Thermal pollution

Thermal pollution is the degradation of water quality by any process that changes ambient water temperature. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. When water used as a coolant is returned to the natural environment at a higher temperature, the change in temperature impacts organisms by (a) decreasing oxygen supply, and (b) affecting ecosystem composition. Urban runoff—storm water discharged to surface waters from roads and parking lots--can also be a source of elevated water temperatures. Humans are a major cause of this.

When a power plant first opens or shuts down for repair or other causes, fish and other organisms adapted to particular temperature range can be killed by the abrupt rise in water temperature known as 'thermal shock'.

Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers. This affects fish (particularly their eggs and larvae), macro-invertebrates and river productivity.

Ecological effects — warm water

Elevated temperature typically decreases the level of dissolved oxygen (DO) in water. The decrease in levels of DO can harm aquatic animals such as fish, amphibians and copepods. Thermal pollution may also increase the metabolic rate of aquatic animals, as enzyme activity, resulting in these organisms consuming more food in a shorter time than if their environment were not changed. An increased metabolic rate may result in food source shortages, causing a sharp decrease in a population. Changes in the environment may also result in a migration of organisms to another, more suitable environment, and to in-migration of fishes that normally only live in warmer waters elsewhere. This leads to competition for fewer resources; the more adapted organisms moving in may have an advantage over organisms that are not used to the warmer temperature. As a result one has the problem of compromising food chains of the old and new environments. Biodiversity can be decreased as a result.

It is known that temperature changes of even one to two degrees Celsius can cause significant changes in organism metabolism and other adverse cellular biology effects. Principal adverse changes can include rendering cell walls less permeable to necessary osmosis, coagulation of cell proteins, and alteration of enzyme metabolism. These cellular level effects can adversely affect mortality and reproduction.

Primary producers are affected by warm water because higher water temperature increases plant growth rates, resulting in a shorter lifespan and species overpopulation. This can cause an algae bloom which reduces the oxygen levels in the water. The higher plant density leads to an increased plant respiration rate because the reduced light intensity decreases photosynthesis. This is similar to the eutrophication that occurs when watercourses are polluted with leached agricultural inorganic fertilizers.

A large increase in temperature can lead to the denaturing of life-supporting enzymes by breaking down hydrogen- and disulphide bonds within the quaternary structure of the enzymes. Decreased enzyme activity in aquatic organisms can cause problems such as the inability to break down lipids, which leads to malnutrition.

In limited cases, warm water has little deleterious effect and may even lead to improved function of the receiving aquatic ecosystem. This phenomenon is seen especially in seasonal waters and is known as thermal enrichment. An extreme case is derived from the

aggregational habits of the manatee, which often uses power plant discharge sites during winter. Projections suggest that manatee populations would decline upon the removal of these discharges.

The temperature can be as high as 70° Fahrenheit for freshwater, 80° F for saltwater, and 85° F for tropical fish.

Ecological effects — cold water

Releases of unnaturally cold water from reservoirs can dramatically change the fish and macro-invertebrate fauna of rivers, and reduce river productivity. In Australia, where many rivers have warmer temperature regimes, native fish species have been eliminated, and macro-invertebrate fauna have been drastically altered and impoverished. The temperatures for freshwater fish can be as low as 50° F, saltwater 75° F, and tropical 80° F.

Control of thermal pollution

Industrial wastewater

In the United States, thermal pollution from industrial sources is generated mostly by power plants, petroleum refineries, pulp and paper mills, chemical plants, steel mills and smelters. Heated water from these sources may be controlled with:

Cooling ponds, man-made bodies of water designed for cooling by evaporation, convection, and radiation

Cooling towers, which transfer waste heat to the atmosphere through evaporation and/or heat transfer

Cogeneration, a process where waste heat is recycled for domestic and/or industrial heating purposes.

Some facilities use once-through cooling (OTC) systems which do not reduce temperature as effectively as the above systems. For example, the Potrero Generating Station in San Francisco, which uses OTC, discharges water to San Francisco Bay approximately 10° C (20° F) above the ambient bay temperature.

