Heat, light, electricity, water and sound, besides a number of things are provided by nature. If the five agents of nature are under control they are rather beneficial to an individual, a society or a nation. If they are in excess and go beyond the control of man or are misused by man they pollute the environment and affect the personal and social health.
Excess of heat (measured in units of temperature) may decompose anything. To take a simple example the burning of coal in mills and factories the chimnies belch carbon dioxide, carbon monoxide and a number of other gases that pollute the atmosphere. Even the un-burnt gas released in a heating process pollutes the environment.
A combination of heat and light that emnates from the sun creates radio activity if the ozone layer grows thin. Electricity generated in the clouds may fall in the shape of lightening burning forests creating pollution. Pollution through dirty water is a common aspect.
That sound (or noise) too pollutes the environment may look funny to many. But it does. It may be some times imperceptible but no less harmful. Noise is directly related to man both in creation and experience. City roads are as much pestered with noise from automobiles, bands, mikes and the down towns with quarrelling men and women and the elite areas with strange associations like the share market that is worst even than the vegetable market as the areas on the banks of rivers with polluted water.
The worse preys of noise pollution are the big cities like New York, London, and Shanghai that have perfect air connection with other cities. A flight a minute disturbs the whole city. Equally infested by noise are the areas by the side of a busy railway track.
That noise too is a serious pollutant is a recent research. It is based on how sound (or noise) affects human ear. It may affect even animals. Before the advent of automobiles horse carriages carried men and material. The driver won't hit the horse. He will move the hunter in air creating sound that jarred the ears of the horse that gave a jerk to let the horse gain speed—exploiting the animal through noise pollution. The excessive pitch of the noise created by the trumpeting of an elephant or the roaring of a I ion pollutes the whole atmosphere of the jungle. So does the cries of an unruly husband in a house or a residential area. It is the ear that tells whether a particular noise pollutes the environment or not. Ear and sound (or noise) has a direct relationship.
The ear has three parts—the outer, the middle and the inner ear. The auricle i.e. the outer ear collects the sound stimuli. They pass through a canal, widest at the middle ear outer wall i.e. the ear drum. The tympanic membrane of the ear drum receives the sound vibrations from the outer ear. The hammer, the anvil and the stirrup are three minute pieces of bone that transmit the vibrations to the inner ear. The inner ear has two organs—one for hearing and the other for balance. Cochlea the hearing organ is a snail 5-aped container. It transmits sound vibrations as nerve impulses to the brain. The brain initiates the whole system of the body. In a way it guides the different organs to respond to the sound in different ways.
The brain activates the pituitary glands. These glands activate the thyroid and adrenal glands to excrete hormones. As it stimulates the sympathetic nervous system it indirectly influences the heart, the stomach, the pupil, blood vessels and motor nerves that control muscle reactions. Such reactions decide the response of our body to sound. Some sounds are jarring or unpleasant to the ear while some are pleasant. The unpleasant sounds create discomfort and affect the nerves. These unpleasant impacts are collectively called as noise pollution.
Almost all the cities and towns come under noise pollution. In big cities like New York, London, Kolkata and Delhi the noisy traffic is the biggest menace. In cities like New York and the capitals of European countries the noise pollution comes from the sky too because of the high frequency of aeroplanes. Some lower level noises like barking dogs and fighting animals during night hours are also pollutants as they disturb sleep. They can be detrimental to health in the long run. The high pitch sounds affect the ear drum and those who have to hear these constantly are more prone to losing their hearing capacity early as they ascend the age ladder. Some people do more work in noisy environment. But they invite great trouble for the future. The constant exposure to noise deteriorates the tender parts of the mid ear. It, in the long run fails to transmit sound impulses to the inner ear. The result is inefficient responses to sound.
Sound is produced by the vibrations of an object and is transmitted in the form of waves. Sound has two important properties—frequency and intensity (loudness). Frequency means pitch. It is measured in Hertz (Hz) units and is determined by the number of times the vibrating waves fluctuate in a second. The pitch is higher if the fluctuation is more. The loudness is measured in decibels (db). A decibel is one-tenth of a bell. It is the physical unit based on the weakest sound that can be caught or detected by human ear. 'bel' is after the name of Alexander Graham Bell who invented the telephone.
