My method of cleaning brushes, for 35 years, has been to dip the brush in white spirit, and stroke the brush in a wooden surface to clean it, dipping several times. Then drying on a tissue, and painting again. Every few minutes, as enamels are cruel to brushes! With little puddles, the wood and the tissue evaporating white spirit under my nose as the lamp warms it.
Basically, I must already have been mad to have used this technique. But familiarity really does breed contempt, and it was what I had done since the 80s, as a child. And it was just 'normal' practice.
Not sure I want tests. I really doubt there's anything they can do to reverse the damage (and I am forcing myself NOT to google this stuff otherwise I will start to imagine all sorts of ailments). So I'll only go for tests if symptoms start to manifest, i.e. my brain begins to melt.
I always had a bad long term memory, so that I have to re-re-re learn chunks of information for what I do. Bit I can't tell if it has got worse!