Land and Water Link

16- May 2004

The Risky Business of Environmental Contaminants

Science can save industry tens of millions of dollars by preventing pollution and directing resources to areas that need it most, according to CSIRO.

But Australia still has a lot to learn from Europe and the USA about the use of ecological risk assessment; a valuable tool in decision-making for environmental management.

Last month, more than 100 scientists, natural resource managers, policy makers and industry leaders met in Adelaide to discuss the latest developments and consider international best practice in the management of environmental risks posed by contaminants – such as pesticides, PAHs, PCBs, and heavy metals (like arsenic, cadmium and chromium). The organisers hoped to generate discussion and promote the wider use of ecological risk assessment in Australia. And by all accounts it was a great success.

‘The workshop was very well attended,’ explains Dr Rai Kookana. ‘And we have been able to facilitate some important connections, which will be critical to the future of research in this area – as it is very much a team effort.’

Teamwork will be essential in the upcoming review of the Australian National Environment Protection Measure (NEPM) for the Assessment of Site Contamination, so the workshop was well timed. As Dr Bruce Kennedy, Executive Offi cer of the National Environmental Protection Council explains: ‘When the NEPM was developed in 1999, it was recognised that regular updating was appropriate in the light of improvements in scientific knowledge and technological practice.’ The review is expected to commence later this year or in early 2005.

According to Dr Kennedy, while the NEPM provides a broad framework, more information about the effects of contaminants on ecosystems – and on specific species – is required to facilitate ecological risk assessment. There is also room for new modelling approaches.

Dr Ray Correll from CSIRO Mathematical and Information Sciences agrees. ‘This is really one of the major outcomes of the workshop – a realisation that the way we do risk assessment here needs to be revised and developed to take Australian conditions into account.

‘A steering committee will be formed, which will need to make some tough decisions about what we are really trying to protect and then develop specific tests.’

Scientists at CSIRO Land and Water led by Dr Rebecca Hamon are examining the risks posed by metals and organic contaminants in soil ecosystems.

Research Director Dr Mike McLaughlin would like to see the NEPM further developed to incorporate new measures for the assessment of contaminated land. ‘At the workshop we presented a possible risk-based framework for new guidelines, modelled on the approach taken by The Australian and New Zealand Guidelines for Fresh and Marine Water Quality 2000’, says Dr McLaughlin.

‘This approach will allow us to integrate ecological considerations into the assessment of soil contamination using a whole range of soil-specific threshold values, which relate to different environmental values – like plant health, soil microbial function, ability to leach away into groundwater and so on. It is being developed by scientists from CSIRO and the Department of Environment and Conservation, New South Wales.

‘The intended outcome is a risk-evaluation decision system where you put in a small set of key parameters (e.g. contaminant, soil pH, organic carbon content, iron content, cation exchange capacity and redox potential) and generate a number for the maximum acceptable contaminant concentration in that particular soil.

‘When the concentration rises above that threshold level, that’s when you need to go in for further assessment and/or remediation’, says Dr McLaughlin.

The concept of individual threshold or trigger levels is better suited to our diverse Australian soils than the current system of regional averages (single-value ‘ecological investigation levels’). For example, when Dr McLaughlin’s team conducted a large survey of remote sites in Australia and South East Asia, concentrations of metals like chromium and nickel were often quite high – in many cases natural, background levels were considerably higher than the respective ecological investigation level used in the NEPM.

Dr Hamon also observed relationships between certain elements (e.g. iron or manganese) with several environmentally important heavy metals. These relationships can be used to calculate more realistic background readings and to estimate the natural quantities of potentially harmful metals, including arsenic, lead and zinc.

CSIRO Contact:
Dr Rai Kookana
Ph: +61-8-8303 8450