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15 Common Water Contaminants & Their Potential Risks

Scott Winfield
Last Updated on
by Scott Winfield

Water is necessary, but contamination can make it unsafe to drink by causing health complications. It is critical to learn, understand, and react to the causes and symptoms of polluted water.

In this article, we will discuss 15 water contaminants you are most likely to encounter and their risks.

Types of Drinking Water Contaminants

Types of Drinking Water Contaminants
Types of Drinking Water Contaminants

According to the Environmental Protection Agency, water-polluting substances fit into four distinct categories. Each subgroup of pollutants affects the physical and chemical properties of water differently, so knowing them will help you identify waterborne threats.

Let’s briefly describe each group and how to recognize them.

1. Physical Pollutants

Physical contaminants primarily refer to pollution caused by rocks and sediments in water. These impurities give liquids visible changes in color, opacity, and texture. As a result, they are among the most obvious pollutants to recognize.

Physical contaminants are extremely common in freshwater bodies where soil erosion happens often. Still water bodies such as large lakes dissolve organisms over time, creating sediment-like materials that pollute water. Drinking still water from lakes or other areas can be dangerous due to pollutants of all kinds.

Water pipelines rarely have trouble with physical pollutants. However, in some cases, the groundwater delivered to households can become contaminated by sediments.

It is more common to encounter physical impurities in above-ground sources. In general, the more quickly a stream or river moves, the less prolific physical contaminants are within it.

Thankfully, unlike other types of water contaminants, physical impurities are not especially dangerous in small quantities. However, a buildup in freshwater sources can kill organisms, creating even more harmful substances in water.

2. Chemical Pollutants

Chemical contaminants are among the most abundant impurities in water sources. They do not alter the characteristics of water as noticeably as physical sediments. Chemical pollutants are both natural and man-made.

Natural chemical pollutants include nitrogen, arsenic, and toxins produced by bacteria. They are often byproducts of runoff, erosion, or organisms within water. These chemicals usually seep into groundwater in small amounts, but they can cause serious health complications through continual exposure and ingestion.

Man-made chemical pollutants include bleach, pesticides, and the corrosion of lead and copper pipelines. Sometimes, these impurities come from improper disposal of chemical wastes like copper sulfate, which are used for pest control and gardening. Soil erosion brings harmful pollutants through streams and down to groundwater, infecting the reservoirs.

Most health complications drinking water can cause are due to chemical pollutants. Common symptoms like nausea, skin discoloration, or worse can occur. Continual absorption of chemical impurities can cause organ damage and increase the risk of cancer.

3. Biological Pollutants

Biological contaminants include microorganisms and microbes. Bacteria, protozoa, viruses, and parasites constitute this category. Most of them are microscopic unless they amass themselves in colonies. Microbes are responsible for waterborne illnesses like cholera and typhoid fever.

Biological pollutants occur in both surface water and groundwater. Water treatment plants use chemicals and filtration to remove as many microbes as possible, but certain kinds are resistant to treatments with chlorine. The main symptom of microbial infection is diarrhea, but nausea, vomiting, and other complications may arise.

Today, most biological contaminants fester in waters that contain large amounts of human or animal feces. Faulty sewage treatment, overflowing waste management areas, and broken aquifers are some cases that can cause these conditions.

Extensive treatment and filtration work well against biological threats.

4. Radiological Pollutants

Radiological components comprise the last category of water contaminants. Almost any ionized chemical can be radioactive, but certain elements like cesium are most common.

Just like arsenic, some elements from rocks called radionuclides erode through rivers over time, polluting groundwater sources.

Similar to chemical contaminants, radiological ones are both naturally-occurring and man-made. Improper disposal of radiological wastes, broken reactors, or nuclear fallout can pollute a water supply.

Once these pollutants fester in a water supply, they harm the aquatic environment, creating more impurities through death and decomposition.

Radioactive elements are closely linked to serious health complications, including cancers. Symptoms and diseases may arise from the repeated intake of polluted water. Radiological threats are impossible to spot with the naked eye.

Although radiological impurities are the least common, they are increasing in magnitude due to heavier reliance on nuclear power.

