| Hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane(DDT), polychlorinated biphenyl(PCBs) and sodium pentachlorophenoxide (Na-PCP) are organochlorines. Though they were banned in 1983 by the government, they can be accumulated in great quantity in the environment and bodies of animals and plants for they are stable, degrade very slowly and remain for long time. They can be accumulated in human bodies by biological enrichment and food chain subsequently. It was shown in lots of reports that organochlorines remained in environmental medium, food and biological samples of human beings.Organochlorines caused a high incidence rate of cancer in experimental rats. They were related to breast cancer, carcinoma of endometrium, cancer of the liver, pancreatic cancer, non-Hodgkin's lymphoma, gastric cancer, etc. in epidemiology. The incidence or death of colorectal cancer might be related with a history of pesticide contact, the pesticide levels in serum, occupational contact of organochlorines and taking chlorinated water. The levels of DDT and PCBs in adipose tissue and plasma might be related to the incidence of breast cancer. However, there were opposite opinions which suggested that organochlorines had no correlation with colorectal cancer and breast cancer.To investigate the relationship between organochlorines and the incidence rates of colorectal cancer and breast cancer and then to offer more information to the mechanism and the prevention and control measures of these two kinds of cancers, we conducted an ecological study in Jiashan.Materials and MethodsThe data of incidence rates of colorectal cancer and breast cancer between 1987 and 2000, population statistics and the map of Jiashan were offered by the Research Institute of Cancer in Jiashan. 11 towns were drawn in Jiashan according to the incidence rates of colorectal cancer and breast cancer and the their positions. 4 or 5 administration villages were drawn in every town, and then 3 or 4 natural villages were drawn randomly. These natural villages were taken as sampling spots. The soil in the paddy fields was collected with five-spot way and rice was collected in five families of each spot randomly. The samples were crushed into powder respectively and detected in Inspection Department of the Center for Disease Prevention and Control in Zhoushan. HCH, DDT and PCBs were detected with gas chromatography and sodium pentachlorophenoxide with methylene blue.The database was established after the initial data was input into the computer with Excel 2000 and the concentration of the indexes was calculated and verified. The data was processed with software of SPSS for windows 11.0, EPI 6.0, SAS 6.12, Matlab6.1 and Maplnfo6.0. Statistical methods included the trend surface analysis of the incidence rates, Wilcoxon signed rank test and Spearman's rank correlation for the contents of the indexes in rice and soil, chi-square test for the incidence rates of the towns, and nonparametric tests for the difference of organochlorines among the towns. Spearman's rank correlation was used subsequently between the incidence rates of cancers and the contents of organochlorines. OR values were calculated and chi-square tendency test was performed at last.Results1. Trend surface analysis of the standardized incidence rates The incidence of colorectal cancer in Jiashan County had an obvious geographical distribution trends, with the summit in the middle towns and the decreasing tendency in the peripheral areas. Three spots with the lowest incidence lay on the east, northwest and southwest, while the incidence rates rose in the northeast. The incidence rate of breast cancer escalated gradually from the southwest to the northeast.2. Organochlorines in the soil and rice and the relationship between them The levels of HCH and DDT in the 143 rice samples and 145 soil ones collected were all in the limit amounts of our6country. The results of Wilcoxon signed rank test showed that the levels of P -HCH, total HCH and Na-PCP...
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