Ecological risk of nonylphenol in China surface waters based on reproductive fitness

Levels of bioavailable manganese in river sediment may elevate reproductive risk in model organism Caenorhabditis elegans

Manganese occurs naturally in sediment, yet anthropogenic sources, such as industrial wastewater and mining, increases Mn concentration. However, the environmental risk of bioavailable Mn is often overlooked and infrequently addressed. A probabilistic risk assessment was conducted to determine the effects of bioavailable Mn in river sediments on reproduction in model organism Caenorhabditis elegans using in utero egg counts and germline apoptosis as biomarkers. The lowest-observed-adverse-effect level (LOAEL) of sediment Mn that decreases in utero egg counts or increases germline apoptosis in C. elegans was 50 or 10 mg of Mn(II) per kg of dry weight sediment, respectively. Effect and exposure analyses were conducted using Hill model-simulated concentration-response curves and Mn concentrations of Laojie River sediment. Risk quotients (RQs) and exceedance risk (ER) analyses showed that bioavailable levels of Mn in Laojie River sediments from downstream sites collected during the dry season elevate reproductive risk as measured by germline apoptosis. These findings suggest that bioavailable levels of Mn in sediment exert negative impacts, and germline apoptosis is a sensitive biomarker for reproductive risk assessment. Our results also suggest that the anthropogenic Mn pollution in river sediment and spatial-seasonal bioavailability of Mn should be considered to improve sediment quality control.

Behavioral disorders caused by nonylphenol and strategies for protection

Nonylphenol (NP) is widely used in daily production and life due to its good emulsification. In this review, we discuss toxicology studies that examined behavioral disorders caused by NP, the corresponding toxicological mechanisms in the central nervous system (CNS), and strategies for protection. Available in vitro and in vivo evidence suggests that exposure to NP during adulthood or early childhood is associated with cognitive dysfunction, including depression-like behaviors, anxiety-like behaviors, and impaired learning and memory. The main mechanisms underlying NP-related cognitive disorders include inflammation, destruction of synaptic plasticity, and destruction of important signaling pathways that affect the synthesis and secretion of neurotransmitters. The effects and mechanisms of NP exposure on CNS-mediated reproductive function, including interference with the expression of hormones, proteins, and enzymes, are discussed. Other abnormal behaviors such as locomotor activity and swimming behavior are also described. Several measures to prevent NP neurotoxicity are summarized. These measures are based on the toxicological mechanisms underlying NP exposure and include external protection and internal self-regulation of the nervous system. Finally, a new treatment idea is proposed based on the gut-brain axis. Characterizing the behavioral changes and underlying toxicity mechanisms associated with NP exposure and investigating the possible methods of treatment will help to expand the understanding of these mechanisms and could lead to more effective treatments.

Improving urban drainage systems to mitigate PPCPs pollution in surface water: A watershed perspective

Parabens are preservatives widely used in pharmaceutical and personal care products (PPCPs). This study investigated urban water pollution by parabens from a watershed perspective. Water and sediment samples were collected from one of the most polluted urban streams in China. Six parabens and five paraben metabolites were frequently detected in the samples, whereas the overall pollution level was intermediate according to a global comparison. The spatial distributions of the chemical concentrations along the river are influenced by multiple factors, and WWTPs appear to be a major factor. In general, the target pollutants were detected at higher concentrations in the dry season than in the wet season, but extraordinary concentration peaks in water were observed downstream of wastewater treatment plants (WWTPs), indicating a dominant contribution from combined sewage overflows (CSOs) during rainfall events. In a representative WWTP-influenced reach, CSOs account for its 97.3% of ∑parabens input and 96.9% of ∑metabolites input in a typical rainfall event. Converting the existing combined sewer systems to separate stormwater drainage systems could reduce the inputs of ∑parabens and ∑metabolites by 86.9-84.5%, respectively. This study highlights the role of urban drainage systems in preventing surface water pollution by PPCPs. CAPSULE: Urban drainage systems play a critical role in controlling pollution by parabens and their metabolites in urban surface water.

