Environmental Engineering Reference
In-Depth Information
If the NAAQS are exceeded within an Air Quality Control Region (AQCR), the state in which
the region is located must develop a plan, called the State Implementation Plan (SIP), which
lays out a strategy of how the region will attain compliance with the NAAQS in a reasonable
time period. The SIP may include emission curtailments from emitting sources, traffic regulations,
tightened inspection schedules and procedures, and other measures. However, research in the past
few decades brought out clearly that air pollutants do not respect political and natural geographic
boundaries. They travel over control regions, state lines, river valleys, mountains, and even over
oceans. Thus, no state can control its air pollution solely by its own means. A regional, national,
and even international approach is necessary to control air pollution over a region, over a continent,
and, for some air pollutants, over the globe. In part, this is the reason that in the United States,
emissions of most air pollutants are regulated on the federal rather than on the state level.
9.2.3
Health and Environmental Effects of Fossil-Fuel-Related
Air Pollutants
Air pollutants, when they exceed certain concentrations, can cause acute or chronic diseases in
humans, animals, and plants. They can impair visibility, cause climatic changes, and damage
materials and structures. Traditionally, the major concern was the impact on human health. That
is why in the United States the standards that are supposed to protect humans are called primary
standards, and those that protect “welfare” are called secondary standards.
Table 9.4 lists some of the health and environmental effects of air pollutants that are related
to fossil fuel use. The listed air pollutants are classified as criteria pollutants by EPA: SO
2
,NO
x
,
O
3
, CO, and particulate matter (PM). For these pollutants, EPA promulgated National Ambient Air
Quality Standards (NAAQS; see Section 9.2.2). The order of listing does not follow any particular
ranking: Some individuals or plants are more sensitive to one kind of pollutant than to another. The
pollutants can cause respiratory diseases, and some are suspected toxigens, mutagens, teratogens,
carcinogens, and possible animal- and plant-disease-causing agents.
2
The definition of the deleterious effects of PM is complicated and contentious. The ambient
standards are given in units of mass per volume (
g/m
3
). Surely, the effects on health and biota are
not dependent as much on mass concentrations of the inhaled particles, but on their quality—that
is, their composition. While ordinary soil and road dust may not cause significant health effects,
particles that contain acidic species, heavy metals, soot, and polycyclic aromatic hydrocarbons
(PAH) may cause respiratory, neurological, and cancerous diseases. It is unlikely that agricultural
workers who inhale a great amount of soil dust suffer as much respiratory and neurological diseases
as urban dwellers who inhale much smaller amounts but potentially more lethal photochemical
smog particles. One reason that EPA and other environmental protection agencies are using mass
concentrations as a standard for PM, rather than chemical composition, is that the determination of
chemical composition requires complicated and expensive analytical instrumentation. Furthermore,
EPA maintains that there is evidence from epidemiological studies that excessive mortality and
morbidity is correlated with mass and size of the particles, regardless of chemical composition.
µ
2
Toxigen: a chemical agent that may cause an increase of mortality or of serious illness, or that may pose a
present or potential hazard to human health. Mutagen: any agent, including radioactive elements, that may
cause biological mutation—that is, alteration of the genes or chromosomes. Teratogen: an agent that may
cause defects or diseases of the embryo. Carcinogen: an agent that may cause cancer.
