Subnational exposure to secondhand smoke in Iran from 1990 to 2013: a systematic review

Every year, almost eight million people die from tobacco-related diseases, among which around 1.2 million die from secondhand smoke (SHS) exposure. Generally, it is estimated that SHS constituents generated in the interval between puffs are approximately 3 times more toxic than those produced at the moment of puffing. There is no risk-free level of SHS exposure, and even brief exposure can be harmful to health. The aim of this study was to assess SHS exposure and its trend in the different provinces of Iran from 1990 to 2013. To collect available data on SHS exposure, a systematic review was performed. We searched international and national databases using a combination of Medical Subject Headings (MeSH) and relevant text words in the titles, abstracts, and/or keywords. Also, the data in national surveys were gathered. The frequency of exposure in different provinces as well as age, sex, and rural/urban areas were extracted. Afterwards, modeling was done to estimate SHS exposure from the smoking data. According to our findings, SHS exposure was more prevalent among young people. Moreover, this exposure was greater in rural areas as compared to urban areas. A national study on 13-15-year-old individuals showed the highest exposure occurred outdoors. In addition, a declining trend was observed on SHS exposure over time. It seems that attention to the importance of SHS exposure in researches in Iran dates back to 2001, and gradually, especially in recent years, further studies have been conducted on SHS exposure.