# Low-Dose Benzene Exposure Monitoring of Oil Refinery Workers: Inhalation and Biomarkers
## 3 Results and Discussion
To distinguish the contribution of workplace activity to metabolite concentrations from the main confounding factors from non-occupational sources, U-B and _t,t_-SA were analyzed concurrently, while specific questions of the questionnaire aimed at identifying possible confounding factors. Only non-smokers were enrolled for this study, and potential passive smoke exposure was verified by U-C determination, while _t,t_-SA was measured, and the results were cross-checked with the questionnaire. Our methodologies successfully identified the correlation between airborne substances and their metabolites due to their \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \begin{tabular}{c} **Toluene** \\ **(\#g/m\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **n-Hexane** \\ **(\#g/m\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **2.5-HD** \\ **(\#g/m\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **Benzene** \\ **(\#g/m\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **U-B** \\ **(\#g/k)** \\ \end{tabular} & \begin{tabular}{c} **_t_-**MA** \\ **(\#g/g crea)** \\ \end{tabular} & \
\begin{tabular}{c} **SPMA** \\ **(\#g/g crea)** \\ \end{tabular} &
\begin{tabular}{c} **Living Area** \\ **(\#g/g crea)** \\ \end{tabular} \\ \hline \hline TIN-TWA & & & & & & & & \\ ACGH [10] & & 72,000 (2) & & & & & & \\ ECHA-UE [20] & & & & & & & & \\ \hline BEI ACGH 2021 & & & 500 & & & 500 & 25 & \\ \hline LISA SIVR 2005 (2017 [10] & & & & & & & & \\ \hline Reference Value [PERSON], et al. [5] & & & & & & & & \\ \hline Sample & & & & & & & & & \\ \hline
1 & 43.4 & 9.0 & 10.8 & 3.9 & 74 & 27.1 & 0.45 & urban \\
2 & 0.4 & \textless{}0.5 & 2.1 & 2.9 & 48 & \textless{}10 & 1.48 & suburban \\  
textless{}10 & \textless{}0.05 & suburban \\
20 & 274.5 & 21.4 & 3.8 & 2.1 & 42 & 26.4 & 0.06 & urban \\ \hline Median & 6.05 & 1.4 & 2.9 & 1.55 & 50.5 & 30.8 & 0.18 & \\ \hline Range & 0.4-893.7 & 0.25-42.4 & 0.8–16.1 & 0.9-83.5 & 18.0-4893.0 & 5.0–79.4 & 0.025-3.96 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Values of personal air samplings and biomonitoring. Legend: free 2.5-HD = hexanedione; U-B = urinary benzene; _t,t_-MA = trans-trans muocnic acid; SPMA = S-phenylmercapputric acid. \begin{table}
\begin{tabular}{c c c} \hline \hline  & & \begin{tabular}{c} **Benzene** \\ **(\#g/m\({}^{3}\))** \\ \end{tabular}  & \ \begin{tabular}{c} **U-B** \\ **(\#g/m\({}^{3}\))** \\ \end{tabular}  & \begin{tabular}{c} **U-B** \\ **(\#g/L)** \\ \end{tabular}  \\ \hline U-B & PC & 0.820 * & - \\ (ng/L) & Significance (two-tailed) & 0.000 & - \\ _t,t_-MA & PC & 0.465 ** & 0.440 \\ (\(\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\sensitivity and specificity. On the other hand, even though our results are promising and in accordance with other studies [39], it should be noticed that the number of samples analyzed to evaluate the correlations is small. Therefore, these correlations should be confirmed with a further study involving a greater number of workers, always bringing attention to confounding factors enrolling the subjects (diet, urinary creatinine, passive smoking). Focusing on the analytical aspects, in chromatography, automated, unattended sample treatment could increase laboratory throughput and diminish costs, offering results of higher precision than manual operated tools, maximizing work efficiency and data consistency/accuracy, and making any procedure applicable for routine analysis [40]. The autosamplers proposed in this study are equipped with several tools available on the market, comprising a barcode reader, automatic change liners and syringes, decapper, heaters, stirrers, shaking and/or filtration modules, solvent addition, and Local Area Network (LAN) connections, expanding the applicability and efficiency of these autosamplers. The proposed methods use full-automation in sample preparation, chromatographic separation, and MS detection, allowing a reduction in sample handling, which is considered one of the most error-prone phases in the analytical process, while boosting sensitivity.