Page 140 - Fundamentals of Air Pollution

8

Effects on Vegetation

and Animals

I. INJURY VERSUS DAMAGE

The U.S. Department of Agriculture makes a distinction between air
pollution damage and air pollution injury. Injury is considered to be any
observable alteration in the plant when exposed to air pollution. Damage
is defined as an economic or aesthetic loss due to interference with the
intended use of a plant. This distinction indicates that injury by air pollution
does not necessarily result in damage because any given injury may not
prevent the pknt from being used as intended, e.g., marketed.
Vegetation reacts with air pollution over a wide range of pollutant concen-
trations and environmental conditions. Many factors influence the out-
come, including plant species, age, nutrient balance, soil conditions, tem-
perature, humidity, and sunlight (1). Any type of observable effect due to
exposure can be termed plant injury. A schematic diagram of the potential
levels of injury with increasing exposure to air pollution is presented in
Fig. 8-1. At low levels of exposure for a given species and pollutant, no
significant effects may be observed. However, as the exposure level in-
creases, a series of potential injuries may occur, including biochemical
alterations, physiological response, visible symptoms, and eventual death.

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