Chlorine Pollutants High in DC Tap Water

Tests Find Hazardous Chlorination Byproducts

July 19, 2007

Chlorine Pollutants High in DC Tap Water: Findings

On March 27, 2007, the Washington Aqueduct and Army Corps of Engineers issued a news release advising the public of its annual chlorine burn from April 7 to May 7. During the burn, the utility adds higher levels of chlorine to the system in an attempt to remove residual films and bacteria from the inside of its delivery pipes. The news release warned home users of kidney dialysis machines and owners of aquatic pets, but failed to advise all 1.1 million customers of the Washington Aqueduct about their potential exposure to increased levels of disinfection byproducts.

In light of this exposure and concern over the potential health effects, the Environmental Working Group decided to test water from the District of Columbia for disinfection byproducts (DBPs), in particular total trihalomethanes (THMs) and haloacetic acids (HAAs). Tap water samples were taken from 19 locations in the District from May 1 to May 4, 2007. These locations were distributed throughout three of the four quadrants in the district (NW, NE and SE) and all eight wards (see Table 1).

The sample water was collected from drinking water sources, such as kitchen taps or water fountains, whenever possible, and sent to the Environmental Engineering and Technology, Inc. laboratories to be analyzed for HAAs and THMs. Unfortunately, the vials containing the THM sample taken from one of the sites (the library) broke in transit to the lab, leaving 18 sites from which we were able to assess THM levels.

Table 1: Results of May 2007 D.C. Tap Water testing

Location Sampled Quadrant Description
of sample
Elementary School NW Kitchen Tap 61.2 83.3 52.5
Residence with
pregnant women #1
NW Bathroom Tap 45.5 49.4 37.5
Residence with
pregnant women #2
  Kitchen Tap 50.8 74.9 42.5
Residence with infant NW Kitchen Tap 62.2 67.7 52.6
Residence with
immunocompromised person #1
NW Kitchen Tap 51.9 57.7 43.7
Residence with
immunocompromised person #2
NW Kitchen Tap 41.5 41.3 34.4
Residence with elderly person NW Kitchen Tap 53.5 69.0 44.8
Residence with woman of
reproductive age #1
SE Kitchen Tap 53.5 55.2 45.2
Residence with woman of
reproductive age #2
NW Kitchen Tap 52.7 57.7 43.0
Office catering to
immunocompromised persons
NW Kitchen Tap 50.4 58.8 42.4
Anacostia Park SE Water Fountain 46.7 66.7 39.6
Fort Dupont Park SE Bathroom Tap 55.5 71.7 47.0
MLK Jr. Library NW Bathroom Tap --- 89.4 ---
The National Zoo NW Bathroom Tap 41.3 63.0 34.7
EPA Headquarters NW Bathroom Tap 38.4 37.2 27.9
Federal Courthouse NW Water Fountain 42.6 59.4 35.5
The Capitol NE Bathroom Tap 30.7 24.1 26.8
The National Mall NW Water Fountain 72.8 46.6 63.3
Union Station NE Bathroom Tap 58.2 57.3 49.3