TOXIC waste dumped across swathes of Clydeside poses “immediate and long-term risks to human health”, politicians have been told.

Officials have long known massive concentrations of cancer-causing Chromium-IV - the poison made famous by the Hollywood movie Erin Brockovich - were buried under Glasgow and South Lanarkshire.

Now, in an unusually blunt briefing to MPs, MSPs and councillors, executives at regeneration agency Clyde Gateway have confirmed the deposits are leaching in to west of Scotland’s river system “whenever it rains”.

They stressed “the nature of the contamination poses immediate or long-term risks to human health and the environment through land, surface water or groundwater pollution”.

The report, which was obtained by The Herald, was distributed after an entire stream, the Polmadie Burn, turned bright green last month in a telltale symptom of toxic pollution from waste containing chromium-VI, chromium ore processing residue or COPR. Its authors make clear this was a wake-up call.

They said: “A stark reminder of the all-too-real dangers to public health from the presence of COPR at Shawfield was provided in February 2019 with an incident at Polmadie Burn.”

This frank language contradicts reassurances given to residents of the new-build scheme next to the burn, Oatlands. A spokesman for the local community council earlier this month told this newspaper: “Glasgow City Council have advised that there is no risk to public health unless the contaminated water is directly ingested or comes into contact with skin.”

Clyde Gateway and local authorities are working to stop pollution entering the Polmadie Burn by re-routeing underground rivers.

However, they do not have the resources to deal with the poison at source, in nearby Shawfield.

This is the site of J&J White Chemicals, a giant factory which shut half a century ago after years of dumping COPR in pits and quarries around Glasgow and Lanarkshire.

But new research suggests the firm - whose owners are no longer around to pay for what would now be considered a major environmental crime - dumped extensively on their own doorstep.

The new report contains the first pictures of underground network of rivers in Shawfield. Taken this month, these show water running almost fluorescent jungle green through culverts.

Earlier this month Clyde Gateway said it lacked “tens of millions” to clean up the site. Now its private document predicts a bill of £54m, including the cost of compulsory purchase orders to remove some of the current landowners.

Clyde Gateway does not have this money.

The report said: “There can be no argument that without intervention by the public sector, of which Clyde Gateway is currently the main vehicle, market failure will remain.

“Sites will not be capable of development, but just as crucially, the contamination will continue to blight communities and pose a health issue for local residents.”

It added: “In short, when it rains in Shawfield, there are accelerated flows of hexavalent chromium into the tributaries and the Clyde – this can only be prevented by converting it to trivalent chromium which is not carried by any ground water and will this not flow.”