Urban runoff

During warm weather, urban runoff can have significant thermal impacts on small streams, as storm water passes over hot parking lots, roads and sidewalks. Storm water management facilities that absorb runoff or direct it into groundwater, such as bio-retention systems and infiltration basins, can reduce these thermal effects. Retention basins tend to be less effective at reducing temperature, as the water may be heated by the sun before being discharged to a receiving stream.

AIDS

During the twenty-year AIDS epidemic, almost twenty-two million people worldwide have died of the disease and an estimated 36 million are living with the HIV virus, which develops into AIDS. The first reported cases of HIV/AIDS in the early 1980s were followed, especially in the West, by rapid scientific advances in naming the disease, finding its cause, and learning about its modes of transmission. This burst of scientific discovery fostered an optimism that AIDS could be conquered. However, by the mid-1980s, the disease was recognized as an international epidemic. It spread explosively across the African continent and to many other parts of the world, including Asia and South America. It is estimated that

90 to 95 percent of AIDS infections occur in developing countries, primarily in sub-Saharan Africa where some of the world’s worst living conditions exist. According to current estimates, 70 percent of those infected with AIDS live in this region. Today, AIDS is called pandemic because it has spread to every inhabited continent in the world.

Globally, AIDS is a disease which has been, and continues to be, primarily a sexually transmitted disease (STD) spread through unprotected sex between heterosexual men and women. It is shortening the life expectancy of working-age adults, dramatically increasing the number of infant and child deaths, shrinking the workforce, creating millions of orphans, widening the gap between rich and poor countries, and reversing developmental gains. Currently, the areas most affected by AIDS are Africa, India, and China. Almost every country in Asia and the Pacific area has recently experienced an increase in HIV infections.

Why AIDS is a major problem in developing countries Wealthier countries have experienced a decrease in AIDS infections due partly to the development of AIDS medicines and the implementation of preventive measures. Government officials, medical scientists, and the public in Western countries have addressed many of the complex issues involved in combating AIDS. While the affluence of developed nations has helped decrease the transmission rates of AIDS in the West, widespread and worsening poverty in developing nations has limited public education about AIDS and the ability to act constructively to combat the disease. Poverty in developing countries has also blocked the development of adequate health care facilities and the purchase of AIDS medicines, even at drastically reduced prices. One estimate of the cost for AIDS drugs for an individual is $12,000 or more per year; however, the entire annual health budget of some African countries allots less than six dollars per person per year.

Although over 90 percent of people with AIDS live in developing countries, it is estimated that 90 percent of the AIDS drugs are consumed by those in the developed world. Large drug companies have not been interested in marketing AIDS drugs to poor countries because these countries have low purchasing power. A heated dispute arose in 1999 between the South African government and its supporters on one side and western pharmaceutical companies, the government of the United States, and the European Union on the other. The South African government attempted to reduce high drug costs by introducing amendments to international drug patent laws, but Western pharmaceutical companies reacted furiously, raising a lawsuit against forty South Africa–based drug companies. The western pharmaceutical companies argued that even if they did provide AIDS drugs more cheaply to developing countries, such nations had no infrastructure to administer the drugs. AIDS activists accused the pharmaceutical companies of putting profits before humanity. The issue was settled when the companies, pressured by worldwide public outrage, dropped their charges against the South African drug companies.

Poverty in developing nations not only blocks access to affordable AIDS medications, it also helps contribute to the spread of the disease. For example, evidence suggests that poor groups in developing countries, including injecting drug users and increasing numbers of commercial sex workers, run a higher risk of contracting AIDS. Many prostitutes reside along long-haul truck routes. Male and female adolescents between the ages of fifteen and nineteen, whose parents cannot provide them with adequate food and clothing, frequent these truck stops to trade sex for money and gifts. In addition, when men cannot find jobs in their villages, they go to bigger cities where they must work for months at a time. The men visit brothels and carry the AIDS infection back to their homes, often infecting their wives; in these countries, women are not expected to question their husbands or suggest the use of condoms. This same situation exists among businessmen, among whom it is not

uncommon or socially unacceptable to have a wife and family as well as multiple sexual partners.

