My doctors tell me the 3 most likely groups to have MM are those in agriculture, the chemical industry and the nuclear industry.
Well if you think how much stuff we spray on food, how much radiation was thrown into the atmosphere in the 50's and 60's (not including Chernobyl)and just how many new and wonderful chemicals are used in everyday products then surely we should all be having MM.
It's not worth worrying about, the past has happened, get on with now and tomorrow. Don't waste energy on if's and but's, they've gone. Follow Eve's little strap line about why worry about tomorrow today.