中国六次核试验辐射对哺乳动物的损伤效应研究

Studies on the radiation effect on mammals from six nuclear tests in China

目的研究中国核试验中不同类型辐射对哺乳动物的近期和远期生物学效应，探讨辐射损伤效应机制。方法1964—1976年间的6次核试验中，在核爆现场和下风向地区布放狗、恒河猴、大白鼠、小白鼠及家兔等哺乳动物，核爆后受到瞬时叮射线和中子外照射，落下灰1射线、13射线的外照射，落下灰131I、133I的内照射（食入及吸入），以及内外复合照射；此外，还有2次、3次重复照射，受照射动物的子代照射。动物回收后进行临床医学、病理学、血液学、生物化学、细胞化学、生殖遗传学、细胞遗传学与辐射剂量学等指标观察测试．前后持续22年。结果核爆后3、7和12个月，受照0．39Gy后，狗的外周血淋巴细胞染色体畸变率分别为8．63％、7．25％和7．63％，与对照组比较，差异有统计学意义（P〈0．01）。在核爆后6个月，受照0．74Gy的恒河猴的染色体畸变率为21．00％，高于对照组（P〈0．01）；核爆后8．5年，恒河猴的染色体畸变率为5．52％，高于对照组（P〈0．01）。核爆后52d，大白鼠受照0．65～4．40Gy后，生殖率下降为30．8％～69．4％，每胎平均仔数减少，与对照组比较，差异有统计学意义（P〈0．01）。狗受照0．75和1．73Gv后，受照后3～7个月精子数量和存活率降为0，且狗精子畸形率增加，达46．79％，高于对照组（P〈0．01）；狗的精子和睾丸超微结构出现严重的损伤变化。骨髓造血功能破坏，外周血白细胞、淋巴细胞持续减少，血清菲啶溴红络合物荧光强度（核酸含量测定）升高，达18．9％（P〈0．05）。受照2．00Gy以上的狗，5年后发生良性肿瘤53．3％，恶性肿瘤33．3％，高于对照组（P〈0．01）。外照射后，狗的睾丸萎缩发病率升高，眼晶状体向内障发病率升高，内照射后甲状腺萎缩发病率升高。放射性灰尘的污染范围大、危害时间长，狗受到落下灰β射线照射后发生皮肤烧伤，恢复慢，有发生癌变的可能。结论哺乳动物核辐射损伤比单纯中子、γ射线、X射线等照射损伤严重、伤情复杂；核辐射后造血细胞、生精细胞敏感，损伤严重，损伤程度取决于受照剂量，且与照射后时间有关。放射性落下灰的危害范围大、持续时间长，落下灰β射线能造成皮肤烧伤。即使低剂量核辐射，也会造成不容低估的危险。

Objective To study the short- and long-tel^a effects of radiation on mammals from China＇s earlier nuclear tests in order to explore the mechanism of radiation injmy. Methods Mammals, such as dogs, rhesus monkeys, and rats among other species, were distributed over the areas downwind of a nuclear test site during 1964 - 1976. They were exposed externally to ~/, neutron and [3 radiation, and internally to 131[, 1331 radiation（ ingestion and inhalation）. Observations of exposed animals and their offspings continued for 22 years and different aspects of clinical medicine, pathology, hematology, biochemistry, eytochemity, reprogeneties, eytogeneties and radiodosimetry were measured. Results At 3, 7 and 9 months after nuclear explosion, frequency of chromosomal aberration in peripheral blood cell of dogs exposed to dose of 0. 39 Gy was 8.63%, 7.25% and 7.63%, respectively, having a statistically significant difference compared to controls （ P 〈 0. 01 ）. The frequency in rhesus monkeys exposed to O. 74 Gy was 21.00% at 6 months since exposure and 5.52% after 8.5 years, higher than controls （ P 〈 O. 01）; 52 days after explosion, the fertility of rats exposed to dose of O. 65 -4.40 Gy declined to 30. 8% - 69. 4% , and average number of newborns per birth tended to decrease, showing a statistically significant difference （P 〈0. 01） compared to controls. Both sperm counts and survival rate of dogs exposed to 0. 75 and 1.73 Gy decreased to 0 at 3 -7 months after exposure, with a mutation frequency of up to 46. 79% which was higher than controls （P 〈 0. 01 ）. The study showed that destroyed uhrastructure of sperm and testes, damaged haemopoietic function in bone marrow, continually decreasing peripheral white blood cells and lymphocytes, as well as increased fluorescence intensity to 18.9% of red phenanhridine bromide complexes （ P 〈 0.01 ）. Five years after exposure, dogs exposed to 2. 00 Gy or more had 53.3% benign tumors and 33.3% maglignant tumors, higher than unexposed controls （ P 〈 0. 01 ）. Increased incidence was found of either orchiatrophy and cataract or thyroid gland atrophy among dogs exposed esternally or internally. Extensive and long-time coverage by radioactive fallout resulted in skin injury to dogs due to β radiation, together with long recovery term and potential for carcinogenesis. Conclusions Nuclear tests have the potential to give rise to more severe injury than neutron alone, γ-rays or X-rays, especially for hematopoietic and spermatogenic cells, depending on doses and time since exposure. Radioactive fallout potentially cause disturbances to large areas and create longterm hazards, with skin injury arising from β radiation in fallout. Even low dose exposure of radiation can pose risks.