26 August 2011

Water pollution

Overview: Water pollution is the contamination of drinking water, ground water, or any other source of water on the planet. Contamination may result from a number of sources, such as chemicals or medications that are improperly disposed of, acid rain, industrial waste, or bacteria.



Overview: Water pollution is the contamination of drinking water, ground water, or any other source of water on the planet. Contamination may result from a number of sources, such as chemicals or medications that are improperly disposed of, acid rain, industrial waste, or bacteria.

Water covers about 70% of the earth and is one of the planet's most vital natural resources. All life depends on this compound of hydrogen and oxygen.

Water is important for health, sanitation/hygiene, agriculture, electricity production, industry and commerce, and recreation.

Nearly all of earth's water is located in saltwater oceans and seas. Freshwater (lakes, ponds, rivers, and streams) makes up the remaining three percent of all of earth's water, though much of it is frozen or located underground. This leaves only 0.01% of the planet's freshwater accessible for drinking, according to the U.S. Centers for Disease Control and Prevention (CDC) and the United States Geological Survey.

Water pollution is classified into two types: point source and nonpoint source (NPS). Point source water pollution is discharged directly into a body of water, such as an ocean, river, or stream. For example, emissions from factories, waste treatment plants, and other facilities may pollute water supplies.

NPS water pollution reaches water sources indirectly. This may occur via rainfall or melted snow moving over and through the ground that carries natural and human-made pollutants, such as salt, sediment, fertilizer, bacteria, toxic chemicals, and more. Runoff eventually deposits these substances into lakes, rivers, wetlands, coastal waters, and ground water. This type of pollution is much more difficult to control, and it accounts for most of the contamination in streams and lakes.

Treatment of watersheds is integral to clean water. Watersheds include all land masses and wetlands because all of these areas drain moisture and water in some amount into tiny underwater streams, marshes, aquifers, rivers, lakes or oceans. In this way, any pollutant or contaminant (even one that does not directly touch a water body) is recognized to impact the safety and quality of water on Earth.

Wetlands (marshes, swamps, and bogs) are areas that are saturated with water. Wetland health is an important part of water quality because wetlands directly connect ground to major water bodies such as rivers, oceans, and lakes. Wetlands are located on every continent, except for Antarctica.

Water pollution may also be classified as industrial (such as chemical waste that is dumped into a stream), municipal (which includes waste water from homes and commercial properties), or agricultural (such as pesticides and fertilizers that seep into ground water). Substances that cause water pollution are also classified into the following categories: organic, inorganic, radioactive, and acid/base. Organic sources of water pollution contain carbon. Examples include detergents, waste from food processing, some cosmetic and personal care products, and volatile organic compounds (VOCs), which are chemicals found in many household items, including paints, disinfectants, and aerosol sprays. Inorganic sources have mineral foundations and include ammonia, chemical industrial waste, and fertilizers that contain nitrates and phosphates. Radioactive substances from nuclear plants and other industrial, scientific, or medical facilities may also contaminate water. Acid generally enters water through industrial waste, such as from mining and through the production of chemicals and batteries.

Most water pollution is caused by sewage, fertilizers, silt, pathogens, and radioactive materials, such as nuclear waste, and heat.

Heat may cause water pollution when warm or hot discharge from a factory enters a water body and then threatens the organisms that live there.

Oil spills also contribute to water pollution. The term oil spill often refers to the accidental release of petroleum from an oil tanker into an ocean or other marine habitat. These spills may take years to clean up and impact sea birds, mammals, vegetation, and other marine life. One of the largest and most notable oil spills in the United States occurred in 1989 when the Exxon Valdez dumped nearly 11 million gallons of crude oil in Prince William Sound off the Alaskan coast. In 1990, the Clean Water Act was amended to include the Oil Pollution Act. This legislation gives the U.S. Environmental Protection Agency (EPA) the right to enforce and oversee the clean up of spills from oil and other hazardous substances on U.S. shores and other navigable waters.

Ocean dumping refers to intentionally putting waste into ocean water while offshore. There are international laws prohibiting ocean dumping, one under the United Nations, and another under an agreement made at the International Convention for the Prevention of Pollution From Ships, and referred to as MARPOL (for marine pollution) 73/78.

Water crisis is a controversial term used by some to describe the quantity and quality of water resources on Earth available to meet the increasing demand placed on them. The United Nations declares this to be a very real situation, citing examples of sewage-contaminated river water that is used for bathing and drinking in Africa, poisoned well water in China, and the lack of access in Africa, among many others. Several World Health Organization (WHO) reports have also noted serious problems regarding access to clean, uncontaminated water in a number of parts of the world. The World Water Council points out that although the world's sources of renewable water have expanded, this growth is not keeping up with the growth of the world population, and the expansion of cities and industry.

