Hollywood actor Michael Sheen has spent years investigating claims that chemical giant Monsanto dumped toxic industrial waste, including polychlorinated biphenyls (PCBs), at multiple sites across Wales during the twentieth century. The findings are set out in a new documentary premiering on 17 August 2026, in which Sheen speaks to residents who developed rare cancers after childhood exposure and to the whistleblower who spent decades trying to warn authorities before his death.
Michael Phillips grew up in the 1980s playing near a chemical lagoon at Llwyneinion, close to Ruabon in Wrexham, where he and his friends fired air guns at corroded barrels that released clouds of coloured powder. He says he had no idea at the time that the barrels contained hazardous chemicals.
Years later, Phillips and several childhood friends were diagnosed with rare forms of cancer, which they now believe may be connected to that exposure. Researcher and whistleblower Douglas Gowan had tried for years to raise alarm about 14 suspect sites, 12 of them in Wales, but he died before regulators acted on his warnings.
What he told me made my blood run cold.
Sheen said that quote came from a conversation with Gowan just months before his death, and it became the starting point for the actor's continued investigation, now released as a documentary.
What did whistleblower Douglas Gowan allege?
Gowan, a former farming consultant, claimed that Monsanto had disposed of vast quantities of industrial chemicals at sites across Wales. Among these were PCBs, which he described in stark terms.
Some of the worst contaminants known to man.
He noted that PCBs were once used in a wide range of everyday products, including lipsticks and household appliances.
This stuff builds up in the environment, builds up in animals and fish, and it builds up in us.
Sheen has since referred to PCBs as "the godfather of forever chemicals", warning that although the danger is invisible, it can quietly damage human health over time.
There is something out there in the forest, there is something in our bodies that can turn against us and tear us apart, but it's not like it is in the horror films. It's invisible. It's a silent killer.
PCBs were prized industrially for their heat resistance, chemical stability and insulating properties, making them common in plastics, paints and electrical equipment throughout the twentieth century. Concerns over their toxicity to humans and wildlife led to bans in many countries from the 1970s onward, but because the chemicals degrade extremely slowly, they persist in landfill sites and can leach into waterways and eventually the sea.
There was no regulation at the time, they could dump it wherever they wanted to.
Who has been affected in Wrexham?
In the 1980s, a fire broke out at the Llwyneinion chemical lagoon near Ruabon and took more than 60 firefighters over 18 hours to extinguish. The effects were reportedly detected as far as 20 miles (32km) away.
Phillips, who watched the blaze as a child, believes his health problems trace back to that exposure, which he says first became apparent in 2001.
I started getting lumps on my shoulder, I caught cancer. I lost a large part of my shoulder that's literally as wide as my hand.
While he was operating, my surgeon said 'this is strange, I've never seen this type of cancer before', and he'd had a distinguished career of 40 years.
Phillips said he was not alone in suffering serious illness after time spent at the site.
I lost a very close friend who used to be [at the lagoon] all the time, more than me. He died of breast cancer.
I have another friend who passed away with brain cancer. I've got another friend who is trying to get over brain cancer, I have another friend who's had all of his lymph glands taken out because they were cancerous.
He said another friend developed the exact same cancer he had, prompting a stark comparison from his surgeon.
For me to catch what I had was like winning the lottery.
For your friend who lives down the road to get exactly the same, he said it's like winning the lottery every day for six months. It's not a coincidence.
Blood tests on Phillips showed PCB levels above the average. Sheen said the fact that any level of PCBs in the blood is now considered normal is itself troubling, given that the chemicals did not exist 90 years ago.
Sheen also had his own blood tested and it revealed 81 different types of PCBs, despite him never having lived near any of the dump sites under investigation.
There is no safe level of PCBs, it's a risk all of us have to try and manage. The lower your level of PCBs, the lower your risk of getting cancer.
How have local authorities responded?
Paul Pemberton, who has served as a Wrexham councillor for more than 20 years, said the Llwyneinion site had been mistreated for decades.
Abused for many many years.
Scientific testing at the site detected cyanide, arsenic and PCBs, and experts concluded a clean-up was necessary, according to Pemberton. He said the council was quoted a remediation cost of around £45m, a sum that would bankrupt the local authority.
However, Wrexham council has said that subsequent investigations and risk assessments found that, while contaminants were present, the site did not meet the legal threshold that would require remediation. In 2017 Gowan argued that the companies responsible "should be made to remediate" the land regardless.
Environmental regulator Natural Resources Wales carried out its own testing of the Llwyneinion acid tar lagoon and concluded that the site did not meet the legal definition of contaminated land. Wrexham council said this meant there was no statutory requirement for remediation, though it continues regular inspections and water monitoring. The council added that it has only received limited information from more recent testing, but remains open to reviewing any new, robust and verifiable evidence.
What happened in Anniston, Alabama?
