What are the Common Water Contaminants?

Water Contaminants

Water contaminants are substances such as heavy metals, agricultural and industrial chemicals, hydrocarbon fuels, radioactive materials, sewage, pharmaceutical drugs, and biologic agents such as bacteria, parasites, and viruses. When these substances contaminate water, they make it unsafe for drinking, cooking, cleaning, swimming, and other activities.

Humans are exposed to water contaminants either through drinking or bathing in contaminated water and sometimes even through consumption of food that was grown or prepared using contaminated water. These contaminants then enter the human body and can pose danger to health by causing disease directly or by acting as poisons or carcinogens.

This article gives an overview of the common water contaminants, which include the following pollutants.

  • Arsenic
  • Fluoride
  • Selenium and Uranium
  • Iron
  • Ammonia
  • Aluminum
  • Barium
  • Chromium
  • Cadmium
  • Copper
  • Bacteria and Viruses
  • Lead
  • Silver
  • Chloramine
  • Perchlorate
  • Mercury
  • Nitrates/Nitrites
  • Polycyclic Aromatic Hydrocarbons (PAH)
  • Pesticides

1. Arsenic

Arsenic is a naturally occurring element in the earth’s crust and can be found throughout the environment including air, water, and land.

Human exposure to arsenic occurs mainly through water, where it is present as a tasteless and odorless chemical, in its highly toxic inorganic form. Arsenic can be both a natural contaminant in countries such as Argentina, China, India, and some parts of the United States, and an industrial and agricultural contaminant of groundwater sources. Drinking arsenic-contaminated groundwater, eating crops irrigated with or food prepared with arsenic-contaminated groundwater are the major sources of human arsenic exposure.

According to World Health Organization (WHO) estimates, over 140 million people in more than 50 countries have been exposed to arsenic levels in drinking water that are higher than their provisional guideline value of 10 μg/L.

Arsenic can cause both acute and long-term effects on human health, which are summarized in this infographic.

Affect of Arsenic on Human Body

Acute arsenic intoxication is uncommon as it requires a high arsenic concentration in drinking water. Nonetheless, acute arsenic intoxication can present most commonly as gastroenteritis manifesting with nausea, vomiting, “rice water” diarrhea, and abdominal pain. More complex cardiovascular, pulmonary, renal, and neurologic symptoms and signs can then compound these gastrointestinal symptoms.

Long-term effects of chronic low-dose arsenic exposure through drinking water are more common and usually appear after more than five years of exposure. The most common manifestations are palmar and plantar hyperkeratosis and characteristic transverse white Aldrich Mees lines across the nail plate.

The International Agency for Research on Cancer has implicated arsenic as a cause of lung, bladder, skin, and kidney cancer and found lung cancer to be the most common cause of death related to long-term arsenic ingestion.

The National Institute of Environmental Health Sciences in the United States has linked arsenic exposure to chronic cough and dyspnea, bronchiectasis, diminished lung function, diabetes, developmental effects in children including low birth weight, spontaneous abortion, decreased cognitive functioning, ischemic heart disease, peripheral vascular disease, and chronic renal disease.

2. Fluoride

Fluoride is a naturally occurring inorganic ion of Fluorine. Fluorides are usually white or colorless and have a characteristically bitter taste. In low concentrations, fluoride is beneficial for dental health and so is sometimes deliberately added to municipal water supplies. In part because higher concentrations are harmful to human health, fluoridation of tap water is a controversial issue and some regions deliberately do not allow it. The chart below displays the percentages of the population drinking fluoridated water in various countries, as recorded by the British Fluoridation Society.

Countries that Fluoridate their Drinking Water

Fluorides are found naturally in several minerals such as fluorspar, cryolite, and fluorapatite. Sodium fluoride, fluorosilicic acid, and sodium hexafluorosilicate are used in trace amounts for municipal water fluoridation.

Fluoride is present in underground water sources throughout the world as a result of environmental leaching and industrial contamination. The United States Environmental Protection Agency in their “Drinking water criteria document on fluoride” reports that approximately 0.2% of the United States population is exposed to over 2.0 mg/liter of fluoride in their drinking water. This pales in comparison to fluoride exposure in other parts of the world. For example, exposure levels were measured at or greater than 8 mg per liter in Tanzania and China.

