The 20th cent. has seen pollution approach crisis proportions throughout the world. At issue is the capacity of the biosphere to disperse, degrade, and assimilate human wastes (see ecology). The biosphere is a closed ecological system with finite resources and is maintained in equilibrium by grand-scale recycling. Under natural conditions organic and certain inorganic materials in the biosphere are continually recycled by processes including photosynthesis and respiration, nitrogen fixation and denitrification (see nitrogen cycle), evaporation and precipitation, and diffusion by wind and water action. But the introduction of massive quantities of waste matter at any point in the biosystem may "overload" it, disrupting the natural recycling mechanisms.
Public awareness that the environment could not absorb limitless amounts of waste came with the Industrial Revolution. By the latter part of the 19th cent. many industrial areas were experiencing severe air pollution caused by the burning of coal to run mills and machinery. The quantities of fly ash, smoke, carbon and sulfur gases, and other wastes had become too great for local environments—like those of London and Pittsburgh—to disperse rapidly. Similarly, industrial effluents and sewage were polluting river systems. Not until after World War II, however, was pollution generally viewed as more than a nuisance that blackened buildings and sullied streams, i.e., as a pervasive threat to human health.
By the 1960s the threat had become great enough, many believed, to challenge the integrity of the ecosystem and the survival of numerous organisms including humans. Population explosion, industrial expansion, and burgeoning truck and automobile use were producing wastes in such gigantic quantities that natural dispersing and recycling processes could not keep pace. Exacerbating the problem was the appearance of new substances that degraded with extreme slowness or not at all: plastics, synthetic fibers, detergents, synthetic fertilizers, synthetic organic pesticides such as DDT, synthetic industrial chemicals such as the polychlorinated biphenyls (PCBs), and the wastes from their manufacture.
Thus waterways and dumps festered with disease-breeding garbage. Industrial wastes created corrosive smogs and, with municipal wastes, polluted inland and marine waters, including drinking supplies. Automobile emissions choked urban and suburban communities. Pesticides and PCBs poisoned fish and birds. These conditions, persisting into the 1970s as year by year waste output increased, evoked demand in many nations, and on the part of the United Nations, for worldwide pollution abatement.
The National Environmental Policy Act in 1969 and the establishment of the Environmental Protection Agency the following year was a turning point in federal regulatory policy. Since then Congress has also passed the Clean Air Act (1970), the Clean Water Act (1972), the Noise Control Act (1979), and the Comprehensive Environmental Response, Compensation, and Liability Act (1980), more commonly known as the Superfund Act, which created a fund to clean up hazardous waste sites. While the United States and many other industrialized nations have acted to control and reduce pollution, many developing nations, such as China, have experienced increased pollution as they have industrialized.
The potential for environmental disaster has been dramatically underscored by such events as the evacuation of Love Canal (1978), the chemical accident at the Union Carbide plant in Bhopal, the oil spills from the tankers Exxon Valdez in Alaska (1989), Braer off the Shetland Islands (1993), and Prestige off Galicia, Spain (2002), and the nuclear accidents at Three Mile Island (1979) and at Chernobyl in Ukraine (1986).
The cost of substantially reducing industrial pollution is high; how to finance it without undue economic burden remains a question. Some experts hold that since population growth automatically increases waste production, pollution can best be combated by population control. Another view is that worldwide proliferation of industry and technology is the chief culprit, posing the threat of global warming and requiring curtailment if pollution is to be conquered. The early 1990s brought discussion of more effective means to calculate the true costs of pollution in terms of its effects on health, productivity, and quality of life. There is considerable agreement, nonetheless, on the need for revised technology to diminish industrial and automotive emissions, to produce degradable wastes, and to dispose of all wastes in ways less damaging to the environment—for example, by returning sewage to the farm as fertilizer and by recycling glass and metal materials. Finally, improvement is required in techniques for preventing pollution by especially hazardous wastes. The difficulty of finding adequate permanent storage locations has been increased by opposition from residents of potential sites, who are concerned about health hazards. In 1997 more than 1.3 million people in the United States were employed in environmental industries related to pollution control.
See B. Commoner, Science and Survival (1966) and The Closing Circle (1971); M. H. Brown, The Toxic Cloud (1987); C. S. Silver, One Earth, One Future (1988); J. Marte et al., Toxics A to Z (1991); M. Feshbach and A. Friendly, Jr., Ecocide in the USSR (1992).
Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the physical systems or living organisms they are in. Pollution can take the form of chemical substances, or energy, such as noise, heat, or light energy. Pollutants, the elements of pollution, can be foreign substances or energies, or naturally occurring; when naturally occurring, they are considered contaminants when they exceed natural levels. Pollution is often classed as point source or nonpoint source pollution.
Sometimes the term pollution is extended to include any substance when it occurs at such unnaturally high concentration within a system that it endangers the stability of that system. For example, water is innocuous and essential for life, and yet at very high concentration, it could be considered a pollutant: if a person were to drink an excessive quantity of water, the physical system could be so overburdened that breakdown and even death could result. Another example is the potential of excessive noise to induce imbalance in a person's mental state, resulting in malfunction and psychosis;
Since travel and widespread information were less common, there did not exist a more general context than that of local consequences in which to consider pollution. Foul air would have been considered a nuissance and wood, or eventually, coal burning produced smoke, which in sufficient concentrations could be a health hazard in proximity to living quarters. Septic contamination or poisoning of a clean drinking water source was very easily fatal to those who depended on it, especially if such a resource was rare. Superstitions predominated and the extent of such concerns would probably have been little more than a sense of moderation and an avoidance of obvious extremes.
The earliest known writings concerned with pollution were Arabic medical treatises written between the 9th and 13th centuries, by physicians such as al-Kindi (Alkindus), Qusta ibn Luqa (Costa ben Luca), Muhammad ibn Zakarīya Rāzi (Rhazes), Ibn Al-Jazzar, al-Tamimi, al-Masihi, Ibn Sina (Avicenna), Ali ibn Ridwan, Ibn Jumay, Isaac Israeli ben Solomon, Abd-el-latif, Ibn al-Quff, and Ibn al-Nafis. Their works covered a number of subjects related to pollution such as air contamination, water contamination, soil contamination, solid waste mishandling, and environmental assessments of certain localities.
King Edward I of England banned the burning of sea-coal by proclamation in London in 1272, after its smoke had become a problem. But the fuel was so common in England that this earliest of names for it was acquired because it could be carted away from some shores by the wheelbarrow. Air pollution would continue to be a problem there, especially later during the industrial revolution, and extending into the recent past with the Great Smog of 1952. This same city also recorded one of the earlier extreme cases of water quality problems with the Great Stink on the Thames of 1858, which led to construction of the London sewerage system soon afterward.
It was the industrial revolution that gave birth to environmental pollution as we know it today. The emergence of great factories and consumption of immense quantities of coal and other fossil fuels gave rise to unprecedented air pollution and the large volume of industrial chemical discharges added to the growing load of untreated human waste. Chicago and Cincinnati were the first two American cities to enact laws ensuring cleaner air in 1881. Other cities followed around the country until early in the 20th century, when the short lived Office of Air Pollution was created under the Department of the Interior. Extreme smog events were experienced by the cities of Los Angeles and Donora, Pennsylvania in the late 1940s, serving as another public reminder.
Pollution began to draw major public attention in the United States between the mid-1950s and early 1970s, when Congress passed the Noise Control Act, the Clean Air Act, the Clean Water Act and the National Environmental Policy Act.
Bad bouts of local pollution helped increase consciousness. PCB dumping in the Hudson River resulted in a ban by the EPA on consumption of its fish in 1974. Long-term dioxin contamination at Love Canal starting in 1947 became a national news story in 1978 and led to the Superfund legislation of 1980. Legal proceedings in the 1990s helped bring to light Chromium-6 releases in California--the champions of whose victims became famous. The pollution of industrial land gave rise to the name brownfield, a term now common in city planning. DDT was banned in most of the developed world after the publication of Rachel Carson's Silent Spring.
The development of nuclear science introduced radioactive contamination, which can remain lethally radioactive for hundreds of thousands of years. Lake Karachay, named by the Worldwatch Institute as the "most polluted spot" on earth, served as a disposal site for the Soviet Union thoroughout the 1950s and 1960s. Second place may go to the to the area of Chelyabinsk U.S.S.R. (see reference below) as the "Most polluted place on the planet".
Nuclear weapons continued to be tested in the Cold War, sometimes near inhabited areas, especially in the earlier stages of their development. The toll on the worst-affected populations and the growth since then in understanding about the critical threat to human health posed by radioactivity has also been a prohibitive complication associated with nuclear power. Though extreme care is practiced in that industry, the potential for disaster suggested by incidents such as those at Three Mile Island and Chernobyl pose a lingering specter of public mistrust. One legacy of nuclear testing before most forms were banned has been significantly raised levels of background radiation.
