Effect of endocrine disruptor nonylphenol on physiologic features and proteome during growth in Arabidopsis thaliana

Nonylphenol and its derivatives: Environmental distribution, treatment strategy, management and future perspectives

In recent years, emerging pollutants, including nonylphenol (NP) and nonylphenol ethoxylate (NPE), have become a prominent topic. These substances are also classified as persistent organic pollutants. NP significantly affects the hormone secretion of organisms and exhibits neurotoxicity, which can affect the human hippocampus. Therefore, various countries are paying increased attention to NP regulation. NPEs are precursors of NPs and are widely used in the manufacture of various detergents and lubricants. NPEs can easily decompose into NPs, which possess strong biological and environmental toxicity. This review primarily addresses the distribution, toxicity mechanisms and performance, degradation technologies, management policies, and green alternative reagents of NPs and NPEs. Traditional treatment measures have been unable to completely remove NP from wastewater. With the progressively tightening management and regulatory policies, identifying proficient and convenient treatment methods and a sustainable substitute reagent with comparable product effectiveness is crucial.

Simple monitoring of endocrine-disrupting chemicals using transgenic Arabidopsis plants expressing medaka estrogen receptor

Endocrine-disrupting chemicals (EDCs) are widespread contaminants that severely affect the endocrine systems of living organisms. In addition to the conventional instrument-based approaches for quantifying organic pollutants, a monitoring method using transgenic plants has also been proposed. Plants carrying a recombinant receptor gene combined with a reporter gene represent a system for the easy detection of ligands that specifically bind to the receptor molecule. Here, the EDC detection sensitivity of transgenic Arabidopsis plants expressing the medaka (Oryzias latipes) estrogen receptor (mER) and green fluorescent protein (GFP) genes, was assessed. Four transgenic Arabidopsis lines, obtained by transformation with expression plasmids constructed using combinations of two types of the ligand-binding domains of mER, the DNA-binding domain of LexA and the transactivation domain of VP16 in the chimeric receptors, showed significant induction of GFP when germinated on a medium contaminated with 1 ng/mL 4-t-octylphenol (OP). The most sensitive XmEV19-2 plants detected 0.1 ng/mL OP and 1 pg/mL 17β-estradiol. GFP expression was suppressed by the insecticides imidacloprid and fipronil, whereas perfluorooctanesulfonic acid induced it at 0.1 ng/mL. Experiments with river water-based medium showed that XmEV19-2 can be used for monitoring polluted waters, detecting OP at concentrations as low as 5 ng/mL. Notably, XmEV19-2 showed a significant decrease in root length when grown on 0.1 ng/mL OP. mER transgenic plants can be a promising tool for simple monitoring of EDCs, without the need for extraction and concentration steps in sample preparation.

Single and mixture toxicity evaluation of three phenolic compounds to the terrestrial ecosystem

Endocrine-disrupting chemicals (EDCs) are primarily studied regarding endocrine-mediated effects in mammals and fish. However, EDCs can cause toxicity by mechanisms outside the endocrine system, and, as they are released continuously into soils, they may pose risks to terrestrial organisms. In this work, the plant Allium cepa and the earthworm Eisenia foetida were used as test systems to evaluate the toxicity and cyto-/geno-toxicity of three environmental phenols known as EDCs (Bisphenol A - BPA, Octylphenol - OP, Nonylphenol - NP). The tested phenols were evaluated in environmentally relevant concentrations (μg/L) and in single forms and mixture. BPA, OP, and NP did not inhibit the seed germination and root development in A. cepa in their single forms and mixture. However, all single forms of the tested phenols caused cellular and DNA damages in A. cepa, and although these effects persist in the mixtures, the effects were verified at lower levels. These phenols caused acute toxicity to E. foetida after 48 h of exposure and at both conditions evaluated (single forms and mixture); however, unlike A. cepa, in earthworms, mixtures and single forms presented the same level of effects, indicating that interspecies physiological different might influence the mixture toxicity. In summary, our results suggest that BPA, OP, and NP are toxicants to earthworm and cyto-/geno-toxicants to monocotyledonous plants at low concentrations. However, interaction among these phenols reduces the magnitude of their individual effects (antagonistic effect) in the plant test system. Therefore, this study draws attention to the need to raise knowledge about the ecotoxicity of phenolic compounds to help predict their ecological risks and protect non-target terrestrial species.

