Mapping out lead’s legacy
vincingly that the lead in the drinking water resulted in lead poisoning in some children,” he says.
DC WASA
Many public-health experts apFrom 2001 to 2004, when lead conplaud the study and say its results taminated the drinking water in Massive contamination could have a long-term impact on Washington, D.C., high levels of this From 2001 to 2004, Washington exprotecting children from lead exponotorious environmental poison perienced one of the most serious sure. In Washington, the response were found in the blood of hundreds episodes of heavy-metal contaminahas been swift. After the study’s reof babies and toddlers, according to tion in drinking water in modern sults were reported on the front page a new ES&T study (DOI 10.1021/ U.S. history, when a switch in water of the Washington Post on January es802789w) that challenges previous disinfectant chemicals from free assessments. chlorine to chloramine In the study, Marc caused an unexpected and Edwards, an environmental massive release of lead (Enengineer at Virginia Polyviron. Sci. Technol. 2004, 38 technic Institute and State [12], 224A-227A). Officials at University; Dana Best, a pethe D.C. Water and Sewer diatrician at Children’s NaAuthority (DC WASA), Washtional Medical Center ington’s water utility, knew (CNMC) in Washington, about the problem, as did D.C.; and Simoni Triantafylthe D.C. Department of lidou, also at Virginia Tech, Health (DC DOH) and the reveal that during U.S. EPA. Yet the lead con2001-2004 the contamitamination of the city’s water nated water caused a major persisted for 3 years before jump in the incidence of the Washington Post inhigh blood levels of lead in formed the public in a story the youngest children they published on January 31, studied, babies under 16 2004. months of age. For several The news about Washingyears, almost 1 in 20 babies ton’s water outraged parents tested by CNMC had blood worried about their chillead levels that exceeded the dren’s health, angered politi“level of concern” set by the cians who had been kept in U.S. Centers for Disease the dark, and created anxiety Control and Prevention among public-health experts (CDC), the researchers who initially feared a comThe dots on this map of Washington, D.C., released by DC WASA in 2008, represent the locations of lead service line pipes in the report. munity-wide crisis. The revFor toddlers, the increases city at that time. elation also spawned public in blood lead levels tended protest in Washington, sev27, 2009, D.C. City Council members to occur in certain neighborhoods eral legal actions, five congressional requested an investigation into where an unlucky combination of hearings, an independent inquiry, a whether public-health agencies and lead service line pipes and highly report by the Government Accountthe water utility “negligently or incontaminated tap water created the ability Office (the congressional tentionally” misled the public about conditions for higher exposure, acwatchdog), and changes in federal the consequences of the high levels cording to the new study. In these drinking-water rules. But in the afterof lead in drinking water, and high-risk neighborhoods, where math of the crisis, public-health offiwhether these organizations should about 22% of Washington’s populacials, including experts from CDC, have tried harder to find a link betion lives, the incidence of high concluded that there had been little tween high levels of lead in the water blood lead levels more than tripled. if any harm. Two publications, a rapand high levels of lead in children’s “We can’t say precisely how many idly produced Morbidity and Mortalblood. children were affected, because there ity Weekly Report (2004, 53, “This new paper is important and is still so much we don’t know. We 268-270) from CDC and an Environvery persuasive,” says pediatrician don’t have much data on the youngmental Health Perspectives (EHP) Michael Shannon at Harvard Mediest and most vulnerable children, for paper (2007, 115, 695-701), funded cal School. “This is the first paper instance,” says Edwards. “But the largely by DC WASA, concluded that about the lead crisis to get it right. massive contamination certainly afthe lead levels in the blood of WashThe authors really show quite confected hundreds of kids for 3 years.” ington’s childrensthe group deemed 10.1021/es8037017
2009 American Chemical Society
Published on Web 02/11/2009
March 15, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 1655
EDWARDS ET AL., DOI 10.1021/ES802789W
