The Power of Information
5 Years in a Row
Top rated, 2003-2007
At EWG, our team of scientists, engineers, policy experts, lawyers and computer programmers pores over government data, legal documents, scientific studies and our own laboratory tests to expose threats to your health and the environment, and to find solutions. Our research brings to light unsettling facts that you have a right to know.
Chlorine Pollutants at High Levels 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 |
TTHM/ppb | HAA/ ppb |
Chloroform/ ppb |
| 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 |
Read more:
• Many samples exceeded legal limit for HAAs
• THM levels often higher than what studies show are safe
