A hazardous playmate

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.

Lead also interferes with the neurons responsible for learning and memory, says neurotoxicologist Tomas Guilarte of the Johns Hopkins Bloomberg School of Public Health in Baltimore. It dismantles proteins on the surface of neurons that respond to a brain chemical called NMDA, which is important for learning new things. It also hinders growth of new neurons in the brain’s learning and memory center.

In 2003, Canfield found that lead levels even below the CDC’s 10 micrograms per deciliter cutoff affected IQs. Going from 1 microgram per deciliter of lead in the blood to 10 micrograms per deciliter, children lost about four to seven IQ points. “There’s a fair bit of controversy around this,” Woolf says. Scientists are still debating the finding and hoping to see it repeated.

Experts say the first thing that is done if a child has lead-contaminated blood is removing him or her from the contaminated environment because lead clears from the system over time. Woolf says the second line of defense is dietary. The child’s diet should contain appropriate amounts of calcium, zinc and iron to displace the lead from the places where it is causing damage. Dairy products and eggs are good sources of calcium and zinc. Foods should be iron-fortified.

Children who have low iron levels are more susceptible to lead poisoning. “If you’re iron deficient, you’re like a magnet for lead,” Woolf says. Once children stop breast-feeding, they lose a great source of iron. “Iron is usually lacking in toddlers’ diets.”

The third line of treatment is drugs. The CDC recommends treating children at 45 micrograms per deciliter and above with chelants, chemicals that grab the lead and pull it into urine. Woolf says it’s up to the doctor’s discretion, based on symptoms, to treat levels lower than 45 micrograms per deciliter. A 2001 study in children with blood levels from 20 to 40 micrograms per deciliter found that chelation therapy cleaned out lead from the bloodstream but didn’t have an effect on intelligence deficiencies. However, Woolf says, the treatment time (three months) may not have been long enough to have an effect.

Many experts think lead poisoning can result in permanent losses in intelligence, but some think the damage can be overcome. A 2003 study by Guilarte showed that lead-poisoned young rats, which then lived lead-free for several weeks, could regain learning skills if housed in an environment enriched with toys, spinning wheels and other rats.

Although the level of exposure from the lead-paint-tainted toys is likely to have been low, they will have contributed to lead levels if kids licked or chewed them, or sucked their hands after handling them. “The Mattel and Fisher-Price toys represent another background source of lead that we don’t need,” Woolf says.