[ASC-media] Media release: toxic availability
jcamedia at starclass.com.au
Mon Aug 30 09:06:28 EST 2004
CERAR Media Release 04/07
TOXIC... BUT IS IT DEADLY?
Across the continent, Australians are increasingly exposed to tens of thousands of toxic sites - the legacy of 150 years of industrial development.
It's far from clear how dangerous most of these sites really are to human health, warn researchers at the Centre for Environmental Risk Assessment and Remediation (CERAR).
"The big sleeper issue is bioavailability - or how readily these toxins can get into the human body and cause damage," says CERAR director Professor Ravi Naidu.
"You could have a site which is heavily polluted, but where the toxins are not readily available and so pose little threat to human health.
"On the other hand, you can have a site where the toxins are highly available and are being moved around by groundwater, plants or soil processes, so they become threatening to humans."
The issue of bioavailability will come under the international spotlight when Australia hosts the 3rd global workshop on "Chemical Bioavailability in the Terrestrial Environment", in Adelaide, South Australia from September 13-15, 2004.
Bioavailability makes a huge difference to whether a contaminated site can be safely and economically sealed - or must be subjected to a costly process of decontamination, says CERAR contamination expert Dr Albert Juhasz.
"Because there are tens of thousands of contaminated sites across our landscape, clean-up now adds millions of dollars to the cost of urban re-development.
"This cost is ultimately paid for by home owners and occupants," he says.
"It also has major implications for the nation's plans to produce Cleaner Cities."
Dr Juhasz says that apart from the pollutants themselves, there are all sorts of geological, chemical and biological processes in the soil which affect whether contaminants are readily bioavailable or not. Every site is different - even if the pollutants are the same.
"The mere presence of a toxin doesn't mean the site is dangerous. What really counts is its chemical form and whether or not it can get into your system.
"For example some forms of arsenic are much more toxic than others: arsenite is about 30 times more toxic than arsenate.
"Some sites are more acidic than others, and this can liberate compounds which are more toxic to humans.
CERAR is presently working in partnership with other researchers (School of Pharmaceutical, Molecular and Biomedical Sciences at UniSA, Institute of Medical and Veterinary Sciences) in trials which involve feeding very low levels of common contaminants to pigs, to see how readily they show up in the animal's blood or urine. The result of these experiments can be related to humans to determine the effects of toxin bioavailability on human health.
Part of the work also involves developing a "glass stomach" - a laboratory digester - to see if the team can create an inexpensive test for determining contaminant bioavailability.
"In all our work at 40 contaminated sites - old railways, sheep dips, mine sites and the like - we found the arsenic bioavailability varied from 1 per cent to 50 per cent, which is a huge range, and shows why you need to do a special test for every individual site.
"It also shows that in some cases, the safest - as well as cheapest - course of action may be to leave the contamination where it is, and not stir it up through a clean-up.
"In others, where the toxins are highly mobile and a threat to residents, you need to adopt a far more rigorous clean-up plan."
CERAR provides specialist services in risk assessment and advice on decontamination of polluted sites in Australia and Asia, and works with organisations ranging from federal and state government departments and private corporations to local government and citizens groups.
Dr Albert Juhasz, CERAR 08 8302 5045
Prof. Ravi Naidu, CERAR 08 8302 5041 or 0407 720 257
August 30, 2004
More information about the ASC-media