Occurrence, uptake, and health risk assessment of nonylphenol in soil-celery system simulating long-term reclaimed water irrigation

Reclaimed water (RW) irrigation provides an effective method to alleviate freshwater resources shortage. However, the residual endocrine disrupting chemicals in RW may cause potential risks to the environment and human body. Pot experiments were conducted to study the occurrence and environmental behavior of nonylphenol (NP) in soil-celery system simulating long-term RW irrigation, and exposure to NP was assessed to identify human health risks. Celery was grown on soil with different initial NP concentrations (0.126-22.9 mg·kg^-1) to simulate the different irrigation years. After harvest, the NP concentrations in roots, stems and leaves were 0.26-1.51, 0.21-0.45 and 0.33-0.74 mg·kg^-1, respectively. The NP concentrations in soil at depths of 5, 10 and 15 cm were 0.047-1.75, 0.088-1.77 and 0.048-1.07 mg·kg^-1, respectively. The results showed a limited NP enrichment capacity of celery and low residual rates of NP in soil-celery system, which were between 6.33% and 26.3%. Both the bioconcentration factors (BCFs) and the residual rates of NP decreased with the initial NP concentrations in soil. The total noncancer hazard quotients (HQs) for human exposure to NP from celery and soil had the order of 10^-4-10^-3, which was lower than the acceptable risk level of 1 and showed safe conditions under long-term RW irrigation.

Reduced phytotoxicity of nonylphenol on tomato (Solanum lycopersicum L.) plants by earthworm casts

Concentrations as high as thousands of milligrams per kilogram (dry weight) of nonylphenol (NP), an endocrine-disrupting chemical of great concern, have been reported in soil. Soil is considered one of the primary pathways for exposure of crop plants to NP. However, there have been few studies on the toxicity of soil NP to crop plants, especially with comprehensive consideration of the application of organic fertiliser which is a common agricultural practice. In this study, tomato plants were grown in soils treated with NP in the presence and/or absence of earthworm casts (EWCs). After four weeks, we tested the physiological and biochemical responses (accumulative levels of hydrogen peroxide (H₂O₂) and superoxide anion radicals (O₂-·), total chlorophyll content, degree of membrane lipid peroxidation, activities of defence-related enzymes, and level of DNA damage) and the changes in plant growth (elongation and biomass). The growth inhibition, reactive oxygen species (H₂O₂ and O₂-·) accumulation, decrease in chlorophyll content, increase in activity of defence-related enzymes (including superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, glutathione S-transferase and glutathione reductase), enhancement of membrane lipid peroxidation, and DNA damage in NP-treated seedlings were clearly reversed by the intervention of EWCs. In particular, the suppressed elongation, biomass, and chlorophyll content in tomato plants exposed to NP alone were significantly restored by EWCs to even greater levels than those of the undisturbed control. In other words, EWCs could efficiently invigorate the photosynthesis of crops via up-regulating the chlorophyll content, thereby overwhelming the NP stress on plant growth. Accordingly, except for reducing the bioavailability of soil NP as reported in our previous study, EWCs could also help crop plants to cope with NP stress by strengthening their stress resistance ability. Our findings are of practical significance for the formulation of strategies to relieve the negative effects of soil NP on crop growth.

