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The single toxicity of diethylstilbestrol (DES) and beta-estradiol 17-valerate (EV) and the joint toxicity of their binary mixtures in equiconcentration to the proliferation of MCF-7 cells were investigated, respectively. Additive index (AI) method was adopted to evaluate the joint toxicity effect. At the same time, 3 x 3 factorial experimental design was used to verify the joint toxiciy types derived from equiconcentration of DES and EV. The results show that the EC50 values of single EV and DES for 24, 48 and 72 h are 6.02, 0.40 and 0.33 nmol x L(-1) and 5.90, 6.98 and 2.90 nmol x L(-1), respectively. The EC50 values of the binary mixtures of DES and EV for 24, 48 and 72 h are 2.33, 0.71 and 0.39 nmol x L(-1). The binary joint effects of DES and EV for 24 h were synergistic, and the joint effects of DES and EV for 48 and 72 h were antagonistic. But synergistic and antagonistic effects are not strong; their values can be found close to the values of additive effects. Factorial experiment results show that combined effects of DES and EV to proliferation of MCF-7 cells for 24, 48 and 72 h three exposure periods are additive effect types. The consistent joint combined effect types can be drawn from both factorial experimental design and equiconcentration ratio of DES and EV to the proliferation of MCF-7 cells. However, the factorial experimental design is simpler and more convenient, and can avoid unnecessary mistakes due to the derivation of EC50 values.

Predicted no-effect concentration (PNEC) is the key for ecological risk assessment and has become a focus of the study. Generally, extrapolation was used to derive PNEC values by different evaluation approaches according to results of single species toxicity test. However, PNEC values were different for the same toxicity data for the same chemicals if extrapolation methods were different. To evaluate PNEC values derived by different assessment methods, PNEC values of pentachlorophenol (PCP) were calculated using three different approaches, i. e. point estimation, statistical evaluation as well as interval evaluation. At the same time, the main factors controlling PNEC values were analyzed. The results showed that PNEC values for PCP by different assessment factors were 0.420 microg x L(-1) for acute toxicity data and 0.500 microg x L(-1) for chronic toxicity data, respectively. The PNEC values for PCP by statistical evaluation were 10.1 microg x L(-1) for probit unit and 8.10 microg x L(-1) for logit unit. The values derived by interval evaluation were 6.00 microg x L(-1) for PNEC-L95% and 11.8 microg x L(-1) for PNEC-L50%, respectively. PNECs obtained by the point estimation were the lowest and lower one order of magnitude than the PNEC values obtained by the other two methods. The PNEC values derived by the statistical assessment and interval evaluation were very similar. In addition, toxicity data type and statistical models have little effect on PNEC value for PCP with a great body of toxicity data. The results indicated that statistical evaluation and interval evaluation methods should be selected to derive PNEC values for well-studied substances like PCP, while point estimation should be used in preliminary screening assessment of chemicals to determine whether the effect is of concern.

In recent years, water pollution accidents resulting in acute aquatic ecological risk and security issues become a research focus. However, in our country, the surface water quality standards and drinking water health standards were used to determine the safety of waters or not in pollution incidents due to lacking safety effect threshold or risk value for protection of aquatic life. In foreign countries, although predicted no effect concentration (PNEC) or risk value (R) of pollutants were provided for protection of aquatic organisms, the PNECs or risk values were derived based on long-term exposure toxicity data NOECs (no observed effect concentrations) and lack of short-term exposure risk or threshold values. For the short-term and high dose exposure in pollution incident, ecological risk assessment methods were discussed according to the procedures of the conventional ecological risk assessment and the water quality criteria establishment of the U.S. EPA for the protection of aquatic organisms in short-term exposure, and had a case study. At the same time, we provide some suggestions for the establishment of ecological risk assessment system in water pollution incidents.

To investigate the pollution levels, occurrence and distribution of estrogens, six estrogens in the surface sediments of Wenyuhe River were analyzed quantitatively by GC/MS following ultrasonicated extraction including diethylstilbestrol (DES), estrone (E1), beta-estradiol(E2), 17alpha-ethynylestradiol(EE2), estriol(E3), and beta-estradiol 17-valerate (EV). Six estrogen concentrations ranged from 0.39-36.6 ng/g and the mean concentration was 10.2 ng/g. E1 and E2 were detected in all samples while other four estrogens were only detected in a few samples, and the concentrations of El was higher than those of E2 in all samples. There were significant correlation relationships between the concentrations of six estrogens and the concentrations of total organic carbon (TOC), total phosphorus (TP) and total nitrogen (TN) in sediments. Considering also the characteristics of the sampling locations and pollution sources, six estrogens should come from wastewater discharges along the river and the contaminated tributaries. The contents of estrogens in this area are medium or slightly higher level compared with other areas abroad.

The toxicity to Photobacterium phosphoreum of different mixture systems of sodium dodecyl sulfate (SDS) and three substituted aromatic compounds according to equiconcentration ratio of 1 : 1, as well as individual toxicity, were determined respectively. The joint toxicity was evaluated by toxicity unit (TU), additive index (AI), similarity parameter (lambda), and mixtures toxicity index (MTI). Four evaluating methods were compared and the modes of joint action of different systems were analyzed primarily. The coherent results were obtained from four different evaluating methods. Conclusions can be drawn that the binary joint effects of phenol and toluene mixed with SDS showed weak synergistic, while the other joint effects of SDS and substituted aromatic compounds were antagonistic. Of the evaluating methods, Toxic Unit is most sensitive with higher value of its parameter. Mechanisms of joint toxicity action could be discussed according to luminescence principle of Photobacterium phosphoreum and molecule structures of the mixture components.