Abstract: Objective: To explore the association between environmental low-dose exposure to crocidolite and malignancy, so as to provide the epidemiologic evidence for malignancy prevention.Methods: A 27-year (February,1984 to January,2011)retrospective cohort study was conducted to evaluate the mortality of the major malignancy in the crocidolite-contaminated area in Dayao county, Yunnan province.Results: There were 1 249 subjects(575 males and 674 females)in the retrospective cohort and 28 848.27 personyears were observed totally.In this cohort,443 person were died,which accounted for 35.4% of the total subjects.Furthermore,121 person were died from cancer, the total mortality was 1535.64 per 100 000 person-years.Hepatic carcinoma(29 cases)was the first cause of tumor death and the mortality was 100.53 per 100 000 person-years(the standarized mortality rate is 51.22 per 100 000 person-years).Lung cancer(27 cases,not including pleura mesothelioma)was the second cause of tumor death and the mortality was 93.59 per 100 000 person-years (the standarized mortality rate is 41.5 per 100 000 person-years).The third cause was pleura mesothelioma,which contained 26 cases, the mortality was 90.13 per 100 000 person-years(the standarized mortality rate is 54.36 per 100 000 person-years).Gastric cancer and intestinal cancer mortality were 45.06 per 100 000 person-years(the standarized mortality rate is 23.68 per 100 000 person-years)and 18.27 per 100 000 person-years(the standarized mortality rate is 54.36 per 100 000 person-years).Multiple regression analysis showed that the exposure factors(producing asbestos stove,using asbestos stove,building the road with asbestos and the time of living in contaminated areas)were associated with the occurrence of malignancy in Dayao county. Meanwhile, the relative risk was higher among the male residents.Conclusions: Liver, lung, stomach, colon cancer,pleural mesothelioma and other malignant tumors are higher than those in Yunnan and the national average.Long-term environmental crocidolite exposure leads to high mortality of cancer among residents in crocidolite-Contaminated Area in Dayao county.