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Chemicals in Drinking Water That May Be Harmful for Your Health 

You should always be aware of the harmful chemicals that are in your drinking water.

Written by:
George Simms
Writer, Plumber, Contractor


There are numerous chemicals in drinking water, but they are generally safe to consume in low concentrations. The Environmental Protection Agency (EPA) issues regulations that water suppliers must follow before delivering drinking water to your home. However, many people have concerns about chemicals in their drinking water regarding potential short and long-term health effects.


Because drinking adequate amounts of water is essential for human health, it's natural to want to know more about the water quality that comes through your faucet.

"As the EPA continually monitors the levels of chemicals in drinking water and any potentially harmful effects, there is plenty of information available for review."

[Possible] Chemicals in Your Water

1. Lead

Lead can enter the water supply when pipes corrode, which can be a particularly serious problem in areas with a high acidity level in the drinking water. The EPA states lead can have adverse short-term side effects such as stomach distress. Lead can cause brain damage in more severe cases, making it a critical concern if it is found in drinking water. 

The maximum allowable lead content is a weighted average of 0.25% calculated across the pipes’ wetted surface, pipe fittings, plumbing fittings, fixtures, and 0.2% for solder and flux. Should a water supplier become aware of the level exceeding these minimum standards, they must contact you as soon as possible and suggest alternative water supplies.

Newer homes use materials such as PVC, or PEX, reducing the risk of lead entering your water supply. However, older homes may still have lead piping, and it is a good idea to replace them with a more modern piping system if you are concerned about lead in your drinking water.

2. Chlorine

Chlorine is one of the most widely used chemicals in drinking water because suppliers deliberately add it to the public water supply. Chlorine is a disinfectant that helps kill viruses, parasites, and bacteria such as salmonella and norovirus. The EPA allows for chlorine levels up to 4 mg per liter in drinking water, but excess chlorination could result in minor or significant health issues. 

People have different levels of sensitivity to chlorine, and the effects depend on how much the person consumes and how much is present in the water. You may notice your water smells or tastes like chlorine, although this does not necessarily indicate your chlorination water levels exceed safe limits.

If you are subject to excessive chlorine exposure, you may experience nausea and vomiting, chest tightness, and watery eyes, amongst other symptoms. In more severe situations, you could have difficulty breathing; seek immediate medical attention if you experience respiratory distress.

3. Arsenic

Arsenic is a naturally occurring chemical found in rocks and soil. Small amounts of arsenic can dissolve into groundwater and subsequently enter the drinking water supply. The EPA currently states that arsenic levels of 0.010 mg per liter are not harmful to human health. However, there can be severe consequences if the chemical is present in higher concentrations. 

Long-term exposure to higher arsenic levels can affect your cardiovascular system, skin, kidneys and lead to various forms of cancer. Because arsenic is tasteless and odorless, you can’t detect if it is in your drinking water. 

However, water supply companies and the EPA monitor the arsenic levels in your drinking water.

"Your physician can also perform tests that determine how much of the chemical is in your body if you are concerned you may be consuming amounts that exceed safe levels."

4. Perchlorate 

Perchlorate is one of the lesser-known  chemicals in drinking water and is both human-made and naturally occurring. Perchlorate is a fertilizer component, although many manufacturers exclude this chemical from their products. 

However, when it is present in the soil, it can travel into water sources and have adverse effects for consumers. Although the kidneys process most perchlorate in your bloodstream, approximately 10% remains in your body and can have devastating consequences. 

Because perchlorate inhibits the thyroid’s iodine uptake, it can lead to hypothyroidism. This condition disrupts how your body regulates temperature, heart rate, and metabolism. The EPA states that it is safe to consume drinking water with a perchlorate level not exceeding four parts per billion (ppb).

5. Mercury 

Mercury is a naturally-occurring chemical element found in rock in the earth's crust, and it is often present in fertilizers and outdoor paints. Mercury can enter the water supply in various ways, making it challenging to prevent contamination. Rocks and soil can release mercury that flows into the water supply via groundwater, and wind and rain can carry it through the atmosphere, depositing it in a water source. 

If consumers improperly dispose of household materials, this can also contribute to increased mercury levels. Items such as batteries contain the chemical which can leak into the environment and mix with groundwater. 

High levels of mercury in drinking water can harm your nervous system, brain, and kidneys, and it’s essential to visit your physician if you suspect you are a victim of mercury poisoning.  The EPA currently approves drinking water with a level of 0.002 mg per liter or below to keep consumers safe from harm.

6. MTBE

Methyl tert-butyl ether (MTBE) is a human-made chemical compound present in gasoline to reduce carbon monoxide and ozone levels produced by auto-emissions. The most likely way MTBE enters the water supply is from leaking pipelines and storage tanks, allowing it to make contact with soil. 

Although MTBE does not absorb easily into soil, it dissolves into groundwater which transports the chemical to streams and lakes that could be a potential water source. If you drink water with unsafe MTBE levels, you may experience dizziness, nausea, headaches, and throat irritation. Experts warn that at high doses, MTBE is a potential human carcinogen.

The EPA does not currently enforce standards on the MTBE levels in drinking water; however, it does provide guidance. By maintaining an MTBE reading of between 20-40mcg per liter, the EPA believes water providers can avoid introducing unpleasant tastes or odors to their supply.

Because MTBE is not subject to the more stringent regulations that apply to other chemicals, you may have concerns about how much of the substance is present in your water supply. You can ask a professional to test your water and provide a report on the levels of any chemicals they find in your drinking water.

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About the Author

George Simms is a Salt Lake City based plumber and contractor, with a focus on aiding homes and businesses (particularly farm) solve problems with hard and contaminated water. Walter is here to share his wealth of job experience and a knowledge of both modern and antique plumbing.

Last Updated on May 20, 2021