The State Government's failure to issue health warnings about the contamination of popular western Sydney swimming spots presents an "unacceptable" risk of disease, a new study says.

Key points: From 90 water samples at a popular swimming spot, six per cent had "hazardous levels" of contamination

From 90 water samples at a popular swimming spot, six per cent had "hazardous levels" of contamination NSW Labor said the results demanded "serious attention" from the Berejiklian Government

NSW Labor said the results demanded "serious attention" from the Berejiklian Government The Environment Minister's department said the Beachwatch program did not have capacity to monitor freshwater or river systems

Research from Western Sydney University claims the Government has failed in its duty of care because its agencies "collect water quality data, but remain silent when bacterial water quality results indicate a potential risk to human health and safety".

Water expert Dr Ian Wright, who led the study, said it was playing with people's lives.

"It's essentially Russian roulette, and we're not talking about bullets, we're talking about bacteria or viruses," he said.

"There is a real risk of contamination, so people face a real risk of disease."

The study examined data provided by Water NSW, collected over a five-year period, and found parts of the Hawkesbury-Nepean River were "susceptible to periods of elevated faecal contamination, particularly after rainfall".

It said the source of the contamination needed to be investigated and managed.

"The community also need to be alerted when water quality is hazardous, and when human contact with water should be avoided," the study said.

"It is unacceptable that microbial data is regularly collected, and at times hazardous levels of faecal bacteria are detected, [and] the results are not shared with potentially vulnerable river users."

Dr Ian Wright said the State Government was failing in its duty of care. ( ABC News: Jonathan Hair )

The sites examined included popular summer swimming spots for residents in Sydney's west, such as where the Nepean River meets the Hawkesbury at Yarramundi Reserve.

Here, 90 water samples were provided to the researchers, with 6 per cent found to be contaminated at a hazardous level.

"We think it is a failure of duty of care to have results like this, and to not share it with the community," Dr Wright said.

He said the NSW Government needed to commit to making water-monitoring data publicly available, and to issue health warnings when rivers became contaminated — as it did for Sydney beaches.

Opposition spokesman for Western Sydney, Greg Warren, said "serious issues that exist within our river system" needed to be made more transparent.

"When you've got levels of bacteria and hazard in our river system where our children are swimming … that demands serious attention," he said.

Where the Nepean River meets the Hawkesbury River at Yarramundi Reserve. ( ABC News: Jonathan Hair )

The ABC contacted Environment Minister Matt Kean for comment on this story, but was told he was unavailable for interview.

His department said the Beachwatch program does not have the capacity to monitor freshwater areas or river systems.

But it said some local councils monitor water quality, and they could provide that data to Beachwatch, which is available online.

At time of publishing this does not happen any further west than Georges River at Oatley in southern Sydney.