Short Answer: Yes, the berkey water filter systems equipped with the standard black berkey filters WILL remove THM (Trihalomethanes) from the water to below lab detectable limits!

Trihalomethanes, or Thms as they commonly referred to, are four chemicals that together with other types of disinfection byproducts form as a result of a chemical reaction that occurs between chlorine (or similar disinfectants that are added to drinking water to kill harmful microbes) and organic and inorganic material that may be present in the water.

The four THMs — bromodichloromethane, dibromochloromethane, tribromomethane (bromoform) and trichloromethane (chloroform) — are regulated by the US Environmental Protection Agency (EPA) under the Stage 1 Disinfectants and Disinfection Byproducts Rule, with a maximum allowable yearly average of all four THM chemicals combined (i.e. total trihalomethane levels) set at 80 parts per billion (ppb).

Health Risks Associated with Exposure to THMs

All four THM chemicals are by products of the chlorination process, which is employed in an effort to rid drinking water from pathogens and make it safe for us to drink. However, THMs are carcinogenic and laboratory experiments have shown that they cause cancer in animals. Of the four THM chemicals, dibromochloromethane poses the greatest cancer risk (0.6 ppb increases the cancer risk by 10-6 ), followed by Bromoform (at 4 ppb), and Chloroform, the most common THM found in drinking water (at 6 ppb).

Other health concerns associated with THM exposure include damage to liver, kidneys, bladder and central nervous system. Studies also show a link between THM exposure and disorders of the reproductive system, including disruption of the menstrual cycle, infertility, miscarriages, stillbirths and birth defects.

But the risk is not limited to drinking tap water alone. A study which was published in the scientific journal Environmental Health Perspectives confirms that bathing and showering are both significant sources of THM exposure, and even inhaling steam from a family member's shower or conducting activities such as dish washing by hand can expose a person to THMs.

How to Remove THMs in Water with a Berkey Water Filter

According to the Water Research Center, THM concentrations tend to rise with temperature, pH, and time, and are also influenced by the level of organic precursors that react with chlorine to form THMs that are present in the water. Consequently, in order to reduce THM levels, it would be prudent for water treatment facilities to reduce or eliminate chlorinating the water before it passes through the filters, and to filter out the precursors that react with chlorine before chlorine is added to the water to disinfect it.

Consumers can also take their own measures to reduce their exposure to THMs. Activated carbon filters, such as the Big Berkey filters fitted with Black Berkey filter cartridges remove THMs to undetectable levels, offering the most effective method of removing unwanted thrihalomethanes and other disinfection byproducts as well as chlorine, organic particulates and other harmful contaminants.