The EPA has rejected Arizona's claim that the Valley's high pollution readings in 2008 were caused solely by dust storms - a judgment that could ultimately result in Arizona losing federal transportation funds.
Under the Clean Air Act, Arizona had to submit a plan showing the Environmental Protection Agency how the state will work to meet air quality standards for some pollutants.
Because of Tuesday's EPA ruling, it will initially disapprove the state's air quality control plan for Phoenix. If the plan fails to reach final approval, the state could have federal transportation funds frozen. It would not affect current, approved transportation plans and projects, according to the EPA.
Arizona is not meeting the national standards for particulate matter, PM-10, a particle smaller than 10 micrometers in diameter. Such particles can pose the greatest health concern because they can be inhaled. These coarse particles are caused by crushing or grinding operations and dust from paved and unpaved roads.
According to a press release from the EPA's San Francisco office, Arizona "had asserted that dust storms were responsible for 10 of the 11 unacceptably high pollution spikes in Phoenix during 2008."
"After thoroughly reviewing the state's data, EPA air-quality scientists determined that a legally significant number of pollution spikes were not the result of regional dust storms," said Jared Blumenfeld, EPA Regional Administrator. "Therefore, the ‘exceptional events' were not supported by the science."
Particulate matter PM-10 can cause breathing and respiratory issues. The elderly, children, and people with chronic lung disease, influenza, or asthma, are especially sensitive to the effects of particulate matter.
Ben Grumbles, director of the Arizona Department of Environmental Quality, which is overseeing the state's air quality plan, issued a statement Tuesday afternoon.
"We are disappointed in EPA San Francisco's decision but we are committed to working with our local and regional agency partners to improve the air quality. We've taken important steps the last couple of years toward that goal with a collaboration of all of the sectors involved. This finding by EPA came about over whether certain data justified special treatment under the Clean Air Act for exceptional events. But we have all acknowledged from day one that a range of sources have contributed to air quality problems," his e-mail read.