Water quality criteria for the protection of human health of 15 toxic metals and their human risk in surface water, China

In the absence of water quality criteria (WQC) support for the current water quality standard (WQS), systematic WQC studies have been carried out in recent years in China. WQC for the protection of human health is established to reflect long-term consumption safety of aquatic products and water. Human health WQC for 15 toxic metals and metalloids based on exposure factors of the Chinese population and 40 field bioaccumulation factors (BAFs) were developed and analyzed in this study. Moreover, age-specific (age 2-5, 6-8, 9-11, 12-14, 15-17, and adult) and region-specific (east, central and west China) WQC were analyzed to better understanding of the impact of specific parameter values on WQC. Human health WQC with consumption of fishes and water, consumption of fishes only, and consumption of water only were derived separately. WQC with consumption of water and organism for Hg, Cd, As, Sb, Se, Zn, Co, Cu, Ni, Pb, Mn, Sn, Ba, and Sr were 0.0264, 0.710, 0.827, 3.48, 22.1, 25.7, 32.2, 32.9, 35.5, 41.8, 72.1, 97.1, 206 and 2.20 × 10³ μg/L, and were 13.3 and 6.67 × 10³ μg/L for Cr(VI) and Cr(III) with consumption of water only. Comparison of age-specific and region-specific WQC showed that the protection for a specific population should be considered in the development of WQC and WQS, as well as cancer effect for carcinogenic metals. Health risk analysis showed that Cd, Cu, Zn, As, Hg and Mn average concentrations in 7, 5, 9, 22, 11 and 5 provinces exceeded the WQC values with consumption of water and aquatic product, showing potential long-term health risk (HQ ≥ 1) to the local population. Therefore, health risks posed by these metals from dietary intake related to surface water should be paying more attention.

Emerging organic contaminants and odorous compounds in secondary effluent wastewater: Identification and advanced treatment

This study aims to address organic micropollutants in secondary effluents from municipal wastewater treatment plants (WWTPs) by first identification of micropollutants in different treatment units, and second by evaluating an advanced treatment process for removals of micropollutants. In secondary effluents, 28 types of pharmaceutical and personal care products (PPCPs), 5 types of endocrine disrupting chemicals (EDCs) and 3 types of odorous compounds are detected with total concentrations of 513 ± 57.8 ng/L, 991 ± 36.5 ng/L, 553 ± 48.3 ng/L, respectively. An integrated process consisting of in-situ ozonation, ceramic membrane filtration (CMF) and biological active carbon (BAC) filtration is investigated in a pilot scale (1000 m³/d) for removal of micropollutants in secondary effluents. The total removal efficiencies of PPCPs, EDCs and odorous compounds are 98.5%, 95.4%, and 91.1%, respectively. Removal mechanisms of emerging organic contaminants (EOCs) and odorous compounds are discussed based on their physicochemical properties. The remarkable removal efficiencies of micropollutants by the pilot system is attributed to synergistic effects of combining ozonation, ceramic membrane filtration and BAC filtration. This study provides a cost-effective and robust technology with the capability of treating secondary effluents for reuse applications.

Ameliorative effect of Alpinia officinarum Hance extract on nonylphenol-induced reproductive toxicity in male rats

Nonylphenol (NP), an endocrine-disrupting chemical, interferes with reproductive function and induces oxidative stress in different organs, including the testis and prostate. Alpinia officinarum Hance (ALP), a plant species of the Zingiberaceae family, has proven antioxidant properties. This study aimed to evaluate the effect of the alcoholic extract of ALP treatment on NP-induced reproductive toxicity and oxidative stress in male rats using biochemical and histopathological biomarkers. Our experimental groups were defined as follows: oil treatment (control), NP 10 mg/kg, ALP 10 mg/kg (ALP HD), NP + ALP 5 mg/kg (NP + ALP LD) and NP + ALP 10 mg/kg (NP + ALP HD). NP administration caused significant cytotoxicity and a significant increase in oxidative stress prostate-specific antigen (PSA) levels accompanied by a significant reduction in testosterone levels. The relative weight of the testis of both NP + ALP LD and NP + ALP HD groups was significantly decreased compared to the control group. Histopathological evaluations revealed destructive effects in testis and prostate tissue samples. In conclusion, ALP administration improved cytotoxicity, oxidative stress, testosterone and PSA levels, and testis and prostate tissue destructive effects induced by the NP in male rats.

