Chloroform in Water

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If you get your water from a public supplier, it likely contains a disinfection byproduct known as chloroform. This colorless, odorless organic compound is incredibly toxic and has life-threatening effects when consumed in excess.

This glossary discusses all the most important information about chloroform in tap water, including how it’s formed, its health risks, and how to remove it from your drinking water.

❔ What is Chloroform?

💡 Chloroform is a disinfection byproduct in the trihalomethanes group that often occurs in tap water treated with chlorine. This common contaminant is one of the four chloromethanes that exist today.

Also known as trichloromethane, methane chloride, or methyl trichloride, chloroform is a colorless liquid with the formula CHCl3.

Chloroform has been used for decades in a variety of industrial and agricultural applications thanks to its versatility (it only burns when subjected to very high temperatures).

It was originally used as a solvent, but due to environmental and safety concerns, this use of chloroform has been greatly reduced today. Chloroform was also one of the first inhaled anesthetics used during surgical procedures, but it is no longer used for this purpose today.

Now, chloroform is still occasionally used as a cleansing agent and an ingredient in dyes, pesticides, resins, fluorocarbon plastics, and fire extinguishers. Chloroform is also used in the rubber and pharmaceutical industries. Additionally, chloroform is used as a solvent by chemical companies to produce compounds. The use of chloroform has greatly decreased since its health effects were discovered.

In Water AsCHCl3
SourcesDisinfection of municipal water supplies
Wastewater treatment and wood pulp chlorination
Potential carcinogen
Contaminant Levels (MCLs)
US EPA: 0.07 mg/L
Potential Health RisksCentral nervous system depression
Increase risk in kidney and liver tumors
TreatmentsGranular Activated Carbon Filters
Reverse osmosis
Water Distillers

🩺 What are the Potential Health Effects of Chloroform?

According to a report by the Environmental Protection Agency, some of the potential health effects of chloroform are:

Short-term exposure:

  • Central nervous system depression

Chronic exposure:

  • Liver effects, including hepatitis and jaundice
  • Depression
  • Irritability
  • Increase in kidney and liver tumors

Chloroform is considered most dangerous when it is inhaled in the atmosphere. However, ingestion of concentrated chloroform has also been known to cause serious illness.

The EPA has classified chloroform as a potential carcinogen, and the contaminant has shown to be cancer-causing in animal studies.

🚰 How Does Chloroform Get Into Drinking Water?

Chloroform gets into water during disinfection. Public water supplies are treated with chlorine, chloramine, or other chemicals to prevent bacterial contamination.

When free chlorine reacts with organic matter in water, chloroform and other trihalomethanes are produced as a by-product. Public water disinfection is the primary source of chloroform in tap water.

The more chlorine used to disinfect your water supply, or the higher the concentration of organic matter in your water, the greater the potential for chloroform production.

municipal drinking water chlorination

Public water disinfection isn’t the only cause of chloroform in drinking water, however. Chloroform enters water naturally through the air, too.

📌 Chloroform is known to linger in the air for a long time, and can move easily from the air to a surface water source. Chloroform easily dissolves in water, but doesn’t stick to soil well. This means it may travel down through soil and pollute groundwater sources during snow or rainfall. For this reason, chloroform is often found in private well water supplies – even if well owners don’t disinfect their water with chlorine.

The greater the chloroform pollution in the area, the higher the likelihood of chloroform in surface and groundwater supplies.

Finally, chloroform is produced as a byproduct during wastewater treatment and wood pulp chlorination. If this water is then used for drinking, it may still have concentrations of chloroform by the time it enters the drinking water system.

📉 Do Water Treatment Facilities Monitor Levels of Chloroform in Drinking Water?

Yes, water treatment facilities are legally required to monitor levels of chloroform in drinking water.

The Environmental Protection Agency (EPA) has established Disinfection Byproducts Rules that protect the public from a number of chemicals and compounds produced by water disinfection. All community and non-community water systems must adhere to these rules, including facilities that serve less than 10,000 people.

There are two EPA Disinfection Byproducts Rules in effect today:

  • Stage 1 Disinfectants and Disinfection Byproducts Rule (DBPR): reduces public exposure to disinfection by-products in drinking water systems.
  • Stage 2 DBPR: Outlines more stringent monitoring requirements for haloacetic acids and trihalomethanes (chloroform is a type of trihalomethane).

📌 Under these Rules, the total annual average trihalomethane amount for chloroform, bromoform, bromodichloromethane, and dibromochloromethane shouldn’t exceed 80 mg/L in public drinking water supplies.

