Chapter 2: Urban and Transboundary Air Pollutions
¾ Recognition of the relationship between non-workplace (i.e., community) air pollution and
respiratory disease dates back to the first use of coal as a combustion source in the fourteenth
¾ Later, in the industrial nations of Europe and North America, whole communities were engulfed
in air pollutants, resulting in serious illness and death among individuals with cardiopulmonary
¾ These episodes occurred in the Meuse Valley of Belgium in 1930; in Donora, Pennsylvania, in
1948; and in London in 1952.
¾ These air pollution emergencies were caused by air stagnation, which resulted in greatly
increased concentrations of atmospheric pollutants, especially sulfur dioxide and suspended
particulates. The worst episode occurred in London.
¾ As a result of these epidemics, scientists and governments paid increased attention to the
health effects of air pollution.
¾ This crisis has several aspects. First, since the atmosphere is dynamic and always changing,
contaminants are transported (sometimes over thousands of miles), diluted, precipitated, and
transformed. Air pollution, therefore, knows no boundaries or national borders.
¾ Second, the primary emissions of sulfur oxides, nitrogen oxides, carbon monoxide, respirable
particulates, and metals are severely polluting cities and towns in Asia, Africa, Latin America,
and Eastern Europe.
¾ Many cities in developing nations and in Eastern Europe are experiencing uncontrolled
industrial expansion, increasing motor vehicle numbers and congestion, and pollution caused by
fuels used for cooking and heating.
¾ World Health Organization (WHO) confirms that this disparity between wealthier and poorer
¾ Third, in nations that have reduced the primary emissions from heavy industry, power plants,
and automobiles, new problems have arisen from pollution by newer industries and from air
pollution caused by secondary formation of acids and ozone.
¾ Finally, although this report is focused on the human health effects of air pollution, there are
also many other aspects of the problem. For example, damage to ecosystems and agriculture
from acid rain, damage to buildings and artwork, and reduced visibility are all attributable to air
Defining Adverse Health Effects
¾ An adverse health effect is any effect that results in altered structure or impaired function or
that represents the beginning of a sequence of events leading to altered structure or function.
Specific Air Pollutants Associated with Adverse Respiratory Effects
¾ Several major types of air pollution are currently recognized to cause adverse respiratory health
effects: sulfur oxides and acidic particulate complexes, photochemical oxidants, and a
miscellaneous category of pollutants arising from industrial sources.
Sulfur Dioxide and Acidic Aerosols
¾ Sulfur dioxide (SO2) is produced by the combustion of sulfur contained in fossil fuel, such as coal
and crude oil. Therefore, the major sources of environmental pollution with sulfur dioxide are
electric power generating plants, oil refineries, and smelters.
¾ Some fuels, sucZ^}(_}oU]µooÇµo(µ-rich. Ex: China uses it a lot.
¾ Sulfur dioxide is a clear, highly water-soluble gas, so it is effectively absorbed by the mucous
membranes of the upper airways, with a much smaller proportion reaching the distal regions of
¾ The sulfur dioxide released into the atmosphere does not remain gaseous. It undergoes
chemical reaction with water, metals, and other pollutants to form aerosols.
¾ These particulate aerosols vary in composition from area to area, but the most common
pollutants resulting from this atmospheric reaction are sulfuric acid, metallic acid, and
¾ Sulfur dioxide, therefore, together with other products of fossil-fuel combustion forms the
heavy urban pollution that typified old London, many cities in developing nations today that
mainly burn coal.
¾ In addition to this smog t a descriptive term generically referring to the visibly cloudy
combination of smoke and fog t an acidic aerosol is formed that has been shown to induce
asthmatic responses in both adults and children.
¾ In a Harvard study: two measures of air acidity showed significant effects. Higher particle acidity
(nmol/m3) was significantly associate d with an increased risk of bronchitis, while higher levels of
gaseous acids were significantly associated with wheeze attacks, chronic wheezing, and any
¾ Because (SO2) is highly water soluble, nearly all of the inspired (SO2) gas is removed in the upper
airways during rest. Exertion (work and exercising) will increase the fraction of (SO2) gas to the
lower airways and therefore help to precipitate bronchocontriction.
¾ ^oîXî(}^hX^Xv]}vo]µo]Çv(}]Æ]]}ooµvX_ (pg. 21).
¾ In addition to the acute bronchoconstrictive effects of sulfur dioxide, there is epidemiologic
evidence for chronic airway obstruction in persons exposed to elevated levels of (SO2).
¾ Particulate air pollution is closely related to (SO2) and aerosols. The term usually refers to
particles suspended in the air after various forms of combustion or other industrial activity.
¾ In the epidemics noted earlier, the air pollution was characterized by high levels of particulates,
sulfur dioxide, and moisture.
Recognition of the relationship between non-workplace (i. e. , community) air pollution and respiratory disease dates back to the first use of coal as a combustion source in the fourteenth century. Later, in the industrial nations of europe and north america, whole communities were engulfed in air pollutants, resulting in serious illness and death among individuals with cardiopulmonary disease. These episodes occurred in the meuse valley of belgium in 1930; in donora, pennsylvania, in. These air pollution emergencies were caused by air stagnation, which resulted in greatly increased concentrations of atmospheric pollutants, especially sulfur dioxide and suspended particulates. As a result of these epidemics, scientists and governments paid increased attention to the health effects of air pollution. First, since the atmosphere is dynamic and always changing, contaminants are transported (sometimes over thousands of miles), diluted, precipitated, and transformed. Air pollution, therefore, knows no boundaries or national borders.