Water systems in the United States : In the United States, water is classified as either public or private.

Public water systems: Public water systems in the United States are regulated by the EPA. The EPA sorts public water systems into two categories, community and non-community. Community systems provide water to a group of 25 or more residential people all year. Non-community water systems provide water to two subgroups: transient (meaning there is a changing population, as with gas stations, campgrounds, and motels) and non-transient (such as schools, factories, hospitals, and businesses).

There are roughly 155,693 public water systems in the United States. Just more than 30% are community systems and about 67% are non-community systems.

Nearly 10% of community water systems in the United States provide water to more than 80% of U.S. residents via large municipal water systems.

Most community water systems are supplied by ground water via aquifers that feed into wells, but more people get water through community water systems that use surface water, such as water from a reservoir or lake.

Private water systems: The EPA classifies private water as either non public or private. Non-public water systems include bottled waters and water from sources like ponds or streams that are not designated for drinking. Private water systems refer to residential wells for single home residences and for wells and other systems that serve 25 or fewer people for at least 60 days out of the year. The EPA does not regulate privately owned water systems such as private wells. It is the well owners' responsibility to make sure their water is safe to drink. In most cases, this means individual home owners need to check with their local or state governments for guidelines on what to test for and how frequently these tests should be performed.

Water systems worldwide: The United Nations (UN) reports that in 2006, 1.1 billion people around the world had no access to an improved source of water that would provide safe water, such as a household water system, a public standpipe (a freestanding outdoor pipe with a tap attached, used where there is no indoor water), collected rainwater, or a protected dug well or spring.

Slightly more than half of developing nations had access to improved sanitation facilities in 2006, according to the UN. Such facilities might be a simple latrine or a connection to a public sewer or septic system. Nearly 25% of people in developing nations lack any type of sanitation, such as a latrine (usually a free-standing structure allowing for hygienic disposal of human waste), and another 15% use facilities that do not prevent contact between humans and waste.

The combination of unsafe drinking water, lack of water for hygiene, and lack of access to sanitation contributes to about 90% of deaths from diarrheal diseases, mostly in developing countries. A report from the United Nations Children's Fund (UNICEF) states that this translates to the death of more than 5,000 children each day because of diarrheal diseases. (These are caused by viruses, bacteria, and other infectious organisms that pass from one person's stool to another person's mouth.)

The UN has marked March 22nd as the annual World Water Day to bring attention to the need for awareness of adequate supplies of clean water around the world for drinking, sanitation, and hygiene.

Until the 1960s, tap water was generally considered safe for consumption in the United States. After the 1960s, concerns of contamination in municipal pipes and storage facilities began to rise, partly because water testing and analysis became more sophisticated. Other events, like the publicity of Love Canal (a Niagara Falls, New York neighborhood where toxic waste was found to have been dumped and undisclosed to the public in the 1970s) also raised alarm. This combination led to the proliferation of bottled water and home filtration systems

Acid rain: Acid rain comes from both natural sources (such as volcano emissions) and man-made sources (such as emissions of sulfur dioxide and nitrogen oxides from the combustion of fossil fuels). According the EPA, about two-thirds of all sulfur dioxide and one-quarter of all nitrogen oxides result from the production of electric power made by burning fossil fuels such as coal. When the gases emitted from this product are released into the atmosphere, they react with water, oxygen, and other substances to form sulfuric acid and nitric acid that are blown by the wind, sometimes for hundreds of miles. These wind-blown chemicals may then fall to earth in rain, mist, fog, snow, dust, or smoke, causing damage to the environment, monuments and gravestones, as well as harming humans when they breathe in the associated particulate matter. Damage to structures and monuments occurs as a result of chemical reactions between stone, iron, and other substances when the sulfuric acid in the rain contacts them. In the environment, acid rain alters the pH (acidity) and aluminum levels in lakes and streams, which is harmful to organisms and animals that live there. Chemical changes in the soil and air, also caused by sulfuric acid in acid rain, are harmful to trees and other plants, as well as microorganisms living in soil.

Eutrophication: This term refers to the process in which a body of water develops excess organic nutrients that encourage algae growth. These algae blooms in turn remove oxygen from the water and threaten other species in this habitat. As a result of this process, ponds or lakes gradually shrink as they fill with organic matter and sediment. Eutrophication sometimes happens naturally, but it may also be caused by urban storm water runoff, fertilizer runoff, and other pollutants.