Large-scale monitoring and ecological risk assessment of persistent toxic substances in riverine, estuarine, and coastal sediments of the Yellow and Bohai seas

The Yellow and Bohai seas comprise one of the most rapidly developing regions in the world, but efforts to assess coastal pollution by persistent toxic substances (PTSs) on wide spatial scale are lacking. The present study aimed to (1) measure the concentrations of PTSs, such as polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), and styrene oligomers (SOs) via large-scale sediment monitoring (total of 125 locations), (2) assess potential ecological risk of PTSs in sediments to coastal ecosystems, (3) estimate various sources and fresh inputs of PTSs, (4) determine distribution patterns of PTSs by human activities and land-use type, and (5) address decadal (2008-2018) changes in distributions of PTSs. The high concentrations of PAHs [> 7000 ng g^-1 dry weight (dw)] in sediments were detected in Nantong in the Yellow Sea of China (YSC) and Huludao and Qinhuangdao in the Bohai Sea (BS), whereas lesser concentrations (< 200 ng g^-1 dw) were detected in the Yellow Sea of Korea (YSK). We found relatively high concentrations of sedimentary APs and SOs in Nantong, Huludao, and Qinhuangdao from the YSC and BS regions, but corresponding concentrations were generally below < 100 ng g^-1 dw in other locations. Concentrations of PAHs at 38 locations (30% of YSC and BS) posed a potential risk to aquatic ecosystems, whereas relatively low risk concentrations occurred in all locations of YSK. The main source of PAHs (concentrated in YSC and BS) were by-products of diesel and gasoline combustion (42% of total concentration), whereas biomass combustion (24%) dominated in YSK. Fresh inputs of PTSs indicated that the generation and use of PTSs continue across all regions and locations. Among PTSs, concentrations of PAHs were significantly associated with location (p < 0.05) relative to land-use within a given region, whereas concentrations of APs and SOs showed no significant relationships (p > 0.05) among or within regions. Over time, concentrations of PAHs have generally declined, but sediment contamination has increased at some locations in China, with sources shifting from a mixture of PAHs types to those linked to diesel and gasoline combustion. Additional studies are needed on the fate and potential ecological risk posed by certain PTSs in hotspots. This is one of the first efforts providing backgrounds on PTS pollution in the large marine ecosystem of the Yellow and Bohai seas.

Occurrence, fate and toxic effects of the industrial endocrine disrupter, nonylphenol, on plants - A review

Nonylphenol (NP) and its detrimental effects on the environment, humans, wildlife, fish and birds is an increasingly important global research focus. The number of investigations on the toxicity and metabolic fate of NP in plants is however limited. This paper reviews the prevalence and source of NP in plants and the effect it has on its morphological, physiological and ultrastructural status. Fruit and vegetables have been found to contain levels of NP that is twenty-fold exceeding the no observable effect level (NOEL) of freshwater algae. Apart from the potential risk this poses to the health of consumers, it can overburden the plant's natural defence system, leading to growth disorders. Plants exposed to NP show signs of overall growth reduction, changes in organelle structure and oxidative damage. These adverse effects may exacerbate the food security dilemma faced by many countries and impede their progress towards attaining the sustainable development goals.

Distribution and ecological risk assessment of PEDCs in the water, sediment and Carex cinerascens of Poyang Lake wetland, China

Phenolic endocrine disrupting chemicals (PEDCs), such as 4-nonylphenol (NP), 4-t-octylphenol (OP), bisphenol A (BPA), and nonylphenol-di-ethoxylate (NP2EO), can cause feminization and carcinogenesis. This study assessed the distributions of NP, OP, BPA, and NP2EO in the water, sediment, and Carex cinerascens of Poyang Lake wetland. The four PEDCs were ubiquitous. The concentrations of NP and OP in the water and sediment of the wetland were significantly lower than those in other regions of China. Average BPA concentrations in the water, sediment, and Carex cinerascens samples were 40.49 ± 18.42 ng/L, 9.840 ± 3.149 ng/g, and 3.25 ± 1.40 ng/g, respectively; the BPA concentration in the water was similar to that of other rivers in China. Average NP2EO concentrations in the wetland were 3125.9 ± 478.1 ng/L, 650.0 ± 209.9 ng/g, and 275.8 ± 59.0 ng/g in the water, sediment, and Carex cinerascens samples, respectively. The predicted no-effect concentrations in sediment for NP, OP, BPA, and NP2EO were estimated to be 75.41, 45.25, 8.22, and 237.5 ng/g, respectively. The risk quotient (RQ) method was used to characterise the ecological risk from these PEDCs. A high ecological risk (RQ ≥ 1) from BPA was observed for 0%, 57.69%, and 5.00% of water, sediment, and C. cinerascens samples, respectively, while a high risk from NP2EO was observed for 71.43%, 96.15%, and 55.00% of samples. Ecological risk varied spatially. The high ecological risk from NP2EO in Poyang Lake wetland may be a result of non-point pollution from rural areas and sewage from Poyang Lake basin.

