Health effects

Highland Park Optimist Club wearing smog-gas masks at banquet, Los Angeles, circa 1954
Smog is a serious problem in many cities and continues to harm human health.[17] Ground-level ozone, sulfur dioxide, nitrogen dioxide and carbon monoxide are especially harmful for senior citizens, children, and people with heart and lung conditions such as emphysema, bronchitis, and asthma.[18] It can inflame breathing passages, decrease the lungs' working capacity, cause shortness of breath, pain when inhaling deeply, wheezing, and coughing. It can cause eye and nose irritation and it dries out the protective membranes of the nose and throat and interferes with the body's ability to fight infection, increasing susceptibility to illness. Hospital admissions and respiratory deaths often increase during periods when ozone levels are high.[19][20]

Levels of unhealthy exposure
The U.S. EPA has developed an Air Quality Index to help explain air pollution levels to the general public. 8 hour average ozone concentrations of 85 to 104 ppbv are described as "Unhealthy for Sensitive Groups", 105 ppbv to 124 ppbv as "unhealthy" and 125 ppb to 404 ppb as "very unhealthy".[18] The "very unhealthy" range for some other pollutants are: 355 μg m−3 - 424 μg m−3 for PM10; 15.5 ppm - 30.4ppm for CO and 0.65 ppm - 1.24 ppm for NO2.[21]

Premature deaths due to cancer and respiratory disease
The Ontario Medical Association announced that smog is responsible for an estimated 9,500 premature deaths in the province each year.[22]

A 20-year American Cancer Society study found that cumulative exposure also increases the likelihood of premature