Aquatic toxicity of di (2-eihylhexyl) phthalate to duckweeds

This study is concerned with the effects of di （2-ethylhexyl） phthalate （DEHP） on two kinds of duckweeds （Spirodela polyrhiza and Lemna minor）.The results indicate that DEHP has aquatic toxicity to Spirodela polyrhiza at 0.4 mg/L and to Lemna minor at over 0.1 mg/L by changing their physiologic-biochemical characteristics.The contents of duckweed chlorophyll and soluble protein decrease with increasing DEHP concentration after 7 d of exposure.DEHP shows the stimulating role in catalase （CAT） and superoxide dismutase （SOD） systems at relative low levels.At 0.01 mg/L and 0.005 mg/L,SOD activities of Spirodela polyrhiza and Lemna minor reach their peak values respectively,while CAT activity reaches its maximum value at 0.05 mg/L and 0.01 mg/L.When DEHP levels are too high,the protection enzyme system would be destroyed and plant growth is inhibited.The analysis of malondialdehyde （MDA） and Fourier transform infrared spectroscopy manifest that DEHP could affect the tested duckweeds by destroying its cell membranes,and Spirodela polyrhiza is more resistant to DEHP exposure than Lemna minor.

Structural Characterization and Aquatic Toxicity Prediction of Esters

Based on the three-dimensional structures of the compounds,the structures of 48 ester compounds were expressed parametrically.Through multiple linear regression and partial least-squares regression,the relationship models between ester compound structures and aquatic toxicity log(1/IGC50)were established.The correlation coefficients(R2)of the models were 0.9974 and 0.9940,and the standard deviations(SD)were 0.0469 and 0.0646,respectively.The stability of the models was evaluated by the leave-one-out internal cross-test.The correlation coefficients(RCV2)of the models of interactive tests were 0.9939 and 0.8952,and the standard deviation(SDCV)was 0.0715 and 0.0925,respectively.The external samples were used to test the predictive ability of the models,and the correlation coefficients(Rtest2)of the external predictions were 0.9955 and 0.9955,and the standard deviations(SDtest)were 0.0720 and 0.0716,respectively.The molecular structure descriptors could successfully represent the structural characteristics of the compounds,and the built models had good fitting effects,strong stability and high prediction accuracy.The present study has a good reference value for the study of the structure-toxicity relationship of toxic compounds in the environment.

Next generation per-and poly-fluoroalkyl substances:Status and trends,aquatic toxicity,and risk assessment

Widespread application of poly-and per-fluoroalkyl substances(PFAS)has resulted in some substances being ubiquitous in environmental matrices.That and their resistance to degradation have allowed them to accumulate in wildlife and humans with potential for toxic effects.While specific substances of concern have been phased-out or banned,other PFAS that are emerging as alternative substances are still produced and are being released into the environment.This review focuses on describing three emerging,replacement PFAS:perfluoroethylcyclohexane sulphonate(PFECHS),6:2 chlorinated polyfluoroalkyl ether sulfonate(6:2 Cl-PFAES),and hexafluoropropylene oxide dimer acid(HFPO-DA).By summarizing their physicochemical properties,environmental fate and transport,and toxic potencies in comparison to other PFAS compounds,this review offers insight into the viabilities of these chemicals as replacement substances.Using the chemical scoring and ranking assessment model,the relative hazards,uncertainties,and data gaps for each chemical were quantified and related to perfluorooctane sulfonic acid(PFOS)and perfluorooctanoic acid(PFOA)based on their chemical and uncertainty scores.The substances were ranked PFOS>6:2 Cl-PFAES>PFOA>HFPO-DA>PFECHS according to their potential toxicity and PFECHS>HFPO-DA>6:2 Cl-PFAES>PFOS>PFOA according to their need for future research.Since future uses of PFAS remain uncertain in the face of governmental regulations and production bans,replacement PFAS will continue to emerge on the world market and in the environment,raising concerns about their general lack of information on mechanisms and toxic potencies.

