Dust in the Wind: Arizona Dust Storms and the Exceptional Events Rule

Abstract

Dust storms are common global weather phenomena that typically occur in subtropical latitudes throughout the world. In Arizona, the fast-moving walls of particles are seasonal, driven by the winds from outflow boundaries of the North American monsoon thunderstorms.The National Oceanic and Atmospheric Administration reports that one to three dust storms per year strike the Phoenix area, although new data from the National Climatic Data Center (NCDC) indicate an increase of activity. The NCDC’s storm-event database shows that eight dust storms struck the greater Phoenix area between July and September of 2011. This dramatic departure from historical averages demands investigation into the public health effects and potential regulatory solutions surrounding the increase in dust storm events near metropolitan areas. One consequence of this increase in activity is dust storms from rural areas blowing into cities and exceeding the air quality standards set forth by the U.S. Environmental Protection Agency (EPA). Under the Clean Air Act, the EPA has established national ambient air quality standards (NAAQS) to address concerns about the impacts of air pollution on public health. The EPA estimates that between 1990 and 2020, the Clean Air *1002 Act will prevent over 230,000 early deaths, primarily from lessening ambient particulate matter. These standards dictate the acceptable levels of carbon monoxide, lead, nitrogen dioxides, ozone, particulate matter (PM10 and PM2.5), and sulfur dioxide.8 When a city fails to maintain the ambient air quality standard for any of these categories, it may be classified as a nonattainment area and then must create a State Implementation Plan. The plan must indicate what steps a locality will take to come into compliance with the NAAQS, and it must receive EPA approval. While the EPA has authority to waive violations of the NAAQS under its exceptional events rule (EER), the agency refused Phoenix’s waiver request after dust storms in 2008 led to multiple violations of standards for particulate matter. The EPA’s position creates the potential for Maricopa County to lose over $1 billion in federal funding unless the Arizona Department of Environmental Quality (ADEQ) can formulate a cleanup plan that receives EPA approval.12 To avoid the potential financial consequences of noncompliance, policy makers have suggested reform to streamline the process for a city to obtain an EER waiver from the EPA.