Water-cleanup experiment caused lead poisoning

Lead concentrations spiked in many children living in the nation's capital after the local water authority altered the treatment used to disinfect drinking water.

About seven-and-a-half years ago, the District of Columbia’s water authority switched from chlorination to an alternative water-disinfection technology: chloramination. The goal had been to reduce the potentially carcinogenic by-products of chlorination that developed in drinking water. And the substitution worked.

LEADEN DRINKS: HEAVY RISKS Babies and toddlers are most vulnerable to lead’s neurotoxicity, which is why the new study probed changes in blood-lead values in these youngsters.

However, an unintended consequence of this improved disinfection technique was the sudden release of copious amounts of lead into the drinking water that serves the nation’s capital.  Until then, notes Marc Edwards of Virginia Tech, no one had realized that chlorine had been playing a role in binding substantial amounts of lead to the interior of plumbing pipes.

What resulted was a “lead crisis” that persisted for several years, until water engineers found a way to tame the chloramination process. However, despite local health officials’ claims to the contrary, District children were dosed with potentially dangerous amounts of lead, report Edwards and two colleagues from Children’s National Medical Center in Washington, D.C.

Environmental Science & Technology posted a new study by this team online today after some details about the findings were leaked this morning in the local paper — the Washington Post — and then mentioned by Edwards in passing, mid-morning, at an American Chemical Society briefing where Edwards was a featured speaker.

Plenty of data indicated what should happen when lead levels in water rise: Concentrations of lead in blood will spike among people drinking the tainted water — especially children. And since lead can poison the neurological development of children, permanently dropping IQs, this was a big concern to pediatricians and public-health officials.

Acknowledging concerns about the possibility of health risks, the local health department surveyed lead levels in children following the District’s switch to chloramination. In 2004 it reported finding no evidence of harm to children from the several-year spike in waterborne lead.

This assessment provoked widespread disbelief, Edwards says, and “prompted us to do our own study.”

His team focused on children who were 16 months or younger when the water crisis occurred — the age when lead-uptake rates and risks of neurological poisoning are greatest. They relied on blood samples from Children’s National Medical Center, which collects more blood-lead samples than any other entity does from District children.

Blood-lead values were correlated with the lead concentrations in water at a child’s home or in his or her neighborhood. (That’s important because chloramination-related lead changes varied dramatically with local plumbing conditions.)

Beginning in the second half of 2001, “the incidence of elevated blood lead abruptly increased by 9.6 times versus the first half of 2001,” Edwards’ team now reports finding. Previously, 0.5 percent of children in this age range had blood-lead concentrations exceeding 10 micrograms per liter. Now the rate was almost 5 percent. And, they found, elevated blood-lead concentrations in young children did not fall back to pre-chloramination values “until about 2005, when lead in water once again met EPA standards.”

From late 2001 through 2004, huge numbers of homes had water contamination that exceeded the U.S. Environmental Protection Agency’s 15 parts per billion “action level” for lead. Some 17 percent of homes exceeded 100 ppb, for instance, and 1 in 100 homes exceeded 1,000 ppb lead.

Argued Edwards this morning, his team’s new data “show that the harm done to children in 2001 to 2004 was indeed significant — and perfectly in keeping with predictions” from earlier published studies.

In fact, no one knows which children were harmed, argues Bruce Lanphear, a pediatric epidemiologist at Simon Fraser University, in Vancouver, who has extensively studied lead impacts in children. “But we can say that on average, these children experienced elevations in lead exposure that are indicative of harm. So on average we might expect to see an increased risk in behavior problems — such as attention-deficit hyperactivity disorder or conduct disorders — and decrements in IQ.”

How big an IQ drop might a three-year exposure to elevated concentrations of waterborne lead cause? “Our best estimate is somewhere between 4 and 7 IQ points” if the lead levels in a child rose from nondetectable to 10 µg/dl, Lanphear says.

And that’s substantial. If a 5-IQ-point drop were averaged across the U.S. population, he explains, “You might see an additional 3.5 million children meet the diagnostic criteria for mental retardation.” So on a population basis, he says, “the impact would be quite substantial, even though for any given child the change might appear subtle.”

In sum, he argues, failing to protect young children from exposure to lead-tainted drinking water “is one more crime against children. “

Although this may sound like a local story, Edwards argues that it’s anything but. He has been acquiring data to show that the situation in DC mirrors what is occurring elsewhere around the nation, if not the world.

He also wants to make sure his new data get widely disseminated. The earlier report by District officials downplaying any health risks “during this period of unprecedented lead levels has been used — not only all over this country but in other countries as well — to justify why lead in water doesn’t matter,” he says. And the data now show, he says, that simply isn’t true.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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