In recent weeks, millions of toys have been recalled because their paint could contain unacceptable levels of lead.
At low levels, lead can seep out into the mouths of babes and potentially damage brains, decreasing their intelligence. Higher lead exposure can cause acute lead poisoning, characterized by symptoms such as lethargy, seizures, coma and even death.
Lead has been decreasing in our bloodstreams for 30 years, ever since the government banned leaded paint and gasoline. It has dropped from about 12 micrograms per deciliter of blood to a little more than 2 micrograms per deciliter. Still, the toxic metal continues to accumulate in children's bodies from many environmental sources and causes health problems.
According to the Centers for Disease Control and Prevention, more than 300,000 children from ages 1 to 5 have lead levels higher than 10 micrograms per deciliter, which the agency considers a level of concern, and in 2005, about 500 children had lead levels exceeding 45 micrograms per deciliter.
"We don't have any physiological use for lead," as we do for the similar metals calcium and iron, says Dr. Alan Woolf, director of the pediatric environmental health center at Children's Hospital Boston. "The body's level should be zip."
Unfortunately, unless one has a test, it's hard to tell that a child harbors lead until the levels get high enough to show physical symptoms. "It's a silent problem," says Richard Canfield of Cornell University in Ithaca, N.Y. Simple blood tests check for lead levels, and the CDC keeps a running tally of states' data. Massachusetts, for example, tests every child going into preschool.
Symptoms such as stomach pain, loss of appetite or tiredness due to anemia crop up by the time blood levels reach 45 micrograms per deciliter. Higher levels, above about 60 micrograms per deciliter, cause lead encephalopathy, which makes children drowsy and difficult to rouse. But even in the absence of symptoms, brain cells can be damaged, and children's intelligence can be affected.
Lead causes problems by interfering with the body's biochemistry. It causes anemia by replacing the iron in hemoglobin, the red blood cell protein that carries oxygen in blood, and by interfering with the enzymes that make heme, the iron-containing molecule in hemoglobin.
