GGR374H1 Chapter Notes - Chapter 2: Time Series, Air Pollution, Urban Air
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 transformed.
•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 sources.
•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.
•The havard six citities study demonstrated a significant association between chronic
cough and bronchitis and hydrogen ion concentration- a measure of acidity- rather
than sulphate levels or total particulate levels.
•Two measures of air acidity showed significant effects
•Higher particle acidity was significantly associated with an increased risk of
bronchitis, while higher levels of gasoues acids were also positively associated with
wheeze attacks, chronic wheezing and any asthmatic symptoms.
•A time series analysis that examined mortality and morbidity in buffalo showed
signficnant positive association between aerosol acidity and increased respiratory
hospital admission and respiratory mortality
•Several studies linked exposure to acidic aerosols and mortality, documenting an
increase in deaths of persons with underlying chronic heart and lung disease who
had been exposed.
•Acidic aerosols results in acid rain, which may threaten aquatic life.
•In addition to the acute bronchoconstrictive effects of sulphur dioxide, there is
epidemiologic evidence for chronic airway obstruction in persons exposed to
elevated levels of SO2.
•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.
•The air pollution was characterized by high levels of particulates, sulphur dioxide,
•Schwartz and Neas found that increases in fine particles were significantly
associated with respiratory symptoms and decrements in peak flow measurements:
•There is evidence that reduced HR V is a risk factor for adverse cardiac events,
including angina, myocardial infraction, life- threatening arrhythmias and
congestive heart failures.
•An air pollutant, both indoor and outdoor, appears to play a central role in this
•The other two most commonly generated industrial and urban pollutants are ozone
and oxides of nitrogen.
•Ozone and nitrogen dioxide have been studied extensively in both animals and
•Gases can cause damage at any site from the upper airways to the alveoli.
•Exposure to ozone and nitrogen dioxide:
•Upper-airway response, as demonstrated by simultaneous nasal and
•Levels of ozone that exceed the federal standard are frequent in cities in southern
California and in the north east.
•Large air masses with ozone concentrations that exceed the federal standard have
been observed under stable meteorological condition that can last several days in
•Gold and colleagues examined the effect of ozone levels and particulates in Mexico
City on peak expiratory flow in 40 schoolchildren ages 8-11.
•O3 concentrations may be elevated in outdoor air and they lower indoors.
•The lower indoor concentrations are attributable to the reaction of O3 with various
•Exposure to photochemical oxidants, particularly ozone can cause
bronchoconstruction in both normal and asthmatic people.
•Carbon monoxide (CO)
•Carbon monoxide is emitted family from internal combustion engies used in motor
•The health effects of carbon monoxide have been documented in clicnical
observation of patients with CO intoxication and in expermintal and
epidemiological studies of persons exposed to low level CO.
•Carbon monoxide is an odourless, colorless gas produced by incomplete
combustion of carbonaceous fuels as wood, gasoline and natural gas.
•The pathophysiology of co position can be conceptualised as antioxygen activity,
since CO is an antimetabolite of oxygen.
•Inhaled CO binds strongly to haemoglobin in the pulmonary capillaries, resulting in
the complex called carboxyhemoglobn.
•The formulation of COHb has two considerable effect: it blocks oxygen carriage by
inactivating haemoglobin, and its presence in the blood shifts the dissocation curve
of oxyhemoglobin to the left so that the relase of remaining oxygen to tissues is
•Carbon monoxide also binds with myglobin to form carboxyoglobin, which may
disturb muscle metabolism.
•Chronic, lower-level exposure to CO has also been postulated to accelerate
atheroscletrotic vascular disease by affecting cholesterol uptake in the arterial wall,
though results from animal and in vitro studies are conflicting
•In addition to containing sulphur dioxide, particulates, and photochemical
pollutants, urban air contains a number of known carcinogens including polycyclic
aromatic hydrocarbons, n-nitroso compounds is assocated with increased risk of
•Population living near coke ovens or exposed to asbettosis insulation at home in
public buildings also may be at risk of lung cancer.
•Airborne exposure to the products of waste incineration, such as dioxins and furans
may be on the increase in some communities.
•Indoor Air pollution:
•Indoor air pollution usally refers to homes and non-factory public buildings.
•Pollution comes from heating and cooking combustion, pesticides, tobacco
emission, abrasion of surfaces, evaporation of vapours and gases, radon, and
microbiological matiearl form people and animals.
•High concentration of pollution indoor settings in either the developed or
developing world can be associated with mucous- membrane irritation, discomfort,
illness and even death.
•There is strong indication that indoor air pollution is associated with acute
respiratory infection in infants and children under age five.
•Current regulation of Air pollution:
•Clean air act in 1970, which required the EPA to define air quality standards
allowing a margin of safety” to protect the publics health.