Sensitive flame-photometric-detector analysis of thiodiglycolic acid in urine as a biological monitor of vinyl chloride

Reduced adiponectin:leptin ratio associated with inhalation exposure to vinyl chloride monomer

The hepatic toxicity of vinyl chloride monomer (VCM) has often been reported, but few studies have assessed insulin resistance or adipose tissue dysfunction. We analyzed the chronic health effects of moderate exposure to VCM on factory workers in Taiwan. Data were collected from personal air samples, urine samples, and immunohistochemical (IHC) examinations of 122 recruited voluntary participants. Air samples were analyzed to assess personal levels of exposure to VCM and ethylene dichloride (EDC). Urine samples were collected from each worker before they started and after they finished their daily shift. Urinary thiodiglycolic acid (TDGA) levels were analyzed using high-performance liquid chromatography-tandem mass spectrometry (HPLC/MS/MS). IHC examinations included liver function and serum adipokine level tests for insulin resistance. Consequently, the participants included for the final analysis were 113. After confounders had been adjusted for, the airborne VCM concentration significantly (P = 0.043) correlated with pre-shift urinary TDGA levels (β = 0.194). A multivariate analysis showed a significant (P = 0.013) inverse correlation between the adiponectin:leptin ratio and the airborne VCM concentration (β = -0.283), which means that exposure to VCM might increase the risk of insulin resistance and adiponectin abnormalities. We hypothesized that pre-shift urinary TDGA levels can be used as exposure biomarkers for the exposure of workers to VCM.

"Dilute-and-shoot" rapid-separation liquid chromatography tandem mass spectrometry method for fast detection of thiodiglycolic acid in urine

A new sensitive rapid-separation liquid chromatography tandem mass spectrometry approach for the determination of thiodiglycolic acid (TDGA) in urine has been developed. The use of the "dilute-and-shoot" method helps to shorten the sample preparation stage and provides a sensitive and direct approach for TDGA determination in urine. Chromatographic separation of the analyte and other urine compounds was achieved using a reverse-phase liquid chromatography column with mobile phases consisting of 0.1% formic acid in water and acetonitrile in a gradient elution mode. For the identification and quantification of TDGA electrospray ionization-tandem mass spectrometry monitoring, two precursor-to-product ion transitions were used. The method demonstrates good linearity and has a detection limit of 50 ng mL⁻¹ in urine.

DNA single strand breaks in peripheral lymphocytes associated with urinary thiodiglycolic acid levels in polyvinyl chloride workers

The association between vinyl chloride monomer (VCM) exposure and DNA damage has been established. However, the relationship between individual exposure and DNA single strand breaks was limited. Since environmental monitoring may not reflect the actual exposure, a useful marker of exposure is needed to assess the individual exposure. In our previous study, we have found a high correlation between air VCM level and urinary thiodiglycolic acid (TdGA) at the commencement of the next shift. Here, we further used comet assay to evaluate the relationship between urinary TdGA levels and DNA single strand breaks in polyvinyl chloride monomer (PVC) workers. Urinary TdGA levels (n=26) at the commencement of the following shift were analyzed. Ten of the 26 workers also had personal air sampling for air VCM exposure. Questionnaires were administered to obtain epidemiological information including detailed history of occupation and lifestyles. Workers experiencing air VCM level greater than 5 ppm had higher tail moment and tail intensity (%) than those experiencing VCM exposure between 1 and 5, or <1 ppm, respectively (P < 0.05). The results also revealed that level of DNA single strand breaks, including tail moment and tail intensity, were increased with urinary TdGA level. The dose-response relationship of urinary TdGA level and DNA single strand breaks was particularly significant among the workers with 4 mg/g Cr of urinary TdGA level, which is equivalent to 5 ppm air VCM level. We concluded that air VCM exposure greater than 5 ppm could induce DNA damage. Further sensitive assay should be developed for the diction of DNA damage when air VCM exposure below 5 ppm.

Urinary thiodiglycolic acid levels for vinyl chloride monomer-exposed polyvinyl chloride workers

Thiodiglycolic acid (TdGA) is the major metabolite of vinyl chloride monomer (VCM) detected in human urine. Although urinary TdGA has been reported to be associated with ambient VCM exposure, the relationship between urinary TdGA and a low level of air VCM is not clear. Questionnaires were administered to 16 polyvinyl chloride manufacturing workers to obtain a detailed history of occupation and lifestyle. For each worker, personal air monitoring for VCM was performed and a time-weighted average for VCM exposure was calculated. The urinary TdGA levels at the end of a work shift, and at the commencement of the next shift, were also assessed for each worker. Urine analysis revealed that TdGA levels at the beginning of the next shift were higher than those at the end of that shift. Workers experiencing a VCM exposure greater than 5 ppm in air revealed a urinary TdGA level significantly greater than those experiencing a VCM exposure of less than 5 ppm (P < 0.05). The best fit of regression for urinary TdGA on air VCM was Y = 1.06 + 0.57X for urine collected at the commencement of the following work shift, where X is the air VCM concentration and Y is the urinary TdGA concentration (r2 = 0.65, P < 0.01). We conclude that the urinary TdGA level is best detected at the commencement of the next shift and that it can be used as an exposure marker for polyvinyl chloride workers when the air VCM level to which they are exposed is greater than 5 ppm.

Determination of thiodiglycolic acid in urine by capillary electrophoresis

A sensitive capillary electrophoretic method was developed for the determination of thiodiglycolic acid (TDA) in urine which avoids the pretreatment of the urine sample. Several carrier electrolytes were examined. The most suitable carrier electrolyte system consisted of potassium hydrogen phthalate (5 mM), 2-(N-morpholino)ethanesulfonic acid (50 mM) and tetradecyltrimethylammonium bromide (0.5 mM), pH 5.2. Ten times diluted fresh midstream void urine was used for the determination. In this way, the concentrations of TDA between 5 and 50 mg/l in undiluted urine samples can be determined.