In addition to these problems, weak educational systems and lack of information about HIV/AIDS contribute to the spread of the disease. Some of those in developing countries do not know that they are infected with AIDS or even what the disease is. Embarrassment about having contracted AIDS as well as discrimination against those who have it can lead to an unhealthy silence and denial. Some governmental leaders in developing nations have not wanted to admit that their country has an AIDS problem. For example, Thabo Mbeki, the deputy president of South Africa, publicly stated that HIV and AIDS were not related issues. Some of these nations also suffer from internal strife, political upheaval, and wars, creating populations of refugees in which AIDS spreads unchecked. Other STD’s and major diseases such as malaria and tuberculosis ravage some of these countries as well, complicating health care problems. Illnesses and deaths among people in their prime working years further impoverish these nations by hurting already weak economies and creating a new generation of “AIDS orphans,” estimated at over eleven million children globally. Clearly, AIDS in developing countries is more than a health issue, as it undermines countries economically by affecting productivity, security, education, health care, civil service systems, social cohesion, and political stability.

These national programs sometimes include working in partnerships with nongovernmental organizations (NGOs). NGOs, at the national level, provide a broad range of services, from confidential counseling and testing to support and legal services for people with AIDS. Some NGOs focus on solidarity, bringing people with AIDS together to fight the disease. Organizations composed of people living with HIV/AIDS are extensive and do international advocacy work to deal with the AIDS epidemic. One such organization, the Global Network of People Living with AIDS (GNP+), encourages members to network and share personal experiences. The organization leads the movement working to establish AIDS self-help groups. NGOs such as Doctors Without Borders, Oxfam, and The AIDS Coalition to Unleash Power have pressed drug companies to reduce their prices to poor countries. These activists are working to get generic versions of AIDS drugs at drastically reduced prices to countries in need.

Although some prevention efforts have succeeded, many analysts believe that the ultimate solution to the global AIDS crisis is the development of a vaccine that will prevent people from contracting AIDS in the first place. Many researchers believe that the development of a preventive vaccine is possible and absolutely necessary in order to eradicate AIDS. However, many pharmaceutical companies do not want to invest in AIDS vaccine research because of the large expense involved and the belief that profits could not be made on the vaccines. Funding for research to develop an AIDS vaccine comes from several sources, mainly the International AIDS Vaccine Initiative (IAVI), UNAIDS, the U.S. National Institutes of Health (NIH), U.S. government agencies, and a few multinational pharmaceutical companies. In 1997 U.S. President Bill Clinton called for the development of an HIV vaccine within a decade and announced a new center for vaccine research. Some researchers believe that a vaccine will be developed in the next five to seven years.

In the meantime, AIDS continues to spread in the developing world. Although successes have occurred, many experts contend that much more needs to be done. They argue that the response to AIDS needs to be of greater duration, greater quality, and greater scope to reach the many areas of life which AIDS touches and affects. Working together with others in the international community utilizing multiple approaches will enhance the ability of developing nations to cope with the disease. The viewpoints in AIDS in Developing

Countries: At Issue explore the HIV/AIDS pandemic which has become an ongoing challenge to human ingenuity and compassion.

Ozone depletion

Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere (ozone layer) since the late 1970s, and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period. The latter phenomenon is commonly referred to as the ozone hole. In addition to this well-known stratospheric ozone depletion, there are also tropospheric ozone depletion events, which occur near the surface in polar regions during spring.

The detailed mechanism by which the polar ozone holes form is different from that for the mid-latitude thinning, but the most important process in both trends is catalytic destruction of ozone by atomic chlorine and bromine. The main source of these halogen atoms in the stratosphere is photodissociation of chlorofluorocarbon (CFC) compounds, commonly called freons, and of bromofluorocarbon compounds known as halons. These compounds are transported into the stratosphere after being emitted at the surface.[2] Both ozone depletion mechanisms strengthened as emissions of CFCs and halons increased.

