期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：1
页码：19-22
DOI：10.1073/pnas.96.1.19
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Domestic, low-level exposure to radon gas is considered a major environmental lung-cancer hazard involving DNA damage to bronchial cells by particles from radon progeny. At domestic exposure levels, the relevant bronchial cells are very rarely traversed by more than one particle, whereas at higher radon levels--at which epidemiological studies in uranium miners allow lung-cancer risks to be quantified with reasonable precision--these bronchial cells are frequently exposed to multiple -particle traversals. Measuring the oncogenic transforming effects of exactly one particle without the confounding effects of multiple traversals has hitherto been unfeasible, resulting in uncertainty in extrapolations of risk from high to domestic radon levels. A technique to assess the effects of single particles uses a charged-particle microbeam, which irradiates individual cells or cell nuclei with predefined exact numbers of particles. Although previously too slow to assess the relevant small oncogenic risks, recent improvements in throughput now permit microbeam irradiation of large cell numbers, allowing the first oncogenic risk measurements for the traversal of exactly one particle through a cell nucleus. Given positive controls to ensure that the dosimetry and biological controls were comparable, the measured oncogenicity from exactly one particle was significantly lower than for a Poisson-distributed mean of one particle, implying that cells traversed by multiple particles contribute most of the risk. If this result applies generally, extrapolation from high-level radon risks (involving cellular traversal by multiple particles) may overestimate low-level (involving only single particles) radon risks.