Fluoride contamination of water does not generally pose a threat until intake levels through drinking water rise over 1-2 mg per liter. At these concentrations, a condition called fluorosis develops. Fluorosis can affect dental enamel making it porous, mottled, and opaque, and can cause bone and joint deformities with joint pain and stiffness due to mineralization of ligaments, cartilage, and periarticular muscles and demineralization of bone.

3. Selenium and Uranium

Elemental selenium is a naturally occurring element that is insoluble in water. In the environment, elemental selenium can be reduced and/or oxidized to selenite and selenate forms which are water-soluble.

Most drinking water contains much less than 10 μg per liter, according to the WHO’s background document on Selenium in Drinking water. Levels of selenium may be significantly higher in seleniferous areas around the world. Drinking water from a seleniferous area in China was reported to contain 50–160 μg of selenium per liter of drinking water. The map below displays water contaminant concentration levels of uranium in drinking water aquifers as recorded by the journal Environmental Science and Technology Letters in the United States.

Levels of Uranium and Nitrates in Drinking Water

Acute ingestion of high doses of selenium, which is highly unlikely to occur from contaminated drinking water, can cause nausea, diarrhea, abdominal pain, chills, tremor, numbness in limbs, irregular menstrual bleeding, and marked hair loss. Long-term exposure to low doses of selenium has been linked with hair and nail loss and brittleness, mottled teeth, discolored skin lesions, and changes in peripheral nerves.

Uranium is found naturally in the environment. It most commonly occurs in granite and various other mineral deposits. It is most commonly used as fuel or as catalysts and staining pigments. Much of the uranium that contaminates drinking water is present because of either leaching from natural deposits or pollution from the milling, nuclear, and agricultural industries.

In the United States, the Environmental Protection Agency (EPA) during the 1980s found a mean uranium concentration of 2.55 µg/liter at 978 drinking-water sites. Uranium can occur at much higher concentrations. Uranium concentrations greater than 20 µg/liter of drinking water were found in some parts of New Mexico in 2002.

The known effects of uranium on the human body include renal damage. Its other effects have not been studied in humans, but animal studies suggest that both acute and chronic exposure to uranium has the potential for carcinogenesis, and mutagenesis, as well as for reproductive and developmental toxicities.

4. Iron

Iron is abundant in nature and combines with sulfur- and oxygen-containing compounds to form sulfides, carbonates, hydroxides, and most commonly oxides. Natural iron from the ground and from man-made sources can contaminate water. This image shows old corroded cast iron pipes.

Rusting Old Cast Iron Water Pipes

Average iron concentrations are 0.7 mg/l in river water, 0.5-10 mg/l in groundwater, and 0.3 mg/l in drinking water, according to the WHO’s background document on iron in drinking water.

Iron concentrations of 40 µg per liter and 0.12 µg per liter can be tasted in distilled and mineralized waters, giving them a strong metallic taste. Iron can also settle out of solution and alter turbidity and color of water, imparting a cloudy or rust-colored appearance once concentrations reach above 0.05–0.1 mg/l in plumbing systems.

Consumption of iron in drinking water is unlikely to pose any harm to health, as iron is an essential element in human nutrition. Humans require a minimum daily amount of iron ranging from 10 to 50 mg/day.

5. Ammonia

Ammonia is a frequently employed chemical used in the production and manufacturing of fertilizers, animal feed, fibers, plastics, explosives, paper, and rubber. Ammonia is also frequently used as a cleaning agent and as a food additive.

Ammonia is most commonly present in drinking water due to disinfection with chloramines or because of leaching from cement mortar used for coating the insides of water pipes.

The WHO’s background document on ammonia in drinking water does not view this chemical's presence in drinking water to have any direct implications on one’s health. The average concentrations of ammonia in drinking water are usually less than 0.2mg per liter. However, concentrations of ammonia at 0.2mg or greater in chlorinated water can cause the formation of chloramines which have an unpleasant taste and smell and can hamper the disinfection process.

6. Aluminum

Aluminum is the most common metallic element on earth. It is frequently found in the environment as aluminum chloride, aluminum hydroxide, aluminum oxide, or aluminum sulfate. It can be found combined with organic matter and other elements. This picture shows what crystalline aluminum oxide looks like, which is quite different from the finished metal we normally think of.

Crystalline Aluminum Oxide

Aluminum is often used as a coagulant during the treatment of municipal water systems. Aluminum salts, most commonly aluminum sulfate, are added to municipal water to reduce organic matter, color, turbidity, and microorganism levels before other treatments.

