Levels and health risk assessments of particulate matters (PM 2.5 and PM 10 ) in indoor/outdoor air of waterpipe cafés in Tehran, Iran.

To determine the concentration of particulate matters (PM2.5 and PM10 ), 36 samples were collected from indoor/outdoor air of hookah cafés (HS), cigarette cafés (CS), both hookah and cigarette (HCS), and no-smoking building (NS) in Tehran City from December 2017 to March 2018. The mean ± SD of PM10 concentration in the indoor air of the cafés in terms of HS, CS, HCS, and NS sites has been 702.35, 220.20, 1156.60, and 60.12 μg/m3 , while for PM2.5 , the values have been 271.92, 111.80, 619.10, and 22.25 μg/m3 , respectively. It was also found that the PM concentration inside the cafés was higher during weekend session (with a higher number of active smokers), than during the weekday sessions. Moreover, the PM levels in the indoor air of the cafés were considerably higher than those of the outdoors (p < 0.05). Based on path analysis, the number of "active smokers" had the highest influence on production of PM inside the cafés, followed by the tobacco type. Finally, the mean excess lifetime cancer risk (ELCR) for PM2.5 in the indoor air of cafés was observed in the range of 0.64 × 10-5 -14.98 × 10-5 . Also, the mean of hazard quotient (HQ) for PM2.5 and PM10 was calculated in range of 0.82-18.4 and 0.16-3.28, respectively, which corresponds to an unacceptably high risk for human health. The PM levels in the indoor air of smoking cafés in Tehran are significantly high, such that it can cause serious risks for the health of both the customers and personnel. Thus, it is necessary that suitable controlling strategies be adopted for this public health threat.