pollution problems," said Sandy Bahr, conservation outreach director for the Grand Canyon chapter of Sierra Club. "We still need to make sure we're limiting the amount of pollution to the greatest degree possible, so all of us in the Valley can breath healthy air. All we have to do is look . . . at the people with asthma admitted to emergency rooms on bad air days to know we have some huge issues."
The Valley also could face new pollution regulations because of ozone pollution, considered a bigger problem in the summer, despite a 2001 order issued by the EPA. The federal agency lowered the safe limits for ozone levels last year, which resulted in a higher number of pollution warnings during the summer. Under state rules, the warnings alert large employers to take steps that reduce the number of employees driving to work.
State and county officials hope the trip-reduction programs and other policies will be enough to bring the Valley within the new ozone limits. Those efforts will be aided by new federal standards for auto emissions that go into effect in 2004.
"They again are dramatically reducing the emissions coming out of the tailpipe," said Lindy Bauer, environmental director for the Maricopa Association of Governments.