Clean Water Act: The groundwork for this act was set in 1948 with the passing of the Federal Pollution Water Control Act. The goal of this Act was to improve water quality and to set national policy on how the government would prevent and handle water pollution. The fast growth of U.S. cities and industry in the early half of the 20th Century led to a widespread pollution of American water supplies and the environment. This situation, and a warning from the Surgeon General saying that water supplies were seriously threatened, led to the enactment of this legislation. In 1972, this Act was expanded to include standards for national water quality, designed to improve water quality and prevent contamination by pollution. In 1977, further amendments were added, and the law became commonly referred to as the Clean Water Act (CWA).

At this point, Congress approved more than 70 changes to the law. Most of these updates strengthened the EPA's ability to control and clean up water pollution, particularly in regard to industrial toxic substances, cleaning up wetlands, and protecting shorelines. The CWA allows the U.S. Government to regulate the discharge of pollutants into U.S. waters, as well as to regulate quality and safety standards for surface waters. (With a permit, certain pollutants may be discharged, provided they meet regulations for quantity and concentration.) It also regulates pollution control standards. The CWA was last amended with the Water Quality Act of 1987. With these amendments, the government began to regulate storm water discharge from industrial and municipal sources and requires regular testing and analysis of waste water.

Effluent water: Effluent water is water that is returned to the environment after industrial use. Effluent water is sometimes used to maintain golf courses and for irrigation.

Drinking water: Drinking water is regulated and protected in the United States under the EPA's Office for Ground water & Drinking Water, which works with the states, EPA regional programs, and other programs. The Office for Ground Water & Drinking Water upholds the Safe Drinking Water Act (SDWA). Passed in 1974 and amended in 1986 and 1996, the SDWA is the federal legislation that maintains the safety of U.S. drinking water supply. The supply also covers sources of drinking water, such as rivers, reservoirs, lakes, springs, and ground water wells.

Tap water: Tap water is also called municipal water or drinking water. The EPA reports that 90% of U.S. water systems are in compliance with their standards for tap water quality. If tap water comes from a water supplier (not a private well), the supplier must provide annual reports on water quality.

Ground water: Ground water flows under the earth's surface, traveling through sand, gravel, and rock cracks in aquifers, which are formations that supply water to streams, rivers, and lakes. Nearly 50% of U.S. citizens get their drinking water from wells. Ground water supports 90% of public drinking water in the United States and around the world and also supports agriculture.

The Ground Water Rule, enacted in 2006, strengthened regulations regarding microbial pathogens (particularly from fecal contamination) in public water systems fed by ground water with more stringent standards. The Centers for Disease Control Division of Parasitic Diseases Healthy Drinking Program aims to cut down the spread of drinking water-associated illness by supporting research, giving advice on prevention of such illness, tracking these illnesses, and responding to outbreaks of illness related to drinking water.

The National Ground Water Association (NGWA) has designated March 8-14 as National Ground Water Awareness Week, which they sponsor. The goals of this campaign are to heighten awareness of the value of ground water in the United States, emphasize the importance of ground water as a valuable resource, and prompt citizens to perform yearly water testing and well maintenance to keep them safe from waterborne illness.

Bottled water: Although tap water is regulated by the EPA, bottled water falls under the jurisdiction of U.S. Food and Drug Administration (FDA). Water is regulated just like food under the Federal Food, Drug, and Cosmetic Act (FFDCA). This Act holds manufacturers responsible for producing safe and truthfully labeled bottled water. There are several types of bottled water, including artesian, mineral, purified, sparkling bottled, and spring, which differ in origin. Opponents of bottled water claim that the quality of bottled water is often no better than unfiltered tap water. Opponents also state that the industry has created an excess of plastic bottles in its wake, and that the environmental cost to transport water is excessive.

Types of water use: Manufacturing and other industries rely on water to produce goods or to run equipment needed to produce goods. Water is necessary for a number of processes, including: fabricating, processing, washing, diluting, cooling, and transporting products, says the U.S. Geological Survey. The largest quantities of water go to production of food, paper, and chemicals.

Water is important in agriculture. More than half of the water that humans take from the earth's fresh water supply is used to water crops. The United States used about 137,000 million gallons of water per day for irrigation (crop watering) in 2000. Nearly 90% of all of this water was used by western states. Together, California, Idaho, Colorado, and Nebraska used half of all water used for irrigation. Though the source of water for irrigation was once primarily surface water, use of ground water has risen dramatically. Water is also critical for raising livestock. One cow drinks 30-45 gallons a day. In 2000, 137,000 million gallons of water were given to livestock daily, with Texas and California using the most.

