I think the 'significant negative effects' can be psychological. To some folks, just the sight of someone 'smoking' causes manifest physical reaction.
Many years ago (long before there were any bans on smoking in public spaces), I was having breakfast with friends at a beach bistro on an outdoors patio.
The tables were packed tightly to accommodate the weekend crowd, and all the tables were occupied. We finished our meal, paid the tab, and waited for the waitress to return with the check. I popped a cigarette in my mouth and was about to light it, but considered the proximity of the other patrons in the vicinity and out of consideration, decided NOT to light it. But I left it in my mouth and was holding it..
A woman at an adjacent table started coughing uncontrollably and really made a scene. Her husband ( boyfriend?) said something like "would you please put out that cigarette?"
Everyone in the area stopped talking and realizing the my cigarette was not lit, started laughing.
So that shows that some people are affected by just the sight of someone smoking.