Seems to me a recent study said that second hand smoke was not harmful despite years of our government saying it was. Frankly, if second hand or third hand smoke was so bad, I should be dead. During my college years I worked part time in a pool hall to get spending money. There were days the smoke haze was so dense it hung around the top of the tables. The situation finally got so bad even the smokers complained and the owner was forced to put in an exhaust fan. I still remember the smell on my clothes and my tongue feeling like I licked an ash tray when I went home.
The outcome of “studies” depends on who is paying for it.