D.C. water study sharpens view of lead threat

By David Brown
Sunday, December 12, 2010; C01

The latest research on the District's decade-long effort to reduce lead in its drinking water is likely to reverberate well beyond the city's borders and add a chapter to one of the more tortuous public health chronicles of the past century.

A report released this month by the Centers for Disease Control and Prevention said the water supplied to almost 15,000 homes might still contain dangerous levels of lead despite the partial replacement of lead pipes at the homes from 2004 to 2008.

The findings called into question what was once one of the city's chief methods of mitigating lead contamination of drinking water. The federal government ordered the District's water authority - now called D.C. Water - to carry out those replacements, but the CDC study found that they didn't solve the problem.

Lead poisoning was once thought to be a serious threat only when it caused such dramatic problems as personality changes, anemia and kidney failure. But lead is now considered a toxin for which there is no safe level, especially in small children. For them, even low concentrations in the blood are associated with reduced IQ, attention deficit and antisocial behavior.

As evidence of lead's hazards accumulated over 50 years, reducing exposure became an important, expensive and contentious goal of government. Lead was removed from gasoline. Lead paint was banned. Children, particularly those living in dilapidated housing in old cities, were tested regularly, and doctors and public health officials stepped in to protect those whose "lead burden" was high.

Now, thanks to the new study, this much is clear: Even when the known exposures to lead are minimized and a city meets the federal government's safety standards, some children may be getting a worrisome amount of lead from the water they drink.

"This really means that the whole way that we've thought about this problem, and have developed public health policies to address it, has to change," said Ellen Silbergeld, a professor at the Johns Hopkins Bloomberg School of Public Health, who serves on a working group of the federal government's Advisory Committee on Childhood Lead Poisoning Prevention.

"We're spreading the word about it [the report]. It went out to our members as a hot news item," said Steve Via, head of regulatory affairs for the American Water Works Association, whose membership includes 4,100 water systems serving about 80 percent of the U.S. population.

'A really big deal'

The source of the problem is no secret. It is lead pipes, some dating from the 1800s, that run from water mains under the street up to houses.

Although water entering a house through a so-called lead service line is exposed to the toxic metal along the entire length of the pipe, municipal water systems own - and control - only the section from the main to the homeowner's property line. If a city's water violates federal lead standards, the first thing the water system must do is treat the water to make it less corrosive and less likely to leach lead from pipes and solder. If that doesn't work, the Environmental Protection Agency orders cities to replace the public part of lead service lines.

But as it turns out, that half-a-loaf strategy is worthless.

Children living in houses in which the city-owned section of lead pipe has been replaced have blood lead levels indistinguishable from those of children living in houses with intact lead pipes. And both groups of children run a significant risk of lead poisoning compared with children in houses with no lead pipes - even when the water system overall meets the federal standard of less than 15 parts per billion of lead.

Curiously, the EPA has no idea how many water utilities in the United States are doing "partial lead service line replacement" and might like to know that, in Washington at least, that procedure made no difference to children's health.

States enforce the federal lead standard. Only recently has the EPA asked them to report the number of water utilities doing partial-pipe replacement. Of the 354 water systems currently in violation, the agency knows of 11 using that laborious and expensive strategy to lower the lead in their water. There could be many more.

In the CDC study, five scientists analyzed routine blood lead tests done on 64,000 District children from 1998 through 2006. They correlated the results with the child's age, whether the child's home was served by a lead pipe and the age of the house. That last variable is crucial because a child's biggest exposure to lead comes from dusty residues of lead paint on floors and walls and in yard dirt. Old houses are much more likely to have lead paint.

What they found was troubling.

About 16 percent of children sampled during the nine-year period had blood lead levels from five to nine micrograms per deciliter. Slightly more than 3 percent had levels exceeding 10 micrograms, the federal government's current definition of "elevated" blood lead. (CDC has lowered the cutoff for "elevated" blood lead four times since the 1970s, and many experts consider the current threshold too high).

The large number of children at risk of lead-induced health problems - 19 percent of the nearly 64,000 children - was just one of the findings.

The study, published in the journal Environmental Research, also found that children living in houses with lead pipes were three times as likely to have elevated blood lead as children in houses without lead pipes.

The youngest children were at the highest risk. Infants and toddlers younger than 16 months old (many drinking formula mixed with water), had a fourfold risk of having blood lead over 10 micrograms. That was true in 1998, 1999 and the first 10 months of 2000, a period in which Washington's lead-in-water level was below 15 parts per billion. Children in houses where lead pipe had been partially replaced were no better off than those in houses whose lead pipes had not been touched.

To the researchers' surprise, the conclusions held even after they took the age of a child's home into account.

"I was expecting that any excess risk might have disappeared once we controlled for the age of housing - in other words that sources of lead other than water were responsible," said Thomas Sinks, a CDC epidemiologist and one of the authors of the study. "What we found is that there remains a contribution from leaded pipes that continues despite compliance" with government lead-in-water standards.

Other experts were impressed by the results.

"This is a really big deal," said Marc Edwards, a Virginia Tech engineer who has warned of the hazards of the District's water for years. "Meeting the EPA lead-in-water standard is not sufficient. Just because you're meeting the 'action level' doesn't mean that your child is not threatened."

