## 3 Results and Discussion
### Results
#### 3.1.2 PCDD/Fs and dIPCBs  
The PCDD/F and dIPCB results obtained in this study are summarized in Tables 3 and 4, respectively. Toxic equivalency factors that were reconsidered by World Health Organization in 2005 were applied to calculate PCDD/F and dIPCB toxic equivalent (TEQ) concentrations [22]. Values below LOQ were assumed to be equal to LOQ (upper-bound concentrations) to evaluate the worst case scenario of exposure. PCDD/F concentrations in PM\({}_{10}\) collected from the industrial area of Eleusis were 145-3472 fg m\({}^{-3}\) (mean 696 fg m\({}^{-3}\)) and the PCDD/F TESq ranged from 287 to 2560 fg WHOTEQ\({}_{2005}\) m\({}^{-3}\) (mean 656 fg WHOTEQ\({}_{2005}\) m\({}^{-3}\)). Lower atmospheric (both particulate and gas phase) concentrations have been reported in a few studies around industrial sites like Shanghai, China where TEQs were calculated between 9.28-423 fg WHO-TEQ\({}_{2005}\) m\({}^{-3}\) (mean 88.9 fg WHOTEQ\({}_{2005}\) m\({}^{-3}\)) [55]. Additionally, in an urban site of Brno, Czech Republic, particulate-bound concentrations of PCDD/Fs ranged from 4.63 to 661 fg m\({}^{-3}\)[56] while in gas phase of background areas in Spain (2.18-19.1, mean 656 fg WHOTEQ\({}_{2005}\) m\({}^{-3}\)) [57]. Similar levels of PCDDFs were measured in the atmosphere (particulate and gas phase) of Umm-Al-Aish oil field, with values of 31.2-516 fg WHOTEQ\({}_{2005}\) m\({}^{-3}\)[20], and in PM10 from Rome with 5.43-734 fg WHOTEQ\({}_{38}\) m\({}^{-3}\)[54]. Higher concentrations were also presented in many industrial sites worldwide (Table 5), and our results were classified among the lowest in global literature. The comparison emphasizes in studies performed in industrial sites even the samples derived from particulate, gas, or both atmospheric phases. To our knowledge, in Greece, only two studies referred to ambient concentrations of PCDD/Fs, with our results being in the same levels with those found \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **PCB-28** & **PCB-52** & **PCB-101** & **PCB-138** & **PCB-153** & **PCB-180** & **\(\mathcal{\Sigma}\)PCBs** \\ \hline \multicolumn{8}{c}{Overall Sampling Campaign (N = 30)} \\ \hline Average & 7.96 & 1.82 & 2.86 & 2.30 & 2.01 & 1.18 & 18.1 \\ Median & 8.25 & 1.71 & 2.56 & 2.26 & 1.83 & 1.11 & 17.4 \\ Range & 4.53–11.7 & 1.09–2.94 & 1.34–5.78 & 1.68–3.80 & 1.18–3.30 & 0.66–1.87 & 11.4–26.6 \\ \hline \multicolumn{8}{c}{Cold Period (N = 15)} \\ \hline Average & 7.36 & 1.93 & 2.47 & 2.26 & 2.34 & 1.29 & 17.6 \\ Median & 7.49 & 1.86 & 2.53 & 2.35 & 2.30 & 1.21 & 17.1 \\ Range & 4.53–9.37 & 1.09–2.94 & 1.63–3.37 & 1.72–3.07 & 1.56–3.30 & 0.80–1.87 & 11.6–22.4 \\ \hline \multicolumn{8}{c}{Warm Period (N = 15)} \\ \hline Average & 8.56 & 1.72 & 3.24 & 2.34 & 1.67 & 1.07 & 18.6 \\ Median & 8.46 & 1.62 & 2.80 & 2.13 & 1.58 & 0.94 & 17.6 \\ Range & 4.60–11.7 & 1.10–2.32 & 1.34–5.78 & 1.68–3.80 & 1.18–2.33 & 0.66–1.73 & 11.4–26.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Average, median, and ranged concentrations of indicator polychlorinated biphenyls (indPCBs) (pg m\({}^{-3}\)) for the overall and seasonally divided sampling period. in particulate phase from the center of Athens (73 fg m\({}^{-3}\) in the background site and 462 fg m\({}^{-3}\) in the urban site) [32] and lower than the particle-bound concentrations measured in Thessaloniki (150-12,890 fg m\({}^{-3}\)) [53]. There is no international standard about reference or target values of PCDD/Fs in the air, however, a review by [PERSON] and [PERSON] (1998) [58] reported some typical values according to the sampling point (background--remote sites: \(<\)10 fg I-TEQ m\({}^{-3}\), rural sites: 20-50 fg I-TEQ m\({}^{-3}\)), urban or industrial sites: 100-400 fg I-TEQ m\({}^{-3}\)). Comparing our results with these values, it is obvious that the industrial area of Thiassion Plain has a significant impact on the ambient air concentration of PCDD/Fs.