15 Most Common Water Contaminants

With the four broad categories in mind, here are fifteen water contaminants you are most likely to hear about or encounter.

Where applicable, I will mention ways to identify them and protect yourself from repeated exposure.

1. Silt

Silt is a catch-all term for bodies of suspended geological particles in water. It is a physical contaminant that many different rocks and sands can cause.

Silt in Water
Silt in water

Clay is one of the most common materials in silt. The main identifying characteristic of silt in water is turbidity or clouding. Improving water transparency requires extensive filtration over a long timeframe.

While silt is a contaminant, it is not dangerous to swallow. Most water sources do have some small amounts of clay or silt, but you should still avoid any drinking source that looks turbid. Clay-contaminated water is unpalatable and unappealing.

At the worst, cloudy silt-filled water can impact tourism and recreation by lowering the quality of life in an area.

2. Iron

Like silt, iron is considered a secondary contaminant. It muddies the water and makes its taste unpalatable but does not harm the human body under normal conditions.

Water with high iron content
Water with high iron content

However, iron in water can cause secondary complications like bacterial growth, pipe clogging, and red stains on fixtures.

Iron is natural in the water, carried by rain and erosion. While one kind is soluble and dissolves completely in water, insoluble iron makes the liquid a reddish-brown turbid color.

Like with silt, extensive iron water treatment improves clarity and taste.

3. Lead

Lead is a contaminant that enters water primarily through plumbing pipes and structures. The EPA has been monitoring lead and copper levels in water since 1991 to prevent exposure risks. Areas with water of a higher natural acidity are at a greater risk of pipe corrosion, causing lead pollutants.

Lead in Drinking Water
Lead in Drinking Water

Lead is a toxic metal to ingest, especially for children. However, it is not dangerous to the skin, so it’s fine to bathe or shower in lead-contaminated water.

Thankfully, it’s no longer legal to use lead pipe in modern plumbing systems, but many old cities still retain their old networks. As a result, you may still experience this contaminant in your water.

Lead water contamination was the main cause of the infamous flint water crisis in 2014.

4. Copper

Similar to lead, copper is a toxic metal that enters water supplies primarily through pipes and home fixtures. It does not cause health complications as serious as lead poisoning, but swallowing a large amount is still harmful. Acidic water areas are at higher risk of copper contamination.

Copper in Water
Copper in water

A working technique to reduce the risk of copper contamination is to let the faucet run for a few minutes before using any water. If you do, the built-up copper flakes will be flushed out, leaving behind a much purer water supply for drinking.

As a preventative, if you are remodeling your kitchen or bathroom, avoid using copper and lead pipes or fixtures.

5. Arsenic

Arsenic is a chemical contaminant that exists in nature as trace material in rocks and sediment. This pollutant can enter groundwater either naturally or due to human activity. Mining, pesticides, and animal feed are some man-made methods that can cause an arsenic presence in water sources.

Arsenic in Water
Arsenic in water

Arsenic is most present in certain groundwater reservoirs across the United States. As of 2019, wells in over 25 states have tested positive for arsenic contamination. Unfortunately, you cannot detect this chemical in water. You cannot smell, taste, or see arsenic in tap water or a groundwater supply.

Thankfully, contractors test wells for arsenic after drilling. If they get a positive reading, they will apply water treatment methods to help filter out the pollutants over time.

6. Trihalomethanes (THMs)

Trihalomethanes are a man-made chemical contaminant that occurs when some organic and decomposed matter reacts with chlorine water treatment. THMs will evaporate out of the water easily. However, some people are still exposed to the chemical through household water sources. Inhaling THMs as they vaporize is also dangerous.


Studies and tests are still underway to precisely determine the risks of THMs. However, many scientists agree that inhaling or ingesting them can increase your risk of various cancers.

Since the chemicals are colorless, they are impossible to detect. Reducing your time spent showering, bathing, and swimming in chlorinated water will be an effective defense. You can also ventilate your bathroom often to lower gas-related risks.

7. Pesticides

Improper disposal and handling of agricultural pesticides can contaminate the groundwater. Pest-killing solutions exist in liquid, solid, and powdered forms. They are considered hazardous waste and should be properly disposed of by professionals.

