The team, led by Southern Cross University's Professor Ed Burton, has found the naturally occurring metal chromium 3 can be converted by extreme bushfire heat into the highly toxic and cancerous chromium 6.

Chromium 6 is the substance spotlighted by renowned American environmentalist Erin Brockovich, who blew the whistle on high concentrations in the water supply of her home town in southern California.

Professor Burton's breakthrough research has confirmed bushfire temperatures of up to 1000 degrees can endanger human health long after the flames have gone out.

"We've seen bushfires create conditions in the surface soil that transform the safe, naturally occurring chromium-3 into the toxic, cancer-causing chromium-6," Professor Burton said.

"Chromium-6 can cause lung cancer and leach into waterways."

Professor Burton, an expert on the geochemistry and mineralogy of soils, sediments and groundwater systems, said frontline firefighters are immediately at risk but the contamination of water within catchment areas posed a wider threat.

"We know that firefighters have higher incidences of chromium in their urine and are more susceptible to cancer than other groups.

"This research is trying to predict with greater accuracy the potential harm of this carcinogenic toxin and to mitigate the risk to human health by seeking to determine the reach and duration of the post-fire danger zone.

"The role of high temperatures in potential chemical contamination has been underplayed, so it's also important to learn which soils are most prone to contamination, and for how long."

While chromium 3 is a healthy nutrient in humans for insulin, sugar and lipid metabolism, its transformation into the DNA-damaging chromium 6 in bushfires was discovered when Professor Burton's team used the Australian Synchrotron particle separator in Melbourne to shine a highly-focussed light - millions of times brighter than the sun - on a series of soil and mineral samples.