Until the publication of Edwards and tional skills, hyperactivity, and poor most vulnerable to lead’s toxic colleagues’ new paper, these inspecclassroom performance,” says Best. effectssdid not shoot up as a result tion reports were the only official Deteriorating lead paint and conof the drinking-water problem. Both evidence linking high levels of lead in taminated dust and soil are the of these studies are based on blood Washington’s drinking water to high main, though not the only, sources lead data collected by DC DOH and levels of lead in children’s blood. of U.S. children’s exposure to lead. In water samples collected by DC Bruce Lanphear, an expert on lead almost one-third of cases, the source WASA. exposure in children at Simon Fraser of a child’s elevated blood lead levels The CDC and EHP studies also University (Canada), applauds the cannot be traced to paint and is seemed to contradict previous studnew work by Edwards. “This is a never found (Environ. Health Peries from Germany, Scotland, and the spect. 2008, 116 [10], U.S., which show that high 1285-1293). Some researchlevels of lead in drinking waers argue that water is overter can markedly raise the looked as a source of levels of lead in children’s exposure. blood. Nevertheless, the CDC and EHP papers have been highly influential. DurBabies most vulnerable ing the past year, officials in In the midst of the lead Toronto, Montreal, and Secrisis, research by a public attle, among other cities, agency identified formulahave cited these two papers fed babies as the populaabout the Washington lead tion most at risk. EPA’s crisis as a justification for National Center for Envidownplaying health conronmental Assessment cerns about elevated levels (NCEA) used the agency’s of lead that have been disIntegrated Exposure UpPb chronology: the November 2000 switch to chloramine as a covered in their own cities’ take Biokinetic Model for disinfectant caused lead to rapidly leach into Washington, D.C., drink- lead in children to assess drinking water. ing water. Tap water lead levels rose during 2001 and remained A 2006 ES&T news story the likely consequences of high until 2005. (2006, 40, 4333-4334) rethe drinking-water conported that at the time, tamination. The results of much more refined estimate of the some public-health experts had this modeling exercise are inproblem in D.C. water supplies than doubts about the CDC study. A cluded in the Supporting Inforthe two previous papers, which left highly influential aspect of the CDC mation in the new ES&T paper by me with the sense that they were report was the finding that even for Edwards et al. NCEA determined trying to minimize the extent of the “worst case” homes with drinkingthat infants up to 1 year in age problem,” he says. water levels greater than 300 parts who drink formula made with tap Water overlooked as a source of per billion (ppb), there was no eviwater are the most vulnerable, dence that blood lead levels rose as a and that the blood lead of the lead exposure result of drinking water. But ES&T typical infant would increase to 6 Since 1975, the reported blood lead revealed that the report failed to note µg/dL if that infant drank formula levels of children in the U.S. have that there was a sampling gap. The made with drinking water that dropped, primarily because of the blood samples were taken months contained 50 ppb lead when it elimination of lead in gasoline, house after the water samples. Most imporwas first sampled. At 100 ppb lead paint, and other products. In additant, the blood samples were taken in drinking water, a typical baby’s tion, water utilities have used chemiafter the public knew about the conblood lead would climb to 11 cal corrosion control to limit tamination and had largely stopped µg/dL, and still higher blood lead leaching from lead water pipes. But drinking the tap water. In 2007, levels would be realized as lead lead is still a leading environmental ES&T wrote that reports of home levels in drinking water increased. poison for children. In 1999, an estiinspections conducted during the With these results pointing clearly mated 310,000 U.S. children had crisis listed drinking water as the to the most vulnerable group, lookblood lead levels greater than the only contaminant source for some ing at the youngest children should CDC level of concern, which is 10 children with high blood lead levels. have been an obvious thing to do at micrograms/deciliter (µg/dL), and 1.4 At the time of the crisis, DC DOH the time, says Lanphear. But it was million had levels between 5 and 9 officials assured the public that there Edwards’s team that set out to hunt µg/dL. “In addition to reductions in were no home inspections linking for the exposure contribution from IQ, lead poisoning in children has drinking water to high blood lead lead in water. And because the rebeen linked to distractability, delevels in children (2007, 41, 10-11). searchers were looking at drinking creased reaction time, poor organiza1656 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / March 15, 2009
EDWARDS ET AL., DOI 10.1021/ES802789W