CFCs and other contributory substances are commonly referred to as ozone-depleting substances (ODS). Since the ozone layer prevents most harmful UVB wavelengths (270–315 nm) of ultraviolet light (UV light) from passing through the Earth's atmosphere, observed and projected decreases in ozone have generated worldwide concern leading to adoption of the Montreal Protocol that bans the production of CFCs and halons as well as related ozone depleting chemicals such as carbon tetrachloride and trichloroethane. It is suspected that a variety of biological consequences such as increases in skin cancer, cataracts. damage to plants, and reduction of plankton populations in the ocean's photic zone may result from the increased UV exposure due to ozone depletion.

Consequences of ozone layer depletion

Since the ozone layer absorbs UVB ultraviolet light from the Sun, ozone layer depletion is expected to increase surface UVB levels, which could lead to damage, including increases in skin cancer. This was the reason for the Montreal Protocol. Although decreases in stratospheric ozone are well-tied to CFCs and there are good theoretical reasons to believe that decreases in ozone will lead to increases in surface UVB, there is no direct observational evidence linking ozone depletion to higher incidence of skin cancer in human beings. This is partly due to the fact that UVA, which has also been implicated in some forms of skin cancer, is not absorbed by ozone, and it is nearly impossible to control statistics for lifestyle changes in the populace.

Increased UV

Ozone, while a minority constituent in the Earth's atmosphere, is responsible for most of the absorption of UVB radiation. The amount of UVB radiation that penetrates through the ozone layer decreases exponentially with the slant-path thickness/density of the layer. Correspondingly, a decrease in atmospheric ozone is expected to give rise to significantly increased levels of UVB near the surface.

Increases in surface UVB due to the ozone hole can be partially inferred by radiative transfer model calculations, but cannot be calculated from direct measurements because of the lack of reliable historical (pre-ozone-hole) surface UV data, although more recent surface UV observation measurement programmes exist (e.g. at Lauder, New Zealand).

Because it is this same UV radiation that creates ozone in the ozone layer from O2 (regular oxygen) in the first place, a reduction in stratospheric ozone would actually tend to increase photochemical production of ozone at lower levels (in the troposphere), although the overall observed trends in total column ozone still show a decrease, largely because ozone produced lower down has a naturally shorter photochemical lifetime, so it is destroyed before the concentrations could reach a level which would compensate for the ozone reduction higher up.

Biological effects

The main public concern regarding the ozone hole has been the effects of increased surface UV and microwave radiation on human health. So far, ozone depletion in most locations has been typically a few percent and, as noted above, no direct evidence of health damage is available in most latitudes. Were the high levels of depletion seen in the ozone hole ever to be common across the globe, the effects could be substantially more dramatic. As the ozone hole over Antarctica has in some instances grown so large as to reach southern parts of Australia and New Zealand, environmentalists have been concerned that the increase in surface UV could be significant.

Effects on humans

UVB (the higher energy UV radiation absorbed by ozone) is generally accepted to be a contributory factor to skin cancer. In addition, increased surface UV leads to increased tropospheric ozone, which is a health risk to humans. The increased surface UV also represents an increase in the vitamin D synthetic capacity of the sunlight.

The cancer preventive effects of vitamin D represent a possible beneficial effect of ozone depletion. In terms of health costs, the possible benefits of increased UV irradiance may outweigh the burden.

1. Basal and Squamous Cell Carcinomas -- The most common forms of skin cancer in humans, basal and squamous cell carcinomas, have been strongly linked to UVB exposure. The mechanism by which UVB induces these cancers is well understood — absorption of UVB radiation causes the pyrimidine bases in the DNA molecule to form dimers, resulting in transcription errors when the DNA replicates. These cancers are relatively mild and rarely fatal, although the treatment of squamous cell carcinoma sometimes requires extensive reconstructive surgery. By combining epidemiological data with results of animal studies, scientists have estimated that a one percent decrease in stratospheric ozone would increase the incidence of these cancers by 2%.

