Ecological Risk Assessment Of Endocrine Disrupting Effects In Agricultural Soils Across China

Soil is an important reservoir for various contaminants.Problems aroused from contaminated soils are an important issue which deleteriously affected ecological safety and public health by complex mixtures of both known and unknown contaminants.At present,most ecological risk assessments of contaminants in soil are through routine chemical analyses that are only included known compounds,and no account is taken for the biological effects such as endocrine disrupting properties.However,most toxic compounds in soil are unknown,and the actual ecological and healthy risk caused by them are the results of chronic and low-dose exposure.The application of in vitro bioassays to determine the total toxic effects of the mixtures of both known and unknown contaminants can provide an adequate assessment of soil pollution.Our previous studies have shown that many persistent organic pollutants such as organochlorine pesticides?OPs?,polychlorinated biphenyls?PCBs?,polycyclic aromatic hydrocarbons?PAHs?,and phthalates?PAEs?were usually detected in agricultural soils across China.These pollutants have been identified as endocrine disrupting chemicals?EDCs?by interfering with steroid hormone receptors,resulting in hormone-like activity or anti-hormone activity.Steroid hormone receptors include estrogen receptor?ER?,androgen receptor?AR?,progesterone receptor?PR?,glucocorticoid receptor?GR?and mineralocorticoid receptor?MR?,which regulate a large number of physiological processes in human and wildlife equipped with the corresponding steroid hormones.It has been reported that a large number of EDCs can interact with ER and AR,while there are few studies regarding the interference of EDCs with PR,GR and MR.Steroid hormone receptors are the potential targets for many unknown contaminants in the soil environment.A battery of bioassays can be used to comprehensively assess the ecological risk of the EDCs pollution in soil.In this study,122 surface soil samples were collected from 31 provinces or regions of China.Organic matters in soil were extracted by Soxhlet method.The total hormonal activities of complex mixtures in agricultural soils ectracts were measured by dual luciferase reporter gene assays for detecting ER,AR,PR,GR and MR agonistic/antagonistic effects.The results showed that:?1?A total of 79%soil extracts had estrogenic activity and the estradiol equivalent?EEQ?ranged from 0 to 7.34 ng EEQ kg^-1 soil?d.w.?with an average of 1.94 ng EEQ kg^-1 soil?d.w.?.The estrogenic activities of soil samples in the northeast,north and southeastern parts of China were high.But only 16%of the soil extracts had anti-estrogenic activities.The tamoxifen equivalent?ER antagonist,TEQ?of soil samples was from 0 to 1535.71?g TEQ kg^-1 soil?d.w.?,with an average of 28.37 ?g TEQ kg^-1 soil?d.w.?.The results showed soil samples from Guizhou,Shanxi,Tibet had significantly high anti-estrogenic activities.?2?A total of 30%soil extracts had androgen-like activities,and the dihydrotestosterone equivalent?DEQ?ranged from 0 to 105.68 ng DEQ kg^-1 soil?d.w.?with an average of 6.88 ng DEQ kg^-1 soil?d.w.?.Soil extracts of Shandong,Zhejiang,Yunnan showed relatively high androgen-like activities.A total of 54%soil extracts showed anti-androgenic activities,and the range of flutamide equivalent?AR antagonist,FEQ?was 0 to 410.17 ?g FEQ kg^-1 soil?d.w.?,with an average of 141.01 ?g FEQ kg^-1 soil?d.w.?.The soil samples from the central,southeastern coastal and southwestern parts of China had high anti-androgenic activities.?3?A total of 32%soil extracts had progesterone activities,and the progesterone equivalent?PEQ?ranged from 0 to 2070.28 ng PEQ kg^-1 soil?d.w.?with an average of 43.10 ng PEQ kg^-1 soil?d.w.?.Among all the samples,the soil extract of Zhangzhou of Fujian showed very high progestin-like activity.A total of 73%soil extracts had anti-progestin activities,and the mifepristone equivalent?PR antagonist,REQ?ranged from 0 to 12.58 ?g REQ kg^-1 soil?d.w.?,the average value was 2.65 ?g REQ kg^-1 soil?d.w.?.Except for Liaoning,Tianjin and Xinjiang,anti-progesterone activities were very commonly identified in the soil samples across China.?4?A total of 35%soil extracts had glucocorticoid activities.Hydrocortisone equivalent?HEQ?ranged from 0 to 148.15 ng HEQ kg^-1 soil?d.w.?,with an average of 18.31 ng HEQ kg^-1 soil?d.w.?.The soil samples from Shanghai,Jiangsu and Liaoning showed significantly high glucocorticoid-like activities.A total of 59%soil extracts had anti-glucocorticoid activities.Mifepristone equivalent?GR antagonist,REQ?ranged from 0 to 12.26 ?g REQ kg^-1 soil?d.w.?,and the average value was 3.23 ?g REQ kg^-1 soil?d.w.?.The anti-glucocorticoid activities of the southern soil samples were higher than that in the northern,and the eastern were higher than the western.?5?A total of 72%and 78%soil extracts had mineralocorticoid-like and anti-mineralocorticoid activities,respectively.The aldosterone equivalent?AEQ?ranged from 0 to 25.64 ng AEQ kg^-1 soil?d.w.?,and the average activity of soil extracts was 1.82 ng AEQ kg^-1 soil?d.w.?.The spironolactone equivalent?MR antagonist,SEQ?ranged from 0 to 87.7?g SEQ kg^-1?d.w.?,and the average anti-mineralocorticoid activity was 27.82?g SEQ kg^-1?d.w.?.Both the mineralocorticoid-like and anti-mineralocorticoid activities were widespread in soil samples throughout the country.In summary,we used a battery of bioassays to screen the total endocrine activities of soil extracts at a national scale,which can provide information on the integrated distribution patterns of EDCs and their adverse impact on ecosystems and human.