3.4 AGRICULTURAL DAMAGE
Agricultural damage constitutes the major damage to vegetation caused by air
pollution (discussed in more detail in Chapter 8). A widely known example is
the destruction of forests by acid rain. Ample evidence exists attesting to this
phenomenon in the U.S., Canada, and in some European countries. Acid rain
causes changes in plant growth that are manifested by stunted growth, lack of
vigor, reduced productivity, and early senescence of leaves. Air pollutants such
as NO 2 , O 3 , PAN and fluoride can also cause serious injuries to plants. Many
fruit trees and vegetables are particularly sensitive to these pollutants.
Assessment of the immediate and long-term economic effects of air
pollution on agriculture is difficult because of the many variables involved.
However, available information indicates that the cost due to decreased crop
yields is staggering. For instance, the 1986 estimated losses to producers caused
by O 3 alone were $1 billion to $5 billion.
1 The estimated cost of damage caused
by acid rain to 32 major crops in the U.S. was $50 billion.
Injuries to plants by air pollution are often manifested by such symptoms as
chlorosis and necrosis. Chlorosis is the fading of natural green color, or
yellowing, of plant leaves, and is due to the destruction of chlorophyll or
interference with chlorophyll biosynthesis. Necrosis refers to localized or
general death of plant tissue and is often characterized by brownish or black
discoloration.
3.5 INTOXICATION OF ANIMALS
Many published reports reveal adverse effects in animals that have been
exposed to gaseous and particulate forms of air pollutants emitted from
industrial facilities. Examples of these facilities include phosphate fertilizer
manufacturing plants, aluminum manufacturing plants, iron and other types of
smelters, and coal-burning power plants. As is widely known, a large number
of air pollutants are emitted from these industrial sources. Animals residing in
areas adjacent to these industrial sources are exposed to the pollutants emitted
from these sources, resulting in injuries. This is explored further in subsequent
chapters.
Similarly, reports of the injuries of fish and wildlife caused by water
pollution also abound. Many diseased sea mammals have been washed ashore
in different parts of the world in recent years, apparently due to damaged
immune systems subsequent to exposure to waterborne toxicants. In the U.S.,
it is estimated that more than one million waterfowls are killed every year
following the ingestion of spent lead pellets left after hunting.
A new type of environmental disease has appeared recently and attracted
the attention of many scientists. Beginning in about 1991, biologists noted
dramatic declines in amphibian populations and increases in deformities in
frogs, with no apparent causes, in remote, high-altitude areas of western U.S.,
Puerto Rico, Costa Rica, Panama, Colombia, and Australia. The declines
34
Environmental Toxicology
[16:54 26/8/04 P:/CRC PRESS/4365 MING-HO.751 (1670)/4365-003.3d]
Ref: 4365 MING-HO YU Chap-003 Page: 34 31-44
Agricultural damage constitutes the major damage to vegetation caused by air
pollution (discussed in more detail in Chapter 8). A widely known example is
the destruction of forests by acid rain. Ample evidence exists attesting to this
phenomenon in the U.S., Canada, and in some European countries. Acid rain
causes changes in plant growth that are manifested by stunted growth, lack of
vigor, reduced productivity, and early senescence of leaves. Air pollutants such
as NO 2 , O 3 , PAN and fluoride can also cause serious injuries to plants. Many
fruit trees and vegetables are particularly sensitive to these pollutants.
Assessment of the immediate and long-term economic effects of air
pollution on agriculture is difficult because of the many variables involved.
However, available information indicates that the cost due to decreased crop
yields is staggering. For instance, the 1986 estimated losses to producers caused
by O 3 alone were $1 billion to $5 billion.
1 The estimated cost of damage caused
by acid rain to 32 major crops in the U.S. was $50 billion.
Injuries to plants by air pollution are often manifested by such symptoms as
chlorosis and necrosis. Chlorosis is the fading of natural green color, or
yellowing, of plant leaves, and is due to the destruction of chlorophyll or
interference with chlorophyll biosynthesis. Necrosis refers to localized or
general death of plant tissue and is often characterized by brownish or black
discoloration.
3.5 INTOXICATION OF ANIMALS
Many published reports reveal adverse effects in animals that have been
exposed to gaseous and particulate forms of air pollutants emitted from
industrial facilities. Examples of these facilities include phosphate fertilizer
manufacturing plants, aluminum manufacturing plants, iron and other types of
smelters, and coal-burning power plants. As is widely known, a large number
of air pollutants are emitted from these industrial sources. Animals residing in
areas adjacent to these industrial sources are exposed to the pollutants emitted
from these sources, resulting in injuries. This is explored further in subsequent
chapters.
Similarly, reports of the injuries of fish and wildlife caused by water
pollution also abound. Many diseased sea mammals have been washed ashore
in different parts of the world in recent years, apparently due to damaged
immune systems subsequent to exposure to waterborne toxicants. In the U.S.,
it is estimated that more than one million waterfowls are killed every year
following the ingestion of spent lead pellets left after hunting.
A new type of environmental disease has appeared recently and attracted
the attention of many scientists. Beginning in about 1991, biologists noted
dramatic declines in amphibian populations and increases in deformities in
frogs, with no apparent causes, in remote, high-altitude areas of western U.S.,
Puerto Rico, Costa Rica, Panama, Colombia, and Australia. The declines
34
Environmental Toxicology
[16:54 26/8/04 P:/CRC PRESS/4365 MING-HO.751 (1670)/4365-003.3d]
Ref: 4365 MING-HO YU Chap-003 Page: 34 31-44