Alcoa has pushed back against concerns over rising mercury emissions at its Wagerup alumina refinery in Western Australia, even as environmental groups move to challenge its operating licence.

The refinery is located about 120 km south of Perth in the Jarrah forest region and it has come under scrutiny after recent data showed a steady increase in mercury emissions in recent years. Emissions reached around 400 kilograms in 2025, nearly double the levels which were recorded in 2022.

The Conservation Council of Western Australia has formally opposed the state’s decision to approve a revised licence for the facility, arguing that the environmental and public health risks linked to the increase have not been fully addressed.

CCWA executive director Matt Roberts said, “It seems Alcoa has seen increased mercury emissions from the Wagerup refinery for at least three years, with no action taken to remedy that.” He added that the situation raises concerns about regulatory oversight and long-term environmental exposure.

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According to a review by the Department of Water and Environmental Regulation (DWER), the rise in emissions has been linked to higher mercury content in bauxite ore as well as declining performance of condensers at the refinery. The regulator concluded that the increase could be tolerated without posing an unacceptable risk.

Alcoa, however, maintained that there had been no sudden or uncontrolled release of mercury. A company spokesperson said the rise reflects changes in recovery processes, along with increased bauxite processing volumes at the site.

“Mercury is a common element found in low concentrations in rocks and ores,” the spokesperson said, adding that variations in ore composition and higher throughput were likely contributing factors.

Environmental groups, however, remain suspicious and unconvinced, saying that mercury is a known neurotoxin and can accumulate over time in soil, water and wildlife, causing a potential threat to ecosystems surrounding the refinery. The group also mentioned about the limited monitoring data about threatening species such as black cockatoos, numbats and western ringtail possums.

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Further concerns were raised about how the emissions increase was identified. According to CCWA, the spike was detected through the National Pollutant Inventory rather than routine compliance reporting, raising questions about monitoring systems.

Independent experts say the actual risk depends on exposure levels. John Mamo, a professor at Curtin University, noted that mercury exists naturally in the environment but can become harmful depending on how it interacts with water and enters ecosystems.

“In nature, mercury is part of the soil architecture of the planet,” he said, adding that exposure risks vary and depend on concentration and duration.

The appeal against the licence is now under review by the Office of the Appeals Convenor, with DWER declining to comment while the process is ongoing.

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