Pesticides in water

While pesticides in water can be deadly, most incidents happen only in small concentrations. However, with enough exposure, you can experience symptoms like dizziness, numbness, and convulsions.

If you live near agricultural areas and encounter these issues from drinking tap water, call the Poison Control Center immediately.

8. Nitrogen

Nitrogen is one of two prominent chemical nutrients that often pollute water sources. It mainly enters waterways through agricultural practices, namely the application of fertilizers.


Plants thrive with nitrogen, but this isn’t always a good thing. A buildup can cause hypoxia in water, killing the environment and harming people who drink it.

Infants under 4 months are especially susceptible to an overabundance of nitrogen in the water. The chemical can restrict oxygen transportation in their blood. High nitrate is also linked to aquifer vulnerability, as this substance can easily seep into the groundwater to pollute it.

If you’re unsure of nitrate contamination in your water, start by doing a nitrate water test.

9. Phosphorus

Phosphorus is the other fertilizer element that can contaminate water. Like with nitrogen, plants grow abundantly due to phosphoric buildups, causing eutrophication. Once they do, they consume a large amount of the water’s oxygen, killing fish and making the liquid harmful to drink.

Phosphorus in water

Phosphorus in water doesn’t do much harm to humans by itself. However, it can encourage algal blooms to grow, many of which secrete toxins that harm people when ingested.

As a result, nitrogen and phosphorus make up a special group of nutrient pollutants. Farmers and agriculturists must take care not to let these chemicals run off into the groundwater.

10. Fluoride

Fluoride is a “good” contaminant in many water sources across the country. Water authorities have purposely added fluoride to drinking supplies for dental health since the 1940s.

Although fluoride has minimal impact on the taste of water, it is beneficial to the human teeth.

Fluoride in water

There have been mixed studies about potential links between fluoride and osteosarcoma, a kind of bone cancer. However, most investigations have not found conclusive evidence. The fluoride in water, though it is a common impurity, won’t cause harm to animals, plants, or human beings.

11. Giardia

Giardia is one of the most common microbial threats that contaminated water can administer. They are parasites that live in human and animal intestines. However, when they’re excreted, they enter shell-like forms called cysts, which protects them until they are ingested again.


Swallowing cysts in water contaminated by faeces is the main way of contracting Giardia.

Long-lasting nausea and diarrhea are key symptoms of Giardia. Infections are far more common in children, so don’t hesitate to contact a doctor if you experience these symptoms after swallowing water from a lake, pool, pond, or river.

12. E. coli

Like Giardia, E. coli is a microbial threat that contaminates water via the stool of humans or animals. Rather than parasites, E. coli is a kind of bacteria. Most strains of the bacteria are harmless, but some can cause severe cramps and vomiting blood.

E. coli
Water contaminated with E. coli

The danger of E. coli is its potency for infection, even in small amounts. Many complications from contaminated water only arise after swallowing a lot, but this bacteria will infect even adults with minimal exposure.

Thankfully, most public water sources treated with chlorine do not cause E. coli outbreaks. However, it is critical to stay vigilant and notify a doctor if you experience symptoms of E.coil contamination such as nausea and diarrhea.

13. Cryptosporidium (“Crypto”)

The CDC lists cryptosporidium as a leading cause of waterborne infection in the United States. Also called “Crypto,” this parasite is shed through stool and lives in human intestines just like Giardia and E. coli. Crypto is far more likely to cause infections through swallowing recreational water like community pools and hot tubs.

Cryptosporidium Water Test

Cryptosporidium parasites are so common because they are resistant to chlorine. They can survive as many as ten days in treated water as cysts. Typically, Crypto infections only last a few weeks, but they can cause severe complications for people with weakened immune systems.

14. Radium

Radium is one of the most common radiological pollutants found in water. It is a naturally-occurring element that forms when elements like thorium and uranium decay. Those components are found as trace amounts in rocks and sands.

Radium Water Test

The dangers of radionuclides lie in their absorption. Fish, animals, and plants can absorb radium from water. However, it can increase the risk of cancer when ingested by humans.

Radium is impossible to see, smell, or taste. Public water systems often test and limit the amount of radium in drinking sources.