2. Malignant Melanoma — Another form of skin cancer, malignant melanoma, is much less common but far more dangerous, being lethal in about 15–20% of the cases diagnosed. The relationship between malignant melanoma and ultraviolet exposure is not yet well understood, but it appears that both UVB and UVA are involved. Experiments on fish suggest that 90 to 95% of malignant melanomas may be due to UVA and visible radiation whereas experiments on opossums suggest a larger role for UVB. Because of this uncertainty, it is difficult to estimate the impact of ozone depletion on melanoma incidence. One study showed that a 10% increase in UVB radiation was associated with a 19% increase in melanomas for men and 16% for women. A study of people in Punta Arenas, at the southern tip of Chile,

showed a 56% increase in melanoma and a 46% increase in nonmelanoma skin cancer over a period of seven years, along with decreased ozone and increased UVB levels.

3. Cortical Cataracts -- Studies are suggestive of an association between ocular cortical cataracts and UV-B exposure, using crude approximations of exposure and various cataract assessment techniques. A detailed assessment of ocular exposure to UV-B was carried out in a study on Chesapeake Bay Watermen, where increases in average annual ocular exposure were associated with increasing risk of cortical opacity. In this highly exposed group of predominantly white males, the evidence linking cortical opacities to sunlight exposure was the strongest to date. However, subsequent data from a population-based study in Beaver Dam, WI suggested the risk may be confined to men. In the Beaver Dam study, the exposures among women were lower than exposures among men, and no association was seen. Moreover, there were no data linking sunlight exposure to risk of cataract in African Americans, although other eye diseases have different prevalences among the different racial groups, and cortical opacity appears to be higher in African Americans compared with whites.

4. Increased Tropospheric Ozone -- Increased surface UV leads to increased tropospheric ozone. Ground-level ozone is generally recognized to be a health risk, as ozone is toxic due to its strong oxidant properties. At this time, ozone at ground level is produced mainly by the action of UV radiation on combustion gases from vehicle exhausts.

Effects on crops

An increase of UV radiation would be expected to affect crops. A number of economically important species of plants, such as rice, depend on cyanobacteria residing on their roots for the retention of nitrogen. Cyanobacteria are sensitive to UV light and they would be affected by its increase.

Ozone depletion and global warming

Although they are often interlinked in the mass media, the connection between global warming and ozone depletion is not strong. There are five areas of linkage:

The same CO2 radiative forcing that produces near-surface global warming is expected to cool the stratosphere. This cooling, in turn, is expected to produce a relative increase in polar ozone (O3) depletion and the frequency of ozone holes.

Conversely, ozone depletion represents a radiative forcing of the climate system. There are two opposing effects: Reduced ozone causes the stratosphere to absorb less solar radiation, thus cooling the stratosphere while warming the troposphere; the resulting colder stratosphere emits less long-wave radiation downward, thus cooling the troposphere. Overall, the cooling dominates; the IPCC concludes that "observed stratospheric O3 losses over the past two decades have caused a negative forcing of the surface-troposphere system” of about −0.15 ± 0.10 watts per square meter (W/m²).

One of the strongest predictions of the greenhouse effect is that the stratosphere will cool. Although this cooling has been observed, it is not trivial to separate the effects of changes in the concentration of greenhouse gases and ozone depletion since both will lead to cooling. However, this can be done by numerical stratospheric modeling. Results from the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory show that above 20 km (12.4 miles), the greenhouse gases dominate the cooling.

Ozone depleting chemicals are also greenhouse gases. The increases in concentrations of these chemicals have produced 0.34 ± 0.03 W/m² of radiative forcing, corresponding to

about 14% of the total radiative forcing from increases in the concentrations of well-mixed greenhouse gases.

The long term modeling of the process, its measurement, study, design of theories and testing take decades to document, gain wide acceptance, and ultimately become the dominant paradigm. Several theories about the destruction of ozone were hypothesized in the 1980s, published in the late 1990s, and are currently being proven. Dr Drew Schindell, and Dr Paul Newman, NASA Goddard, proposed a theory in the late 1990s, using a SGI Origin 2000 supercomputer, that modeled ozone destruction, accounted for 78% of the ozone destroyed. Further refinement of that model accounted for 89% of the ozone destroyed, but pushed back the estimated recovery of the ozone hole from 75 years to 150 years. (An important part of that model is the lack of stratospheric flight due to depletion of fossil fuels.)

