Are the summer temperatures really gone? Recent cool mornings indicate strong possibilities that summer is finally over and autumn has arrived in Pima County. The summertime air pollutant of concern, ground-level ozone, did reach elevated levels this year, which bring us ever closer to violating the U.S. Environmental Protection Agency’s 2015 National Ambient Air Quality Standard. The EPA health standard for ozone was revised to 0.070 parts per million in 2015 to better protect public health. According to data from the Pima County Department of Environmental Quality (PDEQ), the 2017 ground-level ozone season increased the 3-year average to 0.069 ppm in Pima County.
During fall and winter, the less direct angle of the sun reduces the photochemical reaction that forms ground-level ozone. Overnight cool temperatures trap emissions from fireplaces and vehicles in a hazy brown layer close to the ground and change the air quality focus to particulate pollution. Particulate matter comes from a variety of sources including vehicle emissions, industrial processes, wood burning, disturbed vacant land, construction, dirt roads, and mining activities.
The majority of the time our particulate levels are safely below the EPA health standard, but on windy days, during times of wildfires, and on days of special celebrations where fireworks or fireplaces are used, we can see elevated levels of particulates in the air we monitor. People with respiratory and cardiac disease, as well as those with diabetes, are more at risk for health effects when particulate levels are high. According to the American Lung Association’s “State of the Air Report” for 2017, there are about 98,100 people with asthma in Pima County, 66,500 cases of cardiovascular disease, and 83,200 people with diabetes.
Find real-time air pollution levels from PDEQ’s air quality monitoring sites at www.pima.gov/deq. Click in the air section for links to current air quality and actions that you can take to improve the air you breathe.