Researchers collected fish from 23 sites around the UK and tested for a wide range of contaminants. Anglers were also interviewed. Potentially harmful chemicals found included polychlorinated biphenyls (PCBs), man-made organic chemicals whose manufacture in the UK was banned more than 30 years ago, and polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDF), both industrial by-products and environmental contaminants.