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May 1, 2002

Global Climate Change and Air Pollution: Common Origins With Common Solutions

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JAMA. 2002;287(17):2285. doi:10.1001/jama.287.17.2285-JMS0501-4-1

Climate change and air pollution are linked to one another by our increasing use of fossil fuels, including coal, petroleum, and natural gas.1 In the United States fossil fuel combustion accounts for 98% of anthropogenic emissions of carbon dioxide, the predominant greenhouse gas by volume.2 Although increasing levels of ambient carbon dioxide have no known direct adverse health effects, other byproducts of fossil fuel combustion have known impacts on respiratory health.

One such pollutant is ground-level ozone, the major component of smog. Ozone is formed from the reaction of nitrogen oxides and volatile organic compounds, as from power plant emissions and automobile exhaust, in the presence of light and heat. This reaction occurs more rapidly at higher temperatures, explaining, in part, why smog is more marked during the summer months. Global warming would be expected to worsen this form of air pollution.3

Ozone has been linked to decreased pulmonary function in healthy adults, an effect that depends on exposure concentration and duration.4 At low levels (0.3 ppm-0.5 ppm), ozone irritates mucous membranes of the eyes and throat and induces chest tightness. High-level exposure (5.0 ppm-10.0 ppm) for more than one hour can lead to pulmonary edema and death.5 Long-term exposure (4 or more years in areas with summer ozone levels of 80 ppb or more for at least 1 h daily) has been associated with adult-onset asthma in otherwise healthy, nonsmoking individuals.4

More generally, elevated ozone levels have been found to lead to more frequent asthma attacks, emergency department visits, and hospitalizations; increased use of asthma medications; and greater morbidity and mortality in patients with pre-existing pulmonary or cardiovascular disease.6,7 Children are at even greater risk because their respiratory systems are still developing, they spend significantly more time outdoors, and they breathe more air per pound body weight than adults.8 One study found that the relative risk of asthma developing in active children (three or more outdoor sports) living in high ozone environments is 3.3 times greater than those who did not play those sports.9

The burning of fossil fuels produces other major air pollutants including airborne particulates, nitrogen oxides, and sulfur oxides.10 Fine particulate matter (less than 2.5 µm in diameter) is easily inhaled deeply into the lungs where it can be absorbed into the bloodstream or remain embedded in the lung parenchyma. Oxides of nitrogen (NOX) are formed during high-temperature combustion processes, such as those that power automobiles and power plants. Oxides of sulfur (SOX) are formed when fuel containing sulfur (mainly coal and oil) is burned, as during metal smelting and other industrial processes.

One study of never-smoking cohorts grouped by age (7-59 years old) compared areas in southern California with moderate levels of SO2, NO2 and particulate matter (mean values: 0.01 ppm, 0.03 ppm, and 85 µg/m3, respectively) to those with higher levels (mean values: 0.04 ppm, 0.11 ppm, and 101 µg/m3, respectively).11 Chronic exposure to higher levels of these pollutants adversely affected the small and large airways of the lungs, as determined by spirometric parameters, in females older than 7 years and males older than 15 years. A larger, more recent study concluded that fine particulate and sulfur oxide–related pollution is associated with all-cause, lung cancer, and cardiopulmonary mortality, after controlling for cigarette smoking, occupational exposure, and other risk factors.12

Because the burning of fossil fuels is linked to both human-induced climate change and air pollution, there is a common solution: reducing the use of fossil fuels as an energy source. Clearly, this can be accomplished in part by using and developing technologies that increase energy efficiency and by jump-starting the transition from fossil fuels to renewable energy resources.

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Intergovernmental Panel on Climate Change (IPCC), Climate Change 2001: The Scientific Basis: Contribution of Working Group I to the Third Assessment Report of the IPCC. Houghton  JDing  YGriggs  M  et al. eds. Cambridge, England Cambridge University Press2001;
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US Army Corps of Engineers, Occupational Exposure to Ozone.  HQ Environmental Division Lessons December16 1996;
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McConnell  RBerhane  KGilliland  F  et al.  Asthma in exercising children exposed to ozone: a cohort study.  Lancet. 2002;359386- 391Crossref
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Pope III  CABurnett  RTThun  MJ  et al.  Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution.  JAMA. 2002;2871132- 1141Crossref