Biological monitoring of a worker acutely exposed to MBOCA

Abstract

A 30 year-old male polyurethane worker was exposed to an accidental spill of 4,4'-methylene-bis-2-chloroaniline (MBOCA) at a plant producing MBOCA-cured plastic products. Exposure to MBOCA is significant in that this compound is a known animal carcinogen and a suspected human carcinogen. The employee was sprayed over his upper body and extremities with molten MBOCA while cleaning out a clogged hose from a MBOCA and polymer mixing machine. The subsequent environmental and medical evaluation of this episode included serial urinary MBOCA samples from the worker over a 2 week period to allow the calculation of a biological half-life for this compound. This worker experienced a very high dose of MBOCA as judged by his urinary MBOCA levels (peak value of 1,700 ppb 4 hours after exposure). There were no acute symptoms or other laboratory abnormalities noted. The kinetic evaluation resulted in a biological half-life for MBOCA in urine of approximately 23 hours. Assuming a one-compartment model, approximately 94% of an initial MBOCA dose will be eliminated within four days. This is the first report of kinetic analysis on urinary MBOCA excretion in humans. This information suggests that biological monitoring of the urine MBOCA concentrations in exposed workers may miss peak levels following an acute exposure unless the analyses of the urinary MBOCA are performed in a timely fashion. Recommendations to the company included: 1) installation of a warning system or lock-out device on the mixing machine to prevent the opening of the MBOCA hose prior to the release of pressure; and 2) annual medical surveillance of this individual for bladder cancer with urinalysis and urine cytology.

Biological monitoring of workers exposed to 4,4′-methylene-bis-(2-orthochloroaniline) (MOCA)

“…The close correlation observed between``total'' MOCA and``free'' MOCA in urine samples of 40 workers was also noted by Osorio et al (1990) in the urine of one worker sprayed accidentally over his upper body and limbs with molten MOCA; in this case, they reported a lower free/total MOCA ratio than us (35% vs 55%). Using our protocol to thaw frozen urine samples, we observed that on a few of the samples that had been previously analysed, then left at A20°C for several months and reanalysed, there was a 64% mean increase in the apparent MOCA concentration.…”

“…In addition, the heating of urine samples does not take account of the acetylated metabolites of MOCA, and``heat-labile'' MOCA is a more suitable de®nition Jedrzejczak and Gaind 1992;Wu et al 1996). Finally, the term``total'' MOCA should be employed when the urine samples are hydrolysed under strong acid or alkaline conditions (McKerrell et al 1987;Osorio et al 1990). …”

“…Wan et al (1989) considered that free MOCA was the best method of assessment of absorption. Osorio et al (1990) measured free and``total'' MOCA in urine samples of one worker exposed to an accidental spill of MOCA and observed a close correlation between these two biological markers, suggesting urinary monitoring of unconjugated MOCA as a suitable and available method to evaluate exposure to MOCA.…”

Occupational Bladder Cancer in a 4,4′-Methylenebis(2-chloroaniline) (MBOCA)-Exposed Worker

“…Urine samples obtained by Ward et al (1990) from plant workers several months after production ceased also showed detectable MBOCA levels that ranged as high as 50,000 μg/L. Osorio et al (1990) reported a urine MBOCA level of 1,700 μg/L 4 hr postexposure in a worker who was accidentally sprayed with molten MBOCA, but no acute symptoms or other laboratory abnormalities were observed. The urine MBOCA levels in the MBOCA-manufacturing factory workers were much higher than in workers at a polyurethane elastomer factory using MBOCA as a curing agent.…”

Exposure to 4,4′-methylene bis(2-chloroaniline) (MbOCA) in New South Wales, Australia

“…The acute health effects of exposure to MbOCA include irritation and a burning sensation to the skin and eyes, nausea, and gastrointestinal and renal effects 5) . Animal studies have shown that chronic exposure to MbOCA can cause bladder cancer 6 , 7) .…”