## 2 Materials and Methods
### Health Risk Assessment (Methodological Approach)  
The aim of chronic health risk assessment is to evaluate chronic effects of known hazardous compounds. In this work, two approaches were applied with the scope of estimating the impact of IAQ on the staff's health: (a) the non-carcinogenic health risk assessment model, and (b) the cancer-risk assessment model.  
The non-carcinogenic health risk was assessed utilizing the hazard quotient (\(HQ\)) for formaldehyde and benzene according to the Office of Environmental Health Hazard Assessment (OEHHA) [41] and the following equation was applied:  
\[HQ=\frac{CA}{REL} \tag{1}\]  
where \(CA\) is the contaminant's concentration and \(REL\) is the inhalation chronic reference limit (\(REL_{HCHO}\) = 9 \(\mathrm{\mu g/m^{3}}\) according to the International Agency for Research on Cancer and \(REL_{benzene}\) = 3 \(\mathrm{\mu g/m^{3}}\)[42]. Acceptable values for \(HQ\) are lower than unity, while the greater the \(HQ\) value the higher the probability of developing non-cancer effects on humans.  
For the cancer risk assessment due to inhalation exposure, the lifetime cancer risk (\(LCR\)) value was calculated taking into consideration the cancer potency factor (\(CPF\)) and the chronic daily air intake (\(CDI\)) by the formula:  
\[\mathrm{and}\ LCR=CDI*CPF \tag{2}\]The general approach of EPA [43] concerning the computation of chronic daily air Intake (_CDI_) in mg\(\cdot\)kg\({}^{-1}\cdot\)day\({}^{-1}\) was used for the inhalation exposure estimation, by applying the following equation:  
\[CDI=\frac{CA\cdot\text{IR}\text{-}\text{ET}\cdot\text{EF}\cdot\text{ED}}{BW\cdot \text{AT}} \tag{3}\]  
where \(CA\) is the chemical's concentration in the air (mg/m\({}^{3}\)), IR is the inhalation rate (m\({}^{3}\)/h), BW is the average participants' body weight, calculated per building (kg), ET is the exposure time (h/day), EF is the exposure frequency (days/year), ED is the exposure duration (years) and AT is the averaging time (period over which exposure is averaged) in days. ET factor was set to 8 h/day, the EF was set to 236 days considering only working days within the week and 25 days for vacation and ED was set to 30 years, average working years in Greece. AT is assumed to be 70 years for a lifetime risk assessment. EPA recommended values for inhalation rates concerning adults aged 30 to 60 years for light intensity activity were assumed. Cancer risk attributed to a specific pollutant is computed by multiplying the CDI with the pollutant's relevant potency factor. In this study, cancer risk was estimated for benzene and formaldehyde, two compounds classified as human carcinogens according to [1]. The potency factor was set to 0.029 mg\(\cdot\)kg\({}^{-1}\cdot\)day\({}^{-1}\) and 0.045 mg\(\cdot\)kg\({}^{-1}\cdot\)day\({}^{-1}\) for benzene [44,45] and formaldehyde [43] respectively. The cancer risk (LCR) value below 10\({}^{-6}\)-10\({}^{-4}\) is considered acceptable [46, 47, 48, 49], whereas 10\({}^{-6}\) is considered the most tolerable risk. As a final step, the cancer risk of each pollutant was converted to \"chances per million\" (Total Cancer Risk) (1 \(\times\) 10\({}^{6}\)) = Total Cancer Risk in chances per million (4)