15.2.4.2.3. Respiratory disorders

In 1997, approximately 107 million people in the United States lived in counties that did not meet air quality standards for at least one regulated pollutant (Patz et al., 2000). Climate change increases smog (NRC, 1991; Sillman and Samson, 1995; USEPA, 1998a; Patz et al., 2000) and acidic deposition. Climate change is likely to have a positive (worsening) effect on suspended particulates (Maarouf and Smith, 1997). These changes would have an impact on human health. However, at this time there are too few studies on the effect climate change will have on all pollutants to project human health impacts. Studies (Bates and Sitzo, 1987, 1989; Tseng et al., 1992; Burnett et al., 1994; Delfino et al., 1994, 1997; Schwartz, 1994; Thurston et al., 1994) have demonstrated that hospital admissions for respiratory illnesses are increased during contemporary air pollution episodes, when levels of ozone, acid aerosols, or particulates are elevated (Campbell et al., 1995).

Adaptive measures to changing pollution levels include federal legislation and warnings for the general population and susceptible individuals (Patz et al., 2000).

15.2.4.2.3.1. Smog

More than half of all Canadians live in areas in which ground-level ozone may reach unacceptable levels during the summer months (Duncan et al., 1998). Peak 1-hour concentrations during typical pollution episodes in the Windsor-Quebec City corridor often reach 150 ppb. Windsor exceeds standards for ozone air quality (82 ppb) 30 days yr^-1 on average. In the Lower Fraser Valley, ozone concentrations typically are in the 90-110 ppb range during pollution episodes. In the Southern Atlantic region, peak hourly ozone concentrations are in the 90-150 ppb range (Duncan et al., 1998).

Two expert panels from the Canadian Smog Advisory Program have listed a wide range of health effects of ground-level ozone at levels that plausibly may occur in Canada. These effects include pulmonary inflammation, pulmonary function decrements, airway hyper-reactivity, respiratory symptoms, possible increased medication use and physician/emergency room visits among individuals with heart or lung disease, reduced exercise capacity, increased hospital admissions, and possible increased mortality (Stieb et al., 1995). The panels conceptualized potential health effects of air pollution as occurring in a logical "cascade" or "pyramid," ranging from severe, uncommon events (e.g., death) to mild, common effects (e.g., eye, nose, and throat irritation) and asymptomatic changes of unclear clinical significance (e.g., small pulmonary function decrements and pulmonary inflammation) (American Thoracic Society, 1985; Bates, 1992).

Healthy persons can demonstrate effects from ozone exposure when they have an increased respiratory rate (e.g., when they are involved in strenuous activities outdoors) (Brauer et al., 1996). Ozone may pose a particular health threat, however, to those who already suffer from respiratory problems such as asthma, emphysema, or chronic bronchitis (Stieb et al., 1996). These three conditions affect about 7.5% of the Canadian population (Ontario Lung Association, 1991). Ozone also may pose a health threat to young, elderly, and cardiovascular patients (Duncan et al., 1998). An increase in smog also would pose a greater risk to African Americans, who have consistently higher rates of deaths and emergency room visits than caucasians (Mannino et al., 1998).

15.2.4.2.3.2. Acidic deposition

Acidic aerosols—such as sulfur dioxide (SO₂), sulfates, and nitrogen dioxide (NO₂)—have a colloidal affinity to fine particulates, which provide the vector needed to penetrate deeply into the distal lung and airspaces. In general, NO₂ and SO₂ have acute negative impacts on the respiratory system (Campbell et al., 1995).

Several studies (Bates and Sitzo, 1987, 1989; Tseng et al., 1992; Burnett et al., 1994; Delfino et al., 1994; Schwartz, 1994; Thurston et al., 1994) have demonstrated that hospital admissions for respiratory illnesses increase during contemporary air pollution episodes when levels of ozone, acid aerosols, or particulates are elevated (Campbell et al., 1995). A study by Raizenne et al. (1996) that examined the health effects of acid aerosols on children living in 24 communities in the United States and Canada found that long-term exposure had a deleterious effect on lung growth, development, and function. Dockery et al. (1996) found that children living in communities with the highest levels of strong particle acidity were significantly more likely to report at least one episode of bronchitis in the past year compared to children living in the least polluted communities.

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