Fears for heritage site as gas plant expansion approved

Industrial pollution is damaging priceless rock art, an expert says amid protests over a decision to extend the life of a major gas hub.

Woodside's North West Shelf project - which hosts Australia's biggest gas export plant - has been given the green light by the federal government to keep operating until 2070.

The Australian energy giant still has to accept conditions around heritage and air quality at the project on Western Australia's Burrup Peninsula, home to ancient rock art, before the approval is made official.

The approval has angered traditional owners, climate activists and scientists who have researched the impact of industrial pollution on the rock art at Murujuga.

A report into pollution at the site, linked to a $27 million rock art monitoring project, was only released by the WA government a week before federal Environment Minister Murray Watt announced the approval.

Benjamin Smith, an archaeologist at the University of Western Australia, said the executive summary did not reflect the key findings of the 800-page report by Curtin University scientists who he claimed were gagged from speaking publicly about it.

"They were outraged that their report and the integrity of their academic findings had been misrepresented."

Professor Smith told AAP the Curtin scientists felt the summary had "lied about their findings" so he was speaking out about a cover-up by departmental "spin doctors".

The Cook government has dismissed the claims as offensive and factually incorrect.

The Curtin scientists subjected rocks in a climate chamber to acidic pollution equivalent to emissions from the Burrup gas plants and found all the rocks showed evidence of degradation.

Prof Smith said the Curtin research and his own studies showed the pollutants would eat away at the manganese in the rocks until they developed "holes like a Swiss cheese" that then caused the rock surfaces to break down.

"It is direct evidence for the first time from a government study that industrial pollution is damaging the rock art of Murujuga," he said.

The damage could be mitigated by putting scrubbers on the industrial stacks to filter emissions and reduce pollution but the best solution was to switch the plants' power from gas to electricity, Prof Smith said.

"If you transformed all of those plants to electricity ... they could operate cleanly and we could have the perfect solution, which is profitable industry operating responsibly alongside the world's most important rock art site."

Prof Smith said the famous Lascaux caves in France held only a few hundred wall paintings and dated back 17,000 years.

But the rock art at Murujuga has a million images going back at least 50,000 years, including the world's first-known depiction of a human face and images of now-extinct animals.

Murujuga has been put forward as a UNESCO world heritage site, with strong indications it will be accepted as such.

But the application has been referred back to the federal and WA governments with recommendations to stop building on the site, to stop the pollution and to prepare a decommissioning report.