Note that lead in plasma is in dynamic equilibrium with that of bone where
Pb2+ ions can replace Ca2+ in the hydroxy apatite crystals.
Hence it is important to know how long time the woman has lived in the
house containting lead tubes. If several years she may have accumulated a
considerable amount of lead in her skeleton and therefore a lead-free
intake will only sligthly affect the blood level of lead and, consequently,
the transport of lead to the fetus.
It is possible to detect accumulated lead in bone by x-ray of tibia but,
since occupational lead poisoning nowadays is rare, this test is seldomly done.
Presence of lead in the skeleton also is important for the treatment.
Because Ca2+ and Pb2+ behaves similarly you can support the transport of
calcium to the fetus (and hence lower the transport of lead) with a
calcium-rich food intake.
If, on the other side, lead has been accumulated in bone, such a treatment
will release Pb2+ from the skeleton and the plasma level of lead may
increase to toxic levels!
Lead poisoning can also be treated with calcium-EDTA because Pb2+ is more
strongly bound to EDTA than Ca2+ and the lead-EDTA-complex is easily
excreted with the urine. However, as far as I know such treatments has only
been performed on males working in lead industries, not in women and
especially not pregnant women!
Also note that fear can do more harm than moderate exposure to lead.
This is not a simple situation and I should recommend a search in MEDLINE
and/or similar indexing systems (i.e. the Chemical Abstracts) before doing
anything.
Mr Sten Öhman, PhD
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