The Arizona Department of Environmental Quality (ADEQ) has issued a High Pollution Advisory (HPA) for ozone effective for today, Wednesday, Aug. 7, and continuing on Thursday, Aug. 8. ADEQ recommends that people limit outdoor activity while the HPA is in effect, especially children and adults with respiratory problems. The forecast calls for high ozone levels to continue through the weekend.

Ground level ozone forms when two types of pollutants—volatile organic compounds (VOCs) and nitrogen oxides (NOx)—react in sunlight. These pollutants come primarily from automobiles, but also from other sources including industries, power plants and products, such as solvents and paints. Generally, the highest levels of ozone occur in the afternoon.

People most vulnerable to the impacts of air pollution include children, older adults, adults exercising outdoors, people with heart or lung disease and those suffering from asthma and bronchitis. Exposure can increase the number and severity of asthma attacks, cause or aggravate bronchitis or other lung disease and reduce the body’s ability to fight infection. Symptoms may include itchy eyes, nose, and throat, wheezing, coughing, shortness of breath, chest pain and upper respiratory issues.

Maricopa County air quality restrictions are in effect.