Contamination, source and potential risks of pharmaceuticals and personal products (PPCPs) in Baiyangdian Basin, an intensive human intervention area, China

The presence of pharmaceuticals and personal care products (PPCPs) has become a global concern, as it poses a threat to the environment, especially to the aquatic ecosystem. This study focused on 30 PPCPs found in the Baiyangdian basin of the Xiong'an New Area, in the core of Beijing-Tianjin-Hebei region, with intensive human interventions during two seasons. In general, 30 PPCPs were all frequently detected, ranging from 42.3 to 7710 ng/L in May and 48.9 to 1300 ng/L in November. Sulfamethoxazole, ofloxacin, anhydro-erythromycin, carbamazepine, caffeine, and were screened as the predominant PPCPs. The rivers input was an essential source of PPCPs. The source apportionment with a series of analytical methods revealed that domestic sewage was the primary source, and untreated water also crucial for PPCPs contamination. The risk assessment suggested carbamazepine, caffeine, ofloxacin, and anhydro-erythromycin exhibited relatively high ecological risks for protecting most species such as algae, fish, and flowers in the aquatic ecosystem, especially near the outlet of WWTPs. Thus, management strategies for such PPCPs will be needed. Intensive human interventions, including a prohibition of fish breeding, water diversion project, and wastewater treatment in villages, were having an effective role in alleviating PPCPs contamination.

Copper ecological risk assessment using DGT technique and PNEC: A case study in the Brazilian coast

Estuarine systems are vulnerable to metals stress, such as copper (Cu). Thus, the development of applicable tools to improve routine monitoring programs is increasingly necessary. In the present work a comprehensive Ecological Risk Assessment (ERA) was implemented by coupling the Measured Environmental Concentration (MEC), based on labile Cu (DGT) and the total dissolved Cu concentration. Additionally, toxicity data related to site-specific Predicted No Effect Concentration (PNEC) were used. As case study, estuarine areas were selected on Brazilian coast, previously reported as Cu release in shipyard areas. The results indicated an increase in concentrations of dissolved and labile Cu during the application of antifouling paints. In locations where more vessels in maintenance were found, the concentration of Cu-DGT exceeded the PNEC value (0.16 μg.L^-1) and represented an important part of the total dissolved fraction (>93 %). The MEC/PNEC quotients, showed that shipyard areas represent a high ecological risk. Thus, it is highlighted the need for site-specific environmental assessments to manage complex ecosystems and set in environmental legislation. Consequently, the novel coupling of DGT technique and the derivation of a site-specific PNEC represent an easily applicable tool as an alternative to classical ERAs.

Ammonia spatiotemporal distribution and risk assessment for freshwater species in aquatic ecosystem in China

Ammonia has been of concern for its high toxicity to aquatic species and frequent detection in waters worldwide. This study calculated the national aquatic life criteria for ammonia in China. The temporal and spatial distributions were investigated and the multi-tier ecological risks were assessed for ammonia and un-ionized ammonia (NH₃) during 2014-2018 based on a total of 18989 ammonia monitoring data from 110 monitoring sites in seven river basins. The sensitivity comparison of different species taxa to ammonia showed that Perciformes fish should be listed as a priority protected species in the derivation of ammonia criteria. The participation of introduced aquaculture species have no significant impact on the final criteria values (t-test, p > 0.05). The final criterion maximum concentration (CMC) and criterion continuous concentration (CCC) were 10.24 and 3.31 mg/L for ammonia (pH 7.0 and 20 °C). The interannual variation showed that decreasing trends were observed for ammonia and NH₃ pollutions in the past five years. However, the increasing trends were observed for ammonia in Liao River basin, for NH₃ in Yangtze River and Pearl River basins (2014-2018). The significant seasonal and geographical differences of ammonia and NH₃ pollution were found. Moreover, the pollutions of ammonia and NH₃ in some monitoring points of Huai River, Yellow River and Songhua River basins at the provincial borders were significant. The result of ecological risk assessment showed that the average exceedance probability for 5% affected species by NH₃ in long-term exposure was 28.96% in the past five years.

