The Pima County Department of Environmental Quality issued an advisory Friday for ground-level ozone air pollution in the Tucson metropolitan area, encouraging anyone especially sensitive to ozone to avoid physical exertion outside until 6 p.m.
Children, adults who are active outdoors and anyone with respiratory disease are most likely to be sensitive to ozone.
"Intense physical outdoor activity causes faster and deeper breathing, which allows ozone to penetrate into the parts of the lungs that are more likely to be injured," the department said in a statement.
Different types of emissions contribute to creating ground-level ozone, like motor vehicle exhaust and power plant emissions.
The department is encouraging Pima County residents to reduce ozone through the following steps: