The Kelvin River in Glasgow has the highest recorded concentration of toxic TFA of any river in the UK. ‘The researchers who analysed the ice cores hypothesised that CFC replacements might explain this increase in TFA concentrations, but this theory had never actually been tested in a model before,’ says Hart. Since Hart’s study was published, the European Chemicals Agency has moved to reclassify TFA as toxic and as a persistent toxic substance. In the wake of the 2016 Kigali Amendment, which mandated a shift away from refrigerants with a high global warming potential (GWP), the industry has turned to a new generation of CFC replacements: HFOs. ‘We’re phasing out one group of problem-causing chemicals and replacing them with another, without considering the impacts of their replacements.’