The WA Greens have questioned the independence of a state government report that found mining giant BHP was a "dominant source" of dust pollution in the Pilbara town of Newman.
Meanwhile, an expert in environmental engineering says regulators made the wrong decision when they deviated away from national standards on dust pollution in Newman.
Last week, it was revealed air quality targets had been exceeded in Newman due to mining 171 times since 2013, triggering fears from residents and unions over potential health impacts.
Two local BHP mines were identified as a "dominant source" of the dust by the Department of Water and Environmental Regulation [DWER] review.
Documents released through Freedom of Information also revealed DWER intended to bring Newman's air quality target in line with national standards for the review, following Department of Health advice.
However, this was later abandoned after BHP "contested" the decision, and a higher ceiling was ultimately used.
Air quality in Newman has historically allowed for airborne dust concentrations 40 per cent higher than the national environment protection measure [NEPM].
This higher ceiling was still breached 171 times, according to DWER's review.
Greens MP Brad Pettitt said the decision to continue using higher targets rather than national standards raised concerns about the independence of the review.
"I think it raises great concerns, especially for those people who live there day in, day out," he said.
"There is no doubt that we should be having frank and fearless advice from our regulators, that's actually driven by the key evidence.
"It shouldn't be in any way influenced by the commercial needs of a company, big or small."
In 2020, the ABC reported the West Australian Department of Health did not support the departure from national standards for BHP's Newman mines.
Mr Pettitt said this health advice should have been applied in the DWER review.
Gavin Mudd, an associate professor of environmental engineering at RMIT University, said national standards were typically based on health advice or research.
He said the community expected them to be applied consistently.
"I think it's an entirely reasonable proposition that we have national standards, and they therefore should be used and applied consistently," he said.
"So everyone, whether you're in Newman, Perth or Canberra, is treated the same."
Dr Mudd said any deviation from national standards should be based on "an extremely thorough" argument, which he felt had not been made in relation to Newman.
BHP and regulators back report
A BHP spokesperson said the company was consulted for the review and backed the decision to use a higher ceiling due to high levels of naturally occurring dust.
"We had an opportunity to contribute to the review process, and we supported the Department of Health's view that [the higher target] was an appropriate interim standard to use in the Pilbara's naturally dusty environment," the spokesperson said.
The spokesperson said BHP was committed to its $300 million Pilbara Air Quality Program.
A DWER spokesperson said the use of a higher air quality target did not conflict with the most recent health advice.
"Meetings leading up to this advice form part of the deliberative process following which, the Department of Health agreed with the application of the [higher] guidance value," the spokesperson said.
"The department is confident in the independence of the review."
The spokesperson said the WA government acknowledged dust levels in the Pilbara region could be higher than other areas in the state.
"[The government] is taking a whole-of-government approach in Newman to ensure that the impacts of dust are well understood and regulated to the appropriate levels."
A Department of Health [DOH] spokesperson said it preferred the NEPM to be used, but site-specific variations could be made using a "risk-based approach".
The spokesperson said there was no conflict between DOH and DWER regarding the dust pollution target in Newman.
"The current NEPM does not delineate between 'safe' and 'unsafe'. At all levels of exposure, there are small changes in risk as dust concentrations increase," the spokesperson said.
"The increase in the risk between the interim guideline level and the NEPM is low.
"Despite this, the DOH continues to support ongoing mitigation strategies to reduce dust from mining operations and for PM10 [dust] concentrations to be as low as reasonably practicable."