Exposure and tiered ecological risk assessment of phthalate esters in the surface water of Poyang Lake, China

Phthalate esters (PAEs) are a class of endocrine disruptors that are produced and used extensively in China. Given its presence in various products, a great quantity of PAEs flows into different aquatic systems each year. Hence, it is important to study the pollution levels and ecological risk of PAEs. This study investigated the distribution and seasonal variation of six priority PAEs in the surface water of Poyang Lake, the largest freshwater lake in China. In the wet season, the mean concentration of the total PAEs was 0.544 ± 0.173 μg/L, while the dry season concentration (1.003 ± 0.451 μg/L) nearly doubled. The most abundant PAE congeners were di-n-butyl phthalate (DBP), followed by bis (2-ethylhexyl) phthalate (DEHP). To evaluate the ecological risks in Poyang Lake, the predicted no-effect concentrations (PNECs) of four PAEs based on non-lethal effects were derived. For diethyl phthalate (DEP), butyl benzyl phthalate (BBP), DBP, and DEHP, the PNECs were 31.6, 3.30, 2.31, and 0.0210 μg/L, respectively. The tiered ecological risk assessment showed that DEP and BBP posed no risk in Poyang Lake. Meanwhile, DBP posed a potential risk in Poyang Lake, but the risk of DEHP was unacceptable and requires more actions. Specifically, the probabilities of exceeding the threshold for the protection of 95% of the aquatic organisms (HC₅) were 3.30% and 4.43% for DEHP in the wet and dry season, respectively. This study provides an appropriate reference for the surface water management of PAE pollution in China.

Ecological and health risk assessment of perfluorooctane sulfonate in surface and drinking water resources in China

Perfluorooctane sulfonate (PFOS) is a synthetic substance with a great number of applications. However, it persists in the environment and is potentially toxic to organisms. Although China has been the main manufacturer and consumer for PFOS, the national pollution level and potential risk of this chemical are yet to be determined. This study aimed to provide an overview of PFOS contamination in surface and drinking water across China and to assess the potential ecological and health risks. Available monitoring data for PFOS in surface and drinking water were evaluated. PFOS was found to be ubiquitous in China, but the overall level of contamination was low compared with that in other countries. The southeast coastal area of China, with major PFOS-related companies, was characterized by relatively high PFOS exposure concentrations. The most sensitive effects was screened and applied to assess the ecological risk using the joint probability curve method. The probability of exceeding the growth and development toxicity for 5% of aquatic species was 0.65% in Chinese surface waters, while the highest probability of 0.90% was in Tai Lake in east China. Considering the average daily dose (ADD) for the Chinese population, the health risk posed by PFOS through drinking water ranged from 1.31 × 10^-4 to 13.91. Besides the relatively high health risk existed in east China, most health risks in China were acceptable.

The mechanisms in the altered ontogenetic development and lung-related pathology in microcystin-leucine arginine (MC-LR)-paternal-exposed offspring mice

A father's lifetime experience is a major risk factor for a range of diseases in an individual, and the consequences of the exposure can also be transmitted to his offspring. Our previous work has demonstrated that damage to testicular structures and decline in sperm quality in male mice can be caused by microcystin-leucine arginine (MC-LR), but the overall effects of the scope and extent of paternal exposure on health and disease in the offspring remain underexplored. Here, we report that MC-LR-paternal-exposed offspring mice showed reduced litter size and body weight accompanied by increased abnormalities in the lung. Analyses of the small noncoding RNAs (sncRNAs) in the sperm from MC-LR-exposed males demonstrated the downregulation of a wide range of piRNAs enriched for those target genes involved in the regulation of the embryo implantation pathways. Gene and protein expression analyses, as well as biochemical and functional studies, revealed suppressed expression of Hsp90α in testicular tissues from MC-LR-exposed males. Decreased Hsp90α in testicular tissues impaired the development of the offspring. In this study, we revealed that MC-LR alters the expression of Hsp90α in testicular tissues to cause changes in the expression profiles of sperm piRNAs produced by paternal mice. These changes lead to aberrant activation of the Wnt/β-catenin signaling pathway in pulmonary tissues of offspring mice, causing lung tissue damage and abnormal development. We hereby confirmed that MC-LR-induced alterations in epigenetic inheritance are capable of contributing to intergenerational developmental defects in paternal-exposed offspring mice.

