Short-term test for the induction of lung tumor in mouse by chloroprene

In a previous study by the authors, positive results from both a case-control study and a cohort study were reported. In the present study a short-term test for the induction of mouse lung tumor by chloroprene was conducted to confirm whether chloroprene monomer itself can induce tumors. Kunming albino mice weaned at 2 weeks were subjected to inhaling 0, 2.9 +/- 0.3, 19.2 +/- 1.9, and 189.0 +/- 13.3 mg/m3 chloroprene (GC purity, 99.8%) 4 h daily (except Sunday) for 7 months. All survivors were killed at the end of the 8th month or when moribund. No lung tumors were found before the 6th month. Thus, survivors at the 6th month were counted as effective animals. Most lung tumors observed were papilloadenomas (50/57), and a few were adenomas (7/57). The tumor incidence in the 2.9 mg/m3 group was 8.1% in comparison to 1.3% in the control group, with the significance level at P less than 0.05. The higher the concentration, the higher the incidence. Examination of the multiplicity of tumor induction also demonstrated a dose-response relationship, and the number of tumors per mouse in the 189 mg/m3 group was significant at P less than 0.01.