Abstract: BACKGROUND ＆ AIM: To study the effect of smoking in different areas with different environmental mutagens including natural radiation. MATERIALS AND METHODS: Peripheral blood was obtained from 10 smokers who had lived in Beijing for more than 40 years. Individual radiation dose was measured with a pocket dose meter. Chromosomes 1, 2, and 4 were painted for the analysis of translocations. The results were compared with those of 10 and 7 smokers in high background radiation area(HBRA) and its control area(CA), respectively;and 20, 15 and 16 non-smokers in Beijing, HBRA and CA, remote villages, in South China respectively. RESULTS: Frequencies of translocation were (10.6±3.1)‰, (11.1±3.6)‰ and (13.4±3.4)‰ in smokers and (9.6±5.0)‰, (11.7±4.7)‰ and (8.4±3.1)‰ in non-smokers in Beijing, HBRA and CA, respectively. There was a statistically significant difference (P<0.05, Mann-Whitney U test) in the frequencies of translocation between smokers and non-smokers in CA, but the difference between smokers and non-smokers was neither seen in HBRA or in Beijing. CONCLUSION: The effect of smoking seems to be suppressed by the environmental mutagens in Beijing as well as by the elevated level of natural radiation in HBRA.

Key words: hromosome translocations, natural radiation, environmental mutagens, smoking