Periodic density as an endpoint of customized plankton community responses to petroleum hydrocarbons: A level of toxic effect should be matched with a suitable time scale

As an endpoint of community response to contaminants, average periodic density of populations (APDP) has been introduced to model species interactions in a community with 4 planktonic species. An ecological model for the community was developed by means of interspecific relationship including competition and predation to calculate the APDP. As a case study, we reported here the ecotoxicological effects of petroleum hydrocarbons (PHC) collected from Bohai oil field on densities of two algae, Platymonas subcordiformis and Isochrysis galbana, a rotifer, Brachionus plicatilis, and of a cladocera, Penilia avirostris, in single species and a microcosm experiment. Time scales expressing toxic effect increased with increasing levels of toxic effect from molecule to community. Remarkable periodic changes in densities were found during the tests in microcosm experiment, revealing a strong species reaction. The minimum time scale characterizing toxic effect at a community level should be the common cycle of population densities of the microcosm. In addition, the cycles of plankton densities shortened in general with increasing PHC, showing an evident toxic effect on the microcosm. Using APDP as the endpoint, a threshold concentration for the modeled microcosm was calculated to be 0.404 mg-PHC L^-1. The APDP was found to be more sensitive and reliable than the standing crops of populations as the endpoint. This indicated that the APDP, an endpoint at the community level, could be quantitatively related to the endpoints at the population level, and led to the quantitative concentration-toxic effect relationship at the community level.

The toxicity effects and mechanisms of tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and its ecological risk assessment for the protection of freshwater organisms

Tris (1,3-dichloro-2-propyl) phosphate (TDCPP) is a type halogenated organophosphate flame retardants (OPFRs), which has been identified as contaminants of emerging concern (CECs). The use and production of OPFRs began to increase gradually when brominated flame retardants (BFRs) were banned. Halogenated OPFRs, especially TDCPP have been considered to lead to mutagenicity and carcinogenesis and major concerns have been raised regarding their toxicity. In this study, the toxicity effects and mechanisms of TDCPP were summarized and ecological risk assessment was made regarding its potential impact on freshwater organisms. TDCPP has been widely detected in ecosystems throughout the world, with observed toxicity effects on both humans and freshwater organisms. Inhalation of the dust was found to be the main exposure for humans. TDCPP could be metabolized in the human body, and medium stability was achieved in human body with the main metabolite BDCPP. Aside from mutagenicity and carcinogenesis, TDCPP was also found to have the potential for endocrine disruption and impairing the human reproductive system. Furthermore, this study reviewed the results of previous toxicity experiments, including acute toxicity, growth and development toxicity, neurotoxicity, and hepatotoxicity in freshwater organisms. Risk assessment was made using the safety threshold method by comparing the toxicity data with the exposure data in freshwater. HC₅ (hazardous concentration for 5% of organisms) derived based on traditional endpoints of acute toxicity LC₅₀ (median lethal concentration) or EC₅₀ (concentration for 50% of maximal effect) was 877 μg/L. This value was much higher than the exposure concentration levels in the surface water with EXD₉₀ (exposure data with cumulative probability 90%) of 65.22 ng/L. However, based on the growth and development toxicity data, the derived HC₅ was 33.33 ng/L and the calculated MOS (margin of safety) was below 1. Therefore, the results validated the fact that the ecological risk of TDCPP could not be neglected for its growth and development toxicity.

