Fluoride emissions from an aluminium smelter in Victoria's south-west are causing koalas grazing nearby to develop an irreversible and sometimes fatal condition, a study has found.
The study, commissioned by Portland Aluminium operator Alcoa, found fluoride was being deposited on gum trees near its plant in south-west Victoria and contributed to "poor health in some koalas".
The University of Melbourne study was commissioned by the American company in 2020 after dozens of koalas had to be euthanased due to suspected fluoride poisoning, which causes tooth and jaw deformities and weakened bones.
Alcoa has not released the full findings of the study but acknowledged both fluoride deposits and a high population density in blue gums around the plant — on land owned by the company — were contributing to the koalas' poor health.
It said its assessments "found that the deposition of fluoride in trees within close proximity to the smelter does contribute to poor health in some koalas".
As a result, the company said it would gradually harvest the blue gum plantation with significant fluoride deposits and plant more trees further away.
"To reduce the risks fluoride can pose to koalas, Portland Aluminium will gradually harvest its main blue gum plantation and other areas of known koala habitat within close proximity to the smelter over the next two years," an Alcoa spokesperson said.
It also said the fluoride emissions emanating from the plant were within EPA guidelines and did not pose a threat to human health.
The company has developed a plan with Victoria's Department of Environment, Land, Water and Planning (DELWP) and has committed to planting 18 hectares of eucalypt species further away from the smelter to serve as alternative habitat.
Fluorosis previously found in kangaroos at the site
The issue of fluorosis affecting wildlife around the aluminium smelter at Portland is not new.
Similar findings resulted from a six-year study focused on kangaroos and wallabies that started in 2008.
University of Melbourne wildlife researcher Jasmin Hufschmid was involved in both the older study and the recent one focused on koalas.
She did not comment directly on the findings of the recently-completed koala study but said fluoride emissions from the aluminium plant posed the most serious risk to animals within a 1-kilometre radius.
"With aluminium smelters, one of the emissions is fluoride and that gets emitted through the air then deposits on the land, vegetation and water within a certain radius around the smelter," she said.
"It's really the animals that are the closest to the smelter that get the most affected by fluorosis."
She said the effects of chronic fluoride toxicity were serious and could not be effectively treated.
"When you take in a large amount of fluoride over an extended period of time, what happens is the fluoride deposits in mineralised tissues in the body … things like bones and teeth, typically," Dr Hufschmid said.
"The fluoride builds up in those tissues and the body can't excrete them at the same rate they're building up.
"We do put fluoride into our drinking water to assist in dental health. They're quite low levels, about a part per million … the amounts of fluoride that cause problems are far, far higher than that."
She said fluorosis in animals caused teeth to deteriorate badly over time, while in bones the mineral slowly replaced calcium.
"It's much more porous, so it breaks more easily," Dr Hufschmid said.
"You get these lumps and bumps forming on the outside of bones that push on nerves and tendons and things."
After the results of the initial study came out in 2014, the company tried to prevent wallabies and kangaroos from being exposed to fluoride emissions by putting up fencing and replacing vegetation.
Dr Hufschmid said the effects of chronic high-level fluoride exposure were "irreversible".
"Animals that stay within an environment where there is the background of elevated fluoride, we don't have any way of treating that," she said.