15. Radon

Radon is a colorless, odorless gas that forms as radium decays. Water polluted with radium typically also has radon-related risks. It is a carcinogen and the second leading cause of lung cancer in the United States.

Water polluted with Radon

Radon gas issues are most prolific in homes where it rises from the ground through the groundwater. Drafty homes that have piping gaps and aren’t well-sealed are at the greatest risk.

Thankfully, modern technology makes testing and evacuating radon much easier. Still, as a water contaminant, it is responsible for thousands of deaths each year.

What Are the Health Effects of Drinking Contaminated Water?

What Are the Health Effects of Drinking Contaminated Water

Health complications from contaminated water vary by impurity. Many contaminants in the chemical and radiological categories are linked to lung, bone, and brain cancers.

Biological and microbial threats in even trace amounts typically cause vomiting and diarrhea. Almost all contaminants cause nausea and slight discomfort.

Not all contaminants are harmful. Silt, clay, and iron only make water unappetizing and dirty, but they won’t harm you if you swallow them. Fluoride in water is arguably good, even though research on its benefits is still underway.

Thankfully, most harmful contaminants only cause health issues when ingested. Radiological impurities will cause more issues and susceptibility through repeated exposure. Contact your doctor if you experience strange symptoms after ingesting water from a pool, lake, or other aqueous body.

Hospitals have adequate tools for testing for lead, arsenic, and other poisons in your blood. If you are in dire need due to choking, suffocation, or debilitating symptoms, calling the Poison Control Center hotline is your best course of action.

For more information about water contaminants, including uncommon and rare varieties, please consult the Environmental Protection Agency and the Center for Disease Control websites.

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Scott Winfield
Scott Winfield
My name is Scott Winfield and researching and writing about water filters and other strategies to purify water has become my full time passion in recent years. I'm glad that you found our site and you can look forward to authoritative and well researched content here to help you get the best in water.
    1. Hello Bobby, an easy way to test your water is using an at-home water test kit where we provide a link to a recommended kit. If you didn’t want to do it yourself and use a local business we have a recommended water system installer in your area, they are About Time Plumbing and Drain at 813-929-7778.

  1. In a recent broadcast we viewed on water contamination, PERFLUOROOCTANOIC ACID was discussed in detail. Is this a common contaminant in city water in Ventura, California?

    Thank you for your time, attention and response.

    1. Hi Lawrence, thank you for your question. The most definitive way to answer this question is to do a quick water test on your household water and see what’s in there. We have recommended water testing kits on our site, if you’d like to try one of those. That will give you the confidence on what is and isn’t in your water.

  2. It’s great that you talked about how it is important to learn, understand, and react to the causes and symptoms of polluted water. I saw an informercial on the TV last night and it gave some warnings about contaminated water. It is quite alarming, so maybe we should ask for water treatment services.

  3. I live in a condominium located in Palm Beach County. I have been told repeatedly that our pipes would be replaced, which we have recently been assessed for. No one has given me a start date, just the run around. The water that comes out of my faucets leave a pink/yellow slime and/or major soot buildup. It’s disgusting. AND I have pictures of the corroded piping behind the walls. My family has gotten eye infections and skin irritations since moving into this building. What can I do or what are some steps I can take so that I can create a sense of urgency in this matter? After having water tested, and what kind of testing, do I call the health dept or the EPA? Your advice is much needed, please and thank you!!!

    1. Hi Elle, I’m sorry to hear about the state of your water in your condo. It’s not clear if the replacement pipes you’re referring to is by your condo maintenance folks or if you’re talking about your local government and utility. I would escalate to a high level within your condo management organization to make sure this gets a higher priority. If it’s the local government or utility, I would make sure you have communicated with them and documented the issue with a formal complaint or filing. Here’s the information for the Palm Beach County water utility.

  4. Would you address microplastics and pharmaceuticals in the water and which filters are the best to remove these? Thanks

    1. Hi Jill, I would recommend looking at products we’ve reviewed that suit your needs and then you’ll see the capabilities of each that we reviewed. For example, if you’re thinking about an under-sink water filter or a whole-house water system, go to those reviews and you’ll see our results and recommendations.

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