Antioxidative enzyme activities in the Rhodeinae sinensis Gunther and Macrobrachium nipponense and multi-endpoint assessment under tonalide exposure

Tonalide or acetyl hexamethyl tetralin (AHTN) is used as a fragrance additive in various household products. Recently, AHTN has drawn attention owing to its negative health effects on aquatic organisms. Data on AHTN toxicity toward aquatic species are limited. Therefore, this study tested the oxidative stress induced by AHTN exposure on the Rhodeinae sinensis Gunther and Macrobrachium nipponense. In this study, malonaldehyde (MDA) content and the activities of acetyl cholinesterase (AchE), superoxide dismutase (SOD), glutathione S-transferase (GST), and catalase (CAT) in R. sinensis Gunther were tested after 30 days of exposure to 30.093, 34.005, 38.426, 43.421, 49.067, 55.444, 62.652, 70.800, and 80.000 μg/L AHTN, respectively. The MDA, AchE, SOD, GST and CAT in M. nipponense were tested after 40 days of exposure to 60.000, 72.000, 86.400, 103.680, 124.416, 149.299, 179.159, 214.991, and 257.989 μg/L AHTN, respectively. In addition, an integrated biomarker response (IBR) index was utilised to evaluate the integrated toxic effects of AHTN on R. sinensis Gunther and M. nipponense. Finally, the predicted no-effect concentrations (PNECs) of AHTN, based on reproduction, biochemistry, survival, chronic toxicity, and acute toxicity endpoints were derived. The results indicated that low concentrations of AHTN can induce significant changes of oxidative stress biomarkers. The no observed effect concentrations (NOECs) of SOD, GST, AchE, CAT, and MDA were 103.680, 72.000, <60.000, 72.000, and <60.000 μg/L for R. sinensis Gunther and 38.426, 43.421, 30.093, 30.093, and 38.426 μg/L for M. nipponense, respectively. The IBR calculation results showed that 149.299 μg/L AHTN caused the highest toxic effect on R. sinensis Gunther after 30 days of exposure, whereas 70.797 μg/L AHTN caused the greatest damage to M. nipponense after 40 days of exposure. The PNECs of AHTN based on the non-traditional endpoints of biochemistry and reproduction were 0.00145 μg/L and 0.000395 μg/L, respectively, which were significantly lower than the PNEC of 2.636 μg/L for traditional endpoint survival. Therefore, the protection of aquatic organisms based on non-traditional toxicity endpoints should be considered in ecological risk assessment.

Hardness-dependent water quality criteria for cadmium and an ecological risk assessment of the Shaying River Basin, China

Hardness is one important water quality parameter that influences the toxicity of cadmium. Several studies have derived water quality criteria (WQC) for cadmium, but most of these studies did not consider environmental factors. Moreover, few studies considered environmental factors when carrying out ecological risk assessments (ERA) based on environmental factors. In this research, six native aquatic organisms in the Shaying River were adopted to conduct toxicity tests for cadmium. By combining published toxicity data for cadmium with hardness values and toxicity data from this study, hardness-dependent WQC were established. When normalized to a hardness of 100 mg/L CaCO₃, the criterion maximum concentration (CMC) of 6.46 μg/L and criterion continuous concentration (CCC) of 1.49 μg/L in the Shaying River Basin were derived according to the USEPA guidelines. The acute predicted no effect concentrations (PNECs) derived by species sensitivity distribution (SSD) methods based on log-logistic, log-normal and Burr Type III models were 1.03, 2.41 and 1.66 μg/L, respectively. Recommended WQC values finally expressed as a function of hardness: (1) CMC=(1.136672-0.041838 × lnH) × e^{0.9969×lnH-2.6676}; and (2) CCC=(1.101672-0.041838 × lnH) × e^{1.0083×lnH-6.1156}. In addition, three tiers of ERA of cadmium in surface waters were conducted based on hardness obtained during different seasons in the Shaying River using the hazard quotient (HQ), the margin of safety (MOS₁₀), and the joint probability (JPC) methods. In tiered 1, 2, and 3 ERA, cadmium exposure concentrations were standardized to a hardness of 100 mg/L. The three levels of the ERA method in the tiered framework gave consistent results: the ecological risks of cadmium in the Shaying River Basin were at acceptable levels. The present study provides a reference for the derivation of WQC and risk assessment of pollution affected by differences in aquatic species and water quality factors such as hardness.

