Chlorine Pollutants High in DC Tap Water

Tests Find Hazardous Chlorination Byproducts

July 19, 2007

Chlorine Pollutants High in DC Tap Water: Recommendations

Recommendations for consumers:

In 2006, researchers from Universite Laval in Quebec, Canada found that the use of activated-carbon filters is one of the most effective ways for households to reduce THM and HAA concentrations in drinking water (Lévesque, 2006). The study found this method to be more effective than the other methods commonly used to improve the taste, smell and appearance of drinking water - i.e., storing water in the refrigerator for 48 hours prior to consumption and boiling water before storage - and have the added benefit of reducing lead levels which is a particular concern for DC residents.

Carbon filtration systems come in various different forms, including pitchers, faucet-mounted attachments, as well as larger systems that are installed on or under counter tops. Prices vary and may be deceiving since different systems require filter replacement at different frequencies. EWG research shows that pitcher and faucet-mounted systems are typically the most economical, with yearly costs typically in the range of about $100. Counter-top and under-counter systems tend to be more expensive at the outset, though the yearly maintenance costs are often not that much higher than the pitcher and faucet-mounted systems. The prices for all of these systems pale in comparison to the amount that a family of four would spend if they were purchasing bottled water, which EWG estimates to range between $950 and $1,800 per year.

Before purchasing, it is important to do your research, for not water filters using activated carbon remove DBPs. Click here to see a list of some filters that reduce the levels of at least some DBPs. EWG also recommends that consumers examine a recent Consumer Reports study that actually tested more than a dozen of common carbon filters for their ability to remove the THM chloroform. CR found that while many scored “very good” or “excellent,” a number of others scored “fair” or “poor” (Consumer Reports 2007). Click here to find CR’s study. Whatever system you end up purchasing, remember to change the filter according to the manufacturer's guidelines, or it will become clogged and cease to function effectively.

Numerous studies have shown that showering and bathing are important routes of exposure for THMs and certain other DBPs, and may actually contribute more to total exposure than drinking water (OEHHA 2004, Xu and Weisel 2003, Weisel and Laskin ND). One study, for example, found the highest chloroform exposure values among adults taking a 30-minute bath daily (Krishnan 2003). For this reason, consumers should consider purchasing a whole-house filtration system if they want to protect themselves from DBP-related health effects to the fullest extent possible. Consumers should be aware, however, that many whole-house filtration systems don’t actually remove DBPs, and those that do typically cost several hundred dollars to install with yearly maintenance costs that can also run into the hundreds of dollars. This option may also not be worthwhile for those who are more concerned with HAAs than other DBPs, since preliminary research has suggested that showering and bathing are not actually important exposure routes for these compounds (Weisel and Laskin ND).

  • Use a carbon filter to reduce DBPs in your home’s drinking water
  • Consider purchasing a whole-house filtration system to further reduce DBP exposure

Policy recommendations:

Agriculture is the top source of pollution in the Potomac River watershed, but efforts to control agricultural pollution remain largely unfunded. From 1999 through 2005, taxpayers spent five times more money subsidizing farmers in the Potomac River basin as they did on programs to control agricultural pollution - $287 million on subsidies compared to $57 million on conservation and pollution control. In an era of tight federal budgets, political pressure to fully fund farmer subsidies almost always trumps whatever concerns might exist about controlling agricultural pollution. As a result, 4,155 farmers in the Potomac watershed were denied funding for conservation programs in 2004 and 2005 due to lack of available funds.

EWG’s findings argue strongly for keeping sources of tap water clean before they require expensive and potentially harmful treatment with chlorine or chloramines. But until such measures are in place and contaminant levels are dramatically reduced from current levels, EWG recommends that anyone drinking DC tap water use some form of carbon filtration designed to reduce levels of THM and HAAs.

In addition, we recommend that:


  • Farm polices must be reformed to fully fund programs specifically designed to keep agricultural pollutants of all kinds – manure, fertilizer, pesticides and soil – out of tap water supplies.

  • Safety standards for chlorination and chloramine byproducts must be reevaluated in light of research indicating that current regulations are not stringent enough.

  • Greater efforts are put in place to educate the public about the health risks of chlorine and chloramine byproducts and to warn all Aqueduct water consumers of the annual chlorine burn.