Chlorine Pollutants High in DC Tap Water

Tests Find Hazardous Chlorination Byproducts

July 19, 2007

Chlorine Pollutants High in DC Tap Water: Many samples exceeded legal limit for HAAs

Due to the higher than normal chlorine levels added to tap water during the chlorine burn, EWG expected our tests to reveal higher than average levels of chlorination byproducts, particularly THMs. What we found was while THM levels were not significantly increased, many samples contained very high levels of HAAs: HAA levels were their highest since the switch to chloramination in 2001, and 42% of the samples had HAA concentrations higher than the EPA’s legal annual limit for these compounds, known as the maximum contaminant level (MCL). More than two-thirds of the samples were within 95% of the annual MCL. The sample with the highest HAA concentration, the Martin Luther King Jr. Memorial Library, surpassed the annual MCL by almost 50%, rising to a concentration of almost 90ppb.

Notably, the HAA levels in seven locations (37% of our samples) were higher than any of the maximum detected HAA concentrations reported by the water utility in the past 6 years (2001-2006), including samples from two public parks (Fort Dupont Park and Anacostia Park), an elementary school and the residences of pregnant women and infants. This finding is interesting as it implies that HAA levels during the chlorine burn return to those found before Washington Aquaduct switched to chloramines.

Chart showing Washington DC haloacetic acid levels



Source: D.C. tap water samples collected by EWG from May 1 to May 4 2007. Samples analyzed by Environmental Engineering and Technology, Inc. laboratories in Newport News, VA.

Notes: 1. Allowable limit in tap water, the Maximum Contaminant Level (MCL), is set at a level higher than some suspected health risks because EPA sets drinking water standards under the Safe Drinking Water Act by balancing health concerns against treatment costs and feasibility. The MCL is based on the annual average concentration. The unit ppb is parts per billion of HAAs in water or micrograms (µg) per liter.


Chart showing haloacetic acid levels in 7 of 18 locations are higher than any of the maxium levels reported by the water utility in the past 6 years (2001-2006)


Source: HAA test results from D.C. Water and Sewer Authority(DCWASA) are the maximum reported detections from Washington Aqueduct's annual water quality reports for customers( EWG's May 2007 test results from samples collected by EWG from May 1 to May 4 2007 and analized by Environmental Engineering and Technology, Inc. of Newport News, VA

HAAs have been classified by the EPA as possibly carcinogenic to humans because of evidence of carcinogenicity in animals. According to the EPA, long-term consumption of water that has HAA concentrations in excess of the agency’s safety standard is associated with an increased risk of cancer (EPA 2002). A technical bulletin released by the Oregon Department of Human Services (2004) also warned that long-term exposure to HAAs at or above the MCL might cause injury to the brain, nerves, liver, kidneys, eyes and reproductive systems.

While there have been few epidemiological studies on the potential health effects of HAAs, there is evidence suggesting that HAA exposure during the second and third trimesters of pregnancy may be linked to intrauterine growth retardation and low birth weight (Hinckley 2005; Porter 2005). Two HAAs, dichloroacetic acid and trichloroacetic acid, have been shown to cause severe skin and eye irritations in humans (NTP 2005).

Additional studies point to concerns with specific HAAs. Dibromoacetic acid has been shown to disturb the balance of the intestinal tract, whereby increasing the risk of opportunistic bacteria colonizing this tract and cause disease, especially in immunocompromised hosts (Rusin 1997). This particular HAA compound has also been shown to be toxic to the sperm of adult rats at concentrations as low as 10 parts per billion, and to cause a range of neurological effects ranging from awkward gait to tremors and immovable hind limbs at high doses. (Linder 1995).