What About the Environment?

Valley air pollution comes from several sources and is influenced by wind, weather, and topography. The Valley is a broad, shallow basin surrounded by mountains. The topography and mild desert climate make the Valley more vulnerable than most major metropolitan areas to stagnant air conditions. Temperature inversions and stagnation occurs when cooler air and pollution is trapped close to the ground.

Vehicle miles traveled (VMT) are increasing even faster than population is increasing in the Valley.

Primary air pollutants associated with transportation include:

Carbon Monoxide (CO) - 94% of CO in the Valley comes from vehicle tailpipes and off-road equipment (primarily lawn and garden, and construction equipment) exhaust.  CO is produced when fuels are burned. Carbon monoxide levels in the Valley have actually dropped by more than 50% since 1984. Improvements are attributed to cleaner engines, cleaner fuels, the vehicle emission inspection program, and a variety of other programs that improve traffic flow and reduce driving. Carbon Monoxide robs the blood of oxygen. 

Ozone - Forms in the atmosphere when heat and ultraviolet light reacts with oxides of nitrogen (NOx, a product of fuel burning) and volatile organic compounds (VOCs, which come from a variety of sources). 58% of NOx and VOCs comes from vehicles and other off-road mobile sources. In addition to vehicles and off -road equipment, sources of VOCs include paints, solvents, consumer products, and industrial activities. Ozone is primarily a summer air pollution problem. Ozone irritates and damages the lungs.

Particulate Matter  - Tiny airborne particles, most of which are dust and soot.  50% of these particles come from vehicle tailpipes, and the remainder is mostly dust from paved roads, construction activities, etc. The smallest particles, which come primarily form vehicle exhaust, make up the majority of the Brown Cloud. The highest concentrations tend to be found in the Phoenix urban core. Particulate matter can cause a variety of lung and health problems.  

Before any transportation plan can be built in the region, it must pass federal EPA requirements for the three pollutants noted above. The Regional Transportation Plan has undergone this testing and the results are available in the MAG Air Quality Conformity Analysis for the FY 2004-2007 Special Transportation Improvement Program and the Regional Transportation Plan.

• Air Quality Conformity Analysis on the RTP