Michael Sheen made the shocking discovery that he has toxic forever chemicals in his own blood while filming a new documentary for the BBC.

The Welsh actor, 57, explores claims of chemical contamination across his homeland in a two-part series, Buried with Michael Sheen. The show begins with Sheen meeting farming consultant and whistleblower Douglas Gowan, who claims people in Wales have been poisoned by decades of exposure to toxic chemicals in the environment.

Gowan says thousands of tonnes of chemicals known as Polychlorinated Biphenyls (PCBs) have been dumped at sites across Wales and north west England.

PCBs were regarded as wonder chemicals in the 1960s but are now designated as a Group 1 carcinogen and banned globally.

In the documentary, Sheen discovers that residents living near the waste sites have abnormally high levels of PCB in their blood, while many have been diagnosed with rare cancers.

In a new interview with The Daily Telegraph, the star explains that he agreed to be tested as a control – but discovered he had the chemicals in his blood.

“I wasn’t quite expecting how shocked I’d be by that,” he said. “I thought ‘of course I’ll be tested because you won’t find anything’, and then when you get the results, you realise there is no safe level, we all have it in us.”

Sheen, a keen environmental activist, began investigating forever chemicals after coming across Gowan’s research on Brofiscin Quarry, in south Wales, while browsing online.

The Underworld actor has also recalled how “paranoid” he felt after visiting the quarry during filming.

“There was a moment when we'd been to Brofiscin, and I'd been in the field and I hadn't been wearing the wellies at that point,” he said. “I was wearing my own boots, and I remember going back in my car and stopping at the garage to get petrol and then taking my boots off and hosing them down in the garage because I got so paranoid that I might be taking this home.

“There’s moments like that where it is really daunting. It is scary.”

Wales’s environmental regulator, Natural Resources Wales, told the BBC it previously investigated PCB leaks at Brofiscin Quarry, but concluded they did not pose enough of a risk to warrant further action.

Sheen is hoping the documentary will lead to “the people who dump this stuff [being] made responsible”.

“I think it's important to say that the biggest injustice here is that the people who are responsible for this have got away with not having to take responsibility,” he said.

“The next thing, in my opinion, is that local councils – where this potentially contaminated land is – are terrified that if they're financially responsible for doing something about this, that it will bankrupt them. Because they don't have the budgets available.

“Somehow we have to make sure that we are able to move past that point.”

The actor has frequently used his platform to highlight environmental and social injustices, and last year paid off £1m worth of debt for neighbours in his local community of Port Talbot.

The move was part of a two-year project to highlight issues with the current credit system, as part of his documentary Michael Sheen’s Secret Million Pound Giveaway.

The film saw Sheen purchase the credit for £100,000 from the Financial Conduct Authority (FCA), and wipe off debt to the value of £1m, to help over 900 people in south Wales where he grew up.

Sheen has had a busy 2026 and recently took part in the second series of Celebrity Traitors, which is scheduled to air later this year. In September, he’ll also make his debut as the new host of BBC Two quiz show House of Games, having taken over from Richard Osman.

Buried with Michael Sheen comes to BBC Two, BBC One Wales and BBC iPlayer from Monday 17 August at 9pm