‘Code Orange’ day for ozone in Philly area Wednesday due to drifting wildfire smoke

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People in the Philadelphia area who are sensitive to poor air quality should take precautions on Wednesday as smoke from wildfires burning in Canada will help raise levels of ozone over the region.

Wednesday will be a Code Orange day for ozone in Bucks, Chester, Delaware, Montgomery and Philadelphia counties, according to Pennsylvania’s Department of Environmental Protection.

The warning means air quality will be unhealthy for sensitive groups, including young children, older adults and people with lung conditions such as asthma, chronic bronchitis, emphysema and chronic obstructive pulmonary disease.

Ozone can inflame airways and aggravate respiratory issues, causing coughing, wheezing and shortness of breath. It can also cause more frequent asthma attacks.

People in sensitive groups should limit their activity outside, state officials said.

Ozone forms when air pollutants react with sunlight, and Wednesday’s warm temperatures, sunny skies and thin layer of wildfire smoke provide the perfect ingredients.

Pollution from cars and trucks also contributes to ozone, so officials are urging people to drive less and wait to fuel their vehicles until after dark.

Two years ago, wildfire smoke blanketed the Philadelphia region, temporarily sending the city’s air quality index into the hazardous range. The elevated levels of particle pollution in 2023 likely drove a drop in the city’s air quality rating from a lung health organization this spring.