Encyclopedia of Environmental Science and Engineering, Volume I and II

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AIR POLLUTANT EFFECTS

AIR POLLUTANTS

Air pollutants fall into two main categories: (1) those that

are pervasive throughout areas because they are the products

of daily-life activities such as transportation, power genera-

tion, space and water heating, and waste incineration, and

(2) those generated by activities such as chemical, manufac-

turing, and agricultural processing whose pollutant byprod-

ucts tend to be localized in nearby areas or are spread long

distances by tall stacks and prevailing winds.

Air pollutants are also categorized by their emission

characteristics: (1) point sources, such as power plants,

incinerators, and large processing plants; (2) area sources,

such as space and water heating in buildings; and (3) mobile

sources, mainly cars and trucks, but also lawn mowers and

blowers and airplanes.

The United States has established National Ambient Air

Quality Standards (NAAQS) for seven pollutants that are

pervasive and are threats to public health and welfare. The

Clean Air Act, which initiated this program, was passed in

1963 and last amended in 1990. The primary standards are

intended to protect health, and the secondary standards pro-

tect public-welfare interests such as visibility and danger to

animals, crops, and buildings.

The standards reflect, for the most part but not always,

a conservative approach in favor of the protection of health.

It is notable that the public, who in the final analysis must

pay the cost, appears to be firmly committed to enforcement

of the standards without overwhelming concern for costs.

The act requires the states to determine the status of their air

quality and to find and introduce the controls that will enable

them to meet these standards. Their proposal describing how

and when the standards will be met is submitted to the EPA

(U.S. Environmental Protection Agency) as an implementa-

tion plan for approval. Meeting target dates for air-quality

standards has been problematic because the complex system

that has to be managed includes important socioeconomic and

political factors. For example, the close connection between

air quality and daily activities such as transportation, waste

disposal, and the heating of homes and workplaces requires

education of the population to obtain their support for alterna-

tive and perhaps costly lifestyle choices in the vehicles they

purchase, the packaging of articles they choose, and the type

and cost of the fuels they use—choices they may be reluc-

tant to make, even if they will improve the quality of their

air environment. Choices benefiting air quality that carry

disadvantages for important sectors of the economy are usu-

ally skillfully discouraged by some of those sectors.

CONTROL OF CRITERIA POLLUTANTS

Control of the criteria pollutants requires a measurement

program to determine the daily and short-term patterns of

the ambient concentrations, identification of the emitting

sources, and design and implementation of strategies for

their control. A detailed inventory of the sources causing

the pollution is prepared. The effectiveness of control tech-

nology and potential regulatory strategies are evaluated and

their availability determined with consideration given to the

economic and political restraints on their implementation.

In other words, the total system to be managed and its inter-

actions have to be detailed and understood in order to evalu-

ate the potential for successful control of the air pollution

in an area.

The amount of exposure to the pollutants from inde-

pendent or grouped sources depends upon the intensity of

the activities producing the emissions, the effectiveness of

the controls, and the quality of the surveillance instituted to

ensure the continued proper use and maintenance of the con-

trols. A factor that can be overwhelming is the pattern of the

local meteorology and its effectiveness in dispersing emit-

ted pollutants. The effects of dispersions from one area upon

downwind areas should also be considered.

Detailed analysis of data accumulated over many years

using unchanging analytical methods has shown that very

significant changes in an area’s air pollution can take place

from year to year without significant changes in controls, pri-

marily as the result of changes in the local weather patterns.

The combination of 10 years of data at three sampling sites in

New York City showed that its sulfur-dioxide pollution prob-

lems was clearly related to the sulfur content of the fuel that

was burned in the city. The data for a 10-year period were

combined on a week-by-week basis, with the result that the

shape of the 10-year curve for ambient sulfur-dioxide con-

centrations and the long-term temperature curve for the city

could be superimposed with significant success. Therefore,

the sometimes great variations found between years when

little change occurred in controls were caused by variations

in the local atmosphere, demonstrating that the success or

failure of control strategies cannot be evaluated with security

over short intervals of time.

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