# Low-Dose Benzene Exposure Monitoring of Oil Refinery Workers: Inhalation and Biomarkers
## 3 Results and Discussion  
Our study proposes fully-automated, rapid, and high-throughput methods for determining airborne benzene through personal sampling while contemporaneously quantifying, with proficient LOQs, its more sensitive and specific metabolites to evaluate low-dose (<0.1 ppm) benzene exposure scenarios. Calibration curves, linearity parameters, and \(LOD\)/LOQ values are reported in Table 3. All methods proposed present the sensibility, accuracy, and precision required by the current limit value for each substance. In terms of sensitivity and specificity, advances in analytical technologies allow us to find growingly lower concentrations of compounds in biological specimens. This expands the potential of human biomonitoring to include the assessment of environmental exposures, particularly occupational exposure to hazardous compounds. This recent de \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & & \multicolumn{3}{c}{Calibration Curve Parameters} \\  & & & \multicolumn{3}{c}{Response Factor Plot} \\ \cline{3-7}
**Monitoring** & & & & & & \\
**Type** & & & & & & \\
**Analyte** & & & & & & \\
**\(b\) = Intercept** & & & & & & \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} Personal air \\ samplings \\ \end{tabular} } & Benzene & \(m=3.16\,b=0.124\) & 0.99 & 0.034 & 0.15 (0.5) \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{m}^{3}\) & 6\% & 8 (7)\% \\  & n-hexane & \(m=6.33\,b=0.221\) & 0.98 & 0.032 & 0.12 (0.4) \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{m}^{3}\) & 7\% & 8 (9)\% \\ \hline \multirow{6}{*}{
\begin{tabular}{c} Biomonitoring \\ \end{tabular} } & U-B & \(m=1.12\,b=0.362\) & 0.99 & 0.43 & 2.1 (7.1) \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{L}\) & 10\% & 10 (9)\% \\  & \(t_{1}\)-SA & \(m=2.75\,b=0.78\) & 0.98 & 1.45 & 2.4 (8.1) \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{L}\) & 8\% & 5 (5)\% \\  & U-C & \(m=2.62\,b=1.01\) & 0.98 & 0.98 & 2.3 (7.6) \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{L}\) & 8\% & 5 (5)\% \\  & \(t_{1}\)-MA & \(m=6.37\,b=1.04\) & 0.99 & 1.89 & 1.4 (4.6) \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{L}\) & 10\% & 9 (1)\% \\  & SPMA & \(m=6.01\,b=2.1\) & 0.98 & 0.95 & 0.28 (0.1) \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{L}\) & 6\% & 7 (7)\% \\  & 2.5-HD & \(m=28.20\,b=0.11\) & 0.99 & 1.29 & 0.15 (0.5) \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{L}\) & 5\% & 4 (5)\% \\ \hline \hline \end{tabular}  
* 8h sampling time.  
\end{table} 
Table 3: Calibration curve parameters, limit of detection (\(LOD\)), limit of quantification (LOQ) values, accuracy, and repeatability for personal sampling and biomonitoring analytes. (U-B urinary benzene; \(t_{1}\)-SA: _trans-trans_ sorbit acid; U-C: urinary cotinine; \(t_{1}\)-MA _trans-trans_ muconic acid; SPMA: S-phenylmercapquric acid; 2,5-HD: 2,5-hexanedione). velopment of valid biomonitoring methods and pinpointing specific biomarkers led our group to carry out this study to assess different aspects, among which are urine sampling cautions, correlation between airborne benzene concentration and biomarkers, potential dermal route contribution, and biological confounding factors. All enrolled workers performed the personal sampling during their work shift, and the urine along with the questionnaires were gathered at the end of the shift. The urine specimens had to be immediately sealed in an amber vial to prevent losses during sample collection and possible analyte photodegradation; moreover, the handling and storage of urine had to be minimized to maintain unchanged physicochemical characteristics. Particularly, U-B requires special attention because benzene will equilibrate rapidly in the air above the sample, reducing or enriching the analyte in the sample, depending on the benzene concentration above it. For that reason, the sealing of samples must be carried out as fast as possible. Another fundamental aspect to underline is that the only practical occupational approach to collect urine samples is a single voiding before, during, or at the end of the work shift [31].