World Ozone Day

In 1994, the United Nations General Assembly voted to designate the 16th of September as "World Ozone Day", to commemorate the signing of the Montreal Protocol on that date in 1987.

Radioactive contamination

Radioactive contamination is the uncontrolled distribution of radioactive material in a given environment. The amount of radioactive material released in an accident is called the source term.

Sources of Contamination

Radioactive contamination is typically the result of a spill or accident during the production or use of radionuclides (radioisotopes), an unstable nucleus which has excessive energy. Contamination may occur from radioactive gases, liquids or particles. For example, if a radionuclide used in nuclear medicine is accidentally spilled, the material could be spread by people as they walk around. Radioactive contamination may also be an inevitable result of certain processes, such as the release of radioactive xenon in nuclear fuel reprocessing. In cases that radioactive material cannot be contained, it may be diluted to safe concentrations. Nuclear fallout is the distribution of radioactive contamination by a nuclear explosion. For a discussion of environmental contamination by alpha emitters please see actinides in the environment. Containment is what differentiates radioactive material from radioactive contamination. Therefore, radioactive material in sealed and designated containers is not properly referred to as contamination, although the units of measurement might be the same.

Measurement

Radioactive contamination may exist on surfaces or in volumes of material or air. In a nuclear power plant, detection and measurement of radioactivity and contamination is often the job of a Certified Health Physicist.

Surface contamination

Surface contamination is usually expressed in units of radioactivity per unit of area. For SI, this is becquerels per square meter (or Bq/m²). Other units such as picoCuries per 100 cm² or disintegrations per minute per square centimeter (1 dpm/cm² = 166 2/3 Bq/m²) may be used. Surface contamination may either be fixed or removable. In the case of fixed contamination, the radioactive material cannot by definition be spread, but it is still measurable.

Hazards

In practice there is no such thing as zero radioactivity. Not only is the entire world constantly bombarded by cosmic rays, but every living creature on earth contains significant quantities of carbon-14 and most (including humans) contain significant quantities of potassium-40. These tiny levels of radiation are not any more harmful than sunlight, but just as excessive quantities of sunlight can be dangerous, so too can excessive levels of radiation.

Low level contamination

The hazards to people and the environment from radioactive contamination depend on the nature of the radioactive contaminant, the level of contamination, and the extent of the spread of contamination. Low levels of radioactive contamination pose little risk, but can still be detected by radiation instrumentation. In the case of low-level contamination by isotopes with a short half-life, the best course of action may be to simply allow the material to naturally decay. Longer-lived isotopes should be cleaned up and properly disposed of, because even a very low level of radiation can be life-threatening when in long exposure to it. Therefore, whenever there's any radiation in an area, many people take extreme caution when approaching.

High level contamination

High levels of contamination may pose major risks to people and the environment. People can be exposed to potentially lethal radiation levels, both externally and internally, from the spread of contamination following an accident (or a deliberate initiation) involving large quantities of radioactive material. The biological effects of external exposure to radioactive contamination are generally the same as those from an external radiation source not involving radioactive materials, such as x-ray machines, and are dependent on the absorbed dose.

Biological effects

The biological effects of internally deposited radionuclides depend greatly on the activity and the biodistribution and removal rates of the radionuclide, which in turn depends on its chemical form. The biological effects may also depend on the chemical toxicity of the deposited material, independent of its radioactivity. Some radionuclides may be generally distributed throughout the body and rapidly removed, as is the case with tritiated water. Some radionuclides may target specific organs and have much lower removal rates. For instance, the thyroid gland takes up a large percentage of any iodine that enters the body. If large quantities of radioactive iodine are inhaled or ingested, the thyroid may be impaired or destroyed, while other tissues are affected to a lesser extent. Radioactive iodine is a common fission product; it was a major component of the radiation released from the Chernobyl disaster, leading to nine fatal cases of pediatric thyroid cancer and hypothyroidism. On the other hand, radioactive iodine is used in the diagnosis and treatment of many diseases of the thyroid precisely because of the thyroid's selective uptake of iodine.

