An air quality advisory has been issued for the Portland area as hot air from a multi-day heatwave reacts with pollution to form harmful chemicals.
Officials expect elevated levels of ozone pollution, or smog, starting Tuesday afternoon, July 26, according to a statement from the Oregon Department of Environmental Quality.
Ozone levels could be unhealthy for sensitive groups, including children, people over 65, pregnant women and people with heart disease or respiratory problems, officials said.
The advisory is expected to last until Saturday, July 30, according to DEQ. It includes the Portland/Vancouver area and Willamette Valley.
Health officials recommend sensitive groups to limit outdoor activity when pollution levels are high.
Ozone forms when hot temperatures and low winds combine with pollution from cars, gas-powered engines and chemicals in paints and aerosols, officials said. The pollutants react with sunlight and heat to produce ozone and haze.
The pollutant irritates the eyes, nose and lungs, and contributes to breathing problems. People are advised to consult their health care provider if these symptoms worsen.
"Ozone pollution increases throughout the day with exposure to sunlight, so pollution levels tend to be highest during afternoons and early evenings," officials said. "Air quality monitors may show good air quality in the morning, then quickly jump to unhealthy levels later in the day."
Air quality was in the "moderate" range near both Portland's Cully neighborhood and Tualatin by late Tuesday morning, according DEQ air quality monitors. Air quality was in the "good" range elsewhere in the area.
An excessive heat warning is in effect for the Portland area until 9 p.m. Saturday, July 30.
Temperatures reached 99 degrees at the Portland International Airport on Monday, July 25. The daytime high on Tuesday could exceed 100 degrees, according to the National Weather Service.
Multnomah County and Portland plan to open overnight shelters, a day center and misting stations Tuesday afternoon and provide other cooling resources amid dangerous temperatures.
Officials are urging people to limit activities that cause pollution during the heat wave. They recommend using public transit, carpooling or using other transportation than driving, avoiding engine idling, refueling vehicles in the cooler evening hours, and postponing lawn mowing, using leaf blowers, painting and doing aerosol spray projects.
People can check current air quality conditions and advisories on DEQ's Air Quality Index or by downloading the free OregonAIR app on a smartphone.
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