Phoenix Dust Storms Not Only Cause of Poor Air Quality, EPA Says

dust storms chart  

This chart shows a day where the Arizona Department of Environmental Quality has claimed that the air pollution measurements should be excluded from consideration under the Exceptional Events Rule. Note the very high concentrations at W. 43rd while the other monitors are relatively unaffected. This is not consistent with a regional dust storm. We've noted that PM10 levels at W. 43rd often begin to rise at the same time as the nearby industrial facilities begin their work day. An Arizona State University analysis noted that these exceedances are much more likely to occur on weekdays than on weekends.

The U.S. Environmental Protection Agency rejected Arizona's claim that dust storms caused the high pollution readings in Phoenix in 2008, a decision which could have significant implications for the state.


Under the Clean Air Act, states must submit plans showing the EPA how they will meet air quality standards for certain pollutants. Arizona is currently not meeting the national standard for particulate matter, PM-10 (one-seventh the width of a human hair).

The state 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," added Blumenfeld.

This finding will require EPA to initiate disapproval of Arizona's air quality control plan (PM-10) for Phoenix. If a final disapproval is rendered, federal transportation funds to the state could be frozen. In such a scenario, transportation funds would be withheld until the state submits an adequate air quality plan (PM- 10) to EPA. The freeze would not affect current, approved transportation plans and projects.

"I want to acknowledge the collaborative work that ADEQ [Arizona Department of Environmental Quality], the Maricopa Association of Governments, Maricopa County, and the city of Phoenix have done to address existing sources of PM-10," said Blumenfeld. EPA is committed to continuing to provide the state, regional and local agencies technical expertise, monitoring equipment and funding to bring the state into compliance. The federal government already provides $30 million annually to Arizona, through the Congestion Mitigation and Air Quality program. These funds are available to be used to reduce PM-10 emissions.

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