A study tracking the movement of lead in pregnant mothers confirms what people in the Silver Valley have suspected for years: lead can be passed on to children.
The study, reported last week in The New York Times, delivers the first direct evidence that a girl growing up in a lead-polluted environment can expose her unborn child to lead.
“We have been aware of that theory for some time,” said Barbara Miller, a local activist for increased health care. “My response is, now that it’s been confirmed, what are health agencies going to do about it?” The Panhandle Health District has been monitoring blood-lead levels for years in the Bunker Hill Superfund site.
Health workers have taken blood samples from pregnant mothers and umbilical cords, but few to none have had blood-lead levels above 10 micrograms per deciliter of blood - the “threshold of concern” at which lead poisoning is thought to occur, according to health workers.
Dr. Mary-Alice Janzen, an obstetrician in Pinehurst, remembers one patient who had a blood-lead level over the threshold.
“Everyone else was below that,” said Janzen, who is eight months pregnant.
Janzen concentrates on avoiding exposure to lead and taking vitamins to reduce the possibility that lead could be released from her bones into her bloodstream.
“I’m pretty comfortable in terms of my own pregnancy, except I didn’t go to see the (Bunker Hill smoke) stacks blown up,” Janzen said. “I wasn’t sure if they cleaned them. I thought that was a time of increased exposure.”
Lead is among the metals mined in the Silver Valley. In humans, the metal can cause neurological damage and high blood pressure. It’s particularly bad for children, whose brains are developing.
People who have been exposed to lead carry it for a few weeks in their blood before it settles in their bones or tissues. Lead is stored in the bones for 25 years or longer, experts say.
In the recent study, researchers at Macquarie University in Sydney, Australia, followed 13 women who had recently immigrated to Australia from the former Yugoslavia and then became pregnant.
The lead they were exposed to in the Balkans, which was stored in their bones, has a different molecular weight from the lead in Australia.
As their pregnancies progressed, their blood contained greater amounts of the Balkan lead, peaking during the second and third trimesters, according to Dr. William Jameson of the National Institute of Environmental Health Sciences.
By the end of the pregnancy, as much as 60 percent of the total amount of lead in blood came from the women’s bones.
In a second study by Health and Welfare Canada, researchers monitored blood-lead levels of 30 pregnant monkeys before, during and after pregnancy. It also showed that up to 60 percent of the blood lead originated in the bones.
That study also found the fetuses had lead in every organ.
Doctors have long feared that lead will more readily escape the bones of pregnant or lactating women as calcium is released to build the baby’s skeleton and produce milk.
That’s why the Panhandle Health District and doctors typically advise pregnant women to take calcium.
“It’s not just important for mothers. It’s important for everyone. It helps bolster the system,” said Jerry Cobb, who supervises the health district’s lead-monitoring program in the Silver Valley.
The level of blood lead among residents within the Bunker Hill Superfund site has dropped steadily since 1974, when the average was 65 micrograms per deciliter.
The most recent tests, done in 1995, showed the average blood-lead level of children 9 months to 9 years is from 4.6 to 7.3 micrograms per deciliter. The test group included 57 children whose blood lead levels were over 10.
Cobb said the national average is about 3 or 4 micrograms per deciliter.
, DataTimes The following fields overflowed: BYLINE = Susan Drumheller Staff writer The New York Times contributed to this report.