Abstract
Recent reports have indicated a high incidence of liver cancer in rats exposed to MOCA® in a protein-deficient diet and of lung cancer with MOCA® in a normal diet. No clinical evidence of malignancy has been observed in dogs during the third year of a six-year MOCA® feeding study. Although urinary excretion of MOCA® and certain metabolites by operators and mechanics assigned to the manufacturing area has been significant, close medical surveillance has detected no manifest signs or symptoms derived from MOCA® exposure during 16 years of human exposure experience. The cyanosis-anemia syndrome was absent under the industrial hygiene controls applied in the production area. Airborne MOCA® concentrations disclosed by fallout plate, mobile fixed-station, and personnel monitor sampling were below levels which could account for the observed urinary output. Skin absorption from direct contact was concluded to be the major source of absorption. Exposure was effectively controlled by efficient precautionary ventilation, respiratory protection, and protective clothing. A threshold limit value for MOCA® in air alone would not provide an effective control basis. However, biological monitoring by urine analysis does provide a reliable and expedient control system.