A new study by medical researchers in Britain suggests that passive smoking may be more dangerous than was previously thought.
The researchers used a new method to measure passive exposure to smoking, including that in pubs and workplaces.
The study concluded that it could increase the risk of heart disease by over 50%.
Previous research, which had mainly concentrated on people living with smokers, had suggested an increased risk of between 20% and 30%.
The latest study, published in the British Medical Journal, followed 4,500 people over 20 years.
