Answer:
Secondhand smoke can be harmful in many ways. For instance, it affects the heart and blood vessels, increasing the risk of heart attack and stroke in non-smokers. Some studies have linked SHS to mental and emotional changes, too.
Within 20-30 minutes of being exposed to the smoke it causes excess blood clotting, as well as increases the buildup of fat deposits in blood vessels, increasing the risk of heart attack and stroke.
To set boundaries, you could tell people around you to smoke from a distance/outside. In addition, you could persuade them to quit and find out about local charities to help people addicted to smoking.