What's a bigger health risk, pollution or second hand smoke?

Either can be bad: For any exposure to a health hazard the amount and duration have to be considered along with the individual's health status. The term "second hand smoke" is thrown around a lot but it doesn't have any specific meaning. The important thing to remember is that you want to avoid toxins as best you can and keep your body healthy so that it can deal with what you are are exposed to.