Additionally, the EPA produced a separate Maximum Contaminant Level Goal for Chloroform alone:

  • EPA MCLG for chloroform: 0.07 mg/L

Unfortunately, there’s no way to eliminate the potential for chloroform contamination in tap water.

Public water facilities can’t simply stop using chemical disinfectants to decrease the potential concentration of chloroform in water. Disinfection is essential to protect the public from bacteria, viruses, and other pathogens, and chemical disinfection is one of the lowest-cost large-scale methods of water treatment.

laboratory water testing

🔎 How Can I Tell if Chloroform is in My Drinking Water?

As a dense liquid, chloroform is colorless, sweet but mildly pungent-smelling, with a slightly sweet taste. However, in small amounts in drinking water, chloroform is unlikely to have a taste or smell. This means you won’t be able to guess from smelling or tasting your water whether or not it contains chloroform.

The only accurate way to detect chloroform in drinking water is to test a water sample. Laboratory testing is the best testing method for chloroform.

A laboratory will ask you to take a sample of your water and post it to the lab for testing. Your test results will typically be delivered within one to two weeks.

Some laboratories have testing packages that detect individual contaminants, while others might test for other compounds and contaminants that are likely to occur alongside chloroform, like other disinfection byproducts.

Regardless of whether you have well or city water, if you’re concerned about chloroform, get your water tested. Although it’s most commonly produced as a disinfection byproduct, chloroform can also be found naturally in the environment.

water testing with tap score

👩🏽‍⚕️ How Can I Protect My Family from Chloroform in Drinking Water?

In most cases, you won’t be able to prevent chloroform contamination in the first place.

You can, however, remove chloroform from your water before you drink it, protecting your family from this chemical.

Some of the best methods of chloroform removal at home are:

  • Granular activated carbon filters: A high-quality granular activated carbon (GAC) filter should be up for the task of removing small amounts of chloroform from water. GAC filters use adsorption to pull contaminants into their media. As well as chloroform, granular activated carbon can remove other trihalomethanes and chlorine, tastes, and odors. GAC filters are either used as standalone filters (such as in water filter pitchers) or as part of a multi-stage under-sink or whole home filter.
  • Reverse osmosis systems: Reverse osmosis filtration systems use membrane separation to filter contaminants larger than 0.0001 microns out of water. These systems are highly effective at removing trihalomethanes, including chloroform. The RO process is reliable but wasteful – around 1-4 gallons of water are wasted for every 1 gallon produced. Countertop, under-sink, and whole house RO water filters are all available.
  • Nanofiltration: Nanofilters use the same process as RO filters, separating water particles from contaminants with a membrane. Nanofiltration removes virtually all contaminants from water, including trihalomethanes like chloroform. Under-sink nanofilters are most commonly found.
  • Water distillers: The water distillation process boils, evaporates, and condenses water into a separate container. Contaminants that can’t vaporize with water remain in the boiling chamber. Any lingering impurities are removed by an activated carbon filter. Distillation is effective but slow, taking 4-6 hours to purify 1 gallon of water. Countertop distillers are common.
Usws defender whole house ro system after installation

Filters that have been certified by the Water Quality Association (WQA) or the National Sanitation Foundation (NSF) are best for chloroform removal. If a filter is officially certified, it means a third party has tested the system to industry standards and found it capable of living up to the manufacturer’s claims.

If you discover unusually high levels of chloroform in your tap water, switch to bottled water while you decide on the best way to treat the contamination. Make sure to buy bottled water that isn’t chlorinated.

If you own a private well and you chlorinate your water, consider UV purification, which will eliminate the risk of chloroform production in your water. If you use a city water supply and your local water treatment facility disinfects your water with chlorine, contact them to discuss your concerns about disinfection byproducts. While your comments might not incite immediate change, it’s good to make your voice known.

⚠️ How Else Can I Be Exposed to Chloroform?

Aside from drinking chloroform in your water, you might also be exposed to chloroform in the following ways:

  • By inhaling chloroform released into the air from factories that use chloroform industrially, such as pulp and paper mills.
  • By swimming in a chlorinated pool that releases chloroform vapors.
  • By inhaling chloroform found in landfills and hazardous waste sites.
  • By eating foods (such as seafood, bread, meat, dairy products, and vegetables) and drinking beverages that have been produced with chlorinated tap water.
  • By skin contact with water containing a high concentration of chloroform.

📌 Breathing contaminated air and eating contaminated foods are the biggest course of chloroform exposure for most people in the US. Workers in certain environments (such as those working in paper recycling or manufacturing industries or with air conditioner refrigerants) are at the highest risk of being exposed to chloroform.

📝 Where Can I Get More Information?

Follow the links below to learn more about chloroform, its origins, its health effects, and its status as a drinking water contaminant:

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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