Physiological response of crop plants to the endocrine-disrupting chemical nonylphenol in the soil environment

Nonylphenols are endocrine-disrupting chemicals that are used in various industries and are constantly discharged into the terrestrial environment. However, there have been few studies on the phytotoxicity of this chemical in the soil environment. In this study, mung bean (Vigna radiata) and rice (Oryza sativa) were grown in soil containing nonylphenol for 14 and 21 days (reflecting acute and chronic exposure, respectively), and we evaluated physiological responses (chlorophyll content, photosynthetic activity, and stomatal opening size) as well as changes in plant growth (shoot growth and root development) in crop plants grown in soil containing nonylphenol. In mung bean, chlorophyll content and stomata size decreased by exposure to nonylphenol. The decrease in chlorophyll content was attributed to electrolyte leakage due to damage of membrane barrier with increase of cell permeability caused by nonylphenol. Moreover, necrosis of the leaves of mung bean was observed at 2000 mg/kg soil. In rice, shoot growth, chlorophyll content and root development were reduced by chronic exposure to nonylphenol at 2000 mg/kg. Although the exposure concentrations were higher and nonylphenols are non-persistent, their constant release into soil poses a risk to terrestrial ecosystems. Our findings provide information that can be useful for soil ecological risk assessment for nonylphenol in agricultural practices.

Occurrence and bioaccumulation of persistent toxic substances in sediments and biota from intertidal zone of Abu Ali Island, Arabian Gulf

North Abu Ali Island is contaminated by crude oil from exogenous sources with a variety of persistent toxic substances (PTSs) being input into intertidal sediments. We detected an array of PTSs in sediments and benthic biota off north Abu Ali Island (Arabian Gulf), including 35 polycyclic aromatic hydrocarbons (PAHs), 6 alkylphenols (APEOs), 10 styrene oligomers (SOs), and tributyltin. The PTS concentrations were generally greater than those reported in other areas of Arabian Gulf. PAHs mainly originated from petrogenic sources, and APEOs and SOs seem to be of recent origin. Field-based biota-sediment accumulation factors (BSAF) varied by taxa and compounds, but clearly depended on the log K_ow values of individual compounds. Some PTSs exceeded the established guidelines for sediments and biota; we found particularly great BSAFs for alkyl-naphthalenes (C1- and C2-), nonylphenol monoethoxylates, and 2,4,6-triphenyl-1-hexene. Remediation will require on-site clean-up of toxic chemicals together with immediate efforts on preventing input of current pollution sources in the given area.

Distributions of persistent organic contaminants in sediments and their potential impact on macrobenthic faunal community of the Geum River Estuary and Saemangeum Coast, Korea

