If I'm recalling it correctly, I think TFA is trifluoroacetate. When, under the Montreal protocol, we eliminated the CFCs and replaced them with HCFCs, trifluoroacetate started becoming detectable in rain because of what we replaced the CFCs with in refrigerants. So I believe it comes from refrigerants, and it is on the rise. Its effects are not too well understood, if I'm recalling correctly.
On April 3rd, 2014. See this statement in context.