Reducing Lead Levels
in Washington, D.C. Drinking Water
In February 2004, residents of the Washington, D.C. area learned that high levels of lead were detected in portions of their drinking water supply. Tap water flowing into thousands of homes in the nation's capital was found to contain lead in excess of the U.S. Environmental Protection Agency's (EPA) "action level" of 15 parts per billion (ppb). Water entering 157 homes had lead levels higher than 300 ppb. Two readings (24,000 and 48,000 ppb) were so elevated that water quality experts suggested residents might be able to taste the lead in their water. Public and government outrage over the threat of unhealthful drinking water prompted a congressional investigation, ultimately leading to a re-examination of federal water testing and public notification procedures.
Since this potentially serious public health situation came to light in early 2004, steps have been taken at the local and federal levels to understand, cope with, and resolve the problem of lead in the drinking water in the Washington, D.C. area. Water experts speculate that Washington, D.C. probably is not unique in its lead woes, and that other localities will benefit from its difficult experience.
A Test of EPA's Lead and Copper Rule
In 1991, EPA issued a Lead-Copper Rule (LCR), designed to reduce the presence of those two metals in drinking water. According to the rule, if more than 10 percent of taps sampled exceeds the action levels for one of the metals, steps must be taken to reduce those levels and the public must be informed. High lead levels, traced to lead pipes, had been found in Washington, D.C. water as early as the late 1980s, before the rule appeared. At that time the problem was resolved by adjusting the pH of the water with lime, preventing lead leaching of pipes. But lead returned in late 2002. In response, the Washington, D.C. Water and Sewer Authority (WASA) began replacing lead service lines in 2002 at the rate of seven percent per year, as dictated by the LCR. Informing the public adequately, however, was a different matter. Although WASA mailed brochures to affected homes in October 2003 (with a notice about high lead levels in small print on page three, a city official later complained), the public at large was not notified until media reports caused an outcry around March 2004. Later in the spring, during a federal investigation, WASA and EPA officials both acknowledged that they could have done a better job of communicating with the public.
A Case of Warring EPA Rules?
In attempting to determine the cause of the most recent episode of elevated lead levels, several water corrosion experts point to a change in water treatment by the Washington Aqueduct. To comply with a 1998 EPA Disinfection By-Products Rule (DBR), in November, 2000, the Aqueduct began adding ammonia to chlorine to form chloramines. Chloramines are disinfectants that may be used-instead of chlorine alone-to reduce levels of chlorinated disinfection byproducts in drinking water. Chlorinated disinfection byproducts are chemical compounds of potential public health concern resulting from the combination of chlorine and natural organic compounds found in raw water, especially surface water. According to the EPA, the change reduced levels of chlorinated disinfection by-products by 47 percent (from 75 ppb to 40 ppb), on average. But, chemical changes do not occur "in a vacuum." Corrosion scientists postulate that chloramines increased the corrosivity of the Washington, D.C. area drinking water, resulting in lead being leached from pipes and into the water supply.
In an attempt to reduce the risk to residents of chlorinated disinfection by-products, did WASA unwittingly increase the risk to residents of lead? A recent article in Scientific American.com reports that corrosion scientists warned about potential conflicts between these two rules, to no avail. One of a group of scientists, who wish to remain anonymous, is quoted as saying, "We were concerned that drastic changes in water treatment could disturb scales and mobilize metals."ii
According to EPA chemist Michael Schock, chlorination makes water highly oxidizing, causing lead to settle out on the inside walls of pipes as lead oxide scale (PbO2). Chloramination, on the other hand, reduces the oxidizing potential of water, dissolving lead oxide scale, and releasing lead into water. Marc Edwards, a Professor of Engineering at Virginia Tech and former EPA consultant, warned the Agency and the water industry that changes in treatment were likely to cause trouble for home plumbing systems. His research shows that chloramines may mobilize lead from brass water fixtures. He also studied galvanic corrosion which occurs when brass and copper are in contact. In the presence of chloramines, lead leaching from brass in contact with copper proceeds between 4 and 100 times faster than normal. Lending support to this chemical argument, routine pipe flushing, performed in April in which chlorine was substituted for chloramines, resulted in lead level declines in 25-30 percent of homes serviced by lead service pipes. While it is possible that chloramines are corrosive, it is also possible that chlorine simply prevents corrosion.
Many water systems deal with corrosivity by adding the chemical orthophosphate, a corrosion inhibitor, to drinking water. Over time, orthophosphate forms a protective coating of minerals over lead pipe interiors, preventing lead leaching. WASA began adding orthophosphate to a small section of the city in June and has plans to expand this treatment during the summer.
It Comes Down to Lead Pipes
Although there is no definite agreement on the underlying chemical mechanism for lead entering area water, there is no doubt that the source of lead is 23,000 lead water service pipes under the streets. Water service pipes connect individual buildings and residences to the larger pipelines known as water mains. In total there are approximately 130,000 water service pipes under Washington, D.C. Most are made of copper and cast iron. Lead pipes are vestiges of older cities with aging infrastructure. In addition to lead pipes, the metal also may be leached from lead solder and brass fixtures. Exposure to lead is associated with neurological health effects. The most vulnerable groups are children under the age of five and pregnant women and nursing mothers.
The House Committee on Government Reform convened an oversight hearing on March 5 to address the lead problem. The hearing resulted in a letter from three members of the committee to the EPA commending and endorsing the Agency's plan to examine whether the LCR is adequate to protect public health, as required by the Safe Drinking Water Act. EPA has begun a national compliance review of the LCR. Benjamin Grumbles, acting assistant EPA administrator for water has called on the states to provide information on lead levels in various water systems. In early May he reported that as of then, lead did not appear to be a national problem. Legislation to reduce lead-contaminated drinking water and to better notify the public of high lead levels was introduced in the form of identical bills to the House and Senate on May 4.
Going for the Big Fix: Getting the Pipes Out to Get the Lead Out
On July 1, WASA's board of directors approved an ambitious, accelerated $350 million plan to replace all lead service pipes across the city by 2010. The plan was approved despite the prospect of neighborhood disruptions and a probable increase in water rates. Some city leaders, including Mayor Anthony A. Williams, had been in favor of the utility foregoing a complete lead pipe replacement program until results of orthophosphate treatment could be evaluated. But, instead, the city has gone for "the big fix," opting to remove the source of the problem rather than chemically "tweak the system." And WASA has coordinated with a bank to offer low-interest loans to residents who elect to replace the private portion of their service lines. In the coming years, the Washington, D.C. example will be watched closely, especially by other aging cities as they decide how to deal with their own potential water quality problems.
Inc. Daily Environment Report, May 24, 2004
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