One of the reasons for the "drop-in" solution by companies after substance regulation (both as individual or as a group) is that structurally similar substances often have similar functions in the product being applied, and can be manufactured generally without requiring substantial changes in processes, infrastructure, or product testing . Unfortunately, similar toxicological effects are likely to occur as well , and at other times "burden shifting" towards different hazards. A key example is the series of restrictions related to the Montreal Protocol that began with a global phase-out of CFCs . Later, hydrobromofluorocarbons (HBFCs) were introduced as replacements but were only briefly commercialized . They were then replaced with hydrochlorofluorocarbons (HCFCs), which exhibited substantially less ozone-depleting potential, and exhibited the same commercial properties as CFCs . HCFCs were eventually also included under the Montreal Protocol and were again replaced by chemicals with similar chemistry, hydrofluorocarbons (HFCs) . Due to the removal of chlorine atoms from the molecules, HFCs no longer pose a threat to the stratospheric ozone layer , but they are still highly persistent and have high global warming potential. Therefore, in a subsequent amendment to the Montreal Protocol, the Kigali Amendment, HFCs themselves were listed . As a consequence of the Kigali amendment, the industry that manufactures fluorinated gases then sought to substitute HFCs with hydrofluoroolefins (HFOs), which have a short atmospheric lifetime of 6 days . However, these HFOs (almost) exclusively degrade to form trifluoroacetic acid (TFA), a vPvM substance that is ubiquitous in the environment, especially in drinking water systems, but the current understanding of its risk to human health and the environment is limited.