Means of contamination

Radioactive contamination can enter the body through ingestion, inhalation, absorption, or injection. For this reason, it is important to use personal protective equipment when working with radioactive materials. Radioactive contamination may also be ingested as the result of eating contaminated plants and animals or drinking contaminated water or milk from exposed animals. Following a major contamination incident, all potential pathways of internal exposure should be considered.

Sustainable Development

Securing economic development, social equity and justice, and environmental protection is the goal of sustainable development. Although these three factors can work in harmony, they are often found to conflict with one another. During the latter half of the 20th century economic development for a better standard of living has been instrumental in damaging the environment. We are now in a position whereby we are consuming more resources than ever, and polluting the Earth with waste products. More recently, society has grown to realise that we cannot live in a healthy society or economy with so much poverty and environmental degradation. Economic growth will remain the basis for human development, but it must change and become less environmentally destructive. The challenge of sustainable development is to put this understanding into practice, changing our unsustainable ways into more sustainable ones.

The aim of sustainable development is to balance our economic, environmental and social needs, allowing prosperity for now and future generations. Sustainable development consists of a long-term, integrated approach to developing and achieving a healthy community by jointly addressing economic, environmental, and social issues, whilst avoiding the over consumption of key natural resources.

Sustainable development encourages us to conserve and enhance our resource base, by gradually changing the ways in which we develop and use technologies. Countries must be allowed to meet their basic needs of employment, food, energy, water and sanitation. If this is to be done in a sustainable manner, then there is a definite need for a sustainable level of population. Economic growth should be supported and developing nations should be allowed a growth of equal quality to the developed nations.

The UK Government has recognised four objectives for Sustainable Development. These include social progress and equality, environmental protection, conservation of natural resources and stable economic growth. Everybody has the right to a healthy, clean and safe environment. This can be achieved by reducing pollution, poverty, poor housing and unemployment. No one, in this age, or in the future should be treated unfairly. Global environmental threats, such as climate change and poor air quality must be reduced to protect human and environmental health. The use of non-renewable resources such as fossil fuels should not be stopped overnight, but they must be used efficiently and the development of alternatives should be encouraged to help phase them out. Everybody has the right to a good standard of living, with better job opportunities. Economic prosperity is required if our country is to prosper and our businesses must therefore offer a high standard of products that consumers throughout the world want, at the prices they are prepared to pay. For this, we need a workforce equipped with suitable skills and education within a framework to support them.

Population Explosion: Its impact on Environment

Overpopulation is a condition where an organism's numbers exceed the carrying capacity of its habitat. In common parlance, the term usually refers to the relationship between the human population and its environment, the Earth.

Overpopulation does not depend only on the size or density of the population, but on the ratio of population to available sustainable resources. It also depends on the way resources are used and distributed throughout the population. If a given environment has a population of 10 individuals, but there is food or drinking water enough for only 9, then in a closed system where no trade is possible, that environment is overpopulated; if the population is 100 but there is enough food, shelter, and water for 200 for the indefinite future, then it is not overpopulated. Overpopulation can result from an increase in births, a decline in

mortality rates due to medical advances, from an increase in immigration, or from an unsustainable biome and depletion of resources. It is possible for very sparsely-populated areas to be overpopulated, as the area in question may have a meager or non-existent capability to sustain human life (e.g. the middle of the Sahara Desert).

The resources to be considered when evaluating whether an ecological niche is overpopulated include clean water, clean air, food, shelter, warmth, and other resources necessary to sustain life. If the quality of human life is addressed, there may be additional resources considered, such as medical care, education, proper sewage treatment and waste disposal. Overpopulation places competitive stress on the basic life sustaining resources, leading to a diminished quality of life.

If resources required to sustain the organism are being consumed by the organism faster than the resource can be renewed, then the organism is overpopulated. For example, humans are destroying topsoil and consuming fossil fuels much faster than the planet can renew them and those resources are currently required to produce and distribute the necessary quantity of food to feed the population, and therefore humans are overpopulated on Earth.

