What Are Trihalomethanes (THM)?

Trihalomethanes are the result of a reaction between the chlorine used for disinfecting tap water and natural organic and inorganic matter in the water.

When water is disinfected, the reaction between the chlorine (or other disinfectants) and the other matter typically results in the formation of four disinfection byproduct chemicals: chloroform, bromoform, dibromochloromethane, and bromodichloromethane. This group of chemicals is collectively classified as trihalomethanes. Ingesting trihalomethanes is hazardous to your health, and the Environmental Protection Agency (EPA) has mandated that the concentration of THMs – also referred to as total trihalomethanes (TTHM) in water should be lower than 80 parts per billion (ppb).

Important factors in THM formation include the type and concentrations of organic materials in the unfiltered water, the chlorine reaction time, water temperature, and chlorination pH of the water. Chloroform is the most common THM, and because of this, is often the most studied and analyzed of the THMs. Many statistics and conclusions regarding THM exposure are extrapolated from studies examining chloroform exposure.

Concentrations of chloroform are generally higher in chlorinated water originating from surface water than in groundwater, because of higher levels of organic matter in surface water. The extent of formation of chloroform varies with different water treatment processes. Concentrations of chloroform in chlorinated water in treatment plants and distribution systems are approximately twice as high during warmer months as during colder months. This is a consequence of the higher concentrations of precursor organic materials and especially of the higher rates of formation of disinfection byproducts in the unfiltered water during the warmer period. Levels can increase as the chlorinated water moves from the water treatment plant through the distribution system, because of the continued presence of residual chlorine throughout the pipes.

Further increases in concentrations of chloroform in water can occur in domestic hot water tanks; however, storage in the hot water tank increases the level of chloroform twice as much in colder months than in warmer months, when more hot water is required to maintain shower and bath temperatures. This demonstrates that, despite higher base water temperatures during warmer months, concentrations of chloroform are relatively constant for both warmer and colder seasonal periods due to the increased usage of hot water during colder months.

Chloroform (the most common THM) may be absorbed into the body through ingestion, through inhalation, and through skin absorption. The largest source of human exposure to THMs in the U.S. is from the consumption of chlorinated drinking water. Besides consuming water, other water uses in the home may contribute significantly to total chloroform exposure both from breathing in chloroform vaporized into the air and from it passing through the skin during bathing. Swimming in chlorinated pools will also contribute to the total exposure from the same exposure paths. One study observed that a greater percentage of chloroform passed through the skin when bathing water temperatures were increased. Chloroform does not concentrate in plants; therefore, the contribution from food to total chloroform exposure is small.

Why Do People Need Trihalomethanes Water Filters?

Trihalomethanes are chemicals that are not naturally occurring, and are considered environmental pollutants. The EPA has classified many THMs as Cancer Group B carcinogens, with a possible increase in bladder or colorectal cancer over a lifetime of drinking water with high concentrations of THMs – and particularly the THM dibromochloromethane. Other studies have found links between THMs and damage to the heart, lungs, kidneys, liver, and central nervous system. This is a major reason why it is so important to have a trihalomethane filter for your drinking water. It is not enough to use a basic chlorine water filter when TTHM removal is necessary for the healthfulness of your water.

Pregnant women are particularly at risk of THM exposure, as some studies have linked THMs to reproductive problems, including miscarriage. Expectant mothers should therefore especially consider utilizing filters that remove trihalomethanes in water for their home.

Short-Term (Acute) Effects of THMs

In the past, chloroform was commonly used as an inhaled anesthetic. Evidence of chloroform's acute effects on humans comes primarily from these experiences. In addition to central nervous system effects, chloroform anesthesia was associated with cardiac arrhythmias and abnormalities of the liver and kidneys. Inhalation exposure experiments with animals revealed that high levels of chloroform are toxic to both the liver and the kidneys. Skin contact with undiluted chloroform may cause a burning sensation, redness, and blistering.

Long-Term (Chronic) Effects of THMs

Chronic oral exposure of humans to chloroform at high doses results in adverse effects on the central nervous system, liver, kidneys, and heart. Animal studies have shown decreased body weight in rats and mice given chloroform at high oral doses and an increased incidence of respiratory disease at higher doses. At even higher oral doses, liver abnormalities and decreased size of reproductive organs were observed in rats. In animal studies investigating effects of chronic exposure to each of the other THMS – and particularly bromodichloromethane – liver toxicity was observed.

