6 months ago, I was 22 (which wasn't the end of the world... about half of what would be considered toxic by OSHA standards). I've kept on casting trying to be more careful. I gave 2 pints of blood, although the last time was a week ago, and they tell me it takes 2 months to rebuild and mature the cells. Verdict today was 16 μg/dL. I will say that this time when I went in to take blood, they asked if I'd had seafood or an antacid in the last 3 days. I said I had and nobody had ever mentioned it before. I waited 3 days and went in again. Wonder if that screwed up my old test. Anyway, if you're worried about your levels and are able to give blood, go get your oil changed. It apparently helps.