Over the last 30 years, the Geum River Estuary and Saemangeum Coast have been subject to major environmental changes, including dike construction, reclamation, and development of industrial complexes. This study aimed to: 1) investigate the occurrence of polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), and styrene oligomers (SOs), 2) identify the sources of sedimentary organic matter, and 3) determine key environmental factors controlling the macrozoobenthos community structure. A total of 58 surface sediments were collected from the estuary and coastal area in 2014. Specific persistent organic contaminants (POCs), including 24 PAHs, 6 APs, and 10 SOs were measured. PAHs, APs, and SOs were detected in the sediments at all sites, with concentrations varying among sites. Although POCs concentrations were generally below the Canadian sediment quality guidelines, relatively greater concentrations of POCs were found at some sites adjacent to industrial complexes and the estuarine area. Sediment organic carbon, total nitrogen, and the stable carbon isotope ratio (δ¹³C) were determined. Some sites near watergate had about 2-3‰ lighter δ¹³C values compared to other areas, indicating that these sites are affected by terrestrial organic matter. The number of species in the macrofaunal community was significantly correlated with δ¹³C values (p < 0.001), positively, suggesting that the origin of sedimentary organic matter is important for controlling the macrozoobenthos distribution. Overall, this research provides information about the level and sources of sediment pollution, the origins of organic matter, and the relationships with the macrofaunal community.

Ultrastructural and developmental evidence of phytotoxicity on cos lettuce (Lactuca sativa) associated with nonylphenol exposure

It has long been understood that the presence of endocrine disrupter chemicals (EDCs) in water can affect the reproductive, behavioural and regulatory systems of different types of mammals. Thus far, only a handful of studies have examined its impact on plant systems. Present research is limited to the potential uptake of these chemicals by plants and the general phytotoxic effects it can elicit. The aim of this study was to determine what effect an EDC has on developing plant and cell organelles and how it affects it. In this study, cos lettuce plants were exposed to different concentrations of nonylphenol (NP), an EDC, in a static hydroponic system. Changes in plant morphology, mass and length, chlorophyll content, as well as electrolyte leakage were examined. Furthermore an in-depth investigation of the plant cell ultrastructure was carried out with transmission electron microscopy. Results indicated that cos lettuce growth was severely restricted, chlorophyll content was reduced, leakage of electrolytes increased and roots were stunted especially after ≥3200 μg/l NP exposures. The structure of the rough endoplasmic reticulum, vacuole and chloroplast were also changed. This study emphasizes the importance of water quality management, since the presence of an EDC, like NP, can negatively impact the yield and internal structure of one of the world's most significant salad crops, namely lettuce.

The endocrine disruptor nonylphenol induces sublethal toxicity in vascular plant development at environmental concentrations: A risk for riparian plants and irrigated crops?

In recent years, there is a growing concern among the scientific community about the presence of the so-called emergent pollutants in waters of different countries, especially endocrine-disrupting compounds (EDCs) that have the ability to alter the hormonal system. One of the substances found almost ubiquitously and in higher concentrations is the alkylphenol nonylphenol. Albeit this compound is included in priority lists as a probable risk for human health and the environment, little is known about its effects on developing plants. The aim of this work is to assess the acute and sub-chronic toxicity of environmental concentrations of nonylphenol in riparian vascular plant development using spores of the fern Polystichum setiferum and a biomarker-based approach: mitochondrial activity (cell viability), chlorophyll (plant physiology) and DNA content (growth). Mitochondrial activity and DNA content show that nonylphenol induces acute and sub-chronic toxicity at 48 h and after 1 week, respectively. Significant effects are observed in both parameters in fern spores at ng L(-1) but chlorophyll autofluorescence shows little changes. The inhibition of germination by natural allelochemicals has been reported to be related with the active hydroxyl group of phenolic compounds and largely independent of the structural nucleus to which it is attached. Results presented in this study suggest that environmental concentrations of nonylphenol could interfere with higher plant germination development by mimicking natural allelochemicals and/or phytohormones acting as a "phytoendocrine disruptor" likely posing ecophysiological risks.