The scale of decibel is logarithmic i.e. an increase of 1Odb means 10 times increase. But if the increase is 20 db it means 100 times. Thus 30 db would mean a 1000 times increase. A whisper is about 10 db A decent conversation is around 20 db while a normal talk is 30 db To decide a noise pollution we may start with a loud conversation which is 60 db The playing children have a noise scale of 60 to 80 db While the traffic noise may go to 90 db Heavy truck traffic reaches 100 db while a motorcycle reaches 105.
Beat Music amplified electrically reaches 120 db While an aircraft—a jet take off touches 120 db a jet engine (at 25 m. distance) is generally not less than 140 db But the highest and the most harmful is the space vehicle launch noise that reaches 170 db
Looks strange but is equally true that the human ear cannot hear sounds having frequencies higher than 20,000 Hz (20,000 vibrations per second). It explains why one can't hear the extraordinary high pitch sound created by a flying bat which is 20,000 to 1, 00,000 Hz. The sound is at ultrasonic levels. The ultrasonic waves are a tool of research and are useful in the sub-marine echo sounding and in detection of flows in casting, drilling glasses and other processes. As such it is hard to say if they pollute the environment as they do not affect the hearing process.
The speed at which sound travels can of course some times go on polluting the area it covers. Sound can travel in certain media at different speed with which it travels in air. It is 331 meters per second in air at sea level. In water 4965 in per second, in glass it is 6000 in per second while in iron or steel it is generally 15000 m per second. In granite, ice cold water, bricks and even in wood its speed is greater than in air. This explains how sound pollutes sea water through sub-marine and also how noise can pollute the mines and closed buildings too.
But the most experienced pollution through speed is in the air media. That is how the thundering clouds deafen people when the thunder reaches the earth. The railway trains too leave their mark of sound all the way they travel. But the most injurious is the sound of aeroplanes that travels to the earth passage over which they fly. When they start travelling with a speed more than 331m per second they cross, the sound barrier making a quake like vibration in the atmosphere.
Supersonic speed is about 1216 km per hour. It is measured in Mach (after the name of Ernst Mach, a German Scientist who worked it out). Now Mach is the ratio of the speed of flight to the speed of sound. At the speed of sound it is Mach 1, at half it is 0.5, at twice the speed it is mach 2 and so on. Since the modern fast aeroplanes cross the speed barrier they pollute the area all the way when they fly low on cities. As the speed of the plane is more than that of sound the sound remains behind and those in the planes are not affected by it.
Any way noise pollution has been increasing in different ways with the growth of urbanization. Besides taking the environmental pollution, water pollution, nuclear pollution and the depletion of ozone layer seriously the world will have to develop a culture—sophistication in life to remove or lessen noise pollution too or half the world will be partly or totally deaf in decades to come.
For other uses, see Pollution (disambiguation).
For the academic journal, see Environmental Pollution (journal).
Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of chemical substances or energy, such as noise, heat or light. Pollutants, the components of pollution, can be either foreign substances/energies or naturally occurring contaminants. Pollution is often classed as point source or nonpoint source pollution. In 2015, pollution killed 9 million people in the world.
Air pollution has always accompanied civilizations. Pollution started from prehistoric times when man created the first fires. According to a 1983 article in the journal Science, "soot" found on ceilings of prehistoric caves provides ample evidence of the high levels of pollution that was associated with inadequate ventilation of open fires." Metal forging appears to be a key turning point in the creation of significant air pollution levels outside the home. Core samples of glaciers in Greenland indicate increases in pollution associated with Greek, Roman and Chinese metal production, but at that time the pollution was comparatively small and could be handled by nature.
The burning of coal and wood, and the presence of many horses in concentrated areas made the cities the primary sources of pollution. The Industrial Revolution brought an infusion of untreated chemicals and wastes into local streams that served as the water supply. King Edward I of England banned the burning of sea-coal by proclamation in London in 1272, after its smoke became 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.
It was the industrial revolution that gave birth to environmental pollution as we know it today. London 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. Pollution issues escalated as population growth far exceeded view ability of neighborhoods to handle their waste problem. Reformers began to demand sewer systems, and clean water.
In 1870, the sanitary conditions in Berlin were among the worst in Europe. August Bebel recalled conditions before a modern sewer system was built in the late 1870s:
- "Waste-water from the houses collected in the gutters running alongside the curbs and emitted a truly fearsome smell. There were no public toilets in the streets or squares. Visitors, especially women, often became desperate when nature called. In the public buildings the sanitary facilities were unbelievably primitive....As a metropolis, Berlin did not emerge from a state of barbarism into civilization until after 1870."
