Environmental pollution can be defined as the direct or indirect impairment of the environment’s suitability for supporting life by harmful concentrations of materials, whether or not the materials are toxic. Thus, a very-high concentration of a nutrient might be polluting, whereas a deadly poison in great dilution is not.
Earlier in this century, wastes could be discharged into the environment with relative impurity. Two factors have changed this. One is the pollution explosion; more people mean more pollution. The other is the rapid advance of technology and affluence that has occurred in the industrialized nations and which the increased the production of toxic pollutants.
In the course of evolution, the wastes produced by one kind of organism eventually became the life-sustaining nutrients of various other organisms.
Modem human activity, however, has altered this relationship. As world populations have increasingly become concentrated in cities, the natural wastes they produce have contributed significantly to environmental pollution. Yet natural wastes are not the most harmful pollutants being generated.
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Unlike biological wastes, the wastes the result from mining, processing of raw materials, and manufacturing are often highly toxic.
Even when they are biodegradable, that is, can be degraded by natural decomposers in the soil, rivers, lakes, and oceans, some wastes are released into the environment in concentrations and volumes that overwhelm the capacity of the decomposers to degrade them, thereby threatening the existence of many aquatic organisms.
Liquid wastes that are both nonbiodegradable and toxic to one or more forms of life pose more persistent problems. If released into waterways, they kill or prevent the reproduction of much aquatic life and render the water unfit as a source of food organisms and for drinking and recreation. If stored on land, they may contaminate groundwater and thus poison springs, wells, and spring-fed lakes.
Some specific examples of environmental pollution, some of their known ecological effects, and a few approaches to solving the problems they create are briefly examined in the following sections.