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. Trihalomethanes are not healthy to ingest - and the Environmental Protection Agency has mandated that the concentration of THMs - also referred to as total trihalomethanes (TTHM) in water should be lower than 80 parts per billion.
Important factors in THM formation include the type and concentrations of organic materials in the raw water, the chlorine reaction time, temperature, and chlorination pH. 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 is a result of 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 the former. 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 raw 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, when more hot water is required to maintain the shower temperature, as in warmer months, so that concentrations of chloroform in the warm water used for showering are relatively constant for both periods.
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.
Trihalomethanes are non-naturally-occurring chemicals and 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 TTHM 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 water filters that remove trihalomethanes in their home.
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 are toxic to the liver and secondarily to the kidneys. Skin contact with undiluted chloroform may cause a burning sensation, redness, and blistering.
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 still higher doses given orally, liver abnormalities and decreased size of the reproductive organs were observed in rats. In animal studies investigating effects of chronic exposure to each of the other THMS, liver toxicity was observed. Bromodichloromethane also caused kidney toxicity.
Chloroform has been demonstrated by several studies to produce kidney and liver tumors in rats and mice when given 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 carcinogenicity. 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.
Based on the results of animal studies in which bromodichloromethane exposure increased tumors of the large intestine, kidney, and liver, and bromoform increased tumors of the large intestine, they are also classified as Group B2 carcinogens. Dibromochloromethane is classified in Group C, "possible human carcinogen," based on limited animal evidence of an increase in liver tumors.
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 selecting a TTHM filter is verifying that it 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.
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 Standards 42 (Aesthetic Effects - e.g., chlorine and particulates), 53 (Health Effects - e.g., asbestos, lead, and THMs), and 401 (Emerging Compound/Incidental Contaminants - e.g., pharmaceuticals, pesticides, and herbicides) for the reduction of dozens of contaminants. NSF certification assures you of the accurate performance claims of our systems and our water filters that remove trihalomethanes.
If you are interested in a drinking water system, trihalomethane filter, 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.