Encyclopedia of Environmental Science and Engineering, Volume I and II

AIR POLLUTANT EFFECTS 31

• The true dose is not always the simple product of
  the measured concentration and the duration of
  exposure, because of the complexity that can exist
  between exposure and response—the biologically
  active dose can be quite different.


• Individuals whose exposure and symptoms are
  being correlated very often spend the major part
  of their time indoors or traveling, where they may
  be subjected to different pollutants and different
  concentrations.


• Different pollutants will disperse and interact dif-
  ferently with the surroundings, introducing a loca-
  tion factor caused by the relationship of exposed
  individuals to the measurement site—for example,
  sulfur-dioxide concentrations will not vary as much
  as ozone concentrations, because the higher reactiv-
  ity of ozone with structural materials and other com-
  pounds will affect its concentration at the receptor.

INFORMING THE PUBLIC

The aerometric networks established by cities and states have

been gathering and analyzing data about air pollutants for

many years. During these years, attempts were made to inform

the public about the quality of its air environment, which can

change from day to day and even hour to hour, and about the

possible impact that local concentrations are having upon their

health. The relationship between raw air-pollution data and its

health-impact significance is complex; therefore, the attempt

is made to present the information in a simplified manner that

is understandable to the public. Toward this goal, the EPA

has developed an Air Quality Index for daily reporting about

what has been found in the air together with some indication

of its potential effects on health. Important considerations are

the variability in the susceptibility of the exposed population,

meaning that what may have little or no effect on one group

can be a serious concern for others, and that personal patterns

of behavior of the exposed can affect the amounts of pollut-

ants that they breathe. Individuals whose lifestyle requires

them to move throughout an area (indoors, outdoors, and in

vehicles) will receive very different exposures from those who

stay at home, depending upon the pervasiveness of the pol-

lutants. In particular, exposures to carbon monoxide will be

much greater for those whose daily activities requires them

to be in the vicinity of motor vehicles than for those who stay

indoors or travel on railroads and subways.

The Air Quality Index designed by EPA reports the daily

levels of ozone, particulate matter, carbon monoxide, sulfur

dioxide, and nitrogen dioxide on a scale of 0 to 500. The range

corresponds to six different categories of health concern that

are also characterized by colors Table 1.

RISK REDUCTION

Air pollution affects people primarily through the respiratory

system; therefore, the logical way to start minimizing risk

is by avoidance of activities that increase one’s inhalation

of polluted air. When air-pollution levels are high, activities

that cause increases in breathing rate should be minimized

as much as possible, depending upon the importance and

necessity of the activity and the seriousness of the pollution

episode. As an example, jogging in the vicinity of vehicles

where local ventilation is poor, as in the canyon streets of

cities, should be avoided because of the high concentrations

of carbon monoxide and other pollutants usually found in

those areas. This is of special importance to people with

asthma or heart diseases such as angina.

Children who spend their time playing outdoors should

be restrained from overexerting themselves when ozone

levels are high during warm-weather episodes, as should

individuals with asthma or other respiratory diseases or

those who are hypersensitive to ozone.

EFFECTS OF EXPOSURE TO CRITERIA

POLLUTANTS

Respiratory-System Overview

An elementary understanding of studies describing the

adverse health effects caused by the inhalation of gaseous

or particulate air pollutants requires at least an elementary

familiarity with respiratory-tract anatomy and dynamics. The

respiratory tract can be considered to include three sections:

• Nasopharynx—nose and mouth down to epiglottis
  and larynx

TABLE 1

Air Quality Index Health Concerns

0–50 Good (green) Little or no risk

51–100 Moderate (yellow) Concern for unusually sensitive people

101–150 Unhealthy for sensitive groups (orange) The general public is unaffected, but people with health problems such as lung and heart

disease may be affected

151–200 Unhealthy (red) Everyone is affected to some degree, especially those in sensitive groups

201–300 Very unhealthy (purple) A health alert exists; everyone should take precautions, especially those in sensitive groups

301–500 Hazardous (maroon) Everyone is affected and everyone should take precautions

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