elevated blood lead levels in children inquiry commissioned by DC water, not paint, as the source, their nationwide in which there is not a WASA’s board of directors to look approach differs from that of most clear source of exposure to lead in into the origins of the city’s lead coninvestigations of children’s lead expaint, dust, or soil. tamination. The result of that inquiry posure. First, they focused as much is the Holder Report, a 154-page acas possible on the population most Toddlers in high-risk neighborhoods count by Eric Holder (now the U.S. at risk from drinking contaminated To hunt for high blood lead levels in attorney general). According to the watersinfants and very young toddlers, Edwards and colleagues report, in the summer of 2003, a DC toddlers. divided the city into neighborhoods WASA consultant sought large numTo isolate that population was a where the risk of lead exposure from bers of water test results showing challenge, because blood lead data water was high, moderate, or low. low blood lead levels from are not routinely collected people who lived in homes from children this young. with lead pipes. Such results Current statutory blood lead would allow DC WASA to monitoring programs focus exploit a regulatory loophole on 1- and 2-year-olds, beand meet federal lead safety cause children of this age standards. Holder, who was are most likely to be exan attorney with the law firm posed to paint, dust, and soil Covington & Burling at the as they crawl or toddle time, wrote that “[The DC about. WASA consultant] had conBut by using data that ducted a geographic analysis were gathered under the and found that lead service supervision of coauthor Best, lines with high levels of lead who is affiliated with CNMC Throughout Washington, the contaminated water caused a major jump in the incidence of high blood lead levels in the were geographically related. in Washington, Edwards’s youngest children studied, babies 16 months of age and younger. Specifically, certain neighteam was able to identify borhoods in Ward Four had much enough samples from children under This approach is the most likely to higher lead concentrations than 16 months old to give data that are reveal the consequences of Washingother neighborhoods” (Holder Restatistically significant. The researchton’s lead contamination, according port, pp 109, 110). ers found that in 2000, the incidence to several public-health researchers Small-area geograpical analyses of of elevated blood lead levels in this contacted by ES&T. But the techchildren’s blood lead levels have group of children was very low. But niques are not new. been done more than 5 times, notes in the second half of 2001, the inciPrevious studies used this apLanphear. “It is a standard approach dence abruptly rose 9.6× in comproach, including research by for this type of problem,” he adds. parison to the first half of the year. Mary Jean Brown, head of the For the new study, Edwards and In 2002 and 2003, the incidence reCDC’s lead poisoning prevention colleagues based their assessment of mained more than 4× greater than branch and principal author of each neighborhood’s risk on two in 2000. By 2005, the incidence of the 2004 CDC study. In a 2001 featuressthe percentage of lead elevated blood lead levels returned to study, Brown and colleagues dipipes in an area and the percentage 2000 levels after DC WASA added a vided seven major cities internally of homes in which the drinking wacorrosion inhibitor to the water. The on the basis of zip code to see if ter contained more than 100 ppb of linear correlation between the rise in the risk of children’s blood lead lead when the water was first numbers of children with elevated levels differed from one neighborsampled. The researchers estimate blood lead and the levels of lead in hood to another in the same city. that 22% of the D.C. population lives drinking water is very strong across In every city, they found a wide in relatively high-risk neighborhoods, the entire city for this age group. disparity in the prevalence of high just over half lives in moderate-risk These new findings suggest that blood lead levels depending on neighborhoods, and 23% inhabits the health effects in the Washington the zip codes. Noting that analylow-risk locales. population were completely consisses at relatively large geographic In the high-risk neighborhoods, tent with decades of scientific relevels, such as an entire city, can the researchers found increased incisearch linking high lead levels in camouflage pockets of high risk, dence of elevated blood lead levels in water with elevated blood lead in Brown’s team concluded that children up to 30 months old. The children, the authors write. With an analysis at the neighborhood or incidence of elevated blood lead leveye toward the broader implications zip code level is a good way to els in the CNMC data rose from 2.5% of their findings, they also suggest find the highest-risk communities. in 2000, when lead levels in water that high lead levels in drinking waAnother indication that a neighwere low, to 6% in 2003, after lead ter may be a viable explanation for borhood-by-neighborhood analysis is levels in the drinking water had been some of the 30% or more cases of valuable came from an independent March 15, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 1657
