Effect of smoking on chromosomes compared with that of radiation in the residents of a high-background radiation area in China.

Cytogenetic investigation of stable-type aberrations (translocations) was carried out with our improved methods on 28 elderly individuals in a high-background radiation area (HBRA) in China, and on 24 elderly individuals in a control area (CA). The level of radiation in HBRA is 3 to 5 times higher than in CA. The mean frequencies of translocations per 1,000 cells in HBRA and CA were 12.4 +/- 5.3 and 10.0 +/- 3.8, respectively. No significant difference was found in the frequencies between HBRA and CA (P>0.05, Mann-Whitney U test). When elderly individuals in HBRA and CA were classified into four subgroups of HBRA nonsmokers, HBRA smokers, CA nonsmokers, and CA smokers, a significant difference was found in the frequencies between CA smokers and CA nonsmokers (P<0.05, Mann-Whitney U test). Furthermore a tendency of difference (a near T-value of 0.05 level) was found in a comparison of HBRA smokers vs. CA nonsmokers. The present results indicate that the elevated level of natural radiation in HBRA plays a less significant part than smoking in bringing about the induction rate of stable-type aberrations (translocations) in those areas.