Lead disrupts the functioning of almost every brain neurotransmitter, says
David Bellinger, Ph.D., a psychologist and epidemiologist at Children's Hospital
in Boston. Neurotransmitters are chemical messengers between the body's nerve
cells. The messenger calcium, for example, is essential to nerve impulse transmission,
heart activity and blood clotting, but if it doesn't work right, affected systems
may also be askew.
“Lead fits into binding sites that calcium should,” Bellinger
says, “so
it can disturb cellular processes that depend on calcium. But there’s
no unifying theory that explains in detail what lead does to the central nervous
system, which is where lead typically affects children.”
Bellinger estimates that each 10 mcg/dL increase in blood lead lowers a child's
IQ about 1 to 3 points. He adds, “When lead exposure in the uterus is
quite high, the impact can be devastating on the fetus, causing serious neurological
problems.”
High lead exposures can cause a baby to have low birth weight or be born
prematurely, or can result in miscarriage or stillbirth.
“Symptoms of lead poisoning can be highly variable, depending in part on
the age of the child, the amount of lead to which the child is exposed, and how
long the exposure goes on,” says pediatrician Randolph Wykoff, M.D.,
FDA associate commissioner for operations. Children exposed to lead may have
no symptoms, he says, or may report sometimes vague symptoms, including headache,
irritability or abdominal pain.
Higher levels of exposure can be associated with anemia and changes in kidney
function, as well as significant changes in the nervous system that may, at
extreme exposures, include seizures, coma and death.
In adults, lead poisoning can contribute to high blood pressure and damage
to the reproductive organs. Severe lead poisoning can cause subtle loss of
recently acquired skills, listlessness, bizarre behavior, lack of coordination,
vomiting, altered consciousness, and, as with children, seizures, coma and
death. Poisoning without severe brain effects can cause lethargy, appetite
loss, sporadic vomiting, abdominal pain and constipation. By the time symptoms
appear, damage is often already irreversible.
“The most important thing for families to do,” says Baltimore’s
Davoli, “is to learn what steps they can take to prevent lead poisoning.
We don’t want to get to treatment. And they should take their children
to the doctor regularly for checkups and, if the children are at risk, get
blood lead tests done.”
Critical to prevention is focusing on the important lead sources. FDA’s
Rosenthal says, “Dealing with sources of lead means recognizing them
in your family’s environment, knowing which ones contribute significant
exposures, and eliminating or avoiding those exposures.”
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