Study On The Genotoxicity Of The Organic Extracts In Soil And Vegetables Of The Pollution-free Vegetable Farms

Objective: In recent years, more and more attention has been paid to the potential hazardous health effects on human beings caused by persistent organic pollutants (POPs) in the environment. Some studies showed that intaking some kinds of POPs through drinking water and foods might be an important etiological factor for human malignant tumors. Food safety has become a matter of considerable public concern and pollution-free foods are getting more and more popular. To evaluate the genotoxicity of organic pollutants in the soil of pollution-free vegetable farms and the possibility of potential hazardous health effects on human beings induced by the organic pollutants in the soil through vegetable's absorption, the mutagenicity of the organic extracts (OEs) in the soil and vegetable samples collected from two pollution-free vegetable farms and a sewage irrigation area in Tianjin was determined. In order to investigate the pollution source of the organic pollutants in the soil, the mutagenicity of the irrigation water in the above areas was also monitored at the same time.Methods: (1) The irrigation water samples were collected from 2 pollution-free vegetable farms (Farm A and Farm B) and a sewage irrigation area. The Vicia faba root-tips were respectively treated with original water samples, 1/2,1/4,1/8 diluted water samples (diluted by distilled water), distilled water (negative control) andcyclophosphamide (positive control). The mutagenicity of the irrigation water samples was determined by micronucleus test of Vicia faba root-tip cells. (2) The soil samples of Farm A and Farm B were collected in winter and summer respectively and the soil sample of the sewage irrigation area was collected in winter. The organic compounds in the soil samples were extracted using organic solvent (benzene/methanol=4/l) and dissolved in DMSO after vacuum drying. (1) Kunming mice were exposed to OEs at the doses of equivalent to 30 ,15 ,7.5 and 3.75 g/kg(bw) soil respectively through peritoneal injection. The negative and positive control group was administered with 10ml/kg DMSO and 40mg/kg cyclophosphamide (CP) respectively. The effects of OEs on chromosomal damage and DNA damage were detected by mice bone marrow polychromatophilic erythrocyte (PCE) micronucleus test and un-fluorescent staining comet assay of mice peripheral blood lymphocytes. (2) Cultured the Chinese hamster lung (CHL) fibroblast were treated with 0.06, 0.030, 0.015g/ml culture media soil of OEs with and without S9 mixture (+ S9) respectively. The hgprt gene mutation assay and cytokinesis-block micronucleus test of CHL cells were carried out to assess the effects of OEs on gene mutation and chromosomal damage in vitro. (3) The vegetable samples were collected from the pollution-free vegetable farms and the sewage irrigation area and the organic compounds were extracted. Kunming mice were administered with OEs at the doses of equivalent to 20, 10, 5, 2.5g /kg (bw) vegetable respectively through peritoneal injection. The frequency of micronuclei of mice bone marrow PCE was examined.Results: (1) The micronucleus rates of Vicia faba root-tip cells in all dose groups treated with surface water of Farm A were significantly higher than those of thenegative control group (P<0.01 and P<0.05), while the micronucleus rates of Vicia faba root-tip cells treated with shallow well water sample of Farm A and deep well water of Farm B showed no significant differences compared to the negative control group (P>0.05). The frequencies of micronuclei of Vicia faba root-tip cells in all dose groups treated with sewage water sample collected from sewage irrigation area were significantly higher than those of the negative control group (P<0.01andP<0.05).(2) The frequency of micronuclei in PCE cells of mice exposed to 30g/kg OEs of Farm A summer soil sample was significantly higher than that of the negative control group (0.01