If you've been in an environment where people are smoking it, you will absorb it into your system through your hair. Proven fact, accepted in Court.
absorb it THROUGH your hair!? are you sure?
i know they can use hair for drug tests, and strands can still show traces of cannabis quite a few months after smoking but i thought that was just due to hair samples being a good container of DNA, not that your hair just soaks up the green.
shave your head if the worst comes to the worst