极低频磁场与癌症

目的:现代社会中人们处于工业频率(极低频)磁场的包围之中,从细胞学角度进行有关极低频磁场与人类癌症发病之间关系的研究具有重要的理论和实践意义。资料来源:应用计算机检索HighWire1991-01/2006-03期间的相关文章,检索词“extremely low frequency magnetic fields,cancer”,并限定文章语言种类为English。资料选择:浏览相关文献的摘要,对资料进行初审,选取用细胞学和分子生物学手段进行实验,结合流行病学进行研究的文章;尽量选用以不同动物或手段进行研究而结果相同的文献;对照分析有关极低频磁场与癌症关系的的原创和综述文章。有的资料采取回查法,给在某文章中发现有意义的线索后找到该文献,然后详细浏览。资料提炼:共收集到90篇关于极低频磁场与癌症关系的原创性文献和4篇综述文献,分别有29篇和4篇纳入标准。被排除的47篇文章中,32篇与本主题关系不大,5篇时间过早或结论不明确,10篇只采用流行病学研究。并纳入1篇书籍文献。资料综合:①长久以来,关于50Hz或60Hz的极低频磁场有无致癌作用的问题,流行病学与细胞学研究的结果一直不一致。②多数流行病学的统计结果表明,长期或频繁暴露于极低频磁场的人群,患癌症的比率高于非暴露人群,其中患白血病、脑癌和乳腺癌的风险更高。③但细胞学的实验观察表明,暴露于极低频磁场中的正常培养细胞并没有增加分裂或出现癌变信号;在有些报道中,极低频磁场还加速了正常细胞凋亡的过程,降低了癌变的可能性。④许多作者提出,极低频磁场并不能直接导致正常细胞的癌变过程,但可能促进和加强癌倾向细胞以及癌细胞的癌变和死亡进程。⑤这种促进和加强作用可能通过影响细胞信号转导的各个环节和导致基因和转译过程的变化、改变一些酶的活性、增加自由基产生等来实现。结论:极低频磁场可能并不直接导致正常细胞的癌变过程,但可促进和加强癌倾向细胞以及癌细胞的癌变和死亡进程。

Extremely low-frequency magnetic fields and cancers

OBJECTIVE: All the people in modern world are exposed to the industrial frequency magnetism (extremeiy low-frequency magnetic fields, ELFMF). There are important academic and practical significance to understand the influence of ELFMF on human diseases.DATA SOURCES: A computer-based online search was conducted in HighWire database for English literatures about the relation between ELFMF and human cancers from January 1991 to March 2006 by using the key words of "extremely low frequency magnetic fields, cancer".STUDY SELECTION: All the collected literatures were screened. Inclusion criteria: ① To browse the abstracts of the literatures to examine primitively, and select the articles experimented with the cytological, molecular biological and epidemiological methods. ② Choosing the separate articles by studying with different animals but having got the same results.③ Comparing and analyzing the original and reviewed articles about the relations between ELFMF and cancers.DATA EXTRACTION: A total 90 original and 4 reviewed literatures about ELFMF and cancers were collected and 29 and 4 papers were accordance with the criteria, respectively. In the 47 eliminated articles, 32 of them were unrelated or repetitive to our topic, 5 of them were published earlier or the conclusions were ambiguous, and other 10 of them used only the epidemiological methods.DATA SYNTHESIS : ① For a long time, the question whether 50/60 Hz ELFMF has the carcinogenic effects has been disputed in epidemiology and cytology. ② Majority statistical results in epidemiology showed that the crowds exposed to ELFMF for long or frequent time had an higher ratios suffering cancers than the normal, thereinto, the dangerousness such as leucocythemia, brain cancer and breast cancer is especially high. ③ However, the observation in cytology indicated that the normal cultural cells exposed to ELFMF had not increased the cell divisions or appeared cancer signals, and even in some reports, ELFMF may accelerate apoptosis, and reduced the possibility of cancerization. ④ Although ELFMF may not produce cancerization to normal cells, it may act as an promoter or co-promoter of cancer-prone cells, to accelerate the cancerization and exacerbation course of those cells. ⑤ The effect is related to influencing various links of signal transduction, changing translation of gene, changing activities of some enzymes and increasing production of free radicals.CONCLUSION: Although ELFMF may not produce cancerization to normal cells, it may act as an promoter or co-promoter of cancer-prone cells, to accelerate the cancerization and exacerbation course of those cells.