Acute and joint toxicity of three agrochemicals to Chinese tiger frog （Hoplobatrachus chinensis） tadpoles

We studied acute and joint toxicity of three different agrochemicals （chlorantraniliprole, flubendiamide-abamectin and penoxsulam） to Chinese tiger frog （Hoplobatrachus chinensis） tadpoles with the method of stability water tests. Results showed that the three agrochemicals increased tadpole mortality. For acute toxicity, the LC50 values after 24, 48 and 72 h of chlorantraniliprole, flubendiamide-abamectin and penoxsulam exposure were 5.37, 4.90 and 4.68 mg/L; 0.035, 0.025 and 0.021 rag/L; 1.74, 1.45 and 1.29 mg/L, respectively. The safety concentrations （SC） of chlorantraniliprole, fiubendiamide-abamectin and penoxsulam to the tadpoles were 1.23, 0.30 and 0.003 mg/L, respectively. Based on these findings, chlorantraniliprole and penoxsulam were moderately toxic, while flubendiamide-abamectin was highly toxic. All pairwise joint toxicity tests showed moderate toxicity. The LCs0 values after 24, 48 and 72 h of exposure were 7.08, 6.61 and 6.03 mg/L for chlorantra- niliprole＋penoxsulam, with corresponding values of 2.455, 2.328 and 2.183 mg/L for chlorantraniliprole＋flubendiamide-abamectin, and 1.132, 1.084 and 1.050 mg/L for penoxsulam＋flubendiamide-abamectin, with safe concentrations of 1.73, 0.63 and 0.30 mg/L, respectively. For toxic evaluations of pairwise combinations of the three agrochemicals, only the joint toxicity of chlorantraniliprole and flubendiamide-abamectin after 24 h was found to be synergistic, whereas all other tests were antagonistic. Our findings provide valuable information on the toxic effects of agrochemicals on amphibians and how various types of agrochemicals can be reasonably used in agricultural areas.

Quantitative structure-activity relationships for joint toxicity of substituted phenols and anilines to Scenedesmus obliquus

There are often many chemicals coexisting in aquatic ecosystems, and few information on the joint toxicity of a mixture of organic pollutants is available at present. The 48-h toxicity of substituted phenols and anilines and their binary mixtures to Scenedesmus obliquus was determined by the algae inhibition test. The median effective inhibition concentration EC50 values for single compounds and EC50mix values for coexistent compounds were obtained. The n-octanol/water partition coefficient （logPmlx） and the frontier orbital energy gap （AEmlx） for mixtures were calculated. The following two-descriptor quantitative structure-activity relationships （QSARs） models were developed to predict single toxicity and joint toxicity respectively： log（1/ECs0） = 0.445logP - 0.801AE ＋ 9.501 （r2 = 0.876） and log （1/EC50mix） = 0.338logPmix- 0.492AEmix ＋ 6.928 （r^2 = 0.831）. The two equations were found to fit well. In addition, the model derived from the structural parameters of single components in binary mixtures log（1/EC50mix） = 0.2221ogP - 0.277AE ＋ 5.250 （r^2 = 0.879） can be used successfully to predict the toxicity of a mixture.

Joint Toxicity of Beauveria bassiana and Two Insect Growth Regulators on Beet Armyworm,Spodoptera exigua(Hübner)

Joint toxicity of Beauveria bassiana and two insect growth regulators, methoxyfenozide and hexaflumuron, on beet annywonn larvae, Spodoptera exigua （ Htthner）, were investigated. An obvious synergism effect of the two insect growth regulators with B. beauveria was observed. When the insect growth regulators at LC50 concentrations （25 × 10^-6 g/L for methoxyfenozide and 1 000 × 10^ -6 g/L for hexaflumuren） were mixed with B. bassiana at the volume ratio of 4： 1, the mixtures achieved the best efficacy. The co-toxicity co-efficient （CTC） of methexyfenozide and B. bass/ana was 285, and that of hexaflumuron and B. bass/ana was 208. Scanning electron microscope observation of the longitudinal section of S. exigua revealed obviously different patterns of integument in different treatment groups.

