Effect of Natural Radiation Compared with Those of Smoking and Air-Pollution

Abstract

Chromosome translocation is a stable type aberration that accumulates in the body by being exposed to environmental mutagens. In order to compare the biological effect of low dose radiation with those of other environmental mutagens, we investigated the frequency of chromosome translocations in peripheral lymphocytes in 28 healthy and elderly residents of a high-background radiation area (HBRA) in southern China, and in 24 matched residents of a control area (CA). The mean ages of those residents were 63.0 in the HBRA and 63.1 in the CA. The radiation they received in the HBRA was 3 to 5 times higher than that in the CA. The total numbers of cells analyzed were 123,065 in the HBRA and 93,117 in the CA. The mean frequencies of translocations per 1,000 cells in the HBRA and CA were 12.4 ± 5.3 and 10.0 ± 3.8, respectively. No significant difference in frequency was found between the HBRA and CA (P>0.05, Mann-Whitney U test). When those individuals were classified into smokers and nonsmokers, a significant difference was found in the frequencies between smokers and nonsmokers in the CA (P<0.05, Mann-Whitney U test). Furthermore a tendency toward difference (T-value near 0.05) was found in a comparison of smokers in the HBRA vs. nonsmokers in the CA. The present results indicate that the elevated level of natural radiation in the HBRA plays a less significant role than smoking in the induction of stable-type aberrations in those areas.
We also examined age-matched smokers living in Beijing more than 40 years to investigate the effect of air pollution. The frequencies of translocations in these subjects showed a larger individual variation than those in the rural areas.