The concentration of aluminum in drinking water depends on levels found in the source water and whether aluminum coagulants are used during water treatment processes. Water with low pH is more prone to dissolve aluminum, therefore concentrations of aluminum in acidic water are often higher compared to water with near-neutral or alkaline pH.

Surveys conducted in the United States found that the average aluminum concentrations for drinking-water samples ranged from 0.01 to 1.3 mg per liter, and the average aluminum concentrations for drinking-water samples from facilities using aluminum sulfate coagulation ranged from 0.1 to 2.7 mg per liter.

The effects of aluminum on human health are not well studied, but research in the past has shown that there may be a possible association between aluminum ingestion and diseases of the nervous system, particularly Alzheimer’s disease. Aluminum can act as an accumulation sink for other more hazardous contaminants such as arsenic, chromium, manganese, and nickel and can influence the concentrations of lead and copper.

7. Barium

Barium is a naturally occurring alkaline metal. In nature, it does not exist in its elemental form but rather in a combined form with other elements. Common barium compounds include barium sulfide, barium chloride, barium oxide, barium hydroxide, barium sulfate, barium acetate, and barium carbonate.

Barium, mostly barium sulfate and barium carbonate, is found freely in nature as ore deposits. Leaching and erosion of these deposits can contaminate groundwater sources. In 1987 the US EPA determined that barium was present in most surface and groundwater sources at levels less than 0.34 mg/l. Studies around the world in the 1980s and 1990s found barium in drinking water sources (the Netherlands mean of 0.23 mg/L Van Duijvenbooden, 1989; Canada median of 18 µg/L Subramanian & Meranger, 1984; Sweden 1-20 μg/L HSDB, 2014; Norway 9 μg/L, Flaten, 1991).

Based on these studies, the WHO’s background document on barium in drinking water estimates that an average adult in the United States consumes approximately 30 µg of barium per liter of water.

Acute barium intoxication through water is uncommon. Approximately 3-4 g of barium are required to elicit symptoms and signs of barium toxicity, which can include gastroenteritis, hypokalaemia, acute hypertension, cardiac arrhythmia, and skeletal muscle paralysis. Chronic exposure to barium has been associated with hypertensive vascular disease and cardiac disease. The potential health effects of barium consumed in drinking water are shown below.

Health Effects of Barium in Humans

8. Chromium

Chromium, in its various oxidation states, exists throughout nature in soil and rocks. It is used in industrial settings for chrome plating, dye production, textile production, leather tanning, Portland cement, stainless steel production, welding, and wood treatment.

Water pollution by chromium can occur through leaching of naturally occurring chromium from topsoil or rocks and from industrial contamination. Contamination of drinking water with hexavalent, manmade, chromium (Cr[VI]) poses the greatest risk as this form of chromium is particularly toxic to humans. This is discussed in further detail in the video below, covered by CNN.

Chromium polluted water can cause a broad array of negative health effects. Allergies and sensitization to chromium compounds in water frequently occur and can cause contact dermatitis (rashes from touch) as well as renal and liver toxicity. Gastrointestinal irritation, sperm damage, and anemia have also been reported.

Studies in laboratory animals by the United States National Toxicology Program have shown clear increases in gastrointestinal cancers following Hexavalent chromium ingestion. This information is corroborated by studies done in Liaoning Province, China where during the 1960s there was massive contamination of water by waste residues from a ferrochromium production facility. These studies showed that over the following decades, exposed areas had increased mortality from gastrointestinal cancer.

Drinking water contributes substantially to chromium intake, especially when total chromium levels are above 25 μg/liter. The WHO’s publication Guidelines for Drinking-water Quality (GDWQ) reports that approximately 18% of the US population is exposed to drinking water chromium levels between 2 and 60 μg/liter and less than 0.1% to levels between 60 and 120 μg/liter.

9. Cadmium

Cadmium is a metal found naturally in sulfide ores along with zinc and lead. Cadmium is used in various industries for anticorrosive electroplating of steel, electric batteries, electronic components, and nuclear reactors. This picture shows natural cadmium sulfide.

Natural Cadmium Sulfide

Cadmium rarely makes its way into water naturally. Industrial and agricultural contamination of potable water are the main sources of cadmium pollution. Contamination of drinking water may occur from leaching of cadmium from the zinc of galvanized pipes that contain cadmium impurities or cadmium-containing solders in fittings, water heaters, water coolers, and taps.