International catastrophes such as the wreck of the Amoco Cadiz oil tanker off the coast of Brittany in 1978 and the Bhopal disaster in 1984 have demonstrated the universality of such events and the scale on which efforts to address them needed to engage. The borderless nature of atmosphere and oceans inevitably resulted in the implication of pollution on a planetary level with the issue of global warming. Most recently the term persistent organic pollutant (POP) has come to describe a group of chemicals such as PBDEs and PFCs among others. Though their effects remain somewhat less well understood owing to a lack of experimental data, they have been detected in various ecological habitats far removed from industrial activity such as the Arctic, demonstrating diffusion and bioaccumulation after only a relatively brief period of widespread use.
Growing evidence of local and global pollution and an increasingly informed public over time have given rise to environmentalism and the environmental movement, which generally seek to limit human impact on the environment.
The major forms of pollution are listed below along with the particular pollutants relevant to each of them:
The Blacksmith Institute issues annually a list of the world's worst polluted places. In the 2007 issues the ten top nominees are located in Azerbaijan, China, India, Peru, Russia, Ukraine and Zambia.
Some of the more common soil contaminants are chlorinated hydrocarbons (CFH), heavy metals (such as chromium, cadmium--found in rechargeable batteries, and lead--found in lead paint, aviation fuel and still in some countries, gasoline), MTBE, zinc, arsenic and benzene. In 2001 a series of press reports culminating in a book called Fateful Harvest unveiled a widespread practice of recycling industrial byproducts into fertilizer, resulting in the contamination of the soil with various metals. Ordinary municipal landfills are the source of many chemical substances entering the soil environment (and often groundwater), emanating from the wide variety of refuse accepted, especially substances illegally discarded there, or from pre-1970 landfills that may have been subject to little control in the U.S. or EU. There have also been some unusual releases of polychlorinated dibenzodioxins, commonly called dioxins for simplicity, such as TCDD.
Pollution can also be the consequence of a natural disaster. For example, hurricanes often involve water contamination from sewage, and petrochemical spills from ruptured boats or automobiles. Larger scale and environmental damage is not uncommon when coastal oil rigs or refineries are involved. Some sources of pollution, such as nuclear power plants or oil tankers, can produce widespread and potentially hazardous releases when accidents occur.
For mankind, the factor of technology is a distinguishing and critical consideration, both as an enabler and an additional source of byproducts. Short of survival, human concerns include the range from quality of life to health hazards. Since science holds experimental demonstration to be definitive, modern treatment of toxicity or environmental harm involves defining a level at which an effect is observable. Common examples of fields where practical measurement is crucial include automobile emissions control, industrial exposure (eg Occupational Safety and Health Administration (OSHA) PELs), toxicology (eg LD50), and medicine (eg medication and radiation doses).
"The solution to pollution is dilution", is a dictum which summarizes a traditional approach to pollution management whereby sufficiently diluted pollution is not harmful. It is well-suited to some other modern, locally-scoped applications such as laboratory safety procedure and hazardous material release emergency management. But it assumes that the dilutant is in virtually unlimited supply for the application or that resulting dilutions are acceptable in all cases.
Such simple treatment for environmental pollution on a wider scale might have had greater merit in earlier centuries when physical survival was often the highest imperative, human population and densities were lower, technologies were simpler and their byproducts more benign. But these are often no longer the case. Furthermore, advances have enabled measurement of concentrations not possible before. The use of statistical methods in evaluating outcomes has given currency to the principle of probable harm in cases where assessment is warranted but resorting to deterministic models is impractical or unfeasible. In addition, consideration of the environment beyond direct impact on human beings has gained prominence.
Yet in the absence of a superseding principle, this older approach predominates practices throughout the world. It is the basis by which to gauge concentrations of effluent for legal release, exceeding which penalties are assessed or restrictions applied. The regressive cases are those where a controlled level of release is too high or, if enforceable, is neglected. Migration from pollution dilution to elimination in many cases is confronted by challenging economical and technological barriers.
Carbon dioxide, while vital for photosynthesis, is sometimes referred to as pollution, because raised levels of the gas in the atmosphere are affecting the Earth's climate. Disruption of the environment can also highlight the connection between areas of pollution that would normally be classified separately, such as those of water and air. Recent studies have investigated the potential for long-term rising levels of atmospheric carbon dioxide to cause slight but critical increases in the acidity of ocean waters, and the possible effects of this on marine ecosystems.