Studies have been done and experiments that prove some of the effects of second hand smoke. That is the definition of proof. If you want to deny that then you will lose your own credibility. Deny it only if you can disprove it yourself. But the studies have been done and it has been shown that there are negative effects of second hand smoke. From now on declare it proven and stop asking us to prove it anymore. Before you do, try to prove to us that second hand smoke is not harmful. I could go to more websites and find more proof if I wanted but I don't feel like wasting my time.