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The discovery of widespread lead contamination in Washington, D.C. drinking water resulted in a U.S. Congressional investigation that damaged the scientific reputation of the Centers for Disease Control and Prevention (CDC), left thousands of children with lifelong health risks, and led to a re-evaluation of the use of chloramine in public drinking-water systems. Marc Edwards, an expert in plumbing corrosion, discovered lead levels at least 83 times higher than the accepted safe limit while performing research into premature pipe corrosion for the District of Columbia Water and Sewer Authority (WASA). He found that the decision to change from using chlorine to chloramine as a treatment chemical had caused the spike in lead levels. After the ''Washington Post'' ran a series of front-page articles about Edwards's findings, resulting in widespread public concern, the United States House of Representatives conducted an investigation. The House found that the CDC had made "scientifically indefensible" claims in a report that had indicated there was no risk from the high lead levels. The ''Post'' investigation uncovered evidence of widespread misreporting of lead levels at water agencies across the United States, leading to regulatory crackdowns and changes in Environmental Protection Agency policies. The problem was addressed in 2004 by adding additional treatments to the water, preventing the chloramine from dissolving lead in the water mains, solder joints, and fixtures. In 2010, the CDC reported that 15,000 homes in the Washington, D.C. area might still have water supplies with dangerous levels of lead. ==2001–2004: Initial reports of elevated lead== In 2001, more than half the water samples taken from 53 DC-area homes under the procedures required by the EPA's Lead and Copper Rule showed levels of lead exceeding the national standard of 15 parts per billion (ppb).〔 Lead disrupts the physical and mental development of fetuses, babies, and young children, and can cause kidney problems and high blood pressure in adults.〔 The rule does not assume that there is a "safe" level of exposure, but notes that 15 ppb is an "action level" where utilities must take action.〔 The rule was created in 1991, after research showed that drinking water could account for one-fifth of all lead intake.〔 Lead is not normally present in drinking water; it is released from the inside surface of lead service lines (pipes that run from the main to the house), joints connected with lead-based solder, and lead fixtures inside the house. Based on these findings, WASA was required to notify the public and implement plans to replace lead service lines in key areas of the municipal water system. The first media attention came in late 2002, when the ''Washington City Paper'' ran an article about a resident of American University Park whose water tested six to 18 times the EPA Lead and Copper Rule's action level.〔 WASA found that homes in its service area with lead service lines averaged five times the EPA limit for lead during a year-long period.〔 The results were unexpected; the EPA scientist overseeing DC's water suggested that drought conditions might have raised the alkalinity levels of the Potomac River, leading to a change in the pH of the water.〔 As a result, WASA was required to start replacing seven percent of the district's lead service lines each year until the levels dropped below 0.015 milligrams per liter.〔 At the time, about 23,000 WASA customers had lead service lines.〔 In March 2003, Marc Edwards, a professor of civil engineering and expert on corrosion in drinking-water systems, was conducting research into an unexpected increase in pinhole leaks in copper water pipes in the DC area. WASA funded Edwards's research.〔 Suspecting the leaks were caused by a change in the water chemistry, Edwards used a field meter to test for lead in one home's water. The meter could read values up to 140 ppb. His initial reading pegged the meter, so he diluted the sample to ten percent of its original strength. Even so, diluted, the sample still pegged the meter,〔 indicating the water contained at least 1,250 ppb of lead.〔 "Some of it would literally have to be classified as a hazardous waste," Edwards said.〔 After Seema Bhat, a water quality manager at WASA, told her superiors at the agency and at the EPA about the lead levels and warned that federal guidelines required aggressive action, she was fired by the agency. A federal investigator found that she had been improperly terminated.〔 The lead levels required WASA to conduct a wider survey of their water quality. By the fall of 2003, it had tested more than 6,000 homes in the District, finding that two-thirds tested had more than 15 ppb of lead in their water.〔 The survey showed that over 4,000 homes served by WASA had lead levels exceeding the acceptable level.〔 More than a third of the homes surveyed—2,287 out of 6,118—had levels exceeding 50 ppb.〔 The water tested over 300 ppb in 157 homes.〔 Despite this result, WASA did not notify its customers of the risk until November 2003.〔 Although regulations required WASA to include the specific warning "Some homes in this community have elevated lead levels in their drinking water. Lead can pose a significant risk to your health." in the water bills of each affected customer, WASA's notice omitted key parts of the phrase such as "in their drinking water" and "significant".〔 Although Federal law required WASA to hold public meetings to discuss the problem and actions people could take to protect themselves, they advertised the meetings as being "to discuss and solicit public comments on WASA's Safe Drinking Water Act projects", omitting mention of lead.〔 The EPA was required to review the notice before it was sent out; one D.C. Council member, commenting on the EPA's approval of the faulty notice, asked "Where were you, EPA?"〔 The EPA later found that WASA's notice violated federal law because of the omissions.〔 In January 2004, the ''Washington Post'' reported that the mayor and several D.C. Council members had not been informed of the elevated lead levels.〔 The ''Washington City Paper'' said that Carol Schwartz, the councilmember who chaired the Committee on Public Works and the Environment, was not informed of the lead issue until that newspaper contacted her during the last week of January 2004.〔 Early communications from WASA limited the health advisory to pregnant women and small children in homes with lead service leads, but later tests showed the high lead levels were also present in homes with copper service leads.〔 Meanwhile, on January 2, 2004, WASA called Edwards and threatened to cut off his access to monitoring data needed for his research, and divert funding from him to other researchers, unless he stopped working with the homeowners whose water showed high lead levels.〔 Soon after, the EPA discontinued its own contract with Edwards.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lead contamination in Washington, D.C. drinking water」の詳細全文を読む スポンサード リンク
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