Chapter 2: Urban and Transboundary Air Pollution:
•As a result of epidiemics, scientisits increased attention to the health effects of air
pollution- identifiying specific pollutant sources and their transport in the
atmosphere, elucidating exposure-response relationships.
•These crisis have several aspects: first since the atmosphere is dynamic and
always changing, contaminants are transported, diluted precipitated and
•Second, the primary emission of sulphur oxides, nitrogen oxides, carbon
monoxide, resporable particulates and metals are severely polluting cities and
twon in asia, Africa and Latin eastern Europe.
•Poor countries had higher level of total suspended particulates then wealthier
•Third in nations, that have reduced the primary emissions from heavy industry,
power plants and automobiles, new problems have arisen from air pollution
contribute to heavily to the high mortality rates observed from acute respiratory
•Defining adverse health effects:
•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 is
considered an “adverse health effect”
•Specific air pollutants associated with adverse respiratory effects:
•Several types of air pollution are currently recognized to cause adverse respiratory
health effects: sulphur oxides and acidic particulate complexs, photochemical
oxidants, and a miscellaneous category of pollutants arising from industrial
•Sulphur dioxide and acidic aerosols:
•Sulfur dioxide is produced by the combustion of sulphur contained in fossil fuels,
such as coals and crude oil.
•The major sources of environmental pollution with sulphur dioxide are electric
power generating plants, oil refineries, and smelters.
•Slufor dioxide is a clear, highly water soluble gas, so it is effectively absorbed by
mucous membranes of the upper airways, with a much smaller portion reacting
the distal regions of the lung.
•The sulphur dioxide released into the atmosphere does not remain gaseous. It
undergoes chemical reaction with water, metals and other pollutants to form
•Sulphur dioxide therefore, together with other products of fossil fuel combustion
forms the heavy urban pollution.
•Smog a descriptive term generally referring to the visibly cloudy combination
of smoke and fog—an acidic aerosol is formed that has been shown to induce
asthematic responses in both adults and children.