Respiratory Disease

Introduction

Respiratory disease is any disease of the breathing organs, especially the lungs. Air pollutants such as toxic particles and ozone (O₃) are a major cause of respiratory disease, killing hundreds of thousands of people globally every year.

Climate change is related to air pollution and thus to respiratory disease in several ways. First, although carbon dioxide (CO₂) itself is not toxic, the same fossil-fuel burning that releases CO₂, the largest single cause of global warming, also releases toxic air pollution. Second, ground-level ozone formation is speeded by higher temperatures, which global climate change is making more common. Third, changed climate conditions will in some areas increase dust, mold, and air pollution from forest fires, which can increase rates of respiratory disease. Efforts to mitigate global climate change will tend to reduce respiratory disease, both by reducing the pollutants that are emitted along with CO₂ and by reducing the effects of climate change on weather and pollutant formation, which in turn increase rates of respiratory disease.

Historical Background and Scientific Foundations

The effects of climate change on human health are already serious. According to the World Health Organization (WHO), an arm of the United Nations, anthropogenic (human-caused) climate warming and shifts in precipitation over the last 30 years were, as of 2005, already causing 150,000 deaths per year and could cause 300,000 deaths per year by 2030. Not all these changes were due to respiratory disease: direct heat stress during heat waves, altered transmission of infectious diseases, and starvation from failed agriculture are other ways in which climate change threatens human health.

Air pollution, which climate change is likely to worsen, is a major cause of preventable disease and death, causing (as of 1997) about 700,000 deaths per year worldwide. In the United States, reducing pollution from coal-fired power plants could save 18,700 lives per year; reducing emissions from just nine of the worst coal plants in the Midwest would annually save approximately 300 lives, prevent 2,000 hospital admissions for respiratory and cardiac emergencies, and prevent 10,000 asthma attacks.

The pollutants of most concern to human health are fine particulate matter (small particles released by fuel combustion or burning biomass) and ozone. Ozone is beneficial in the ozone layer of the stratosphere, where it blocks harmful ultraviolet light from the sun, but is poison- ous if inhaled. Ground-level (low-altitude, breathable) ozone, the main ingredient of smog, is not released directly by fuel-burning but is a secondary pollutant formed when nitric oxide (NO), nitrogen dioxide (NO₂), and organic compounds such as methane and carbon monoxide react in warm air in the presence of sunlight. (Stratospheric ozone is formed by the action of ultraviolet light on ordinary molecular oxygen, O₂.) Elevated ozone causes increased hospitalizations of several kinds of respiratory disease, including asthma, allergic rhinitis, chronic obstructive pulmonary disease, and pneumonia.

Although exact predictions of how changing climate will affect ozone formation and other forms of pollution are not yet possible, increasing warmth in most areas will tend to increase ozone formation. Above 90°F (32°C), temperature and production of ground-level O₃ are strongly correlated.

A 2004 study by Kim Knowlton and colleagues found that in the 31 counties of the New York metropolitan region, a 4.5% increase in O₃-related deaths may occur by the 2050s as compared to the 1990s average of 1,278 deaths per year. A 2001 study by H. R. Anderson and colleagues suggested that O₃-related deaths in the United Kingdom could increase 10% by 2020 and 20% by 2050 due to climate change alone, apart from population increase. In the early 2000s, concentrations of ozone were increasing in most regions of the world.

WORDS TO KNOW

ANTHROPOGENIC: Made by people or resulting from human activities. Usually used in the context of emissions that are produced as a result of human activities.

BIOMASS: The sum total of living and once-living matter contained within a given geographic area. Plant and animal materials that are used as fuel sources.

FOSSIL FUELS: Fuels formed by biological processes and transformed into solid or fluid minerals over geological time. Fossil fuels include coal, petroleum, and natural gas. Fossil fuels are non-renewable on the timescale of human civilization, because their natural replenishment would take many millions of years.