Cadmium water pollution does not appear to be a major concern. In 1989 the WHO conducted tests to detect cadmium levels in over 110 stations around the world and found the median concentration of dissolved cadmium in water to be less than 1 µg/L, and the daily intake from drinking water to be usually less than 2 μg per day.

Acute cadmium toxicity is rare, but chronic exposure to cadmium has been associated with renal disease and associated loss of protein, phosphorus, and calcium leading to the development of kidney stones and osteomalacia. This clinical picture has been termed “Itai Itai” disease, which was detected in Toyama Prefecture, Japan, starting around 1912 following mass cadmium contamination of water sources as a result of mining of silver, lead, copper, and zinc.

10. Copper

Copper is a transitional metal that is used heavily in the manufacturing industry, due to its versatility. Copper can be used for manufacturing wiring, pipes, valves, fittings, coins, utensils, and building materials. Production of fungicides, algicides, insecticides, fertilizers, and wood preservatives utilizes copper.

Copper can be found in all types of water, including drinking water. Concentrations of copper in municipal water systems are highly variable and dependent on characteristics of the water such as pH and hardness, as well as on copper availability in the municipal distribution system.

The primary source of copper contamination is most often the corrosion of interior copper plumbing. It is estimated that individuals consume 0.1-1 mg of copper per day from drinking water, according to the WHO’s background document on copper in drinking water. This number can be significantly higher if standing or partially flushed water from a distribution system that includes copper pipes or fittings is consumed.

Dissolved copper imparts a turquoise color as well as an unpleasant metallic, bitter taste to drinking water when its concentration reaches 2.4-2.6 mg per liter.

High levels of exposure (4-400 mg of copper per kilogram of body weight) can produce gastrointestinal bleeding, haematuria, intravascular hemolysis, methemoglobinemia, hepatocellular toxicity, acute renal failure, and oliguria. Though this is highly unlikely to occur from drinking copper contaminated water.

Low doses of copper result in symptoms characteristic of food poisoning such as headache, nausea, vomiting, and diarrhea. This video shows the impact of copper contamination on the water, soil, and people near a long-closed mine in Uganda.

11. Bacteria and Viruses

Bacteria and viruses are termed bio-contaminant pollutants.

Bacterial waterborne disorders are associated with organisms such as Escherichia coli (E. coli), Mycobacterium avium, Legionella species, Helicobacter pylori, and Cyanobacteria species.

Drinking water may be contaminated by a variety of viruses which include Hepatitis A, enteroviruses, echoviruses, coxsackievirus, Norwalk virus, rotavirus, caliciviruses, and adenoviruses.

Although these bio-contaminants can cause a vast array of illnesses, the most common health effect of waterborne biocontamination is an acute diarrheal disease. Loose watery stools, which are often accompanied by vomiting and fever, characterize this disease. According to WHO statistics, acute diarrheal disease-related to biocontamination of drinking water by bacteria and viruses affects nearly 1.7 billion children globally and is the second leading cause of death in this demographic, claiming 525,000 lives each year.

12. Lead

Lead is one of the most common heavy elements found on earth.

Lead contamination of water occurs in small amounts from the dissolution of natural sources, but primarily via leaching from old household plumbing systems (pipes, solder, fittings, or service connections) that contain lead. This is what occurred in ancient Roman pipes, and the infamous Flint, Michigan water crisis, as detailed in this video from Vox.

A typical adult has an average daily intake of lead from water of 5 µg/l, according to estimates in the WHO’s background document on lead in drinking water. Globally they estimate that over 240 million people are exposed to lead-contaminated water, and over 850 thousand deaths per year can be attributed to these exposures.

Lead exposure can cause central nervous system problems such as headaches, fatigue, muscle weakness, delirium, seizures, polyneuropathy with wrist or foot drop, encephalopathy, and paresthesias. Other symptoms of lead exposure can include kidney disease, anemia, severe abdominal pain (lead colic), constipation, linear hyperpigmentation on gums, as well as a wide variety of hematologic symptoms and signs.

13. Silver

Silver nitrate and silver chloride are the most important silver compounds that contaminate drinking water.

Silver is used in a variety of industrial manufacturing processes, and soluble silver compounds may be used as external antiseptic agents, disinfectants, and as bacteriostatic agents.

