The Australian Workers Union (AWU) is urging Rio Tinto to spend more on maintaining its aluminium plants in the wake of the Queensland Alumina Limited (QAL) refinery in Gladstone discharging the toxic by-product 'red mud' into a residential area.
Earlier this week, the company said a gasket at the refinery failed.
The Department of Environment and Heritage Protection says "caustic fumes" may cause skin and respiratory irritation but Queensland Alumina says the release was concentrated below safe exposure levels.
AWU spokesman Tony Beers says the incident is a wake-up call.
"It's no different to the late '90s when there were budgetary cuts, workforce reductions," he said.
"We saw a number of incidents on plants like the one at QAL which caused major concerns not only for the safety and welfare of the workers on site but the broader community." He says the company needs to spend more on upkeep.
"It is important in high-risk plants such as QAL and the Yarwun alumina refinery that they ensure that capital expenditure is there to maintain these plants in good working order to ensure safety of not only their employees but the broader community," he said.