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Health and Environmental Effects
HEALTH AND ENVIRONMENTAL EFFECTS
Breathing air with smog has adverse and varied consequences for human health, with the cardio-respiratory system being the main target of concern. Wherever its location and whether visible or not, smog is hazardous to human health.
Ground-level ozone has been linked with a broad spectrum of human health effects. Because of its reactivity, ozone can injure biological tissues and cells. Exposure to ozone has been associated with mortality, hospital admissions, emergency department visits and other adverse health effects.
Exposure to airborne particles at the levels typically found in North American urban areas is associated with a variety of adverse effects. Particles can irritate the eyes, nose, and throat and cause coughing, breathing difficulties, reductions in lung functions, and an increase in the use of asthma medication. Exposure to particles is also associated with an increase in the number of emergency department visits, an increase in hospitalizations of people with cardiac and respiratory disease, and in premature morality.
There is clear evidence of the harmful effects of these pollutants throughout the range of concentrations to which Canadians are exposed. This means that any reduction in the ambient levels of these pollutants provides a reduction in population health risk.
Negative effects on the environment associated with these pollutants include visibility impairment and ecosystem acidification (for PM), and crop damage and greater vulnerability to diseases in some tree species (for ozone).
All of these adverse effects lead to significant economic losses and reductions in productivity as a result of absenteeism from school and work, in creased medical care and hospitalizations, and reduced product quality and yields.
PM and ground-level ozone are two principal components that comprise smog. These pollutants pose serious health and environmental concerns. Ozone is a secondary pollutant because it is not emitted directly to the atmosphere but rather is formed in air from complex reactions between the precursor gases NOx and VOC in the presence of sunlight. PM has both a primary and a secondary component. Primary PM is released directly to the atmosphere from combustion or mechanical processes. Secondary PM is formed in the atmosphere from the precursor gases SO2, NOx, VOC and NH3. PM and ozone can be transported by prevailing air flows over long distances, making them not only a concern for urban centres across Canada but also for many smaller communities and rural areas.
Breathing air with smog has adverse and varied consequences for human health, with the cardio-respiratory system being the main target of concern. There is clear evidence of the harmful effects of PM2.5 and ozone throughout the range of concentrations to which Canadians are exposed.
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