The average concentration of silver in natural drinking waters in the United States is 0.2–0.3 μg per liter, while the average concentration of silver in drinking water that was treated with silver for disinfection was as high as 5 µg per liter, according to the WHO’s background document on silver in drinking water. Under most circumstances, the contribution of silver-contaminated drinking water to overall human exposure to silver is usually very low.

Chronic occupational exposure to silver is known to cause a condition called Argyria, which is characterized by the deposition of silver in the skin, hair, and various organs. These effects are shown in the images below, although Argyria is unlikely to result from drinking water contamination.

The Effects of Argyria Condition in Humans

14. Chloramine

Chloramines (mono-, di-, tri-) are produced when chlorine and ammonia mix in water, and remain there as “residuals”. The formation of these colorless, unstable liquids is dependent on their concentrations and the physicochemical properties of water.

Chloramines are used to disinfect drinking water. They are used in pipes between treatment plants and homes because they are a longer-lasting disinfectant, according to the US EPA. They ‌possess moderate biocidal activity against bacteria and low biocidal activity against viruses.

Chloramines can alter the taste and smell of water at very low concentrations. Concentrations below 5 mg/L and sometimes as low as 0.3 mg/L can be reliably tested by individuals, according to the WHO’s background document on chloramines in drinking water.

Approximately 75% of municipal water systems in the US have finished water with chloramine residual levels of 1.0 to 3.0 mg/L.

There is no specific evidence linking chloramines to adverse health outcomes, although reports of an association between chloramines and methemoglobinemia as well as colon and bladder cancer are discussed by the WHO.

This picture shows chloramine powder manufactured in Germany in 1940.

Chloramine Powder from 1940 Germany

15. Perchlorate

Perchlorates are chemicals containing the ClO-4 perchlorate ion. Water pollution by perchlorate can occur through industrial contamination or from perchlorate that is naturally occurring. Perchlorate has been used industrially as an oxidizer in solid rocket propellants, slurry explosives, road flares, and airbag inflation systems.

Perchlorate water pollution inhibits iodide uptake by the thyroid gland. Iodide is the main component of thyroid hormone, and blocking iodide uptake into the thyroid gland can decrease thyroid hormone production which plays a key role in numerous physiologic processes. This is called hypothyroidism and is of particular concern in fetuses and children as thyroid hormones are critical for their normal brain and neurologic development. A study from the National Institute of Health in the United States found that decreased thyroid hormones during pregnancy and early childhood lead to decreased cognitive development and IQ.

The United States Water Works Association found that within the US, perchlorate contamination of drinking water was a widespread issue. They detected perchlorate in the drinking water of at least 26 states and approximately 5% of public water systems.

The surface soil of Mars contains about 1% perchlorate, a major challenge that will need to be overcome to produce a safe, locally grown food supply in any future colony. In this video, planetary scientists Jani Radebaugh and Dan Durda explain the health problems perchlorate would have for people on the planet if they can not remove perchlorate from food and water.

16. Mercury

Mercury is a metallic element that occurs naturally in the environment. Mercury used to have broad use in manufacturing industries, but the spectrum of uses is decreasing due to environmental concerns and legislation in many countries.

Mercury pollution is a serious problem in South America, Africa, and other regions where illegal gold mining operations use mercury to purify gold into finished form. Mercury has contaminated soils, water, and air (because it is burned off the finished gold) and caused widespread illness. This VICE News investigation shows the harrowing impacts of Mercury in Colombia.

Mercury occurs naturally in groundwater and surface waters at concentrations of less than 0.5 μg/L, according to the WHO’s background document on mercury in drinking water. Geographic variations have a profound effect on these concentrations. Rainfall may also contain mercury in the range of 5–100 ng/L, which may contaminate groundwater sources.

It is estimated that drinking mercury-contaminated water provides an average daily intake of 1µg of mercury. As such, mercury in drinking water is considered to be a minor source of exposure to mercury except in circumstances of significant pollution. Acute intoxication with mercury can include gastroenteritis and renal failure, which are not as common.

Chronic exposure can produce Minamata disease which is characterized by glomerulonephritis, ataxia, erethism (abnormal irritability), tremor, polyneuropathy, as well as characteristic gingival and/or buccal inflammation with bluish‑violet discoloration of the gum margins. Mercury has been shown to have the ability to cause fetal defects, known as teratogenicity. This video explains the discovery of Minamata disease in Japan in the 1950s following the release of mercury into local waters which built up in locally consumed seafood.

