Is this an irrational fear?

I'm a high school student and I think I have an irrational fear. Could you please tell me if this is irrational? At my school, I know there are individuals that take drugs. My fear is that being around the places they've been around will cause me to ACCIDENTALLY take in their drugs (like bacterial cross-contamination, except with drugs). So, is this fear irrational? It's been really irking me. Please give a thoughful answer. THANKS.