Encyclopedia of Environmental Science and Engineering, Volume I and II

82 AIR POLLUTION SOURCES

Part 1. Pollutant Emissions (continued)

Pollutant types Sources and abundance Abatement and control

of an individual exposed to CO can be greatly

reduced. CO is highly toxic at concentrations

greater than 1000 ppm. Death results from

asphyxiation since body tissues, especially the

brain, are deprived of a sufficient supply of

oxygen. Because it is colorless, odorless and

tasteless, individuals exposed to toxic

concentrations are unaware of its presence.

However, the concentrations of CO commonly

encountered in urban environments are usually

only a fraction of those levels which cause

asphyxiation. Low-level CO exposure affects

the central nervous system with typical

behavioral changes including decreased time

interval recognition, impairment of brightness,

delayed reaction time to visual stimuli,

decrease in drying performance and, at

concentrations of 100 ppm, dizziness,

headache, fatigue and loss of coordinatation.

Cigarette smoke contains especially high levels

of CO (15,000 to 55,000 ppm) which bind to

approximately 3 to 10% of a smoker’s

hemoglobin. The effects of these high levels

would be extremely harmful if it were not for

the intermittent nature of the exposure. The

inhalation of air between drags greatly reduces

the toxic dose. The major effect of CO in

cigarette smoke appears to be to increase the

risk of angina pectoris patients to myocardial

infarcation and sudden death. However,

cigarette smoke contains many harmful

substances and it is difficult to specifically

assess the harmful effects of CO and its exact

role in cardiovascular diseases.

b. Carbon Dioxide: Carbon dioxide (CO 2 is the most commonly

emitted air contaminant. It is a product of the

complete combustion of carbon in the

presence of O 2 as shown in reactions (1) and

(2) previously.

CO 2 is produced naturally through the

decomposition, weathering and combustion of

organic matter. Human and animal respiration

also contribute CO 2 to the atmosphere. The

combustion of coal, oil and natural gas in both

stationary and mobile sources is responsible

for 90% of anthropogenic CO 2 emissions

throughout the world. Solid waste disposal

and agricultural burning account for the

remaining 10%. Coke ovens and smelters emit

significant amounts of CO 2 on a localized

basis.

The oceans absorb approximately

50% of anthropogenic CO 2

emissions since CO 2 is highly

soluble in water. Green plants also

consume large amounts of CO 2 for

use in photosynthesis. The use of

alternate sources of energy such as

nuclear, solar or chemically derived

energy is the preferred method to

control emissions of CO 2.

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