Assessment of occupational exposure to 4,4'-methylene-bis-(2-chloroaniline) "MOCA" by a new sensitive method for biological monitoring.

A new specific and sensitive method for the urinary determination of 4,4'-methylene-bis-(2-chloroaniline) ("MOCA"), a known carcinogen in rats, mice and dogs, has been developed. After a brief study on rats to determine some peculiarities in "MOCA" urinary excretion, this method was used to assess occupational exposure in French industrial firms. Both the manufacture of "MOCA" and its use as a curing agent in the production of polyurethane elastomers were surveyed. "MOCA" excretion levels were distributed from non-detectable (less than 0.5 microgram/l) up to 1600 microgram/l. Concentrations of N-acetyl metabolites, when present, were largely lower than "MOCA" levels. The results seemed to reflect workers' overall exposure fairly. Preventive measures following analytical determinations often led to an obvious lowering of excretion levels.