Water is also used for swimming and soaking in pools, spas, and water parks, as well as at beaches, on lakes, rivers, and oceans. These are all sites where recreational water illnesses (RWI) may be spread by ingesting, breathing, or coming into contact with contaminated water. Symptoms of RWIs may include gastrointestinal, skin, ear, respiratory, eye, neurologic, and wound infections. Diarrhea, which is the most common RWI according to the CDC, is often caused by Cryptosporidium, Giardia, Shigella, norovirus and E. coli O157:H7.


Types of water pollution :

General: Water pollution may be classified as either point-source or nonpoint-source water pollution (NPS).

Point-source water pollution: This type of water pollution involves contaminants that are discharged directly into a body of water, such as an ocean, lake, river, or stream. For example, emissions from factories, waste treatment plants, and other facilities may lead to water pollution.

Nonpoint-source water pollution: Nonpoint-source water pollution arrives indirectly to a water source, via the atmosphere (such as gas emissions from cars) or through ground water and soil (such as fertilizer or pesticides from a farm that run off into a stream or river). This type of pollution is much more difficult to control, and it accounts for most of the contamination in streams and lakes.

Contamination from air pollutants: Toxic air pollutants may affect the quality of soil and water, and therefore, nearby plants, fish, and other wildlife. When humans ingest contaminated food or water, they are susceptible to health risks.

Industrial contamination: The Clean Water Act is said to prevent the more than 700 million tons of pollutants from being released into water in the United States. Yet, according to the United Nations' World Water Development Report, tons of heavy metals, solvents, toxic sludge, and other industrial wastes get into fresh water each year. In developing countries, nearly three-quarters of all industrial wastes are discharged directly into streams and rivers.

Green house gases. Greenhouse gases increase the effect of the earth's atmospheric, heat-trapping layer. The gases, which occur both naturally and from man-made sources (such as fossil fuels), prevent sunlight from bouncing back from earth into the atmosphere. As a result, more heat is kept close to the earth, which in turn raises the temperature on earth. Researchers have shown that a long-term effect of this increase in earth's overall temperature may change weather patterns, raise sea levels, and cause more severe weather. The consequences may put fresh water supplies at risk. Researchers suspect that as sea levels rise, aquifers could become contaminated with salt water not just on the shoreline, but some distance inland, too. Droughts may also cause a drop in water supply from lakes and other water sources.

Chemical poisoning: Chemicals that most often cause pollution in water supplies include: asbestos, carbon monoxide, hydrogen sulfide, lead, nitrogen oxides, halogenated hydrocarbons, and pesticides. Toxic chemicals can be found everywhere, even in drinking water.

Sometimes chemical pollutants enter the water as a result of illegal dumping. This type of dumping may be large-scale and include industrial waste or may be to scale on an individual level.

About 3,000 of the natural and synthetic chemicals in the world are known to cause significant health problems, such as cancer and birth defects. Poisoning due to daily exposure to chemicals is difficult to diagnose, and the extent of damage is more difficult to assess.

Aluminum poisoning: Aluminum may be toxic to the brain and nervous systems in large quantities. It is estimated that an average person takes in between three and 10 milligrams of aluminum per day, from a number of sources. Aluminum is found naturally in the air, water, and soil. It is also used to make cooking pots and pans, utensils, and foil. Other items, such as over-the-counter pain killers, anti-inflammatories, and douche preparations, may also contain aluminum. Aluminum, an additive in most baking powders, is used in food processing, and is present in antiperspirants, toothpaste, dental amalgams, bleached flour, grated cheese, table salt, and beer (especially when the beer is in aluminum cans). The government reports that most fresh water sources, such as lakes and streams, typically have less than 0.1 milligram per liter (mg/L) of aluminum and that little aluminum is ingested via drinking water. Reports from some cities show aluminum concentrations of up to 1 milligram per liter (mg/L) of drinking water, most likely because water may be treated with aluminum salts as part of the process to make it drinking water. The U.S. Environmental Protection Agency (EPA) recommends that drinking water contain 0.05 to 0.2mg/L. The biggest concerns of health experts center on exposure from multiple threats, which may increase an individual's aluminum intake much more dramatically than a single source.

Lead poisoning: Lead is a highly toxic substance. Lead exposure may produce a wide range of adverse health effects on the heart, kidneys, reproductive system, and circulatory system. Exposure in utero or during early childhood may cause slow growth, developmental delays, kidney damage, nervous system damage, seizures, and unconsciousness.

Lead may leach into drinking water from certain types of plumbing materials (lead pipes, copper pipes with lead solder, and brass faucets). While water is usually not the primary source of exposure to lead for children with elevated blood lead levels, formula-fed infants are at an increased risk of lead poisoning if their formula is made with lead-contaminated water.

