Chapter 4
Toxic Action of Pollutants
4.1 INTRODUCTION
When present at a sufficiently high concentration, a pollutant can elicit adverse
effects on the living processes of an organism. To exert damage to an exposed
organism, a pollutant must first enter the host and reach its target site. A
complex pathway exists between the time of initial toxicant exposure and the
manifestation of damage by the organism. This chapter discusses general ways
in which environmental pollutants exert their actions on plants, animals, and
humans.
4.2 PLANTS
4.2.1 SOURCES OF POLLUTION
For the most part, environmental pollution is an anthropogenic (human-made)
problem. As mentioned previously, the most important source of atmospheric
pollution in the U.S. is motor vehicles. Other major sources include industrial
activities, power generation, space heating, and refuse burning. The composition of pollutants from different sources differs markedly, with industry
emitting the most diverse range of pollutants. While carbon monoxide (CO) is
the major component of pollution by motor vehicles, sulfur oxides (SO x ) are
primary pollutants of industry, power generation, and space heating. In some
large cities, such as Los Angeles, accumulation of ozone (O 3 ), peroxyacyl
nitrate (PAN), and other photochemical oxidants constitute the major
atmospheric pollution problem.
4.2.2 POLLUTANT UPTAKE
Terrestrial plants may be exposed to environmental pollutants in two main
ways. One is exposure of forage to air pollutants, another is uptake of toxicants
by roots growing in contaminated soils. Vegetation growing near industrial
facilities, such as smelters, aluminum refineries, and coal-burning power plants,
may absorb airborne pollutants through the leaves and become injured. The
pollutants may be in gaseous form, such as sulfur dioxide (SO 2 ), nitrogen
dioxide (NO 2 ), and hydrofluoric acid (HF), or in particulate form, such as the
oxides or salts of metals contained in fly ash (Figure 4.1).
[16:54 26/8/04 P:/CRC PRESS/4365 MING-HO.751 (1670)/4365-004.3d]
Ref: 4365 MING-HO YU Chap-004 Page: 45 45-64
45
Toxic Action of Pollutants
4.1 INTRODUCTION
When present at a sufficiently high concentration, a pollutant can elicit adverse
effects on the living processes of an organism. To exert damage to an exposed
organism, a pollutant must first enter the host and reach its target site. A
complex pathway exists between the time of initial toxicant exposure and the
manifestation of damage by the organism. This chapter discusses general ways
in which environmental pollutants exert their actions on plants, animals, and
humans.
4.2 PLANTS
4.2.1 SOURCES OF POLLUTION
For the most part, environmental pollution is an anthropogenic (human-made)
problem. As mentioned previously, the most important source of atmospheric
pollution in the U.S. is motor vehicles. Other major sources include industrial
activities, power generation, space heating, and refuse burning. The composition of pollutants from different sources differs markedly, with industry
emitting the most diverse range of pollutants. While carbon monoxide (CO) is
the major component of pollution by motor vehicles, sulfur oxides (SO x ) are
primary pollutants of industry, power generation, and space heating. In some
large cities, such as Los Angeles, accumulation of ozone (O 3 ), peroxyacyl
nitrate (PAN), and other photochemical oxidants constitute the major
atmospheric pollution problem.
4.2.2 POLLUTANT UPTAKE
Terrestrial plants may be exposed to environmental pollutants in two main
ways. One is exposure of forage to air pollutants, another is uptake of toxicants
by roots growing in contaminated soils. Vegetation growing near industrial
facilities, such as smelters, aluminum refineries, and coal-burning power plants,
may absorb airborne pollutants through the leaves and become injured. The
pollutants may be in gaseous form, such as sulfur dioxide (SO 2 ), nitrogen
dioxide (NO 2 ), and hydrofluoric acid (HF), or in particulate form, such as the
oxides or salts of metals contained in fly ash (Figure 4.1).
[16:54 26/8/04 P:/CRC PRESS/4365 MING-HO.751 (1670)/4365-004.3d]
Ref: 4365 MING-HO YU Chap-004 Page: 45 45-64
45