We have observed properties of radioactive fallout originated from the first, the second, the third, the fourth and the fifth Chinese nuclear explosions. The differences in gross beta-activities, activities per unit volume and their particle sizes of highly radioactive particles are discussed with relation to the differences in burst conditions among the five explosions from which they originated.It was found that radioactivities of the highly radioactive particles were roughly proportional to their volumes. The differences in the radioactive decay rates of highly radioactive fallout particles were found in connection with their colors.From the results of decay characteristics of gross beta-activities and γ-ray spectra of fallout samples, it was found that the contribution of radioactivities of 239Np in samples from the fifth Chinese explosion was larger than that from the third Chinese explosion.In comparison between the γ-ray spectra of highly radioactive fallout particles from the third and the fifth Chinese explosions, the particles from the third Chinese explosion were enriched in 95Zr+95Nb and impoverished in 103Ru, while on the particles from the fifth Chinese explosion, the reverse of phenomenon above mentioned was observed.
To study the effect of low-dose (rate) radiation on human health, we analyzed chromosomes of peripheral lymphocytes of residents in a high background radiation area (HBRA) and compared the results with those obtained from residents in a control area (CA) in Guangdong Province, China. Unstable types of chromosome aberrations (dicentrics and rings) were studied in 22 members of eight families in HBRA and 17 members of five families in CA. Each family consists of three generations. On average 2,600 cells per subject were analyzed. 27 adults and six children in HBRA and 25 adults and eight children in CA were studied with respect to translocations. On average 4,741 cells per subject were examined. We found an increase of the frequency of dicentrics and rings in HBRA, where the natural radiation level is three to five times higher than in the control area. But the increase of translocations in HBRA was within the range of individual variation in the controls.
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