Healthcare professionals recommend testing water for lead at a local health department if the water comes from a well or if the building has lead pipes, faucets or fitting made of brass (which contains lead), or copper pipes that have been soldered in a building that is either five or more years old or has soft water. Private wells should be checked to make sure the equipment is working properly once each year, ideally in the spring, according to The U.S. Centers for Disease Control. In addition, drinking water from private wells should be tested at least once per year for safety.

Mercury poisoning: Mercury exposure may lead to excessive mercury levels in the body that may permanently damage or fatally injure the brain and kidneys. Mercury may also cause allergic reactions if it is absorbed through the skin. Adverse effects vary depending on how much entered the body, how it entered, length of exposure, and how the individual's body responds.

People are at risk when they consume mercury-contaminated fish and when they are exposed to spilled mercury. Fish absorb methylmercury from water as it passes over their gills and as they feed on aquatic organisms. Larger predator fish, such as swordfish and tuna, are exposed to higher levels of methylmercury from their prey. Methylmercury binds tightly to the proteins in fish tissue, including muscle. Cooking does not significantly reduce the methylmercury content of the fish.

The FDA suggests that fishermen and women check with state or local governments for advisories about water bodies or fish species. These advisories provide up-to-date public health information on local areas and warn of areas or species where mercury (or other contamination) is of concern.

Mercury pollution is released into the air from the burning of fossil fuels. Mercury vapor is easily transported in the atmosphere, deposited on land and water, and then, in part, released again into the atmosphere. Trace amounts are dispersed in bodies of water, where bacteria may cause chemical changes that transform mercury to methylmercury, a more toxic form.

Radon poisoning: Radon is a naturally occurring, odorless, and colorless gas produced by the breakdown of uranium in soil, rock, and water. Radon exposure generally occurs in the home or workplace. Radon sometimes enters a home through well water. It may also seep in through cracks in floors and walls and gaps around pipes and other fittings.

Waterborne outbreaks. A waterborne outbreak occurs when pathogens, chemicals, or toxins enter water. An outbreak is defined by the presence of two or more infections that come from the same source and are traced to the same water exposure. Outbreaks can be spread by inhaling, ingesting, or coming into contact with contaminated water. According to the U.S. Geological Survey, the largest outbreak of this nature in the United States took place in 1993 in Milwaukee, Wisconsin. The presence of the protozoan Cryptosporidium in drinking water caused 403,000 people to get sick and led to 104 deaths.

Waterborne diseases are caused by the spread of pathogens through contaminated water. Examples include amebiasis, buruli ulcer, campylobacter, cholera, cryptosporidiosis, cyclosporiasis, guinea-worm disease, escherichia coli, fascioliasis, giardiasis, hepatitis, leptospirosis, norovirus, rotavirus, salmonella, schistosomiasis, shigellosis, and typhoid fever.

Lack of clean water for sanitation and hygiene may also lead to diseases such as lice, lymphatic filariasis, ringworm, scabies, soil transmitted helminthiasis, and trachoma, according to the U.S. Centers for Disease Control and Prevention (CDC). Many neglected tropical diseases (NTD) are also linked to poor or unsafe drinking water and a lack of proper sanitation and hygiene. The term NTD refers to a group of tropical diseases that are widespread among poor populations in Africa, Central and South America, and Asia, and include Buruli ulcer, dengue/dengue hemorrhagic fever, guinea-worm disease, fascioliasis, lymphatic filariasis, onchocerciasis, schistosomiasis, and trachoma.

Personal choices: Modern society is normally described as a consumer society, which is based on the goal of constantly increasing the production and consumption of consumer goods. This lifestyle directly contributes to water pollution. Packaging for goods and foods that contain dye, for example, are eventually deposited in landfills and make their way into ground water. Chemical-based cleaners with toxic chemicals that are washed down household drains are another example. Relying on cars adds to emissions of acid and hydrocarbon, which end up in water supplies.

Recycling, limiting purchases of such goods, substituting less harmful products for potentially dangerous ones (such as replacing cleaners containing harmful chemicals with those that have only natural ingredients), and relying more on walking and cycling and less on automobiles for transportation are all options to help reduce water pollution.

Techniques for treating waste water :

Household sewage: Household sewage is treated by sewage plants in urban areas and by private septic tanks in areas where there are no municipal facilities.

Sewage treatment plants: Municipal treatment plants are typically run by local government. These plants manage pollutants, such as suspended solids, fecal coliform bacteria, pH, and biochemical oxygen demand (BOD), and in some cases, may also treat pathogens and nutrients, as well.