The primitive conditions were intolerable for a world national capital, and the Imperial German government brought in its scientists, engineers and urban planners to not only solve the deficiencies but to forge Berlin as the world's model city. A British expert in 1906 concluded that Berlin represented "the most complete application of science, order and method of public life," adding "it is a marvel of civic administration, the most modern and most perfectly organized city that there is."
The emergence of great factories and consumption of immense quantities of coal 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. Pollution became a major issue in the United States in the early twentieth century, as progressive reformers took issue with air pollution caused by coal burning, water pollution caused by bad sanitation, and street pollution caused by the 3 million horses who worked in American cities in 1900, generating large quantities of urine and manure. As historian Martin Melosi notes, The generation that first saw automobiles replacing the horses saw cars as "miracles of cleanliness.". By the 1940s, however, automobile-caused smog was a major issue in Los Angeles.
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. Air pollution would continue to be a problem in England, especially later during the industrial revolution, and extending into the recent past with the Great Smog of 1952.
Awareness of atmospheric pollution spread widely after World War II, with fears triggered by reports of radioactive fallout from atomic warfare and testing. Then a non-nuclear event, The Great Smog of 1952 in London, killed at least 4000 people. This prompted some of the first major modern environmental legislation, The Clean Air Act of 1956.
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.
Severe incidents of 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. The pollution of industrial land gave rise to the name brownfield, a term now common in city planning.
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 throughout the 1950s and 1960s. Chelyabinsk, Russia, is considered the "Most polluted place on the planet".
Nuclear weapons continued to be tested in the Cold War, 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. Worldwide publicity has been intense on those disasters. Widespread support for test ban treaties has ended almost all nuclear testing in the atmosphere.
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.
A much more recently discovered problem is the Great Pacific Garbage Patch, a huge concentration of plastics, chemical sludge and other debris which has been collected into a large area of the Pacific Ocean by the North Pacific Gyre. This is a less well known pollution problem than the others described above, but nonetheless has multiple and serious consequences such as increasing wildlife mortality, the spread of invasive species and human ingestion of toxic chemicals. Organizations such as 5 Gyres have researched the pollution and, along with artists like Marina DeBris, are working toward publicizing the issue.
Pollution introduced by light at night is becoming a global problem, more severe in urban centres, but nonetheless contaminating also large territories, far away from towns.
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.
Forms of pollution
The major forms of pollution are listed below along with the particular contaminant relevant to each of them:
- Light pollution: includes light trespass, over-illumination and astronomical interference.
- Littering: the criminal throwing of inappropriate man-made objects, unremoved, onto public and private properties.
- Noise pollution: which encompasses roadway noise, aircraft noise, industrial noise as well as high-intensity sonar.
- Soil contamination occurs when chemicals are released by spill or underground leakage. Among the most significant soil contaminants are hydrocarbons, heavy metals, MTBE,herbicides, pesticides and chlorinated hydrocarbons.
- Radioactive contamination, resulting from 20th century activities in atomic physics, such as nuclear power generation and nuclear weapons research, manufacture and deployment. (See alpha emitters and actinides in the environment.)
- Thermal pollution, is a temperature change in natural water bodies caused by human influence, such as use of water as coolant in a power plant.
- Visual pollution, which can refer to the presence of overhead power lines, motorway billboards, scarred landforms (as from strip mining), open storage of trash, municipal solid waste or space debris.
- Water pollution, by the discharge of wastewater from commercial and industrial waste (intentionally or through spills) into surface waters; discharges of untreated domestic sewage, and chemical contaminants, such as chlorine, from treated sewage; release of waste and contaminants into surface runoff flowing to surface waters (including urban runoff and agricultural runoff, which may contain chemical fertilizers and pesticides); waste disposal and leaching into groundwater; eutrophication and littering.
- Plastic pollution: involves the accumulation of plastic products in the environment that adversely affects wildlife, wildlife habitat, or humans.
Main article: Pollutant
A pollutant is a waste material that pollutes air, water or soil. Three factors determine the severity of a pollutant: its chemical nature, the concentration and the persistence.
