Cancer is caused when people are exposed to cigarette smoke regularly. The sad reality is the fact that people who are exposed to cigarette smoke are vulnerable to cancer because they are getting exposed to smoke in a direct manner which is release when you lit a cigarette. I have heard that this is much more dangerous. This is also called secondhand smoking.
The person who is inhaling the smokes of another person who smokes the cigarette proper is suffering more damage than the smoker. This have been proven scientifically and it's why I can never stay a person who smokes.
Yeah, it's called passive smoking. It's exactly what @Ja sa bong mentioned.
You're putting yourself in more harm when you're smoking passively. The person that you're close to that's making you to smoke passively doesn't experience the level of harm that you're going through.