Method for the Determination of Benzene Metabolite t,t-Muconic Acid in Urine by HPLC-UV with an Ion Exclusion Column

False positives and false negatives in benzene biological monitoring

Benzene is a commonly used industrial chemical that is a significant environmental pollutant. Occupational health specialists and industrial toxicologists are concerned with determining the exact amount of exposure to chemicals in the workplace. There are two main approaches to assess chemical exposure; air monitoring and biological monitoring. Air monitoring has limitations, which biological monitoring overcomes and could be used as a supplement to it. However, there are several factors that influence biological monitoring results. It would be possible to assess exposure more accurately if these factors were taken into account. This study aimed to review published papers for recognizing and discussing parameters that could affect benzene biological monitoring. Two types of effects can be distinguished: positive and negative effects. Factors causing positive effects will increase the metabolite concentration in urine more than expected. Furthermore, the parameters that decrease the urinary metabolite level were referred to as false negatives. From the papers, sixteen influential factors were extracted that might affect benzene biological monitoring results. Identified factors were clarified in terms of their nature and mechanism of action. It is also important to note that some factors influence the quantity and quality of the influence of other factors. As a result of this study, a decision-making protocol was developed for interpreting the final results of benzene biological monitoring.

Exposure assessment of wastewater treatment plant employees to BTEX: a biological monitoring approach

To monitor employees' work safety and exposure against air contaminants, Trans, trans-muconic acid, Hippuric acid, Methyl hippuric acid, Mandelic acid and Phenylglyoxylic acid can be used as reliable biomarkers of exposure to benzene, toluene, ethylbenzene, and xylene (BTEX) compounds. This study aims to determine the level of urinary metabolites of BTEX compounds using biological monitoring in the employees of a wastewater treatment plant (WWTP) in the south of Iran. The study was performed on 56 employees of the WWTP of one of the southern cities of Iran in 2020. Urine samples (n total = 112) consisting of 60 samples of employees working in the operation section (exposed group) and 52 samples of employees working in the administrative section (control group) in the WWTP were collected before and at the end of their shift. The mean concentration of urinary metabolites of BTEX of both groups ranged from 546.43 (μg/g cr) for trans, trans-muconic acid to 0.006 (μg/g cr) for methyl hippuric acid, which indicates that most of the evaluated metabolites showed a higher concentration than their occupational threshold limit value urine (p < 0.05). Regression analysis results showed a significant correlation (p < 0.05) between age and utilization of flame heaters with changes in the measured BTEX metabolites in the urine. The results of this study illustrate that WWTPs should be considered as one of the workplaces with potential sources of BTEX exposure for employees. Future investigations are recommended to perform itemized appraisals of BTEX intake sources, particularly in employees of the operational sections of WWTP.

Solidified floating organic droplet microextraction coupled with HPLC for rapid determination of trans, trans muconic acid in benzene biomonitoring

Benzene is one of the carcinogenic compounds in the work environments. Exposure assessment of benzene through biological monitoring is an acceptable way to accurately measure the real exposure in order to conducting the health risk assessment, but it is always complicated, laborious, time consuming and costly process. A new sensitive, simple, fast and environmental friendly method was developed for the determination of urinary metabolite of benzene, trans trans muconic acid (t,t-MA) by dispersive liquid-liquid micro extraction based on solidification of floating organic droplet coupled with high-performance liquid chromatography with ultra violet detector. Central composite design methodology was utilized to evaluate the effective factors on the extraction output of the target metabolite. The calibration curve was plotted in the concentration ranges of 0.02-5 µg mL^-1. The precision and accuracy of the method were assayed via the relative standard deviation (RSD%) and relative recovery (RR%) using spiked samples with three replications. The RR% and RSD% of the optimized method were 86.9-91.3% and 4.3-6.3% respectively. The limit of detection (LOD) of the method was 0.006 µg mL^-1. The level of t,t-MA in real samples was ranged from 0.54 to 1.64 mg/g creatinine. We demonstrated that t,t-MA can be extracted and determined by an inexpensive, simple and fast method.

A smart supramolecular device for the detection of t,t-muconic acid in urine

An indicator displacement assay is applied in the fluorescence detection of urinary t,t-muconic acid at the occupational level.