SUPPORTING INFORMATION, EDWARDS ET AL., DOI 10.1021/ES802789W
WASA about apparent problems in the data and analysis that support the 2004 CDC report. Several months ago, Howard Frumkin, who directs the National Center for Environmental Health at CDC, was asked by ES&T about the The incidence of high blood lead levels more than tripled in CDC report. toddlers who lived in Washington neighborhoods most Frumkin replied, affected by the drinking-water contamination. “We have a clear high for a few years. The incidence message, there is no threshold for of elevated blood lead levels dropped lead exposure. We clarified this on rapidly in the high-risk neighborour website. There was a problem hoods in 2004, after the public bewith lead in water, but it was not a came aware of the problem and crisis. We did not see extremely elbegan to drink more bottled water evated lead levels in children’s and use more water filters. blood.” “When you look at a situation in Frumkin noted that some of detail like this, the problem often the data CDC used was concomes into sharper focus,” says Martrolled by other groups. “Look at tha Keating, a former EPA scientist the [2004 CDC] report,” he said. who is now a research associate at “At several points in the report Duke University’s Children’s Enviit says that WASA reported data ronmental Health Initiative, a multithat remains in the hands of contaminant research group that DOH. It is not our data,” he studies lead in water. stressed. Furthermore, in neighborhoods Speaking about the database where the risk was high, the reused for CDC’s 2004 paper, he searchers found a strong relationship said, “The data used was the between the increased incidence of best available for a rapid field elevated blood lead versus the lead investigation. No public-health content of the drinking water. In database is perfect. But this damoderate-risk parts of the city, the tabase is not so flawed that it correlation was weaker, and it was fails. We did a sensitivity analyvery weak in the lowest-risk parts of sis to see what happens if data the city. Using zip codes and inforare misclassified. That sensitivity mation about lead pipes and lead in analysis shows that there would water, Edwards’s team identified four need to be a very large amount zip codes as high risk. Two of the zip of data misclassification to alter codes are in Ward 4. This agrees with the conclusions of the study.” findings documented in the Holder To fully document the effects Report. of the contamination, he added, ES&T has made numerous at“would take a complex epidetempts since 2004 to speak with scimiological analysis more attuned entists from CDC, DC DOH, and DC to confounders.”
1658 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / March 15, 2009
On January 17, 2007, Marc Edwards filed a complaint of scientific misconduct with Allyn Nakashima, CDC’s associate directorofscienceatthetime,allegingthat authors of the 2004 CDC report, including Mary Jean Brown, were well aware of limitations in the data and failed to correct their report and interpretations. Edwards contended that failure to report and correct these flaws was a possible breach of scientific conduct. The CDC did not amend the report. In August 2007, the CDC webpage titled “LeadinWater:QuestionsandAnswers” ran a new message, stating that “because no threshold for adverse health effects in young children has been demonstrated (no safe blood level has been identified), all sources of lead exposure for childrenshouldbecontrolledoreliminated.” In September 2007, James Stephens, CDC’s associate director of science at the time, wrote to Edwards informing him that “the questions you raised pertained to data collected by others outside of CDC” and “we have examined CDC’s role in the study and have found no evidence of misconduct.” Stephens advised him to address his remaining concerns to the D.C. inspector general. Edwards is also an expert witness for a Washington, D.C., resident in a lawsuitagainstDCWASAregarding pinhole leaks in copper plumbing due to corrosive water. That lawsuit is unrelated to the subject matter presented in Edwards’s recent ES&T study. sRebecca Renner
In response to ES&T’s newly published research, Frumkin says, “CDC welcomes new research. Scientific investigation of a known health hazard such as lead, including work that clarifies routes of exposure and helps quantify exposure risks, is the foundation of sound public-health action.”). —REBECCA RENNER
