Regular exposure to second hand smoke nearly doubles the risk of coronary artery disease, according to a major study which is bound to have profound public health implications.

The study, led by Ichiro Kawachi of the Harvard School of Public Health, followed 32046 healthy, non-smoking women enrolled in the nurses health study for a period of 10 years (Circulation 1997;95:2374-9). The nurses health study is a longitudinal health data survey involving over 121 000 nurses that started in 1976.

When the passive smoking part of the study started in 1982, the women, aged 36-61, filled out detailed questionnaires in which they indicated their exposure to second hand smoke at home and in the workplace, including the number of years in which they …