Well, this should hopefully come as a shock to no one, but smoking is harmful to your health. Now that we have that out of the way, it should also be quite apparent that being around smoke and smokers is not quite healthy either.
Consumer Reports posted a study conducted by British researchers that sought to determine the health effects of the presence of cigarette smoke in a car. The study was apparently the largest of its kind, and comprised over 100 car trips, by 17 drivers. Of that number, 14 drivers were smokers, introducing the tobacco smoke in 66 of the trips; 34 trips were without smoke.
The amount of interior air pollution was recorded in micrograms per cubic meter, of which the World Health Organization says 25 is a safe level. While smoke-free cars averaged roughly 7.4 micrograms per cubic meter, the smoking cars averaged 85. The study found peak pollution averaged at about 385 micrograms per cubic meter, and one scientist even found readings as high as 880. Scientists found that open windows and air conditioning did not protect passengers from encountering pollution greater than WHO's safety guidelines.
According to one of the study's authors, children are more likely to be affected by this air pollution, as they have faster breathing rates, lack a fully developed immune system, and do not have the freedom of movement to remove themselves from the source.
Consumer Reports points out that Arkansas, Hawaii, Louisiana, Maine and Maryland, as well as some countries have either banned, or plan to ban smoking in private vehicles.