Septic tanks: These devices treat waste water from homes and small businesses and then release it into the soil.

Industrial waste water: Waste water that contains large amounts of conventional pollutants (such as oil), toxic pollutants (such as heavy metals, volatile organic compounds (VOCs)), or pollutants such as ammonia are required to operate treatment systems designed to handle these substances. In some cases, a pre-treatment system takes out toxic matter and forwards the partially-treated waste water to a municipal system. When waste water is produced in large quantities, manufacturers tend to have systems that can complete treatment. A number of strategies can be used to remove pollutants from industrial waste water. Skimming and solvents are used to remove oil from sea water after a spill, for example. Large industries, such as refineries, use special separating devices to remove oil or gas. Activated sludge and filtering systems are used to remove biodegradable elements that come from plants or animals. A trickling filter, for example, runs waste water through a layer of peat moss or gravel plus a layer of microbial slime with oxidizing agents to clean it.

Agricultural waste water: Treating agricultural waste water involves a wide range of techniques and technologies designed to deal with the particular products being produced. These range from runoff from fertilizer and pesticides, waste water and waste milk from dairies, and waste from animals and slaughterhouses, for example. Animal waste may be simply covered or contained to prevent runoff. Sometimes special lagoons are built to contain waste so it runs off or seeps out gradually, or mixed with straw and made into compost. Waste from dairy milking facilities may be sent to sewage plants and mixed with human waste, or spread over land and used as fertilizer. Water from cleaning vegetables, which may contain traces of pesticides, as well as chlorine from the washing process, is usually filtered and recycled into soil.

The development of sustainable farming practices, designed to have less impact on the earth and environment, should help minimize water pollution from agricultural sources. There is controversy over which practices qualify as truly sustainable, but many recognize organic farming, crop rotation, and urban farming practices, such as vertical farming, as sustainable practices.

Researchers are studying new techniques to help minimize water pollution in the agricultural industry. For instance, they are investigating the effectiveness of carefully placed vegetated buffer strips and straw mulch to lower the impact of harmful microorganisms from animal waste and storm water runoff.

Storm water: Development and urbanization inevitably leads to the production of urban runoff. When storm water picks up contaminants such as gasoline, oil, garbage, fertilizer, substances like nickel, copper, and lead found in paving, etc., it is called urban runoff. Some of this water is prevented from sinking into the ground by impervious surfaces such as asphalt, cement, and concrete, as well as by building roofs and other man-made structures. However, some of the urban runoff enters drains and water sources and may end up in ground water.

Storm water is managed in terms of quantity and quality, sometimes both at the same time. Prevention of water pollution from storm water includes using low-impact development practices, building "green" roofs, and installing mitigation systems, such as constructed wetlands, retention basins, and infiltration basins, and using biofilters.

Waterborne pathogens: Bacteria levels are monitored at all state beaches and some local beaches to help ensure safe swimming. Advisories are posted on the EPA Web site. The CDC offers guidelines on how to control germs and pathogens in pools and spas with chlorine disinfection. Chlorine can kill bacteria such as E. coli, viruses such as hepatitis A, and parasites such as Giardia and Cryptosporidium. The spread of feces or germs that may cause infections may also pose a health threat in public swimming facilities. Lack of disinfection in pools and spas may cause outbreaks of skin infections, such as Pseudomonas dermatitis or hot-tub rash, caused by uncontrolled bacteria. Ozone is also used in place of chlorine to control and kill bacteria and microorganisms in public water used for drinking.


General: Water may be contaminated with a number of agents. According to the U.S. Centers for Disease Control (CDC), the number of outbreaks of waterborne disease has recently increased in the United States. In addition, natural disasters such as earthquakes, hurricanes, and floods, which can also threaten clean water, are on the rise. Water may also be accidentally or purposely contaminated by humans who add pathogens, chemicals, or toxic substances.

Toxic pollutants, such as mercury or chemicals in pesticides, for example, may contaminate fish and other organisms living in water. In addition, pollutants that get into soil may contaminate fruits and vegetables. Animals that eat such contaminated vegetables may produce eggs or milk that also contain toxins.

Researchers from the University of California, Berkeley, used epidemiologic studies and other data to estimate the number of acute gastrointestinal illness that may be attributed to public drinking water in the United States. They believe there are between 4.26 and 11.69 million cases per year, but acknowledge that new data will help them set a more accurate figure.

