I imagine the smoking room was partly a safety feature. It was pressurised and located somewhere where hydrogen wouldn't leak. So you now have all of the smokers do it somewhere safe instead of trying to light up in secret somewhere unsafe.
Our brains are becoming more plastic by volume than neurons. I'm not sure we have a leg to stand on when lecturing the past.
You get bad side effects from smoking the next day (stale taste, off breath, tingling gums or coughing). And frankly, immediately: bad smell.
We're still not even sure what nanoplastics do to human biochemistry.