N-acetyl-S-(n-propyl)-l-cysteine in urine from workers exposed to 1-bromopropane in foam cushion spray adhesives

Physiologically based pharmacokinetic modeling for 1-bromopropane in F344 rats using gas uptake inhalation experiments

1-Bromopropane (1-BP) was introduced into the workplace as an alternative to ozone-depleting solvents and increasingly used in manufacturing industry. The potential exposure to 1-BP and the current reports of adverse effects associated with occupational exposure to high levels of 1-BP have increased the need to understand the mechanism of 1-BP toxicity in animal models as a mean of understanding risk in workers. Physiologically based pharmacokinetic (PBPK) model for 1-BP has been developed to examine 2 metabolic pathway assumptions for gas-uptake inhalation study. Based on previous gas-uptake experiments in the Fischer 344 rat, the PBPK model was developed by simulating the 1-BP concentration in a closed chamber. In the model, we tested the hypothesis that metabolism responsibilities were shared by the p450 CYP2E1 and glutathione (GSH) conjugation. The results showed that 2 metabolic pathways adequately simulated 1-BP closed chamber concentration. Furthermore, the above model was tested by simulating the gas-uptake data of the female rats pretreated with 1-aminobenzotrizole, a general P450 suicide inhibitor, or d,l-buthionine (S,R)-sulfoximine, an inhibitor of GSH synthesis, prior to exposure to 800 ppm 1-BP. The comparative investigation on the metabolic pathway of 1-BP through the PBPK modeling in both sexes provides critical information for understanding the role of p450 and GSH in the metabolism of 1-BP and eventually helps to quantitatively extrapolate current animal studies to human.

Comparison and evaluation of urinary biomarkers for occupational exposure to spray adhesives containing 1-bromopropane

Three metabolites of 1-bromopropane (1-BP) were measured in urine samples collected from 30 workers exposed to 1-BP at two facilities making furniture seat cushions and evaluated for use as biomarkers of exposure. The mercapturic acid metabolite, N-acetyl-S-(n-propyl)-l-cysteine (AcPrCys), 3-bromopropionic acid (3-BPA), and bromide ion levels (Br(-)) were quantitated for this evaluation. The high exposure group consisted of 13 workers employed as adhesive sprayers who assembled foam cushions using 1-BP containing spray adhesives and the low exposure group consisted of 17 non-sprayers, who worked in various jobs without spraying adhesives. All workers' urine voids were collected over the same 48 h period at work, and at home before bedtime, and upon awakening. Urinary AcPrCys and Br(-) levels were elevated in the sprayers compared to that of non-sprayers. Following HPLC-MS/MS analysis of mercapturic acid metabolite levels, 50 urine samples having the highest levels of AcPrCys were analyzed for 3-BPA. No 3-BPA was detected in any of the samples. The data collected from this study demonstrate that AcPrCys and Br(-) are effective biomarkers of 1-BP exposure, but 3-BPA is not.