LEAD Action News vol 1 no 1 Feb 1993
Pregnancy, lead and bone mobilisation study
To understand more about lead in pregnancy, an Australian-US team is asking for help from immigrant females, especially those who intend to have children in Australia. They are using a method which enables them to determine the source of the lead - a lead isotope 'fingerprinting' method (this is not a radioactive method). They want to see if most of the lead in blood has come out of the women's bones, or from environmental sources such as air, food or water.
The researchers have found the lead isotope profiles in the southern Australian population (mainly females) are relatively uniform but quite different from those in most other countries of the world. As lead in the body appears to change in its 'fingerprint' when a person moves from one environment to another (eg from Europe or Southeast Asia to Australia), they wish to monitor mothers-to-be from other countries - especially Poland, Romania, Russia, Czechoslovakia and Lebanon.
To minimise variables such as differences in the source of lead in food, air and water, they wish to enlist females from one or two countries, or even better, from the one region in each of those countries. Their results will be compared with Australian-born females whose parents originally came from the same countries.
To understand more about bone mobilisation during pregnancy, the team will be making measurements of bone density and other tests.
By participating in this study you will assist in understanding more about bone mobilisation and lead during pregnancy. This information will help not only in producing healthier children but also in lessening potential health problems for mothers during childbirth.
Reasons for the study
During pregnancy, the bones of the mother can be dissolved (mobilised) to assist in the development of her child. Under some rare circumstances, the mobilisation of bone can result in spinal weakness (degradation).
Lead is mainly stored in bones, and with mobilisation of bone during pregnancy, the lead is thought to be released from the skeleton and transferred across the placenta to the foetus. Lead has no useful function in the body and can result in diminished intellectual development and behavioural problems in children, even at low levels of exposure.
The mechanisms of bone mobilisation and the timing and amount of lead released from the skeleton are poorly known. It is very important to know more about bone mobilisation and lead, especially for women of child-bearing age and for those who may have been exposed to high levels of lead in their workplace and their home environment.
Pb isotope fingerprinting in environmental and health studies
The lead isotope fingerprinting method was developed by Dr Brian Gulson and his team at the CSIRO for application in the minerals industry. The same fingerprinting approach is an extremely powerful and sensitive method for determining the source of lead (and associated metals such as zinc) in the environment and in animals.
Besides a major study to determine the source of lead in humans in the Broken Hill mining community (funded by CSIRO and the NSW Government), Dr Gulson is heading the project on lead and bone mobilisation during pregnancy, titled 'Biokinetics of Lead in Human Pregnancy'. The Biokinetics project is funded dominantly by the US National Institute of Environmental Health Sciences.
Lead has four isotopes - 208, 207, 206 and 204 - which vary in abundance depending on their geological and or industrial source. The abundances ('fingerprint', signatures or profiles) are generally expressed in terms of ratios such as 206Pb/204Pb; a 206Pb/204Pb value of 16.0 found, for example in the Broken Hill mines, means that the abundance of 206Pb is 16 times that of 204Pb.
The lead isotope finger printing method makes use of the fact that the abundance of the isotopes of Pb from one geological source is different to that of another geological source.
For example, the Pb from the Broken Hill lead-zinc-silver ores has a totally different profile (a 206Pb/204Pb of 16.0) to that of Pb, from say, the Rosebery ores on the west coast of Tasmania (206Pb/204Pb of 18.3). The profiles or abundances of the Pb ores are also usually quite different from those of Pb in the common rocks which surround the mineral deposits.
In using the fingerprinting method for determining the source of Pb in people, the researchers compare the Pb isotope profiles in the blood and/or urine (but can also use nails and teeth) with those found in the potential environmental sources such as air, food, water and dust.
In simple terms, the closer the similarity in isotope profiles between that in blood and environmental source or sources indicates that the environmental source may be a significant contributor to the Pb in blood.
Obtaining Pb isotope profiles requires exacting and sophisticated analytical procedures. Because of the very low amounts of Pb in most samples (in the parts per billion range), Pb is separated from the materials in 'clean' laboratories and the isotope abundances or profiles are measured (as ratios) using a thermal ionisation mass spectrometer.
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