RESEARCHERS in the US have produced a scanner that may provide a quick
and painless way of determining how much lead people have in their bodies.
The device, developed at the University Hospital at Stony Brook, New York,
will come as good news to doctors, who have been waiting for a simple and
effective way of screening their patients for lead.
Lead poisoning is one of the most serious environmental threats to children’s
health. Even at low concentrations, the metal may damage the brain and other
organs, and health authorities in the US have recently reduced the threshold
for acceptable levels of lead in the body.
According to researchers at Brookhaven National Laboratory, Long Island,
more than three million American children may need treatment for lead poisoning.
But without a workable screening programme, doctors can treat only a fraction
A simple blood test reveals only recent exposure to lead, because the
metal quickly finds its way from the bloodstream into the bone. The problem
is that a number of processes will unlock minerals from the bones and free
them to circulate in the body. The minerals enter the bloodstream at, for
example, pregnancy, lactation, osteo porosis and the spurts of growth at
A child exposed to lead in, say, an apartment with old, peeling paint,
may suffer damage and show high levels of lead in the blood. If the child
moves to another home, the blood may return to normal after a few months,
but the total amount of lead in the body will remain high. In adults, up
to 95 per cent of the body’s lead is concentrated in the skeleton. Even
years after exposure the lead can harm the body when it goes back into the
The standard method that doctors use to measure lead levels and treat
lead poison ing is to introduce a chemical called ethylenediaminetetraacetic
acid (EDTA) intravenously into the body. EDTA draws lead out of the bone
and binds to it. The body then excretes the compound in the urine, which
clinicians analyse for lead. However, doctors cannot screen people with
this test, because it is painful and requires the patient to stay in hospital
for up to three days.
Now, Lucian Wielopolski of the University Hospital at Stony Brook and
colleagues have developed a scanner that could provide doctors with a way
of screening people for the level of the metal in their body. The scanner
uses X-rays to measure the amount of lead in bone.
Wielopolski’s scanner irradiates the femur with low-energy X-rays and
measures the fluorescence of the lead in the bone. The greater the fluorescence,
the greater the amount of lead.
Wielopolski calibrated his device by scanning bones from amputated limbs,
then analysing samples of the bones to determine the levels of lead they
contain. He compared the results his machine gave with the EDTA test on
the same samples, and found that they gave very similar results.
The low-energy X-rays used by the scanner penetrate only a few millimetres
of tissue, so the test works only on bones or organs which are close to
the skin, such as the femur.
Wielopolski and his colleagues have set up a company to sell their scanner,
but they feel that they still need to improve their machine before it can
be used for routine testing. Each scan takes more than 16 minutes, which
is a long time for anyone, especially a child, to be strapped into a scanner.
Wielopolski hopes to bring the time down to five minutes or less.
John Rosen, a pediatrician working with Wielopolski, hopes that the
scanner will be more than just a screening tool. He is now beginning research
on lead in pregnant women.
‘We know that the body mobilises lead as well as calcium from the maternal
skeleton during pregnancy, and moves to the fetus,’ he says. No one knows
what constitutes a dangerous level of lead to the fetus nor how much lead
the fetus receives from its mother.
‘We would like to know to what extent lead toxicity is an inter-generational
disease,’ says Rosen. Researchers could find out by scanning pregnant women
and their children.
The ultimate goal would be to develop a medical or environmental treatment
for women who have lead poisoning and who intend to have children. Rosen
says that, later this year, he will be doing research on primates, to see
how much lead females transfer to their offspring.
The scanner can detect almost any element present in the skin or bone.
Wielopolski has used it to determine levels of several elements, including
strontium, copper, zinc, iron and bromine.
He has also used the scanner to measure the levels of iron in the hands
of patients with thalassaemia, an inherited blood disorder.