I didn't think it was going to harm me
Why didn't you think that it would harm you?
It didn't when I was in middle school so why would it when I'm in college
I don't know what it is, but remember that you're a human like everyone else and can be harmed by something that is dangerous. There is no good reason to assume that you can't get hurt and you should do your best to stay out of danger or stay away from things that might be able to hurt you.
It doesn't matter if I don't think it harms me.
By being so overconfident you are inviting trouble for yourself. You should be cautious of things that could harm you in any way. If you want to live a healthy life, don't take things so lightly.