Waterborne diseases: Waterborne diseases are caused by the spread of pathogens through contaminated water and include amebiasis, buruli ulcer, campylobacter, cholera, cryptosporidiosis, cyclosporiasis, guinea-worm disease, escherichia coli, fascioliasis, giardiasis, hepatitis, leptospirosis, norovirus, rotavirus, salmonella, schistosomiasis, shigellosis, and typhoid fever. Most waterborne diseases cause diarrheal illness, which the CDC reports are responsible for 1.5 million deaths around the world each year. This results from a lack of safe water and proper sanitation and hygiene. Other waterborne diseases may result in malnutrition, skin infections, and organ damage.

Data collected in the United States from 2005 to 2006 suggest that Legionella pathogens have been the most common cause of outbreaks among those recently reported by the Water Borne Disease Outbreak Surveillance System. The data also show that many waterborne disease outbreaks are found in ground water, as opposed to surface water. It is suspected that this is because private water systems do not have to be disinfected, but those that serve the public do. The report also indicates that most of the cases where drinking water has been contaminated do not involve public water systems.

Data collected in the United States by the CDC from 2005 to 2006 suggest a significant increase in reports of waterborne disease outbreaks connected with recreational use and aquatic facilities. Most of the incidents happened during the summer and involved gastrointestinal illness, often due to issues with water quality, poor facility design, and maintenance.

One of the biggest waterborne disease outbreaks in the United States occurred in 1993 in Wisconsin. More 400,000 people became ill with diarrhea, as a result of the parasite Cryptosporidium, which was found in Milwaukee's municipal drinking water supply. According to a report in the New England Journal of Medicine, crypotspordium oocysts (thick-walled structures) went through the city's filtration system at a water treatment plant, and were not identified via water-quality testing.

The National Water Quality Inventory (2000) states that agricultural nonpoint source (NPS) pollution (runoff from rain or snowmelt that carries pollutants) from industrial and sewage treatment plants has the most impact on water quality in rivers and lakes. It is also the number-two contributor to wetland damage and is a significant cause of contamination to surveyed estuaries and ground water.

Environmental medicine: Practitioners of environmental medicine aim to minimize or eliminate a patient's exposure to specific environmental stressors, such as contaminated ground water, exposure to radon gas, or mercury poisoning through fish and seafood. The goal is to create an environment of clean air, water, and food. For instance, a patient may be instructed to put tap water through a water filter before drinking it.


General: Water pollution has varied and far-reaching effects. Impact may include, but is not limited to, contamination of drinking water; spread of waterborne disease to animals and humans; poisoning of animals, humans, and vegetation; and disruption of aquatic ecosystems.

The water supply in the United States is considered to be one of the safest in the world, according to the U.S. Centers for Disease Control and Prevention (CDC). Public water in the United States is regulated by the Environmental Protection Agency (EPA). Private water companies are monitored by the U.S. Food and Drug Administration (FDA).

Many medical experts suggest that climate change may contribute to the rise in deadly diseases and serious environmental consequences, including water pollution. For example, a rise in sea levels may lead to the contamination of water supplies. In addition, more frequent and more severe weather may lead to droughts and floods, which in turn may lead to water contamination and cause an increase in water borne disease outbreaks.

Air pollutants: Toxic air pollutants may also affect the quality of water, and therefore, soil, nearby plants, fish, and other wildlife. Ingesting foods and beverages that have been contaminated with polluted water may have ill effects on humans and other animals.

Airborne pollution may lead to acid rain. This may damage waterways, plants, structures and vehicles, and also increase the acidity in soil.

Research also suggests that the chemical compounds released in cigarette smoke include toxic metals such as arsenic and mercury, carcinogens (cancer-causing substances) such as pesticides and benzene, and poisons such as carbon monoxide (CO) and ammonia. These compounds may contaminate bodies of water and the plants and animals within them.

Lack of sanitation: The combination of unsafe drinking water, lack of water for hygiene, and lack of access to sanitation contributes to about 90% of deaths from diarrheal diseases, mostly in developing countries. The United Nations Children's Fund (UNICEF) reports that this translates to more than 5,000 diarrhea-related deaths in children each day.

Half of the world's population does not have access to clean water, making it a common cause of conflict. Wars in underdeveloped nations are often over control of resources, including water.

Regions with unsafe drinking water and poor sanitation and hygiene have high rates of tropical disease. The CDC reports that millions of people are infected with neglected tropical diseases (NTD), such as Guinea Worm Disease (GWD), Buruli ulcer, trachoma, and schistosomiasis.

GWD is a parasitic infection that is spread through contaminated drinking water. In 2007, more than 9,500 cases were reported, mostly in the African countries of Sudan and Ghana.

Trachoma, the number-one cause of preventable blindness across the globe, may occur without proper hygiene and sanitation. Nearly 41 million people have trachoma, and roughly another 10 million are either blind or visually impaired because of trachoma.

