Qalyan, Narghile, Shisha and pregnant women's exposure to passive smoking in Iran.

I read Mirahmadizadeh and Nakhaee’s paper [1] on the prevalence of smoking qalyân/narghile (the local water pipe) among pregnant women in Southern Iran with great interest. While I share their concern over the prevalence, they should have cited and discussed a relevant study by Mansour Sulaiman from Saudi Arabia [2] , noting that although prenatal exposure to shisha smoke in animals lowered the response to novel environments, passive exposure to the smoke of the local pipe (shisha) during pregnancy had no effects on the gestational period, number of pups, birth weight, and body weight growth [2] . In Mirahmadizadeh and Nakhaee’s study [1] , exposure to passive non-cigarette smoking reached 11.5%. Fortunately, the nature of the smoke was very different in both cases. A few years ago, a US team noted that, unlike cigarettes, there was almost no sidestream smoke with hookah smoking [3] . More recently, Egyptian and Saudi researchers stated in a study on the radiological hazards of this type of smoking: ‘the only second-hand smoke that should be taken into account is the one rejected by the smoker, i.e. the one filtered by the hookah at the level of the bowl, inside the water, along the hose and then by the smoker’s lungs themselves. In this respect, experts have found that the bulk of studies covering more than one century indicate that, ‘‘on average, 60–80% of the mainstream smoke particulate matter is retained in the lungs after inhalation’’ (Baker and Dixon, 2006)’ [4] . I hope these observations will be useful to health care practitioners in Iran.