Effect on Environment

Overpopulation has substantially adversely impacted the environment of Earth starting at least as early as the 20th century. There are also economic consequences of this environmental degradation in the form of ecosystem services attrition. Beyond the scientifically verifiable harm to the environment, some assert the moral right of other species to simply exist rather than become extinct. Environmental author Jeremy Rifkin has said that "our burgeoning population and urban way of life have been purchased at the expense of vast ecosystems and habitats. ... It's no accident that as we celebrate the urbanization of the world, we are quickly approaching another historic watershed: the disappearance of the wild."

Further, even in countries which have both large population growth and major ecological problems, it is not necessarily true that curbing the population growth will make a major contribution towards resolving all environmental problems. However, as developing countries with high populations become more industrialized, pollution and consumption will invariably increase.

The Worldwatch Institute said the booming economies of China and India are planetary powers that are shaping the global biosphere. The report states:

The world's ecological capacity is simply insufficient to satisfy the ambitions of China, India, Japan, Europe and the United States as well as the aspirations of the rest of the world in a sustainable way

It said that if China and India were to consume as much resources per capita as United States or Japan in 2030 together they would require a full planet Earth to meet their needs. In the longterm these effects can lead to increased conflict over dwindling resources and in the worst case a Malthusian catastrophe.

Effects of overpopulation

Some problems associated with or exacerbated by human overpopulation:

Inadequate fresh water for drinking water use as well as sewage treatment and effluent discharge. Some countries, like Saudi Arabia, use energy-expensive desalination to solve the problem of water shortages.

Depletion of natural resources, especially fossil fuels

Increased levels of air pollution, water pollution, soil contamination and noise pollution. Once a country has industrialized and become wealthy, a combination of government regulation and technological innovation causes pollution to decline substantially, even as the population continues to grow.

Deforestation and loss of ecosystems that sustain global atmospheric oxygen and carbon dioxide balance; about eight million hectares of forest are lost each year.

Changes in atmospheric composition and consequent global warming.

Irreversible loss of arable land and increases in desertification Deforestation and desertification can be reversed by adopting property rights, and this policy is successful even while the human population continues to grow.

Mass species extinctions. from reduced habitat in tropical forests due to slash-and-burn techniques that sometimes are practiced by shifting cultivators, especially in countries with rapidly expanding rural populations; present extinction rates may be as high as 140,000 species lost per year. As of 2008, the IUCN Red List lists a total of 717 animal species having gone extinct during recorded human history.

High infant and child mortality. High rates of infant mortality are caused by poverty. Rich countries with high population densities have low rates of infant mortality.

Intensive factory farming to support large populations. It results in human threats including the evolution and spread of antibiotic resistant bacteria diseases, excessive air and water pollution, and new virus that infect humans.

Increased chance of the emergence of new epidemics and pandemics For many environmental and social reasons, including overcrowded living conditions, malnutrition and inadequate, inaccessible, or non-existent health care, the poor are more likely to be exposed to infectious diseases.

Starvation, malnutrition or poor diet with ill health and diet-deficiency diseases (e.g. rickets). However, rich countries with high population densities do not have famine.

Poverty coupled with inflation in some regions and a resulting low level of capital formation. Poverty and inflation are aggravated by bad government and bad economic policies. Many countries with high population densities have eliminated absolute poverty and keep their inflation rates very low.

Low life expectancy in countries with fastest growing populations

Unhygienic living conditions for many based upon water resource depletion, discharge of raw sewage and solid waste disposal. However, this problem can be reduced with the adoption of sewers. For example, after Karachi, Pakistan installed sewers, its infant mortality rate fell substantially.

Elevated crime rate due to drug cartels and increased theft by people stealing resources to survive

Conflict over scarce resources and crowding, leading to increased levels of warfare

Less Personal Freedom / More Restrictive Laws. Laws regulate interactions between humans. Law "serves as a primary social mediator of relations between people." The higher the population density, the more frequent such interactions become, and thus there develops a need for more laws to regulate these interactions.

Some economists, such as Thomas Sowell and Walter E. Williams argue that third world poverty and famine are caused in part by bad government and bad economic policies. Most biologists and sociologists see overpopulation as a serious threat to the quality of human life