Tap water in 4,500 Boston properties flows through aging lead pipes that could be exposing city residents to higher lead levels than is allowed by federal law.
Lead levels in most of those homes are unknown, but the results of tests on a tiny sampling of the properties, released yesterday by the Massachusetts Water Resources Authority, found some with lead levels that exceeded federal standards.
And many of the properties are in neighborhoods that already have high rates of childhood lead poisoning, a fact environmental groups cited yesterday to demand more aggressive action on the part of the city and MWRA officials.
''It's important to us that the people at risk are communicated with and told how to avoid this exposure," said Peter Shelley of the Conservation Law Foundation, which released a map yesterday showing the distribution of homes with lead pipes. ''We need more homes to be tested."
Children are particularly sensitive to the effects of lead, which can reduce IQ and cause a host of other developmental problems.
Although lead pipes are just one potential source of lead -- old paint contains lead, as do brass plumbing fixtures -- they could exacerbate an existing lead poisoning problem, scientists said.
''Lead in drinking water rarely contributes large amounts of lead exposure to people," said Joel Schwartz, professor of environmental health at the Harvard School of Public Health. But he said lead in drinking water probably contributes to a child's total lead exposure, because in New England, ''we tend to have corrosive water and old pipes."
People who live in buildings with lead pipes or who have brass fixtures should run tapwater for at least 15 seconds before using it for drinking or cooking, to flush out most of the lead that has accumulated in the pipes. They can also try to isolate the source of lead to fixtures or old pipes and replace lead pipes that run from their house to their property line. Boston officials have started a new program that contributes $1,000 to the estimated $2,000 replacement cost.
That is just one of the programs Boston and MWRA officials pointed to yesterday, to show that they have already made a priority of replacing lead pipes, both those owned by the public and by property owners. These programs have already resulted in dramatic declines in lead levels in drinking water across the region, they said.
The MWRA has altered water chemistry in the last decade to make its water less corrosive; it is corrosion that causes the pipes to release their lead. The Boston Water and Sewer Commission has removed all but about 1,000 of the publicly owned lead service lines, pipes leading from water mains to people's property lines. And the MWRA gives zero interest loans to communities to replace pipes.
''This is one of our highest priorities," said Stephen Estes-Smargiassi, planning director for the water resources authority, which oversees the region's water system.
Overall, the 47-community system is in compliance with federal standards, but nine communities, including Boston, had some properties that exceeded the standard, according to a sample from 440 homes. The authority's small sampling in Belmont, Framingham, Malden, Medford, Norwood, Quincy, Somerville, and Watertown also showed levels of lead exceeding the 15 parts per billion allowed by law.
''We are concerned about it," said Estes-Smargiassi. ''We are working with homeowners. . . . We call the ones with high lead levels."
But the problem is complicated. In Boston, property owners, not the city, own the piece of pipe that links buildings to public water lines.
And, it is not even clear if the lead pipes are raising lead levels in tap water. Inside a dwelling, brass water fixtures can contain 8 percent lead, and MWRA officials say such fixtures are more likely than pipes to contribute to lead in the tap water.
Officials recommend removing aging lead pipes to eliminate all potential sources of lead.
The sampling the MWRA does is only designed to track whether its anticorrosion methods are working, not to figure out if drinking water is lead-free across the region.
That's why the authority only takes samples from a handful of older houses in each community. Of the 25 samples taken in Boston, one-third were above the level considered acceptable by the US Environmental Protection Agency. Only 10 percent are legally allowed to exceed that standard.
The Conservation Law Foundation requested the addresses of all the properties in Boston with lead pipes and mapped those addresses, comparing the neighborhoods that have high concentrations of lead piping with neighborhoods where childhood lead poisoning is known to be high.
Across Boston last year, 647 children under the age of 6 were known to have lead poisoning, a sharp reduction since 1993, when more than 5,000 children had lead poisoning.
That drop is mostly credited to programs that have raised awareness about the dangers of lead paint. New studies, however, suggest that children may suffer the ill effects of lead poisoning when exposed to very little lead, raising concerns that drinking water may be contributing to health problems.
Advocates from the nonprofit Clean Water Action and The Lead Action Collaborative have petitioned the City Council to hold a hearing next month to consider strengthening lead testing laws and better notifying tenants, not only property owners.
''There isn't enough testing," said Ryan Torres, executive director of the Lead Action Collaborative. ''There is no safe lead level. That's why we still have so much work to do."
Beth Daley can be reached by e-mail at firstname.lastname@example.org