Shower Filters May Be Critical THM Defense

A study says chlorination by-products are absorbed at high rates in showers. by Ted Montuori, News Editor Some consumers who are worried about trihalomethanes (THMs), by-products of chlorination that have been associated with health risks, have typically felt that tap-water treatment alone was a full defense. However, a new study shows that consumers may be as exposed to THMs when they take showers, as to when they drink water.

Researchers at the University of North Carolina (UNC) at Chapel Hill’s School of Public Health say THMs can sometimes get into the blood stream via a shower at levels four times greater THM levels in tap water. High THM concentrations have been linked to cancer and other reproductive problems after long-term exposure. The Study The study—conducted over four weeks in 1999 on 50 women in Cobb County, MA, and Corpus Christi, TX—was done to evaluate whether health workers could use THM levels in drinking water to predict concentrations in people’s blood. THM concentrations in blood were measure before and after showers.

Researchers found that after subjects took showers, the THM levels in their blood streams were actually four times higher than the THM levels of the water coming out of their taps. The research showed that THMs were getting into blood as a result of water use but could not address whether concentrations were harmful or if they were linked to any health problem, according to Amy M. Miles, a co-author of the report about the study.

Research support came from the American Water Works Research Foundation, Denver; the Centers for Diseases Control and Prevention, Atlanta; and the US Environmental Protection Agency (EPA). The groups will perform a follow-up study that will include additional variables, such as having each subject shower for a specified amount of time, and showering with the bathroom door closed so no THMs can escape the area, according to Miles. Consumers may be as exposed to THMs when they take showers as when they drink water.

Shower Filters can Help If anything, the study showed that consumers who are worried about removing THMS from their water need to consider their showers, and not just their drinking-water taps. Some shower filters (Omica, Pelican) can remove THMs, as well as the potentially lethal gas radon, according to John Douglas, president of Paragon Water Systems Inc., Clearwater, FL.

Shower filters are often made of copper and zinc granules, known as oxidation-reduction (redox) media. There are many formulations of this media that get varying degrees of results, depending on the chemical nature of the water going to the consumers home, Douglas said. “After installing your shower filter, my roommate took the first shower and going into the steam filled room after he was done smelled very noticeably different. I never dreamed that such poison fumes came from tap water… my skin and hair feel better but I especially appreciate the lack of fumes and full water flow.” N.G., Hamden, CT THMs: Effects Debated In August 2000, researchers at the IWK Grace Health Centre, Dalhousie University and Queen’s University, Kingston, Canada, reported they found a link between high levels of chlorine by-products in drinking water and still-births. THM contamination in a Virginia drinking water supply sparked more than 160 lawsuits filed last year from women who attribute THMs to miscarriages and stillborn babies they suffered during the 1990s.

But there are some opposing views to the link with reproductive problems. In August 2000, results of a study by researchers from Kaohsiung Medical University and Memorial Hospital, Taiwan, reported no correlation between chlorine disinfection and low birth weight.

However, the research found a statistically significant link between pre-term delivery and disinfection by-products. THMs: A History THMs are a group of four organic chemicals—bromoform, chloroform, dibromochloromethane and dichlorobromomethane—that form in water when chlorine being used as a disinfectant reacts with natural organic matter. They became a public health concern because of their suspected carcinogenic nature, and in November 1998, the EPA lowered the maximum contaminant level of the four species in drinking water, from 100 parts per billion (ppb) to 80 ppb. The amount of THMs in drinking water depends significantly on concentrations of chlorine and raw water found in a water supply.

– T.M., Water Technology,, July 2002