In the late 1920s, Thomas Midgley, Jr. improved the process of synthesis and led the effort to use chlorofluorocarbons, CFCs, as refrigerants: to replace ammonia (NH3), chloromethane (CH3Cl), and sulfur dioxide (SO2), all of which are toxic but were in common use. In searching for a new refrigerant, the requirements for the compound were that it had to have a low boiling point, low toxicity, and to be generally non-reactive. However, Thomas Midgley Jr. purportedly seriously considered the alternate possibility of pushing for the use of BFCs, bromofluorocarbons, instead of CFCs. BFC's are extremely unreactive, stable and inert, non-flammable and non-toxic- in all of these regards, more so than CFC's. And at room temperature, they're also usually colourless gases or liquids which evaporate easily. However, their boiling points are slightly higher than CFCs, so he went along with CFCs instead.
So then, what would have happened in an alternate timeline where he'd elected to go along with BFCs instead of CFCs, and it had been BFCs (or 'Halon') which had been adopted and seen widespread use instead of CFCs ('Freon')? Especially given that BFCs have markedly longer atmospheric lifetimes than CFCs, are even more potent as greenhouse gases, and are at least twice as potent when it comes to ozone depletion? How much more environmental damage would their adoption have caused in this TL, and what would the knock-on effects have been- for instance, how much bigger would the holes in the ozone layer have gotten, and could they have potentially grown beyond the planet's capacity to recover? And if so, how much more damage could have been inflicted upon ecologies (especially in polar and sub-polar regions), and the human population?