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  • Air quality exceeded EPA ozone standard yesterday and could be high today

    May 06, 2020 | Read More News
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    Yesterday, Pima County Department of Environmental Quality’s (PDEQ) air quality monitors near Tangerine Road, Saguaro Park East and Children’s Memorial Park recorded exceedances of the EPA health standard for ground-level ozone. These were the first ozone exceedances reported in Pima County since the 2020 ozone season began in April. For comparison purposes, the Phoenix area has exceeded the ozone standard 5 days so far in 2020. 

    Today is also forecasted to have elevated ozone, so individuals who are sensitive to ozone may want to limit their level of exertion when outside. 


    PDEQ is issuing another Air Quality Health Watch today because conditions are similar to yesterday, although we are seeing some beneficial breezes that could help to ventilate the valley.

    As opposed to the protective ozone layer above us, ground-level ozone is an air pollutant that is formed by a photochemical reaction that occurs when intense sunlight reacts with emissions from multiple sources such as motor vehicles, gasoline fumes, paint and chemical fumes, gas-powered lawn and garden equipment, power plants, industries and certain types of vegetation. When elevated, ozone can cause shortness of breath, difficulty breathing and can aggravate preexisting respiratory diseases. 

    Yesterday’s reading of 105 on the Air Quality Index was the highest ozone reading since August of 2018. That year there were five days when ozone exceeded the EPA health standard, which was enough to violate the EPA health standard for ozone. In 2019, there was only one exceedance day for ozone.

    “Weather, upper atmospheric conditions along with wind direction play a big part in the creation of ground-level ozone,” said Beth Gorman, Senior Program Manager for Pima County Department of Environmental Quality. “Those things we can’t control. But we can try to minimize the other piece of the ozone puzzle which are the volatile organic compounds and nitrogen oxide emissions to avoid continued exceedance days,” Gorman said.

    “Reducing emissions that create ozone this summer could help avoid another ozone violation and regulatory restrictions on businesses. Combining trips, working from home, avoiding engine idling, refueling after 6 p.m. and conserving electricity are ways we can each take action to improve air quality in Pima County,” said Gorman. 

    Real-time air quality data is available on the PDEQ website at www.pima.gov/deq. In addition, Arizona Department of Environmental Quality provides 5-day air quality forecasts for the metropolitan Tucson area.