RESEARCHERS have sounded alarm bells over water quality in the Blue Mountains, claiming the world-heritage listed site is suffering some of the worst environmental pollution in the world.

They have warned of a dead zone downstream from the Centennial Coal mine, which since the 1980s has been allowed to discharge mine waste into the Wollangambe River, in accordance with its licence.

“This is very, very sick,” University of Western Sydney environmental science lecturer Ian Wright told

ABC news

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The pollution from the mine extends at least 22 kilometres downstream, and includes thermal pollution, increased salinity and increased concentrations of zinc and nickel,” he said.

He said the mine pollution levels could be some of the world’s worst, and claimed the result was downstream insect numbers had dropped by ‘about 90 per cent” in the river which runs deep into the Wollemi National Park.

Dr Wright and colleagues have been studying the effect of the Clarence Colliery on the Wollangambe River for several years, ABC reported.

Dr Wright said they discovered pollution — salinity levels ten times that of other waterways, and high levels of metals like nickel and zinc — not just at the mine discharge point, but up to 22 kilometres downstream.

Parts of the river Dr Wright described as an “ecological desert”.

“We had hours where we would only find one or two animals, and they are the species that are really tolerant,” he told ABC.

AN EPA spokesman said the agency had changed the mine’s operating licence to reduce the amount of metals and salt that could be in the discharge water.

“The science is very clear, there are impacts there, we need to make changes and that’s why we’re going to be tightening the licence,” Mr Whytcross said.

“We are tightening limits comparable with the World Heritage area that this creek is in so that the water quality can improve and the critters can come back and be healthy,” he said.

It is hoped this will enable the water to be suitable for drinking.”

Dr Wright's study was published in the Journal of Water, Air, Soil Pollution.

Centennial Coal was not immediately available for comment when contacted by news.com.au, but spokeswoman Katie Brassil previously told the ABC the EPA is finalising the five-year review of Centennial’s Environmental Protection Licence (EPL).

“This process included extensive aquatic ecology, ecotoxicology and macroinvertebrate investigations and monitoring in consultation with the EPA, Office of Environment and Heritage, and community stakeholders including Dr Ian Wright,” she said.

“As a result of this review Clarence will operate under a new EPL, which will include agreed reductions in metal concentration limits for all water discharged to the Wollangambe.

“Clarence will also be required to comply with a Pollution Reduction Programme (PRP), also to be issued by the EPA, which will result in Centennial formalising options to address all water quality issues and to meet specific water quality milestones.”