How dangerous is lead?

Last January, the Washington Post revealed that corroding lead pipes were contaminating the city's drinking water. Officials at the local Water and Sewer Authority had known about the lead in the water since 2002 and had quietly notified those whose drinking water had been found to have elevated lead levels. But it was after the Post"broke" the story that Washingtonians evinced the type of righteous indignation that often accompanies perceived cases of bureaucratic indifference to the public's health.

Lead, after all, has a terrible reputation. One need only do a quick Web search to learn that the element has been blamed for everything from the fall of Rome to the fact that kids are "loosing [sic] their minds." So, many Washingtonians understandably jumped to the worst-case scenario: Was the water silently emitting toxic levels of lead into the locals' bodies, and, more ominously, into the brains and tiny bodies of their children?

In one of a host of stories—many more than 100 to date—the Post has published on the topic, a reporter summarized the metal's myriad nasty effects: "Studies have shown that children exposed to lead have reduced potential for lifetime achievement and increased risk of social and behavioral problems. ... Some epidemiologists report evidence that lead's effects on children can remain undetected for decades until psychiatric diseases, such as schizophrenia, emerge. Others have attributed impulsive and antisocial behavior and juvenile delinquency to lead exposure."

Schizophrenia, underachievement, delinquency—obviously scary stuff. But is the amount of lead in the D.C. water—many of the thousands of homes tested this year have levels only a few micrograms over the Environmental Protection Agency's legal limit of 15 parts per billion—really as menacing as all that?

To get a sense of the potential risks posed by lead, as well as the debate that informs reactions to even relatively low-level exposures like this one, you first need to know one thing: It is, basically, all about children (and pregnant or breast-feeding women). Experts, it seems, don't worry much about the effect of low-level lead exposure on adults. (At higher levels, however—such as those found in many workplaces, like construction sites or lead-recycling plants, where lead is utilized—the metal may, according to an expert paraphrased in the Post, "affect fertility and sexual function, interfere with kidney function, cause muscle aches and possibly act as a carcinogen.")

Beyond the fact that environmental workplace-conditions rarely trigger the type of public outcry they might deserve, there are some scientific reasons to focus on children's lead exposure. Because children are nearer to the ground—where soil and dust laced with lead can accumulate—and are more likely to "mouth" their (lead-contaminated) fingers, they are considered more vulnerable. A child's still-developing nervous system may also be more susceptible to lead's ill effects. Furthermore, children under the age of 6 apparently absorb far more lead in proportion to their size than do older kids or adults. But what does this mean for those D.C. children whose drinking water flows through lead pipes?

First, a bit of history is in order. Lead has been used for thousands of years for everything from bullets to fancy crystal tableware to water pipes. Today, lead is integral to umpteen useful products: the bibs that shield you from X-rays, the screen on your computer, the battery in your car. Given its wide use, lead is ubiquitous—found in air, soil, dust, paint, and water contaminated by corroding pipes. (Lead dust and lead paint are considered the most prevalent source of contamination.) Therefore, humans can't really avoid inhaling or ingesting it. And because the metal somehow "mimics" the essential mineral calcium, the human body apparently doesn't register that lead is toxic. Instead, lead moves in the body as calcium does: coursing through the blood, finding its way into soft tissues of the liver, kidneys, and the brain, where it may disrupt normal functioning; settling into bones and teeth, where it can be stored for decades.

This all sounds bad, particularly if you're talking about a child. But our instinctively emotional reaction might just be preventing us from keeping current lead scares in perspective. The amount of lead most children today are exposed to is, by and large, small compared with the amount of lead to which American children were historically exposed.

Indeed, bans on leaded gas and leaded house paint, initiated in the 1970s, have resulted in dramatic declines in children's blood-lead levels. (In 1986, Congress amended the Safe Drinking Water Act to limit, though not ban, the use of lead in plumbing, but obviously many old lead pipes and fixtures, such as those in D.C., remain.) Whereas in 1976 nearly 90 percent of American children ages 1 to 5 had blood levels of lead higher than 10 micrograms per deciliter—the standard of "concern" recognized by the Centers for Disease Control—by 2001, the percentage was down to 2.2 percent. Extreme cases of lead poisoning—marked by blood levels higher than 70 micrograms per deciliter, and characterized by terrible symptoms such as brain swelling and coma, sometimes death—were, in the early 20^th century, a relatively commonplace occurrence in children but are now rare.

In D.C., it's unclear whether lead in the water is affecting children's blood-lead levels. Not every District child has been tested, but of the 1,692 kids under age 6 who were evaluated as of late-April, 35—2.1 percent of those tested—had blood-lead levels higher than 10 micrograms per deciliter. Among the 13 children living in houses where the water-lead levels were more than 20 times the EPA-threshold, none had elevated blood-lead levels.