Joint toxicity of methamidophos and cadmium acting on Abelmoschus manihot

Joint toxicity of methamidophos and cadmium(Cd) on the ornamental Abelmoschus manihot was firstly examined and compared with single-factor effects of the two pollutants using ecotoxicological indexes including the inhibitory rate of seed germination, root elongation and inhibitory concentration 50%(IC_ 50). The results indicated that methamidophos and Cd had unobvious(p>0.05) effects on seed germination of the ornamental. There were significant(p<0.05) inhibitory effects of Cd on root elongation of the tested plant. When the concentration of added Cd was low(<20 mg/L), significant antagonistic effects on root elongation were observed. And synergic effects were observed when Cd was added in high dose(>20 mg/L). However, the analysis of joint effects indicated that there were antagonistic effects between Cd and methamidophos under all the treatments. At the high concentration of Cd, joint toxicity of methamidophos and Cd was more dependent on concentration of Cd.

Evaluation and Prediction of Joint Toxicity of Aniline and Its Derivatives to Photobacterium Phosphoreum

The single toxicity of aniline and its derivatives and the joint toxicity of the binary mixtures of aniline and each of its derivatives with the toxic unit ratios of 1∶1, 1∶4, 4∶1 to photobacterium phosphoreum were determined, respectively. The toxic unit and the additive index were used to evaluate the joint toxicity. The result shows that the joint toxicity of each of the binary mixtures of aniline and each of its derivatives is mainly simple addition of the toxicities of the two compounds. On this basis, the QSAR equation that was built from the single toxicity of aniline was used to predict the toxicity of the derivatives of aniline in the mixtures. Good agreement between the predicted and experimental values was found with R 2=0.921.

Joint Toxicity Determination of Clopyralid,Picloram and Benazolin Mixtures on Broad-leaved Weed Lapsana apogonoides Maxim.in Rape Fields

[Objectives]This study was conducted to investigate the compounding of three herbicides:clopyralid,picloram and benazolin,so as to improve the effectiveness of herbicides.[Methods]With Lapsana apogonoides Maxim.as the target and clopyralid,picloram and benazolin as the test agents,seven gradient concentrations were set up to determine the joint toxicity of the three agents.[Results]When the compounding ratio of picloram,clopyralid and benazolin was 2∶1∶6,the maximum co-toxicity coefficient was 290.0.[Conclusions]The compounding of picloram,clopyralid and benazolin has a significant synergistic effect on L.apogonoides,which reduces production costs and environmental pressure,providing technical support for the effective control of broad-leaved weeds such as L.apogonoides.

Studies on acute toxicity of three heavy metal ions to Artemia

Studies on acute toxicity of Cu2+,Mn2+and Zn2^to Artemianauplii(36h)and adults were carried out at15±3°C in the natural seawater where salinity is30using single-factor acute toxicity;on this basis,equi-toxicity test was used to evaluate the effect of joint toxicity of Cu2+,Mn2+and Zn2+to Artemia nauplii(36h)in the same conditions.Results show that Artemia has different tolerances for the three heavy metal ions when it is in different growth period,and the interaction of heavy metal ions varied with growth period,adults are more sensitive of the three heavy metals;The48h LC50of these three heavy metal to the Artemia nauplii is4.0,27.19and115.95mg/L,and to the adults is1.31,6.86and34.23mg/L;the order of toxicity of cuprum,manganese and zinc for Artemia nauplii and adults was Cu2^>Mn2+>Zn2+;the safe concentration of the three heavy metal ions(Cu2+,Mn2+and Zn2+)to Artemia nauplii(36h)and adults were0.4,2.72,11.6,0.13,0.69and3.42mg/L.The results of combined toxicity test showed that Cu-Mn,Cu-Zn and Mn-Zn were all antagonistic to the Artemia naupli.

Toxic Effects of Cd^(2+),Pb^(2+) and Hg^(2+) on Colpoda inflata

The toxic effects of heavy metal ions, Hg2＋, Pb2＋ and Cd2＋ on Colpoda inflata were studied, finding that the growth of C. inflata had been inhibited signifi- cantly under different concentrations of heavy metal ions. The acute toxicities of Cd2＋, Pb2＋ and Hg2＋ to C. inflata went in the order of Hg2＋, Pb2＋, Cd2＋. The results of joint toxicity showed that the types and magnitudes of joint actions were different at different solution compositions. The joint toxicity of Cd2＋ and Pb2＋ at the concentration proportion of 1：1 and toxic proportion of 1：1 were all antagonism. At the concentration proportion of 1：1, the joint toxicity of Pb2＋ and Hg2＋ was synergistic, and it changed from antagonism to synergistic at the toxic proportion of 1：1. The joint toxicily of Hg2. and Cd2＋ at the concentration proportion of 1：1 was synergistic, and it was antagonist at toxic proportion of 1：1. At the concentration proportion of 1：1：1, the joint toxicity of Cd2＋, Pb2. and Hg2＋ was synergistic, and it changed from antago- nism to synergistic under toxicity proportion of 1：1：1.