Carcinogenic Effects of THMs

Chloroform has been demonstrated by several studies to produce kidney and liver tumors in rats and mice when administered orally. In studies of human populations using chlorinated drinking water in which chloroform is the predominant THM, small increases in the incidence of rectal, colon, and bladder cancer have been consistently observed, with evidence strongest for bladder cancer. However, because other possible carcinogens were found in this water, it is impossible to identify chloroform as the sole carcinogenic agent. This is why chloroform has been classified by the U.S. Environmental Protection Agency as a Group B2 or "probable human carcinogen," based on sufficient animal evidence and inadequate human evidence of their carcinogenic nature. Evidence from animal studies now strongly indicates that chloroform exposure causes cancer only after first producing sustained cell toxicity. Because a certain threshold level of exposure is necessary to cause cell toxicity, cancer from chloroform exposure can only occur if that threshold is exceeded.

Bromodichloromethane and bromoform are also classified as Group B2 carcinogens: Bromodichloromethane exposure in animals increased tumors of the large intestine, kidney, and liver, and bromoform exposure in animals increased tumors of the large intestine.

Dibromochloromethane is classified as a Group C carcinogen – "possible human carcinogen" – based on limited animal evidence of an increase in liver tumors.

Developmental / Reproductive Effects of THMs

Published studies in which chloroform was administered to animals indicate that chloroform has the potential to cause birth defects, miscarriages, and delays in fetal development. Results have generally been inconclusive regarding exposure to THMs and adverse developmental or reproductive effects in humans. However, the results of a recent study suggest an increased risk of early-term miscarriage from high levels of THMs in tap water, particularly bromodichloromethane. This reinforces the importance of a trihalomethane filter for drinking water in the home.

How to Remove Trihalomethanes From Drinking Water

Activated carbon filtration has been recognized by experts as an effective method for the treatment of THMs in drinking water.

Although filtered water pitchers or self-contained faucet-mount filters may offer a modicum of ability at trihalomethanes removal in drinking water, solid carbon block technology serves as a more effective option for trihalomethanes water filters. A key step in solving how to remove trihalomethanes from drinking water is to verify that a given filter is certified to remove THMs – especially if it is NSF-certified for THM reduction under NSF/ANSI Standard 53.

Some bottled water brands and manufacturers put forth bottled water as an alternative solution to TTHM removal in drinking water, but there is no NSF certification to verify such claims. Furthermore, bottled water is ultimately limited in its applications compared to filtered tap water; bottled water does not serve as a viable solution to THM in water used for washing and preparing food, or in water used for cooking food. Therefore, bottled water is not an effective solution regarding how to remove trihalomethanes from drinking water.
Through a combination of mechanisms including mechanical filtration, physisorption, chemisorption and catalysis, Multipure's solid carbon block filters can effectively reduce the presence of THMs in water, as well as treat the presence of other drinking water contaminants such as asbestos, cysts, particulates, lead, mercury, PCBs, radon, toxaphene, and chlorine.  
Multipure's Aqualuxe, Aquaperform, Aquaversa and Aquamini drinking water systems are NSF-certified according to NSF/ANSI Standard 42 (Aesthetic Effects - e.g., chlorine and particulates), Standard 53 (Health Effects - e.g., asbestos, lead, and THMs), and Standard 401 (Emerging Compound/Incidental Contaminants – e.g., pharmaceuticals, pesticides, and herbicides) for the reduction of the THMs level and the contaminant level of dozens of potential health-risk pollutants in water. Multipure’s NSF certifications assure you of the quality of our water filtration systems, and the ability of our carbon filters to remove trihalomethanes in the water, leaving you with clean water that is healthier for you.  

Order Your Trihalomethane Filter and Other Multipure Products Now

Multipure offers superior drinking water filtration systems and replacement filters that remove THMs from drinking water as well as dozens of additional contaminants. Multipure not only treats THMs in the water, but also offers water disinfection products to ensure cleaner, healthier water for you and your family.

If you are interested in drinking water treatment systems, filters for trihalomethanes, or other Multipure products beyond TTHM water filters or trihalomethanes removal, please contact your local Multipure Independent Builder for more information or check out our products in the Multipure Store.