While Giammar was working with phosphates and soils, the media began reporting that lead levels in the tap water in Washington, D.C., were higher than before and indeed were higher than national drinking water standards allowed.
Lead, as Giammar says, is a "xenobiotic" element (literally foreign to living systems). Unlike some metals, it serves no biological purpose and only does harm. But lead pipes weren't outlawed in new construction until 1978.
That the district knew it had a problem was remarkable in itself. The levels of lead in drinking water weren't regulated until 1991, when the Lead and Copper Rule was passed.
The lead levels in Washington, D.C., drinking water began to rise in 2001.
The case of Washington, D.C., water
The lead levels rose for an interesting reason, says Giammar. The district water utility was trying to improve water quality.
In the U.S., he explains, water is delivered with a disinfectant still in it. There are two ways of chlorinating water to disinfect it. Utilities either use free chlorine, which is essentially bleach, or they use chloramines, which are essentially bleach combined with ammonia.
Free chlorine is a better disinfectant but it also forms higher concentrations of chlorinated disinfection byproducts things like chloroform that we don't want in our drinking water, Giammar says.
In an effort to decrease the concentrations of disinfection byproducts, the district switched from chlorine to chloramine.
This is where the water chemistry comes in. "The lead pipe, in itself, is not much of a concern," Giammar says. Pure lead, lead 0 as it's called, is not particularly reactive or soluble, which is one of the reasons people made plumbing out of it. Lead pipes last much longer than iron pipes.
But lead can oxidize essentially corrode. The lead species that then form determine how much lead ends up in the wat
|Contact: Diana Lutz|
Washington University in St. Louis