Polystyrene nanoplastics aggravated ecotoxicological effects of polychlorinated biphenyls in on zebrafish(Danio rerio)embryos

In view of the accumulation of nanoplastics(NPs)in the food chain of environment and animals,and the good adsorption properties of nano-plastics to toxic substances,it is necessary to explore the influence of NPs in living organisms.In this study,single and joint toxicological effects of polystyrene nanoplastics(PS-NPs,size 80 nm)and polychlorinated biphenyls(PCBs),were explored in freshwater aquatic animal model zebrafish(Danio rerio).Our study found that exposure to single PS-NPs induced mild acute toxicity,albeit the combined exposure of PS-NPs and polychlorinated biphenyls aggravated the toxicity of PCBs in a dose-dependent manner.Results from gene expression profiling showed that NPs exposure could activate detoxification process,resulting in a slight up-regulation of antioxidant genes(sod1,gstp1),bone development genes(bmp2,bmp4)and cardiac gene(tbx20);while PCBs suppressed the detoxification through down-regulation of these genes,and the addition of NPs will exacerbate the impact of PCBs on gene suppression.Importantly,the results of in vivo purification experiments found that NPs showed prolonged retention in liver,intestine and gills of zebrafish and they might have crossed biological barrier and accumulate in lipid-rich tissues and excretion does not appear as the significant pathway for their elimination.In conclusion,the toxic effects of polychlorinated biphenyls on chorionic protected embryos were not significant as zebrafish chorion plays an important role in resisting the invasion of pollutants;PCBs can seriously damage the bone and heart development of zebrafish,while the presence of NPs significantly enhanced the toxicity of PCBs in zebrafish,which is an alarming concern for growing NPs levels and ecological safety in aquatic environment.

Epidermal microorganisms contributed to the toxic mechanism of nZVI and TCEP in earthworms by robbing metal elements and nutrients

Disrupting effects of pollutants on symbiotic microbiota have been regarded as an important mechanism of host toxicity,with most current research focusing on the intestinal microbiota.In fact,the epidermal microbiota,which participates in the nutrient exchange between hosts and environments,could play a crucial role in host toxicity via community changes.To compare the contributions of intestinal and epidermal symbiotic microorganisms to host toxicity,this study designed single and combined scenarios of soil contamination[nano zerovalent iron(nZVI)and tris(2-chloroethyl)phosphate(TCEP)],and revealed the coupling mechanisms between intestinal/epidermal symbiotic bacterial communities and earthworm toxicological endpoints.Microbiome analysis showed that 15%of intestinal microbes were highly correlated with host endpoints,compared to 45%of epidermal microbes showing a similar correlation.Functional comparisons revealed that key species on the epidermis were mainly heterotrophic microbes with genetic abilities to utilize metal elements and carbohydrate nutrients.Further verifications demonstrated that when facing the co-contamination of nZVI and TCEP,certain symbiotic microorganisms became dominant and consumed zinc,copper,and manganese along with saccharides and amino acids,which may be responsible for the nutritional deficiencies in the host earthworms.The findings can enrich the understanding of the coupling relationship between symbiotic microorganisms and host toxicity,highlighting the importance of epidermal microorganisms in host resistance to environmental pollution.

Individual and joint toxic effects of cadmium sulfate and α-naphthoflavone on the development of zebrafish embryo