Lack of proper sanitation increases the risk of soil-transmitted helminths (parasites such as flatworms and roundworms), which infect more than one billion people around the world.

Worldwide, diarrhea-related illnesses caused by food and water poisoning are among the leading causes of death. Travelers to developing countries often encounter food poisoning in the form of traveler's diarrhea. Traveler's diarrhea typically develops after ingesting food or water that is contaminated with infectious agents from feces, including various bacteria, viruses, and parasites. The most common cause of traveler's diarrhea is enterotoxigenic Escherichia coli (ETEC) bacteria.

Industrial waste: Perhaps the most famous U.S. case of industrial contamination of public drinking water took place in the 1950s and 1960s in Hinkley, California. Activist Erin Brockovich was a key player in making a case against Pacific Gas and Electric Company of California, which allegedly was responsible for allowing waste water that contained hexavalent chromium, a carcinogen, to leach into ground water near one of its plants. The contamination was thought to have spread over an area roughly two by one miles in area. The lawsuit was settled for more than $300 million in 1996.

Consumption-based lifestyles: One issue with consumer-based societies, such as the United States, is waste management. When a manufacturer increases the volume of output and reduces the cost of production by dumping polluted water or chemicals into the environment, there is a high probability of negative effects on the health of surrounding populations and wildlife. The environmental impacts of waste disposal include spreading landfills, water pollution, air pollution, and energy consumption.

Water is almost always required by manufacturers, so the growth of consumer products industry often leads to depleted water supplies, which may negatively affect food production and sanitation.

The EPA considers that many textile manufacturing facilities generate hazardous waste; this industry may also contribute to water pollution. With the rise in production in the fashion industry, demand for man-made fibers, especially polyester, has nearly doubled in the last 15 years. Manufacturing synthetic fabrics releases volatile organic compounds (VOCs), particulate matter, and acid gases such as hydrogen chloride, all of which may cause or aggravate respiratory disease. Solvents and other by-products of polyester production are often dumped into waste water.

Agriculture: The quantities of manure and methane produced by industrial farming may become toxic. Animal waste that is not properly contained and disposed of may seep into ground water or run off into bodies of water.

Similarly, pesticides used on crops and antibiotics used on animals may also seep into ground water or run off into various bodies of water, including streams, lakes, bays, and wetlands. Researchers are also concerned about the effects of pesticide-contaminated water on human health, as it has been associated with low-birth-weight infants, an increased risk of breast cancer, and reduced sperm counts.

Slaughterhouse waste may also contaminate water sources.


Treatment of water: Treating water varies by source.

Agriculture: Researchers are studying new techniques to help minimize water pollution in the agricultural industry. For instance, they are investigating the effectiveness of using carefully placed vegetated buffer strips and straw mulch to lower the impact of harmful microorganisms from animal waste and storm water runoff.

Storm water: Development and urbanization inevitably leads to the production of urban runoff. When storm water picks up contaminants such as gasoline, oil, garbage, fertilizer, substances like nickel, copper, and lead found in paving, etc., it is called urban runoff. Some of this water is prevented from sinking into the ground by impervious surfaces such as asphalt, cement, and concrete, as well as by building roofs and other man-made structures. However, some urban runoff enters drains and water sources and may end up in ground water.

Storm water is managed in terms of quantity and quality, sometimes both at the same time. Prevention of water pollution from storm water includes using low-impact development practices, building "green" roofs, and installing mitigation systems, such as constructed wetlands, retention basins, and infiltration basins, and using biofilters.

Coastal health threats: A 2009 study explains that although innovative techniques are helping researchers better understand pathogens in coastal areas, other advances are necessary. The author calls for a need for improved techniques that will help identify potentially harmful microbes in environmental samples. In addition, there is a need for more research to improve the understanding of water-transmitted diseases and the microbes that cause it. Researchers aim to establish a system that can set off early warnings when the health of an ecosystem is at risk.

Drinking water: The U.S. Environmental Protection Agency (EPA) is focusing research on the following issues in regard to the portable water industry: corrosion control, formation and removal of by-products of ozonation microbials and disinfection by-products (DBPs) and chlorination DBPs, and the removal of pathogenic protozoa, (such as Cryptosporidium and Giardia lamblia).

Concerns about safe drinking water have led to new products to address the problem. A California company, for example, developed a way for consumers to get drinking water from the air in their home. Their water cooler-sized appliance runs on electricity, and condenses moisture in the air, filters it, and stores it in hot and cold dispensers. They claim this filtered water is 99.99% free of all chemicals, solids and contaminants.


This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (

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