2.5. Statistical analysis
Other variables including; the floor level in which the cafés were located (i.e., basement/ground floor), types of ventilation systems (natural and artificial), types of the tobacco smoked (i.e., regular or Ximelagatran flavored), and employees\' general information were collected using a self-designed questionnaire. Levels of BTEX in indoor air were compared with occupational exposure limit levels. Data obtained were analyzed by t-test and nonparametric tests using SPSS version 16 and the confidence level was set at 95%. Path analysis was performed using Amos 21 in order to identify the factors that significantly affect the BTEX concentrations. Finally, a risk assessment was evaluated from the measured BTEX concentrations by using Eqs. (1), (2), (3), (4) and (5) (Majumdar et al., 2011), and tabulated in Table 2.
Details of risk assessment parameters (EPA, 2005).ValueUnitConcentration of the tracheids pollutant (C)–mg/m3Inhalation rate, adult (IRa)0.83m3/hExposure duration, adult (EDa)8h/dBody weight, adult (BWa)70kgDays per week exposure (D)6dWeeks of exposure (WK)48WeekYears of exposure (YE)30YYears in lifetime (YL)70YSlope factor or carcinogenic potency slope (SF)Benzene = 0.029 (Guo et al., 2004)(mg/kg·d)Reference dose (RfD)Benzene = 0.00855Toluene = 1.4Ethylbenzene = 0.286Xylene = 0.029(mg/kg·d)RfD = RfC (inhalation reference concentration mg/m3) × 20 (assumed adult inhalation rate m3/d) × 1/BWa (kg); based on RfCs for USEPA, IRIS (benzene = 0.03 mg/m3, toluene = 5 mg/m3, ethylbenzene = 1 mg/m3, xylenes = 0.1 mg/m3) (USEPA, 2007).Full-size tableTable optionsView in workspaceDownload as CSV