Seasonal and spatial distribution of 4-nonylphenol and 4-tert-octylphenol in the sediment of Kaohsiung Harbor, Taiwan

The 4-nonylphenol (4-NP) and 4-tert-octylphenol (4-t-OP) were investigated in the surface sediments of Kaohsiung Harbor, Taiwan. The concentrations were between 18 and 27,882 ng g(-1)dw (average 101 ± 3,580 ng g(-1)dw) and 1.1 and 1,150 ng g(-1)dw (average 44 ± 174 ng g(-1)dw) for 4-NP and 4-t-OP, respectively. The concentrations of 4-NP and 4-t-OP in the river mouths' sediments are apparently higher and gradually decrease nearer the Harbor. The results showed that the river mouths' alkylphenol (AP) concentration in the wet season was higher than that in the dry season; in the channels and Harbor entrances, the AP values in the dry season were similar or even higher than those in the wet season. The correlation analysis indicated that total organic carbon (TOC) and organic matter (OM) played an important role in controlling the concentration level of 4-NP and 4-t-OP in the sediments. However, in the pollution hotspot, the direct inflow of pollutants would be the crucial factor that determines the concentration and distribution of organic pollutants in sediments. According to the evaluation of the potential ecological risk, the 4-NP concentration in the harbor had an 87% probability of exceed PNEC (39 ng g(-1), predicted no effect concentration) which means that the sediments of Kaohsiung Harbor probably pose a potential ecological risk to aquatic life, as is especially the case with those in the river mouths with relatively high EEQ values (estrogen equivalent concentration).

Alteration of hepatic anti-oxidant systems by 4-nonylphenol, a metabolite of alkylphenol polyethoxylate detergents, in Far Eastern catfish Silurus asotus

OBJECTIVES

This study aimed to estimate the effects of 4-nonylphenol (NP), a ubiquitously present surfactant in aquatic environments, on the anti-oxidant systems of the liver in the Far Eastern catfish Silurus asotus.

METHODS

Changes in biochemical parameters involved in glutathione (GSH)-related and other anti-oxidant systems were analyzed following 4 weeks of 4-NP administration (0.1 and 1.0 mg/kg diet) via a formulated diet to catfish.

RESULTS

4-NP exposure induced an elevation in hepatic lipid peroxide levels and an accompanying decrease in reduced state GSH after 2 weeks, suggesting pro-oxidant effects of the chemical in catfish. This oxidative stress was associated with an inhibition of the GSH-utilizing enzyme glutathione peroxidase at the same time point. This inhibition was restored after 4 weeks. The activities of other anti-oxidant enzymes, i.e., glutathione reductase, superoxide dismutase and catalase were increased after 4 weeks. These enzyme increases occurred more strongly at the higher 4-NP concentration (1.0 mg/kg diet).

CONCLUSIONS

4-NP given to catfish at 0.1 to 1.0 mg/kg diet, concentrations relevant to environmental levels, depletes the endogenous anti-oxidant molecule GSH and temporarily inhibits GSH-related anti-oxidant enzymes. Such declines in anti-oxidant capacity and elevated oxidative stress seem to be compensated eventually by subsequent activation of various anti-oxidant enzyme systems.

Photosynthetic and molecular responses of the marine diatom Thalassiosira pseudonana to triphenyltin exposure