This paper aims to evaluate the individual and joint toxicities of cadmium sulfate （CdSO4） and α-naphthoflavone （ANF） in zebrafish embryos. As a result, CdSO4 caused both lethal and sub-lethal effects, such as 24 h post-fertilization （hpf） death and 72 hpf delayed hatching. However, ANF only caused sub-lethal effects, including 48 hpf cardiac edema and 72 hpf delayed hatching. Taking 24 hpf death and 48 hpf cardiac edema as endpoints, the toxicities of CdSO4 and ANF were significantly enhanced by each other. Consistently, both CdSO4 and ANF caused significant oxidative stress, including decreases in the reduced glutathione （GSH） level, inhibition of superoxide dis- mutase （SOD） activity, as well as increases in malondialdehyde （MDA） content in zebrafish embryos, but these mixtures produced much more significant alterations on the biomarkers. Co-treatment of CdSO4 and ANF significantly down-regulated the mRNA level of multidrug resistance-associated protein （mrp） 1 and cytochrome P450 （cyp） la, which constituted the protective mechanisms for zebraflsh embryos to chemical toxins. In conclusion, co-treatment of CdSO4 and ANF exhibited a much more severe damage in zebraflsh embryos than individual treatment. Meanwhile, production of oxidative stress and altered expression of mrpl and cypla could be important components of such joint toxicity.

Assessment of toxicity of two nitroaromatic compounds in the freshwater fish Cyprinus carpio

This study was conducted to evaluate the toxicological response ofp-nitrotoluene and p-nitroaniline to the key fish species, Cyprinus carpio. A freshwater fish bioassay based on the 96 h LC50 was used to estimate the single and joint toxicity of the two chemicals. The toxicity of p-nitrotoluene was greater than that of pnitroaniline based on 96 h LCso values of 40.74 mg.L^-1 and 48.99mg.L^-1, respectively. Both compounds had moderate toxicity toward Cyprinus carpio, and this toxicity increased with the exposure duration and con- centration. Binary mixtures of the compounds were more toxic than the individual compounds at 96 h, and they acted upon partial addition. When the exposure time was longer, the toxicity increased for mixtures of compounds with the same concentration or toxicity. The results of this study suggest that exposure to a combination of these chemicals would result in a higher environmental risk in aquatic systems than exposure to either compound alone. Further research is needed to investigate the combined effects and sublethal toxicity of p-nitrotoluene and p- nitroaniline, since they are both still used in China.

Ecotoxicological effects of polycyclic musks and cadmium on seed germination and seedling growth of wheat(Triticum aestivum)

Single and joint toxic effects of polycyclic musks including 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[g]-2- benzopyran （HHCB） and 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronapthalene （AHTN） and cadmium （Cd） on seed germination and seedling growth of wheat （Triticum aestivum） were investigated. The results showed that the toxicity sequence of HHCB toxic to wheat seed germination and seedling growth was similar to that of AHTN, that is, germination rate 〉 shoot elongation 〉 root elongation, while the toxicity of Cd was in the sequence of root elongation 〉 shoot elongation 〉 germination rate, according to the LC50 and EC50 values. It is suggested that polycyclic musks and Cd had different toxicological mechanisms. Root and shoot elongation of wheat might be good bioindicators for the contamination of polycyclic musks and Cd in soil. The mixture of polycyclic musks and Cd had synergistic effects on T. aestivum according to the equi-toxic mixture approach when root elongation was selected as the toxicological endpoint. Thus, the joint toxicity of HHCB and Cd was significantly higher than the single toxicity of HHCB or Cd, which was also confirmed by the EC50mix value of the mixture （EC50mix = 0.530 TUrnix）. The EC50mix value of the mixture of AHTN and Cd was 0.614 TUmix, which indicated that the mixture toxicity was strengthened when AHTN coexisted with Cd.

The toxic effects of three active pharmaceutical ingredients(APIs)with different efficacy to Vibrio fischeri

The environmental residues of active pharmaceutical ingredients(APIs)are associated with environmental risks and health problems,the influence to environment have become a matter of public concern.In this paper,the individual and joint toxicities to vibrio fischeri of three APIs,including ibuprofen,azithromycin,and triclosan were investigated.The EC50 endpoint values of the above tested APIs were 36.5×10^-5 mol L^-1,30.26×10^-5 mol L^-1,and 0.0155×10^-5 mol L^-1 respectively.It was indicated that the endpoint toxicities to vibrio fischeri for different mixtures are higher than those of the individual toxins.The joint toxicities of the multiple systems of three pharmaceuticals were evaluated by the additive index,toxicity unit,and mixed toxicity index methods.The consistent evaluation results were obtained.It was observed that antagonistic effects in binary and ternary systems were appeared different antagonistic strengths.It was deduced that different functional groups of the studied pharmaceuticals could affect the physiological and biochemical reaction processes of organisms.The obtained data of the acute toxicities of pharmaceuticals to vibrio fischeri can facilitate the evaluation of the environmental risks associated with emerging pollutants.