Human activities inevitably and increasingly introduce material and energy into the environment; when that material or energy endangers or is liable to endanger man's health, his well-being or his resources, indirectly or directly, it is called a pollutant. A substance may be considered a pollutant simply because it is in the wrong place, at the wrong time, and in the wrong quantity.
Pollutants can affect man with direct effects such as: acute effects from exposure to a toxic pollutant reaching man through air, water or food; long-term effects due to prolonged exposure to a pollutant at levels lower than those giving rise to overt toxic effects; synergistic interaction between pollutants or between a pollutant and malnutrition or disease; genetic effects that are manifested in future generations. Indirect effects on man may result from reduction of the food supply or deterioration of the environment. Such effects include: damage to plants and animals; disruption of ecological cycles such that a previously harmless species becomes a pest; damage to the human habitat (air pollutants that destroy forests and corrode buildings); water pollutants that destroy the recreational value of inland waters; alteration of the global climate (this is considered to be a future threat).
The emissions of sulphur and nitrogen oxides and concentrations of atmospheric ozone have increased, agricultural and industrial wastes have been accumulating, lake acidification has taken place, forests and water quality have been declining. The volume of garbage and waste is constantly increasing, due in particular to increases in population, changes in living habits, increases in packaging material and increases in consumption. The capacity of waste and garbage disposal installations has long been left far behind. Water resources are to an increasing extent being polluted by the constantly growing volume of waste water from households and industry. The river Vistula, which flows through Warsaw, annually disgorges into the Baltic Sea 5,000 tonnes of phosphorus, 90,000 tonnes of nitrogen, 130 tonnes of oil, three tonnes of phenol and lead, as well as unknown quantities of cadmium, mercury and zinc.
Technical progress and mechanization has in recent decades led to a rapid increase in noise. About every fifth worker in Germany is subjected to a noise level of 90 dB or over. The atmosphere is being polluted by dust, smoke and exhaust gases from industry, motor vehicles and domestic heating. In the former Soviet Union fifty million people live in areas where the air pollution levels are 10 times the minimum health standard. In the Urals the city of Nizhny Tagil, for example, industrial enterprises emit nearly 700,000 tons of poisonous substances into the air every year.
Three factors determine the magnitude and nature of the pollution problem, whether at the local or global level: the size of the human population; the rate of production and consumption; and the level and use of technology. But while the total stress resulting from these factors is increasing, the capacity of the environment to deal with their side effects is decreasing. It is for this reason that pollutants must be controlled. Pollution of one sort or another occurs throughout human societies and the effects of any given pollutant are frequently the same wherever they are felt. The present situation results principally from the unbridled application of technology in industrialized countries. Developing countries, however, are already encountering the same problems and are increasingly having to deal with the same pollutants. During this century both population growth and rapid industrialization have combined to poison the atmosphere; contaminate lakes, rivers and even oceans; erode the soil; and destroy many forms of life in the developed countries. Pollution cannot be contained within national boundaries. Wind and rain, ocean currents, migrating birds and fish carry pesticides, inorganic nitrogen fertilizer, oil, and atomic wastes to the far reaches of our planet.