"This is very different from what CDC was telling us in the past," said Lynn Goldman, dean of the school of public health at George Washington University and an expert on lead poisoning. "What is not clear to me is what the CDC actually recommends on the basis of this."

What's safe?

How big is the threat from small elevations of blood lead the children experienced? Research over the past two decades suggests that the effects are small but measurable, and all negative.

A study published in 2007 that looked at 534 children, ages 6 to 10, in Boston and rural Maine found that "children with blood lead levels of 5-10 . . . had significantly lower scores on IQ, achievement, attention, and working memory than did children . . . who had levels of 1-2." A working group of experts assembled by CDC in 2004 examined many studies and concluded that there are "at least in part, causal adverse impacts of lead on children's cognitive function at blood lead levels less than 10."

The current lead levels in the District's water stem from decisions made over the past decade, usually with the goal of improving public health.

The water District residents drink is collected, treated and sold to the city by the Washington Aqueduct, a federal entity run by the U.S. Army Corps of Engineers. To disinfect its water, the Aqueduct used to employ chlorine, a chemical that can react with compounds in water and produce byproducts that cause cancer.

To avoid that problem, many cities - including Washington in 2000 - switched to a "safer" chemical, chloramine. But it turns out that chlorine suppresses corrosion of pipes, including lead ones, and chloramine does not. The leaching of lead from pipes and solder increased after the city switched disinfectants, and eventually the lead concentration exceeded 15 parts per billion.

'Good intentions'

When the EPA started regulating lead in tap water in the early 1990s, one of its enforcement tools was a requirement that a water system in violation replace lead pipes in total. But several organizations, including the American Water Works Association, sued, saying that to comply, government would have to make improvements on private property. In 2000, a court agreed.

After the EPA revised its rules to require only replacement of publicly owned lead pipe, several studies showed that partial replacement lowered the amount of lead in water. But there were no studies showing that it lowered the amount of lead in children.

Many experts, in fact, doubted that partial replacement would achieve much. Not only were they right, it also turns out that the strategy can temporarily make things worse. Removing half the pipe can jar loose protective deposits inside the remaining section. Lead in the water can spike after the work is done and take months to return to normal. That's now recognized as a serious enough problem that the CDC put out a warning about it this year.

On June 17, 2004, the District's water authority agreed with EPA to replace a specified number of lead service lines per year.

The water agency offered property owners a discount price of $100 per foot if they agreed to replace their part of the pipes. The average length of the pipe on city property was 30 feet, and on private property, 20 feet. Through September 2009, the District replaced its portion of 17,654 lead service lines, but the privately owned section was replaced in only 2,832 of those lines, 16 percent of the total.

After four years and $80 million, the lead in the District's water returned to a level less than the 15 parts-per-billion limit. But pipe replacement probably had very little to do with it.

That's because in June 2004 the Washington Aqueduct started adding a chemical called orthophosphate to the water. It creates a film on the inside of pipes, reducing corrosion and the leaching of lead and other metals. By January 2006, the orthophosphate treatment had brought the city into compliance.

The latest reading this year was 7 parts per billion. The sampling is intentionally done in high-risk houses. Out of 100 houses with full or partial lead service lines, 90 percent must have water lead concentrations below 15 parts per billion for the city to pass.

Once the District came into compliance, it no longer had to follow the EPA's order to replace a certain number of lead service lines each year.

The accelerated program ended in September 2008, although the utility continues to replace lead pipes when it encounters them in the course of other work or if a customer decides to replace the private portion.

"We never wanted to do partial lead replacements in the first place," said D.C. Water's general manager, George Hawkins. "It was a requirement, and at the time, it was thought to be a good idea. There were good intentions."

At the moment, 13,395 lead service lines remain on public property, he said.

There are also 17,622 lines whose material is not known, although experience suggests that somewhat fewer than half are made of lead.

By rough estimate, the city would need to replace all or part of 25,000 service lines, at a cost of well over $200 million, to make its water system as lead-free as possible. It would also take a change in law to compel homeowners to change their pipes or to fully reimburse them.

The way forward

Other cities have taken on such herculean tasks.

Madison, Wis., with 230,000 people and 65,000 households, is nearing the end of a 10-year project to replace all of its lead service lines. It is using a twin strategy of inducement and punishment. The city rebates to homeowners half the cost of the work, up to a maximum of $1,000. Those who refuse face a fine so high that just about none have refused, said Tom Heikkinen, general manager of the utility.

Saskatoon, Saskatchewan, which is about the size of Madison, is replacing all the lines and charging homeowners 40 percent of the cost of the work, up to $2,000, and putting it on their tax bills.

D.C. Water is addressing the problem case-by-case, offering free testing to residents and providing water filters to houses after all or part of a lead service line is replaced.

"We are not currently contemplating replacing all of the lead service lines in the District, public and private," Hawkins said.

A spokesman for the EPA said the agency still requires partial-pipe replacement when a water system cannot comply by other means. But, he said, "we are taking very seriously this new CDC study. It is eye-opening and shows that we need to continue assessing how effective this strategy is."

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