Cost of pollution
Pollution has cost. Manufacturing activities that cause air pollution impose health and clean-up costs on the whole of society, whereas the neighbors of an individual who chooses to fire-proof his home may benefit from a reduced risk of a fire spreading to their own homes. A manufacturing activity that causes air pollution is an example of a negative externality in production. A negative externality in production occurs “when a firm’s production reduces the well-being of others who are not compensated by the firm." For example, if a laundry firm exists near a polluting steel manufacturing firm, there will be increased costs for the laundry firm because of the dirt and smoke produced by the steel manufacturing firm. If external costs exist, such as those created by pollution, the manufacturer will choose to produce more of the product than would be produced if the manufacturer were required to pay all associated environmental costs. Because responsibility or consequence for self-directed action lies partly outside the self, an element of externalization is involved. If there are external benefits, such as in public safety, less of the good may be produced than would be the case if the producer were to receive payment for the external benefits to others. However, goods and services that involve negative externalities in production, such as those that produce pollution, tend to be over-produced and underpriced since the externality is not being priced into the market.
Pollution can also create costs for the firms producing the pollution. Sometimes firms choose, or are forced by regulation, to reduce the amount of pollution that they are producing. The associated costs of doing this are called abatement costs, or marginal abatement costs if measured by each additional unit. In 2005 pollution abatement capital expenditures and operating costs in the US amounted to nearly $27 million.
Socially Optimal Level of Pollution
Society derives some indirect utility from pollution, otherwise there would be no incentive to pollute. This utility comes from the consumption of goods and services that create pollution. Therefore, it is important that policymakers attempt to balance these indirect benefits with the costs of pollution in order to achieve an efficient outcome.
It is possible to use environmental economics to determine which level of pollution is deemed the social optimum. For economists, pollution is an “external cost and occurs only when one or more individuals suffer a loss of welfare,” however, there exists a socially optimal level of pollution at which welfare is maximized. This is because consumers derive utility from the good or service manufactured, which will outweigh the social cost of pollution until a certain point. At this point the damage of one extra unit of pollution to society, the marginal cost of pollution, is exactly equal to the marginal benefit of consuming one more unit of the good or service.
In markets with pollution, or other negative externalities in production, the free market equilibrium will not account for the costs of pollution on society. If the social costs of pollution are higher than the private costs incurred by the firm, then the true supply curve will be higher. The point at which the social marginal cost and market demand intersect gives the socially optimal level of pollution. At this point, the quantity will be lower and the price will be higher in comparison to the free market equilibrium. Therefore, the free market outcome could be considered a market failure because it “does not maximize efficiency”.
This model can be used as a basis to evaluate different methods of internalizing the externality. Some examples include tariffs, a carbon tax and cap and trade systems.
Sources and causes
Air pollution comes from both natural and human-made (anthropogenic) sources. However, globally human-made pollutants from combustion, construction, mining, agriculture and warfare are increasingly significant in the air pollution equation.
Motor vehicle emissions are one of the leading causes of air pollution.China, United States, Russia, IndiaMexico, and Japan are the world leaders in air pollution emissions. Principal stationary pollution sources include chemical plants, coal-fired power plants, oil refineries,petrochemical plants, nuclear waste disposal activity, incinerators, large livestock farms (dairy cows, pigs, poultry, etc.), PVC factories, metals production factories, plastics factories, and other heavy industry. Agricultural air pollution comes from contemporary practices which include clear felling and burning of natural vegetation as well as spraying of pesticides and herbicides
About 400 million metric tons of hazardous wastes are generated each year. The United States alone produces about 250 million metric tons. Americans constitute less than 5% of the world's population, but produce roughly 25% of the world’s CO2, and generate approximately 30% of world’s waste. In 2007, China has overtaken the United States as the world's biggest producer of CO2, while still far behind based on per capita pollution - ranked 78th among the world's nations.
In February 2007, a report by the Intergovernmental Panel on Climate Change (IPCC), representing the work of 2,500 scientists, economists, and policymakers from more than 120 countries, said that humans have been the primary cause of global warming since 1950. Humans have ways to cut greenhouse gas emissions and avoid the consequences of global warming, a major climate report concluded. But to change the climate, the transition from fossil fuels like coal and oil needs to occur within decades, according to the final report this year from the UN's Intergovernmental Panel on Climate Change (IPCC).
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.
In the case of noise pollution the dominant source class is the motor vehicle, producing about ninety percent of all unwanted noise worldwide.
