One-year time sequence inhalation toxicity study of vinyl chloride in rats. I. Growth, mortality, haematology, clinical chemistry and organ weights.

Wistar rats were exposed to atmospheres containing O (control) or 5000 ppm vinyl chloride monomer (VCM), 7 h/day, 5 days/week, for a period of 52 weeks. After 4, 13, 26 and 52 weeks each time 10 rats/sex/group were killed and subjected to extensive examinations. The present paper deals with growth, mortality, haematology, clinical chemistry and organ weights. Slight growth retardation throughout the experimental period and high mortality in the second half of the study were observed in VCM-exposed animals. Some of the haematological parameters and biochemical blood parameters were slightly influenced by VCM after an experimental period of 52 weeks only. Blood clotting time was generally slightly shorter in VCM-exposed rats than in controls. There were minor indications of increased potassium contents of the blood serum in VCM-exposed animals during the first half of the test period. The kidneys were adversely affected by VCM as appeared from increased blood urea nitrogen levels and relative kidney weights. After 52 weeks increased weights of heart and spleen, and slight signs of anaemia were noticed in VCM-exposed rats. The present study did not produce obviously suitable parameters for early diagnosing "VCM-disease" in man.