The regular Oxygen that we breathe is 2 oxygen atoms hooked together to make an oxygen molecule O2. Ozone is an oxygen molecule that has 3 oxygen atoms (O3). That third oxygen atom makes it reactive- especially with mucous membranes and lung tissue- which leads to health problems when people or animals are exposed to too much ozone. Ozone becomes a health issue in the urban deserts on hot, sunny days- because summertime conditions are perfect for forming it.
People with lung disease, children, older adults, and people who are active outdoors may be particularly sensitive to ozone. Ozone pollution makes lung diseases such as asthma worse and can cause breathing difficulties even in healthy individuals. The result is more time spent in hospital emergency rooms, as well as additional sick days and even premature deaths.
While cars are among the main source of ozone-forming pollutants (the chemical precursors to ozone), ozone’s formation is dependent on heat and sunlight. Ground-level ozone is formed when a complex set of chemical reactions is triggered by heat and the sun. Ozone is a major part of urban smog. That’s why we hear warnings of “bad-air days” due to ozone pollution most often during the summer and on cloud-free days.
Ozone can also be transported long distances by wind. Due to prevailing easterly wind patterns, the worst of the Phoenix smog is blown and concentrated in the canyons of the Superstition Mountains. In fact, the highest levels of ground level ozone in Arizona were recorded within the Superstition Wilderness.
When you hear that we’re having an ozone alert, it makes sense to limit outdoor physical activity in the afternoon- especially if you have pre-existing lung problems. One way you can stay prepared is by signing up for air quality alerts provided by the Arizona Department of Environmental Quality.