Increased cancer risk link in Victorian goldfield region
Innovative research using a geospatial analytical approach has linked an increased cancer risk to soil arsenic levels in Victoria’s goldfield region, which comprises about one third of the state. Many communities grew up around historical gold mining sites, and because arsenic – a known carcinogen – naturally occurs around gold ores, it can be concentrated in some residential soils and mine waste. The processed tailings often contain arsenic in excess of 1000 mg/kg - over 100 times that of normal residential soils.
Epidemiologist Dr Dora Pearce, currently researching influenza epidemiology in VIRGo (Vaccine and Immunisation Research Group) within the Melbourne School of Population and Global Health, conducted this research for her PhD at the University of Ballarat. Dr Pearce’s doctoral research comprised two complementary studies. The major study harnessed geospatially referenced data, using a Geospatial Information System (GIS) to draw together 20 years of cancer data (1984 to 2003), recently released by the Victorian Cancer Registry, geochemical data from the University of Ballarat and GeoScience Victoria, and demographic data from the Australian Bureau of Statistics.
“The geochemical data was used to derive an exposure metric reflecting soil arsenic levels in 61 contiguous Statistical Local Areas,” she said. “An exposure metric is an indicator of what the potential average population exposure could be. Oddly, this data was available because arsenic is used as an indicator in gold exploration, but it gave us a much more accurate and reliable picture than any previous study.” This study was published in 2012 in the Journal of Exposure Science and Environmental Epidemiology.
Dr Pearce found that for residents living in socioeconomically disadvantaged areas, those in areas within the highest soil arsenic quintile faced cancer risks slightly above those in the lowest quintile. Only some more common cancers were considered individually: melanoma risk for males in the highest quintile was 50% higher than for males in areas within the lowest quintile – a factor of 1.5. For women, melanoma risk increased by around 30%. Risk of colon cancer in males and females, and prostate cancer, was around 20% higher. These risks, while relatively low, could be avoided, she said.
The other component of Dr Pearce’s PhD showed that arsenic concentrations in children’s toenails and residential soils were correlated, and synchrotron-based X-ray microprobe techniques, used to explore arsenic patterns and speciation in toenail clippings, indicated some systemic absorption due to periodic exposures: confirming that the health threat was ongoing. “This problem has not gone away.
”She said the research results have important implications for addressing the hazards of arsenic in soil and tailings from past, present and future goldmining operations across Australia.The demand for affordable land has pushed housing into areas abutting old tailings dumps. Arsenic can be ingested by swallowing contaminated soil through hand-to-mouth actions and by breathing in dust. “This means young children are most at risk and it’s a concern that kids love playing on these heaps,” she said.
Dr Pearce has called for a coordinated approach by local councils and state government departments and regulatory agencies to address the continuing risks to residents near gold mine tailings. But she would rather see scarce funds spent on public education and localised remedial action than a major program of soil testing.
“To approach this issue systematically would be a huge task, and further research to investigate exposures and cancer risk at individual level would be time consuming and costly,” Dr Pearce said.
“An alternative approach would be to go ahead and rehabilitate obvious mine waste around areas where people are living. We know arsenic can cause cancer – it’s better to act now to reduce the health risks."
Caption: Location map of the study area within Victoria showing 61 Statistical Local Areas (SLAs), comprising 36 core SLAs (white) and 25 peripheral SLAs (dark grey).