Wales was reportedly not Monsanto's first site for PCB disposal. The company initially discharged PCBs into waterways around Anniston, Alabama.
In 1993, the entire town of Anniston sued Monsanto over chemical contamination, in what became one of the largest single-town lawsuits in United States history. Donald Stewart, one of the attorneys who worked on the case, said the litigation was eventually settled for $300m.
Internal Monsanto documents reportedly showed the company knew about the toxicity of PCBs as far back as 1949, raising the question of how it continued to expose communities to the chemicals for decades afterward. Stewart offered one explanation.
If you look at this area, it's working people. They were people who wouldn't be able to fight back.
What do internal Monsanto documents show?
Journalists Dan Ashby and Lucy Taylor, who assisted Sheen with the investigation, uncovered a 1972 internal memo in which Monsanto reportedly acknowledged that PCBs posed a worldwide problem, an environmental danger and a risk to human health, and indicated it was scaling back production at Anniston as a result.
Despite that, the same period saw proposals to expand capacity at Monsanto's Newport plant to manufacture five million additional kilograms of PCBs.
They're doing it in Newport because the legal risk in America is so much.
Ashby said the shift was compounded by a lack of UK regulation at the time.
Then the government in the UK told industry we're not going to put any restrictions on importing PCBs. So they begin importing from around the world, hundreds of tonnes of PCBs.
Gowan suggested the choice of locations may not have been accidental.
If one wanted to be cynical about it, you could say that almost they were choosing places where chronic health issues might be hidden behind pre-existing health issues.
People grew up with the knowledge that... they were in an area that had coal mining, heavy industry, the environment was contaminated, and there were health problems.
Where are the sites of concern in Wales?
Twelve locations in Wales were identified by Gowan as sites requiring further scrutiny, out of 14 in total across the wider investigation. Environmental chemist Dr Dave Megson sampled all 14 sites as part of the research underpinning the documentary.
Sheen and his production team presented their findings to the Welsh Parliament, calling for further testing to be carried out at the identified sites.
These people deserve more.
They deserve their concerns to be met with proper research and appropriate action. Douglas spent most of his life fighting to get the truth out there.
The fact we all have traces of this chemical in our blood shows that we all have skin in the game. We've got to get together, we've got to fight this.
The broader question of chemical contamination affecting Welsh waterways has surfaced elsewhere. Separate research previously highlighted how chemicals from pet flea treatments have been found at harmful levels in Welsh rivers, entering the water system through wastewater and sewer misconnections and prompting revised veterinary guidance. A similar pattern of industrial legacy contamination has also been documented in England, where a golf course in Cheshire was found to sit atop a toxic chemical waste landfill dating back more than a century.
How did Gowan's decades-long campaign begin?
According to a report by WalesOnline, Gowan's investigation began after he was called out to examine a deformed calf near Llantrisant in Rhondda Cynon Taf in 1967, which led him to the nearby landfill at Brofiscin Quarry. Sampling there detected PCBs escaping the site in water, and Gowan feared the chemicals were entering the food chain via fields, cattle, meat and milk, the same report said.
Sheen first met Gowan nearly a decade before his death, and the documentary draws on confidential documents supplied to a national broadcaster, according to a national broadcaster's report. That same report describes the television investigation as a continuation of an earlier podcast series, titled Buried: The Last Witness, which it says inspired the new documentary. Nation.Cymru has additionally reported that the allegations extend beyond Wales, covering hazardous industrial chemicals dumped across both Wales and north-west England, according to Nation.Cymru.
What has the Welsh government said?
Kirsty Luff of Friends of the Earth Cymru has called for a full public inquiry into the scale and impact of toxic sites across Wales. She warned that climate change could worsen the risk, as more frequent and intense flooding could bring buried contaminants back to the surface, spreading them across fields and into watercourses.
A Welsh government spokesperson said addressing contaminated land remains a key priority.
Our industrial heritage has left us with a difficult legacy that can affect both people and places - we want to ensure this does not pose a risk to our communities or our natural environment.
A survey of local authorities carried out by Natural Resources Wales in 2015 identified more than 9,000 potential sites requiring further investigation.
While not all of these sites will pose a risk to human health or the environment, this figure demonstrates the scale of the issue facing regulators in Wales.
We now intend to develop a Wales-wide strategy to progressively restore post-industrial land, so that communities are no longer exposed to potential risks.
What happens next?
The documentary, referred to in the original broadcaster announcement as Buried with Michael Sheen, is scheduled to air on BBC Two, BBC One Wales and BBC from 17 August 2026 at 21:00 BST. However, according to a national broadcaster's report, the series is titled simply Buried and runs as a two-part investigation across the same channels, while Nation.Cymru similarly confirms the 17 August premiere on BBC Two alongside broadcast on BBC One Wales and BBC , with further scheduling details expected. Nation.Cymru also reports that the series is fronted alongside investigative journalists Dan Ashby and Lucy Taylor.
