flufdriver,
I think you've got it precisely backwards. 187nj sounds to me like someone very young, very 'straight', who hasn't tried drugs of any type and doesn't want to. Hence his/her unnecessary panic. But it's not even relevant. He/she asked about passive cannabis smoking and the medical, not your/our views on the drug culture.
Shunter is spot on. They don't test for drug use. Even if they did, and even if you'd actually smoked cannabis, it would be out of your system by then.
Like Shunter, I gave up cannabis use, and the social scene that went with it, when I grew up and put away childish things. That was more years ago than I care to remember or to admit to.
But I do actually remember enough of the facts to know what I'm talking about. So 187nj, please don't worry.