Helena, Montana, does not often make global headlines, but in 2003 the small capital city became known for briefly achieving one of the most astounding public health triumphs ever recorded. In June of the previous year, Helena had implemented a comprehensive smoking ban in its workplaces, bars, restaurants, and casinos. In the first six months of the ban, the rate of heart attacks in the city plummeted by nearly 60 percent. Just as remarkably, when a judge struck down the smoking ban in November of that year, the rate of heart attacks shot right back up to its previous level.
Article source: http://www.slate.com/articles/health_and_science/medical_examiner/2017/02/secondhand_smoke_isn_t_as_bad_as_we_thought.html