Last September JAMA published a paper by Otsuka et al which pointed out that just 30 minutes of secondhand smoke exposure clobbered the ability of coronary arteries (the arteries that supply blood to the heart) to dilate to the same extent that being an active smoker did.
Jim Repace has just published a letter in JAMA at
pointing out that the levels of secondhand smoke that caused this large effect were lower than is observed in many bars.