Arizona Department of Environmental Quality (ADEQ) officials announced this week the new, lower ozone standard U.S. Environmental Protection Agency (EPA) announced yesterday (0.070 parts per million) presents a major challenge for Arizona to achieve based on the State’s unique geographic, meteorological, and mix of emissions sources.
ADEQ and its partners currently monitor ozone concentrations in 10 of Arizona’s 15 counties, including Cochise, Coconino, Gila, La Paz, Maricopa, Navajo, Pima, Pinal, Yavapai, and Yuma. According to EPA, areas already see ozone levels below 70 parts per billion on most days. However, nine of Arizona’s 10 monitored counties report ozone levels in excess of EPA’s new standard too frequently. Navajo is the sole county in Arizona consistently in compliance with the new standard.
“Implementation of this new, lower standard will be difficult in Arizona,” said ADEQ Air Quality Division Director Eric Massey. “Emissions and options to reduce them are few, particularly in rural areas like La Paz County.”
Arizona’s geographical location plays a significant role in ozone formation and levels – air pollution does not recognize political boundaries. Despite the most stringent ozone controls in the country, Arizona’s upwind neighbor, California, has struggled with ozone levels for decades. Transport of international emissions, both in North America and beyond, adds to the complexity. Arizona is also well known for its sunshine, a critical contributor to ozone creation.
Vehicles and other internal combustion engines are the primary source of ozone and its precursor pollutants locally; Arizona’s industries are not a significant source. EPA and the State of California are the only jurisdictions with authority to require vehicle emissions reductions. EPA alone can require emissions reductions from other internal combustion engines. Arizona will therefore rely heavily on EPA’s new Tier 3 vehicle emissions standards and non-road engine limitations as part of its pollution control strategy.
Arizona has one year to recommend to EPA whether to classify its monitored counties’ air quality as being in or out of attainment with the new, lower ozone standard. ADEQ will engage in a stakeholder process and invite public participation in developing recommendations.