GREENHOUSE GAS MITIGATION TECHNOLOGIES: Technological methods for reducing (mitigating) releases of greenhouse gases. Such technologies include schemes to sequester carbon dioxide by injecting it into underground reservoirs, burnoff of methane from landfills, substitute low- or no-carbon fuels for carbon-based fuels, and more. As of the early 2000s, such technologies had made little impact on global greenhouse emissions.

OZONE: An almost colorless, gaseous form of oxygen with an odor similar to weak chlorine. A relatively unstable compound of three atoms of oxygen, ozone constitutes, on average, less than one part per million (ppm) of the gases in the atmosphere. (Peak ozone concentration in the stratosphere can get as high as 10 ppm.) Yet ozone in the stratosphere absorbs nearly all of the biologically damaging solar ultraviolet radiation before it reaches Earth's surface, where it can cause skin cancer, cataracts, and immune deficiencies, and can harm crops and aquatic ecosystems.

ULTRAVIOLET: Light that vibrates or oscillates at a frequency of between 7.5 10¹⁴ and 3 10¹⁶ Hz (oscillations per second), more rapid than the highest-frequency color visible to the human eye, which is violet (hence the term “ultraviolet,” literally above-violet). Ultraviolet light is absorbed by ozone (O₃) in Earth's stratosphere. This absorption serves both to shield the surface from this biologically harmful form of radiation and to heat the stratosphere, with important consequences for the global climate system.

Air pollution from forest and brush fires due to warmer, drier conditions may increase under climate change. Local concentrations and long-range transport of air pollution, dust, and allergens are also likely to change. In areas where precipitation increases, a rise in mold growth will likely occur as unusual floods and heavier rains and winds cause water to intrude into buildings.

Impacts and Issues

Some measures proposed to mitigate climate change, especially reduced burning of fossil fuels, would have large direct benefits on rates of respiratory disease. A 2001 study by Luis Cifuentes and colleagues, simulating the effects of climate change on air pollution and respiratory disease in four large cities having a combined population of 45 million—Mexico City, New York, Santiago, and Sao Paulo—found that greenhouse gas mitigation technologies applied from 2001 to 2020 would reduce particulate matter pollution and ground-level ozone by about 10%, preventing 646,000 premature deaths and 65,000 cases of chronic bronchitis (long-lasting irritation of the midsize air passages of the lungs).

Careless implementation of some anti-greenhouse technologies could increase some risks of respiratory disease. Specifically, burning of biomass fuels can pollute the air as badly as burning fossil fuels, and making buildings more energy-efficient without providing for sufficient air flow can heighten indoor concentrations of radon, a natural radioactive gas that seeps out of the ground in some areas. Radon is the main cause of lung cancer in non-smokers.

See Also Infectious Disease and Climate Change.

BIBLIOGRAPHY

Periodicals

Cifuentes, Luis, et al. “Hidden Health Benefits of Greenhouse Gas Mitigation.” Science 293 (2001): 1257–1259.

Epstein, Paul. “Climate and Health.” Science 285 (1999): 347–348.

Knowlton, Kim, et al. “Assessing Ozone-Related Health Impacts under a Changing Climate.” Environmental Health Perspectives 112 (2004):1,557–1,563.

Patz, Jonathan A. “Impact of Regional Climate Change on Human Health.” Nature 438 (2005): 310–317.

Web Sites

Anderson, H. R., et al. “Air Pollution and Climate Change.” UK Department of Health, 2001.
<http://www.dh.gov.uk/assetRoot/04/06/89/15/04068915.pdf> (accessed November 20, 2007).

“Pollution and Air Quality: The Connections Between Climate Change, Air Quality, and Respiratory Health.” The Canadian Lung Association, April 16, 2007. <http://www.lung.ca/protect-protegez/pollution-pollution/climate-climatique/index_e.php> (accessed November 20, 2007).

Simpson, Michael. “Global Climate Change: Federal Research on Possible Human Health Effects.” Congressional Research Service Report for Congress, February 10, 2006. <http://www.ncseonline.org/NLE/CRSreports/06Mar/RL31519.pdf> (accessed November 20, 2007).

Larry Gilman