This study aimed to investigate the responses of the marine diatom Thalassiosira pseudonana upon waterborne exposure to triphenyltin chloride (TPTCl) through determining their photosynthetic response, growth performance, and expressions of genes and proteins. Based on the growth inhibition test, the 96-h IC50 (i.e., median inhibition concentration) was found to be 1.09 μg/L (95% confidence interval (CI): 0.89-1.34 μg/L). According to photosynthetic parameters, the 96-h EC50s (i.e., median effect concentrations) were estimated at 1.54 μg/L (95% CI: 1.40-1.69 μg/L) and 1.51 μg/L (95% CI: 1.44-1.58 μg/L) for the maximum quantum yield of photosystem II (PSII) photochemistry (ΦPo) and the effective quantum yield of photochemical energy conversion in PSII (Φ2), respectively. Non-photochemical quenching in the algae was increased at low concentrations of TPTCl (0.5-1.0 μg/L) but it decreased gradually when the TPTCl concentration further increased from 1.0 to 2.5 μg/L. Results of gene expressions showed that lipid metabolism related genes were not influenced by TPTCl at 0.5 or 1.0 μg/L, while silica shell formation genes were down-regulated at 0.5 μg/L. Photosynthesis related genes were up-regulated at 0.5 μg/L TPTCl but were down-regulated at 1.0 μg/L TPTCl. Proteomics analysis revealed that relatively less proteins could be detected after exposure to 1.0 μg/L TPTCl (only about 50-60 spots) compared with that observed in the 0.5μg/L TPTCl treatment and two control groups (each with about 290-300 protein spots). At 0.5 μg/L TPTCl, five proteins were differentially expressed when compared with the seawater control and solvent control, and most of these proteins are involved in defence function to protect the biological systems from reactive oxygen species that generated by TPTCl. These proteins include oxygen-evolving enhancer protein 1 precursor, fucoxanthin chlorophyll a/c protein - LI818 clade, and mitochondrial manganese superoxide dismutase, which can function to maintain the capacity of PSII and stabilize the photosynthesis efficiency as reflected by the unchanged ΦPo and Φ2 values at 0.5 μg/L TPTCl. In contrast, the excess toxicity that caused by TPTCl at the high concentration (1.0 μg/L TPTCl) might directly damage the proteins, inhibit their expression, and/or cause the suppression of metabolism as indicated by the down-regulation of most studied proteins and genes, which could ultimately inhibit the photosynthesis and growth of the algae. Overall, this study comprehensively elucidated the toxicity effects of TPT on T. pseudonana, and partially revealed the molecular toxic mechanisms and corresponding defence responses in this model algal species.

Ecological risk assessment of nonylphenol in coastal waters of China based on species sensitivity distribution model

Nonylphenol (NP) is an endocrine disruptor and causes feminization and carcinogenesis in various organisms. Consequently, the environmental distribution and ecological risks of NP have received wide concern. China accounts for approximately 10% of the total NP usage in the world, but the water quality criteria of NP have not been established in China and the ecological risks of this pollutant cannot be properly assessed. This study thus aims to determine the predicted no effect concentration (PNEC) of NP and to assess the ecological risks of NP in coastal waters of China with the PNEC as water quality criteria. To obtain the HC5 (hazardous concentration for 5% of biological species) and PNEC estimates, the species sensitivity distributions (SSDs) models were built with chronic toxicity data of NP on aquatic organisms screened from the US Environmental Protection Agency (USEPA) ECOTOX database. The results showed that the PNEC for NP in freshwater and seawater was 0.48 μg L(-1) and 0.28 μg L(-1), respectively. The RQ (risk quotient) values of NP in coastal waters of China ranged from 0.01 to 69.7. About 60% of the reported areas showed a high ecological risk with an RQ value ≥ 1.00. NP therefore exists ubiquitously in coastal waters of China and it poses various risks to aquatic ecosystems in the country. This study demonstrates that the SSD methodology can provide a feasible tool for the establishment of water quality criteria for emergent new pollutants when sufficient toxicity data is available.

Effect of octylphenol on physiologic features during growth in Arabidopsis thaliana

Alkylphenol ethoxylates are widely used as detergents, emulsifiers, solubilizers, wetting agents and dispersants. Octylphenol (OP) ethoxylates, one of alkylphenol ethoxylates, represent 15-20% of the market, and their metabolic residues may be discharged to surface waters, sediments and soils as a persistent and ubiquitous pollutant. We tested the response of Arabidopsis thaliana to different concentrations of OP. OP affected the germination percentage and mean germination period. 10d treatment with OP, especially high concentration (10 and 50 mg L(-1)), decreased shoot and root biomass and root length of 30 d-old A. thaliana. Content of chlorophyll was decreased but that of proline was increased in leaves with OP treatment. OP caused oxidative stress in leaves; malondialdehyde content was increased, and the activities of ascorbate peroxidase, catalase and superoxide dismutase were induced. OP affects the physiologic and morphologic features of A. thaliana during growth. Because plants might be exposed to OP for a long time in the surroundings, more attention needs to be paid to the effect of OP on plants.