Actor Michael Sheen has made a new BBC iPlayer documentary investigating claims that chemical giant Monsanto dumped huge quantities of toxic industrial waste, including PCBs, at sites across Wales decades ago, allegedly contributing to rare cancers among people who lived nearby. The investigation was prompted by whistleblower Douglas Gowan, a former farming consultant who spent years trying to raise the alarm about 14 contaminated sites, 12 of them in Wales, and spoke to Sheen shortly before his death.

Gowan described PCBs, once used in products ranging from lipsticks to electrical equipment, as among the worst contaminants known to man, warning they build up in the environment, wildlife and human bodies, and calling them the "godfather of forever chemicals". A notable case involves Michael Phillips, who as a child in the 1980s played near a chemical lagoon at Llwyneinion near Ruabon, Wrexham, where a fire in the 1980s took 60 firefighters over 18 hours to control and whose effects were felt up to 20 miles away; Phillips later developed a rare cancer, as did several friends who also visited the site, one of whom has since died. Eastman Chemical Company, which now holds responsibility for Monsanto's UK legacy production, did not respond to requests for comment from Sheen's team or the BBC.