Micronuclei in peripheral lymphocytes and exfoliated urothelial cells of workers exposed to 4,4 '-methylenebis-(2-chloroaniline) (MOCA)

4,4'-Methylenebis-(2-chloroaniline) (MOCA) is used in the manufacture of po lyurethane, The IARC classifies MOCA as a probable human carcinogen. Sugges ted changes to guidelines for health surveillance of MOCA-exposed workers i n Australia include a reduction in acceptable levels of urinary MOCA to bel ow 15 mu mol/mol creatinine. Twelve male workers aged 24 and 42 years were recruited into this study from four work locations where MOCA is used. Exfo liated urothelial cells from prework urine samples on a midweek work day we re assessed for micronucleus (MN) frequencies, Postwork urine samples were analysed for total MOCA. Blood samples collected on the same day were cultu red for 96 h and cytochalasin-B-blocked cells were scored for MN. Eighteen male control subjects (23-59 years) provided corresponding urine and bleed samples. Median urinary MOCA concentrations were 6.5 mu mol/mol creatinine (range 0.4-48.6 mu mol/mol creatinine) in postwork samples of MOCA-exposed workers. MOCA was not detected in urine of control workers, Mean MN frequen cies were higher in urothelial cells and lymphocytes of MOCA workers (14.27 +/- 0.56 and 13.25 +/- 0.48 MN/1000 cells) than in controls (6.90 +/- 0.18 and 9.24 +/- 0.9 MN/1000 cells). The mean number of micronucleate cells wa s also higher in both tissues of exposed workers (9.69 +/- 0.32 and 8.54 +/ - 0.14 MN cells/1000 cells) than in controls (5.18 +/- 0.11 and 5.93 +/- 0. 13 MN cells/1000). There was no correlation between postwork urinary MOCA c oncentrations and MN frequencies in either tissue. This study suggests that exposures to MOCA in South Australia are similar to those of a decade ago and are at levels similar to those currently acceptable in Australia. These are associated with genotoxic effects in urothelial cells and peripheral b lood lymphocytes. It may be prudent to reduce MOCA exposures in line with p roposed guidance values. (C) 1999 Elsevier Science B.V. All rights reserved .