Toxic waste sites exposed in Michael Sheen documentary 'tip of the iceberg'

A former Monsanto worker who spent three years helping seal toxic waste underground said staff had "cheap" protective equipment and were not told what they were burying.

Stephen Constance worked at the chemical giant's Newport factory in the 1990s and came forward after the BBC documentary Buried with Michael Sheen highlighted Wales' toxic waste legacy.

But the 14 sites identified in the programme are just the tip of the iceberg and there are about 20,000 high-concern sites in the UK, said Dr David Megson, the scientist involved in the documentary.

Eastman Chemical Company, which is responsible for Monsanto's legacy production in the UK, did not respond when asked to comment.

Constance was one of dozens of people who contacted BBC Wales after coverage of Sheen's investigation into Monsanto and the dumping of polychlorinated biphenyls (PCBs).

Researcher and whistleblower Douglas Gowan spent 50 years trying to persuade authorities to investigate what he believed was widespread dumping of industrial chemicals.

These included PCBs, which he called "some of the worst contaminants known to man", and were widely used in the 20th Century, including for lipstick and white goods.

They were banned in the UK in the 1970s and have since been banned by 151 countries.

Looking back, he said it was "quite evident that nobody was fully appraised of the potential hazard that they were exposed to".

The material was already buried when Constance arrived and it was his job to dig a 6m-deep trench around the outside of the mound before it was sealed using plastic membrane sheets and liquid clay.

While he believes this prevented airborne contamination, he is unsure if it would have stopped contamination into the Earth due to the high water table linked to the tides.

When asked if he felt safe, he said: "In terms of what we knew was there and what we were potentially exposed to, no."

Constance is in remission from cancer after having follicular lymphoma , external .

"I'm not suggesting in any way at all that it's linked, but the thought did cross my mind," he said.