17. Nitrates/Nitrites

Nitrates are naturally occurring chemicals that form when nitrogen is combined with oxygen or ozone. Although nitrates are commonly found in food and food preservatives, the most common source of nitrates is industrial fertilizers.

Ingestion of water contaminated with nitrates causes the conversion of nitrate to nitrite in the body. Nitrite can bind to hemoglobin in red blood cells to form methemoglobin. This compound binds to oxygen more tightly than hemoglobin and is less effective at releasing oxygen to tissues. This phenomenon is ‌dangerous in infants and causes “blue baby syndrome” which is characterized by difficulty breathing, vomiting, diarrhea, and cyanosis (a bluish-purple discoloration of the skin because of poor oxygen concentration in blood). Infants who drink water containing high concentrations of nitrate can become gravely ill and, if untreated, may even die.

Environmental pollution of bays and estuaries by nitrates is an ecological problem that can be hazardous to human health. Nitrates are an important source of nutrition for aquatic algae and plants, but too much can cause excessive growth, known as blooms. These pictures show algal blooms seen up close and from the air to illustrate how large they can become.

Algae Blooms Seen from Space and Ground Level

Certain types of algae blooms produce biotoxins harmful to humans. These can make their way up the animal food chain and eventually reach humans. The clearest example of this is human paralytic, neurotoxic, and diarrhetic shellfish poisoning, which results from the consumption of mussels or oysters that have been harvested from waters that experienced algae blooms.

Nitrate water contamination is a serious problem, especially in countries with prominent agricultural industries. A US Environmental Working Group analysis of data from 10 states, found that community tap water systems in the Midwest, Southwest, Atlantic Coast, and California which supply over 21 million people contained nitrate levels at or above 3 mg/L. This shows contamination above naturally occurring levels according to the US EPA.

18. Polycyclic Aromatic Hydrocarbons (PAH)

Polycyclic Aromatic Hydrocarbons (PAHs) are a heterogeneous group of compounds that all contain two or more fused aromatic rings of carbon and hydrogen atoms. They occur in hydrocarbons including oil, gasoline, and coal. They are released into the environment when coal, oil, gas, wood, garbage, or tobacco are burned, according to the US Centers for Disease Control (CDC).

Fortunately, PAHs are not highly soluble and are not usually found in drinking water in notable concentrations. The most common PAH found in drinking water is fluoranthene, which leaches from coal tar coatings of cast iron or ductile iron drinking-water distribution pipes, used to protect them from corrosion.

The level of PAHs in uncontaminated groundwater ranges from 0 to 5 ng/L, while their concentrations in contaminated groundwater may exceed 10 μg/L, according to the WHO’s guidelines for drinking-water quality. Typical concentrations of PAH in drinking water range from 1 to 11 ng/L. This diagram from the US EPA shows how PAHs can enter the water supply.

How Polycyclic Aromatic Hydrocarbons (PAH) Enters the Water Supply

Acute intoxication with PAH is not documented, but there are a variety of long-term adverse effects. PAHs are carcinogenic to humans and have been liked with cancers of the lung, skin, esophagus, colon, pancreas, bladder, and breast.

19. Pesticides

Agricultural pesticide chemicals such as organomercurials, chlorpyrifos, azinphos-methyl, atrazine, alachlor, diazinon, carbaryl, and fipronil used to control weeds, insects and other pests produce serious water pollution problems. These chemicals have been shown to have a wide range of damaging effects ranging from male sterility and cancers to poor childhood neurodevelopment.

According to the United States Geological Survey (USGS), there are hundreds of different pesticide chemicals including herbicides, insecticides, and fungicides used in the United States. The USGS reports that approximately 390 million kilograms of these chemicals are used annually with some of them contaminating critical sources of drinking water. A recent 2021 USGS study reported that 16 "urban signature pesticides" (USPs) were consistently found in small streams in urban centers across five regions of the United States.

The diagram below from the Water Science School displays how pesticides are transported through streams and runoff water throughout the environment.

How Pesticides get into the Ecosystem

How Dangerous are the Contaminants of Water for People's Health?