Influence of dissolved organic carbon on multimedia distribution and toxicity of fipronil and its transformation products in lotic waterways

Environmental fate and ecological impacts of fipronil and its transformation products(FIPs)in aquatic environment have caused worldwide attention,however,the influence of dissolved organic carbon(DOC)on multimedia distribution,bioavailability,and toxicity of FIPs in field waterways was largely unknown.Here,we collected 11 companion water and sediment samples along a lotic stream in Guangzhou,South China.FIPs were ubiquitous with total water concentrations ranging from 1.22 to 43.2 ng/L(14.8±12.9 ng/L)and fipronil sulfone was predominant in both water and sediment.More than 70%of FIPs in aqueous phase were bound to DOC and the KDOC values of FIPs were approximately 1–2 orders of magnitude higher than K_(d-s)/K_(OC),emphasizing the significance of DOC in phase partitioning and transport of FIPs in aquatic environment.Water and sediment samples were more toxic to Chironomus dilutus than Hyallela azteca,and FIPs(especially fipronil sulfone)pronouncedly contributed toxicity to C.dilutus.Toxic units(TU)based on freely dissolved concentrations in water determined by solid phase microextraction significantly improved toxicity estimation of FIPs to the invertebrates compared to TUs based on aqueous concentrations.The present study highlights the significance of DOC association on fate and ecological risk of hydrophobic insecticides in lotic ecosystem.

Pharmaceutical compounds in aquatic environment in China： locally screening and environmental risk assessment

An environmental risk assessment was performed for pharmaceutical compounds present in the aquatic environment of China. Predicted environmental concentration （PEC） of the compounds were calculated according to European Medicines Evaluation Agency （EMEA） guidelines. Available ecotoxicological data compromised by applying a very conservative assessment factor （AF） were employed to calculate the predicted noeffect concentration （PNEC）. The screening principle and the risk assessment were based on risk quotient （RQ）, which derived from the PEC and related PNEC values. PEC results indicated that all the compounds except sulfadimethoxine and levocamitine, should carry out phase II risk assessment in EMEA guideline. RQ values suggested that more than 36 pharmaceuticals may be imposed health threats to the aquatic environment; especially the antibiotic therapeutic class including amoxicillin, sulfasalazine, trimethoprim, oxytetracycline and erythromycin showed high RQ values. These substances with high RQ value （RQ≥ 1） were regarded as top- priority pharmaceuticals for control in the aquatic environment of China. However, the antibiotic substances which had low risk quotient （RQ 〈 1）, should be reassessed by its potentially induced resistance under low concentration in future.

Endocrine disruptors in teleosts:Evaluating environmental risks and biomarkers

Endocrine disruptors(EDs)are synthetic or natural chemical molecules occurring in environment that have the potential to impart adverse effects on homeostasis of endocrine axis leading to neurological,developmental,immunological and reproductive disarray at organismal level.A wide range of structurally diverse EDs such as,sex-steroid hormone mimics,pesticides and fertilizers,prevail in the environment originating from waste of industries,pharmaceutics,sewage treatment plants and agriculture.In addition,some metals,such as Cu,Hg and Zn,have endocrine disrupting potency in their metallic as well as synthesized nano-particulate forms.There is an increasing concern in research for the plausible threat posed by EDs that can disrupt the endocrine system in aquatic fauna as these compounds are frequently discharged or run-off into water stream.Fishes are well known bio-indicators to understand toxicity of EDs as they are vulnerable to endocrine disruption.Furthermore,EDs have the potential to affect fish-feeding higher vertebrates including mammals and subsequently human,as they make their way up on the food web pyramid due to biomagnification.In light of this,several observations suggesting adverse effects of EDs and the mechanism contributing to endocrine disruption in fish are discussed extensively in this review.This article highlights the necessity to choose a credible model for assessing the toxic effects exerted by EDs.Furthermore,the toxic effects of EDs will be comprehensively reviewed with reference to sexual plasticity,neuroendocrine mechanisms,thyroid and immune modulation,gonadal development and maturation as well as changes in transcriptome/genome profile using fish models to imply ED-induced aquatic pollution in a larger perspective.For decades now,studies on EDs have challenged traditional concepts in toxicology to develop new molecular markers to improve methodologies and to assess the ecological risks associated with field conditions.In this regard,it is imperative to highlight the development of modern diagnostic tools including biosensors to monitor the inadvertent usage of EDs and the resultant environmental risks.Lastly,current limitations in knowledge along with future research perspectives in the field are also highlighted in this article.