Pot and Medical Device Manufacturing

California is set to vote on marijuana legalization later this year. I'm pretty much a live and let live guy, but how is this going to effect California's fairly large drug and medical device industry? I'm sure people will debate this, but lets cut right to how companies will see it:

In California you will have a much higher chance of someone stoned building your product and on average stoned people make worse decisions than non stoned people.

This probably doesn't matter if you're renting movies at BlockBuster, but small mistakes in medical devices can cost lives and / or millions of dollars. Right now most companies mitigate the risk of drug use by screening on hire and periodic screening. How would you mitigate in the future, or is my fear overblown? I don't think legalizing pot will help manufacturing in California, obviously that is not the only consideration, but an important one I think.