Further information: Soil pollution § Health effects, Toxic hotspots, and List of pollution-related diseases
Adverse air quality can kill many organisms including humans. Ozone pollution can cause respiratory disease, cardiovascular disease, throat inflammation, chest pain, and congestion. Water pollution causes approximately 14,000 deaths per day, mostly due to contamination of drinking water by untreated sewage in developing countries. An estimated 500 million Indians have no access to a proper toilet, Over ten million people in India fell ill with waterborne illnesses in 2013, and 1,535 people died, most of them children. Nearly 500 million Chinese lack access to safe drinking water. A 2010 analysis estimated that 1.2 million people died prematurely each year in China because of air pollution. The WHO estimated in 2007 that air pollution causes half a million deaths per year in India. Studies have estimated that the number of people killed annually in the United States could be over 50,000.
Oil spills can cause skin irritations and rashes. Noise pollution induces hearing loss, high blood pressure, stress, and sleep disturbance. Mercury has been linked to developmental deficits in children and neurologic symptoms. Older people are majorly exposed to diseases induced by air pollution. Those with heart or lung disorders are at additional risk. Children and infants are also at serious risk. Lead and other heavy metals have been shown to cause neurological problems. Chemical and radioactive substances can causecancer and as well asbirth defects.
An October 2017 study by the Lancet Commission on Pollution and Health found that global pollution, specifically toxic air, water, soils and workplaces, kill nine million people annually, which is triple the number of deaths caused by AIDS, tuberculosis and malaria combined, and 15 times higher than deaths caused by wars and other forms of human violence. The study concluded that "pollution is one of the great existential challenges of the Anthropocene era. Pollution endangers the stability of the Earth’s support systems and threatens the continuing survival of human societies."
Pollution has been found to be present widely in the environment. There are a number of effects of this:
Environmental health information
The Toxicology and Environmental Health Information Program (TEHIP) at the United States National Library of Medicine (NLM) maintains a comprehensive toxicology and environmental health web site that includes access to resources produced by TEHIP and by other government agencies and organizations. This web site includes links to databases, bibliographies, tutorials, and other scientific and consumer-oriented resources. TEHIP also is responsible for the Toxicology Data Network (TOXNET) an integrated system of toxicology and environmental health databases that are available free of charge on the web.
TOXMAP is a Geographic Information System (GIS) that is part of TOXNET. TOXMAP uses maps of the United States to help users visually explore data from the United States Environmental Protection Agency's (EPA) Toxics Release Inventory and Superfund Basic Research Programs.
A number of studies show that pollution has an adverse effect on the productivity of both indoor and outdoor workers.
Regulation and monitoring
Main article: Regulation and monitoring of pollution
To protect the environment from the adverse effects of pollution, many nations worldwide have enacted legislation to regulate various types of pollution as well as to mitigate the adverse effects of pollution.
Pollution control is a term used in environmental management. It means the control of emissions and effluents into air, water or soil. Without pollution control, the waste products from overconsumption, heating, agriculture, mining, manufacturing, transportation and other human activities, whether they accumulate or disperse, will degrade the environment. In the hierarchy of controls, pollution prevention and waste minimization are more desirable than pollution control. In the field of land development, low impact development is a similar technique for the prevention of urban runoff.
Pollution control devices
The earliest precursor of pollution generated by life forms would have been a natural function of their existence. The attendant consequences on viability and population levels fell within the sphere of natural selection. These would have included the demise of a population locally or ultimately, species extinction. Processes that were untenable would have resulted in a new balance brought about by changes and adaptations. At the extremes, for any form of life, consideration of pollution is superseded by that of survival.
For humankind, 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 (e.g. Occupational Safety and Health Administration (OSHA) PELs), toxicology (e.g. LD50), and medicine (e.g. 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 infeasible. 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. One such superseding principle is contained in modern hazardous waste laws in developed countries, as the process of diluting hazardous waste to make it non-hazardous is usually a regulated treatment process. Migration from pollution dilution to elimination in many cases can be confronted by challenging economical and technological barriers.
Greenhouse gases and global warming
Main article: Global warming
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.
Most polluting industries
The Pure Earth, an international non-for-profit organization dedicated to eliminating life-threatening pollution in the developing world, issues an annual list of some of the world's most polluting industries.
World’s worst polluted places
The Pure Earth issues an annual list of some of the world's worst polluted places.
- Agbogbloshie, Ghana
- Chernobyl*, Ukraine
- Citarum River, Indonesia
- Dzershinsk*, Russia
- Hazaribagh, Bangladesh
- Kabwe*, Zambia
- Kalimantan, Indonesia
- Matanza Riachuelo, Argentina
- Niger River Delta, Nigeria
- Norilsk*, Russia
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