Most studies are based on imprecise recall and anecdotal evidence concerning the exact amount of exposure to environmental tobacco smoke.

BBC: NEWS | Health | Cancer alert for smoking parents

"The US Environmental Protection Agency has classified environmental tobacco smoke as a known human (class A) carcinogen, " he added.

BBC: NEWS | UK | Northern Ireland | Legal threat over passive smoking

Secondhand smoke, which is also called environmental tobacco smoke, is smoke inhaled involuntarily.

CNN: Is secondhand smoke really that risky?

The environmental tobacco smoke particulate matter reached levels 15 times those measured outdoors.

BBC: Image of a smoke filled room

"The best way of addressing public concerns about environmental tobacco smoke is through the provision of designated non-smoking and smoking areas with good ventilation, " he said.

BBC: Image of a smoke filled room

Smoking bans could have an effect on reducing heart attacks or heart disease generally by one of two major routes: either by inducing current smokers to quit or by reducing the exposure of non-smokers to environmental tobacco smoke (ETS).

FORBES: Do Smoking Bans Really Save Lives? If So, Whose?