Assessing Exposure to 4, 4'-Methylene bis(2-chloroaniline) (MBOCA) in the Workplace

Abstract

The chemical 4, 4'-methylenebis (2-chloroaniline) (MBOCA) is used commercially as a curing agent for cast polyurethane products. While MBOCA has a low vapor pressure suggesting little likelihood of airborne vapor concentrations, worker exposure to MBOCA is indicated by its presence in urine, suggesting that MBOCA is readily absorbed through the skin. This study was conducted to assess various environmental exposure measurements (air samples, surface wipes, and skin pads) with comparison to biomonitoring (urine samples) results. The inhalation exposures to MBOCA measured by personal sampling were below 1 μg/m³; however, the area sampling indicated air concentrations up to 92 μg/m³. Wipe sampling indicated moderate contamination of the workplace by MBOCA dust (up to 19 μg/100 cm²). The average MBOCA concentration found on skin pads worn on workers' hands was generally less than 10 μg/set, with a high of 25 μg/set. Sixty-six percent of urine samples had detectable concentrations of MBOCA (up to 159 μg/L). The urinary MBOCA results were generally consistent with the workers' potential for exposure as predicted by their proximity to MBOCA sources in their duties, the use of personal protective equipment, and general work practices.