The contaminants of water vary in danger to people’s health from no noticeable effects at low concentrations to extreme danger including cancer and life-threatening diarrheal diseases.

Water pollution from heavy metals and chemicals such as arsenic, mercury, chromium, and lead cause chronic damage to organs including the liver, kidney, brain, endocrine, and reproductive organs. Contaminants such as arsenic, fluoride, nitrate, and PAHs can cause a variety of cancers that involve the gastrointestinal, urinary, and reproductive tracts among others.

Biological contaminants cause a variety of “Water-Related Diseases'' according to the WHO. These most commonly include diarrheal diseases such as cholera, typhoid, amoebic and bacillary dysentery that affect over 1 billion people and cause 2.2 to 5 million deaths annually.

The high level of danger from these contaminants and their associated conditions are clear when we look at morbidity and mortality associated with water contaminants. The WHO recently reported that approximately 2 billion people around the world lacked safe drinking water, and that approximately 829 thousand people, of which 297 thousand were children aged under the age of 5 years, were estimated to die each year from water pollution-related diseases, chiefly infectious diarrhea. This map gives the number of people without access to safe drinking water by country as of 2020.

Population Without Access to Safe Drinking Water

What Types of Water Include more Contaminants?

Surface water and groundwater are the types of water that include more contaminants compared to drinking water. Drinking water has fewer contaminants because it has been rigorously tested and if necessary treated to remove contaminants.

Groundwater, according to the USGS, is water that exists underground in saturated zones beneath the land surface called aquifers. Surface water is freshwater that is derived from streams, rivers, lakes, and reservoirs.

A great deal of both groundwater and surface water is polluted throughout the world, but to a different extent. More than 22% of groundwater samples contained at least one contaminant at a concentration of potential concern for human health, according to the National Water-Quality Assessment Program undertaken by the United States Geological survey.

Surface water generally has even more contaminants than groundwater. The US EPA in its National Rivers, Streams, and Lakes assessment found that almost 50% of rivers and streams and nearly 30% of lakes within the United States are polluted and unfit for consumption or even recreational use. This is to be expected as surface water is much easier to pollute with the runoff of pesticide-contaminated agricultural water and indiscriminate disposal of industrial, municipal, and domestic wastes in water channels, rivers, streams, and lakes.

Does Iceberg Water Include fewer Contaminants?

Iceberg water contains fewer contaminants than surface and groundwater on average. This is because icebergs are originally pure snow that fell centuries or millennia ago before modern pollution and was then compacted and preserved inside a glacier. Icebergs have a density similar to concrete, which prevents contaminants from penetrating inside. Water derived from icebergs thus has extreme chemical and physical purity.

How to Learn What Water Contaminants are in Your Area

You can learn what water contaminants are in your area from regional government services, including municipalities, environmental agencies, and utilities. These organizations are required to provide annual water quality reports to their consumers. These reports contain information about the quality parameters of potable water, among which are measured levels of the various mineral, metal, chemical, and biological contaminants.

To obtain this information, the simplest method is to do an internet search for “water quality report” and the name of the region in which you are interested. Adding the name of the government agency or utility responsible for the area will help further narrow the search. In the European Union, such information is available on the website of the European Environment Agency. Below is a sample water quality report, retrieved from Thames Water Utilities Limited in the UK.

Sample Water Quality Report

How to Remove Water Contaminants in Your Water?

You can remove water contaminants from your water via point-of-entry or point-of-use systems. Point-of-entry systems are installed after the water meter and treat all the water that enters a building. Point-of-use systems are attached to specific outlets such as kitchen and bathroom sinks and remove contaminants only from the water delivered through those taps.

The most frequently used contaminant removal systems include the following.

  • Filtration systems use physical, chemical, or biological processes that remove contaminants from drinking water.
  • Distillation systems essentially boil the water and collect the steam in a separate condensation chamber, while leaving behind many solid and dissolved contaminants.
  • Disinfection systems use chemical (chlorine, ozone) or physical (UV light, electronic radiation, heat) agents to kill and/or inactivate pathogenic microorganisms.

In developed countries, there is no need to remove contaminants from household water as local municipal and governmental organizations regulate their levels and keep their concentrations at “acceptable” levels. Yet some individuals still choose to further reduce contaminant levels in their household water to remove specific pollutants or to improve the organoleptic properties of their water. Homes supplied by well water are more likely to need purification systems depending on the quality of the local groundwater.

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