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Utahns will hear about "unhealthy" and "moderate" air quality conditions much more frequently this summer and may be asked to modify their daily routines more often — but it isn't because air quality suddenly got worse.

Last fall, the Environmental Protection Agency set a new standard for ambient ground-level ozone, cutting the allowable concentration of the pollutant by five parts per billion. While the downward shift may not seem especially large, it will have a noticeable impact on Utah's air-quality forecasts, said Bryce Bird, director of the Utah Division of Air Quality.

The color-coded Air Quality Index with which most Utahns are familiar has been modified to reflect the new ozone standard, Bird said. Air quality will now be considered "yellow," or moderate, at ozone concentrations exceeding 55 parts per billion instead of 60 parts per billion; "orange" at 70 parts per billion; and "red" at 85 parts per billion.

Ozone is a secondary pollutant that forms in the atmosphere when other chemicals, such as those emitted by cars, react with sunlight. Exposure to high concentrations of ozone burns the inside of the lungs and is associated with permanent lung damage.

Had the new standard been in effect last summer, Bird said Utahns would have seen 15 additional orange or red air quality days.

Residents will also see calls for "voluntary" and "mandatory" air quality action days increase, as the threshold for these designations has also tightened. On both voluntary- and mandatory-action days, individuals will be asked to reduce how much they drive their cars and choose cleaner transportation options.

Despite assertions by state Department of Environmental Quality regulators last fall that Utah would be able to meet the new standard, Bird said it now appears the state will gain two new nonattainment areas — one on the Wasatch Front and the other in the Uinta Basin.

A geographical area is given a nonattainment status when it is unable to meet federal air quality regulations. The environmental regulators responsible for the designated area are required to address the situation and, if they do not make adequate progress over time, the EPA may impose increasingly strict rules of its own and can, in extreme circumstances, step in to directly manage the nonattainment area.

The EPA is currently in the process of reclassifying the severity of the Wasatch Front's nonattainment status for small particle pollution.

It does not appear that the Wasatch Front and the Uinta Basin will be able to abide by the new ozone standard, Bird said, so the state will likely propose nonattainment status for both this October.

Tooele County could be included in the Wasatch Front nonattanment designation, depending on how the area performs this summer. The county has been toeing the line under the new standard, and Bird said the DAQ recently decided to move its ozone monitors from Tooele City to Erda, where higher ozone concentrations have been detected.

The rest of Utah already appears to comply with the new standard, Bird said.

The EPA will decide whether to accept the state's proposal by fall 2017, at which point Utah will have three years to attain the standard. If Utah does not achieve attainment in either area by 2020, state regulators will be required to craft a formal plan for reducing ozone.

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