| Objectives:The purpose of this study was to research the damage effect of Salmonella typhimurium TA1535/PSK1002 on DNA which induced by the organic extracts of drinking water from the waterworks in three northern cities by using SOS/umu test;to assess the genotoxicity of the organic extracts,and predict the carcinogenic risk of drinking water;to provide the experimental basis for the study of puting this test as one of the drinking water genotoxicity testing method of in vitro into the drinking water standard management.Methods:The water samples including the source water,finished water and peripheral water were collected from the waterworks in three northern cities,which were marked as city A,city B and city C;The organic pollutants in water samples were enriched by HLB solid phase extraction column and acetone elutriant;to set up the exposure dose equal to the raw water of 2000 mL,1000 mL,500 mL,200 mL,100 mL,50mL,and to assay the cytotoxicity and genotoxicity by using SOS/umu test;to evaluate the cytotoxicity and genotoxicity of organic extracts from water samples by calculate the bacterial growth rate（G）and induction ratio（IR）;to calculate the equivalent concentration of organic extracts of water samples was equivalent to the 4-NQO and the carcinogenic risk index,and to predict the carcinogenic risk of drinking water.Results:（1）The water samples in the high dose were showed significant cytotoxicity,the dose which was equal to the raw water of 2000 mL,1000 mL,500 mL,the results of the water samples exposed at low doses（equivalent to the raw water of 200 mL,100 mL,50 mL）as follows:the source water and finished water in city A showed a significant genotoxicity under the condition of absence of S9;the water samples of the city B in the low dose didn’t showed a significant genotoxicity under the two conditions;the peripheral water of the first waterwork and the source water,finished water and peripheral water of the second waterwork in city C showed a significant genotoxicity under the condition of absence of S9;the peripheral water of the first waterwork,the source water and peripheral water of the second waterwork and the finished water of the third waterwork in city C showed a significant genotoxicity under the condition of adding S9.（2）When the carcinogenic risk was 10-6,the calculation of the equivalent concentration of 4-NQO was 0.110μg·L-1,the value set carcinogenic risk prediction benchmark value of genetic toxicity to water safe to drink..According to the organic extracts of water equivalent concentration equivalent to 4-NQO and carcinogenic risk index（P）,the results showed that the water samples in the city A and city B and city C were all within the control standard(10-6-10-4).The 4-NQO equivalent concentration of the source water,finished water and peripheral water of the waterwork in city A were lower than the baseline value,and The 4-NQO equivalent concentration of the source water and finished water of the waterwork in city B were lower than the baseline value,and in the city C,expect the peripheral water of the third waterwork,the 4-NQO equivalent concentration of other water samples in the city C werw higher than the baseline values except for the peripheral water of the third waterwork.Conclusion:（1）Because of its simple operation process,low requirement for aseptic operation,short experimental period,good reproducibility,high sensitivity in detecting the genetic toxicity of organic extracts of drinking water,the SOS/umu test can be applied as a rapid and effective tool for the emergency water pollution incidents,and conducted the cancer risk assessment on the samples of water with the 4-NQO equivalent concentration was feasible.（2）The results of SOS/umu test showed that the genotoxicity of water organic extract from city A has a certain degree,and the genotoxicity was strengthening after chlorination;organic pollutants in water mainly by direct carcinogens,it can cause DNA damage without require metabolic activation;the water samples of the city B didn’t showed a significant genotoxicity;the genotoxicity of water organic extract from city C has a certain degree,the genetic toxicity of the second and third waterwork was:source water>finished water>peripheral water,the genetic toxicity of peripheral water is greater than the source water and finished water in the first waterwork.（3）According to 4-NQO equivalent concentration,the carcinogenic risk of the water samples which from city A,city B and city C all could be accepted,and the carcinogenic risk of the water samples which from city A was lower than that of the water samples which city B and city C. |
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