DEAD Swan River dolphins have been found riddled with toxic pollutants that have been linked with cancer and are restricted in some countries and several Australian States.

Just days after Premier Colin Barnett declared the Swan River was in good health, documents show the waterway appears to be contaminated with potentially dangerous chemicals.

The documents also reveal Perth’s aquifers, which provide almost half the city’s drinking water, may be contaminated and that the Environment Minister knew about the situation in June but said nothing.

At issue are chemicals known as perfluorinated compounds, or PFCs, found in a number of Swan River dolphins at the highest levels recorded in Australia.

The long-lived compounds, commonly used in firefighting foams, have been banned or restricted elsewhere amid fears they could be carcinogenic.

They were discovered in the Swan River dolphins after tissue samples from the animals were sent to South Australia last year as part of an inquiry into the deaths of dolphins in the State.

Previously undisclosed correspondence shows the Swan River dolphins had the highest levels of PFCs in the country — up to 100 times higher than dolphins from Bunbury.

Potential sources of the pollutants included a drain near Perth Airport that flows into the Swan River, along with Pearce Airbase via Ellen Brook.

While the health and environmental implications of PFCs remain inconclusive, US regulators believe the “weight of evidence” supports the conclusion the chemicals are a hazard.

In South Australia, regulators have warned high doses of PFCs may suppress the immune systems of affected animals and they should be limited to “essential use” only.

Environment Minister Albert Jacob said he was informed of the findings in June but had been advised the chemicals had not caused the dolphins’ deaths.

He said the Health Department had also advised that there were no human health implications from the levels of PFCs detected.