Occurrence, toxicity and ecological risk of larvicidal oil in the coastal marine ecosystem of Hong Kong

Application of larvicidal oil (LO) is the most common practice in Hong Kong to control mosquitos, and hence prevent mosquito-borne diseases and protect human health. Globally, this study represented the first comprehensive assessment of toxicity and risk posed by LO to marine organisms. We found concentrations of LO ranged from 0.08 to 0.66 mg/L in coastal seawaters of Hong Kong. Waterborne exposure to water-accommodated fractions of LO resulted in growth inhibition to two microalgal species (72-h EC₅₀: 1.92-2.90 mg/L) and acute mortality to three marine animals (96-h LC₅₀: 3.41-8.10 mg/L). From these toxicity results, a concentration that considered to be hazardous to 5% of species (HC₅) was predicted at 1.45 mg/L, while the predicted no-effect concentration was determined to be 0.29 mg/L. The hazard quotient of LO exceeded 1 at 9 out of 15 sites, indicating moderate-to-high ecological risk to exposure of LO in the marine environment of Hong Kong.

Toxic Effects of Nonylphenol on Neonatal Testicular Development in Mouse Organ Culture

Nonylphenol (NP) is an alkylphenol that is widely used in chemical manufacturing. Exposure to this toxic environmental contaminant has been shown to negatively affect the reproductive system. Herein, we evaluated the toxicity of NP in mouse testes, while using in vitro organ culture. Mouse testicular fragments (MTFs), derived from five-day postpartum neonatal mouse testes, were exposed to different concentrations of NP (1-50 μM) for 30 days. The results showed that NP impaired germ cell development and maintenance. Furthermore, NP significantly downregulated the transcript levels of both undifferentiated and differentiated germ cell marker genes relative to those in controls. In particular, a high dose of NP (50 µM) led to complete germ cell depletion and resulted in spermatogenic failure, despite the presence of Sertoli and Leydig cells. In addition, the mRNA expression of steroidogenic enzymes, such as steroidogenic acute regulatory protein (STAR), Cytochrome P450 Family 11 Subfamily A Member 1 (Cyp11α1), Cytochrome P450 17A1 (Cyp17α1), and androgen receptor (AR), increased with increasing concentration of NP. Conversely, the expression of estrogen receptor alpha (ESR1) and Cytochrome P450 family 19 subfamily A member 1 (Cyp19α1) in NP-exposed MTFs decreased when compared to that of the control. Taken together, this study demonstrates that NP has a negative effect on prepubertal spermatogenesis and germ cell maintenance and it disrupts steroidogenesis and induces hormonal imbalance in MTFs.

Current understanding of potential ecological risks of retinoic acids and their metabolites in aquatic environments

In animals, retinoic acids (RAs), one of the main derivatives of vitamin A, are crucial for a variety of physiological processes. RAs, including all-trans-RA, 9-cis-RA, 13-cis-RA, and their corresponding metabolites (i.e., all-trans-4-oxo-RA, 9-cis-4-oxo-RA and 13-cis-4-oxo-RA) can be excreted through urination from humans and animals. Sewage treatment plants (STPs) are a significant source of RAs and 4-oxo-RAs into aquatic environments. RAs and 4-oxo-RAs can be identified and quantified by use of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). RAs and 4-oxo-RAs have been reported in various environmental matrices including rivers, lakes, reservoirs and coastal marine environments as well as in sewage effluents discharged from STPs. Greater concentrations of RAs and 4-oxo-RAs have been observed during blooms of cyanobacteria and microalgae, suggesting that cyanobacteria and microalgae are natural sources of RAs and 4-oxo-RAs in aquatic environments. These potential sources of RAs and 4-oxo-RAs raise concerns about their concentrations and risks in aquatic environments because excessive intake of these chemicals can result in abnormal morphological development in animals. Teratogenic effects were observed in amphibians, fish embryos, gastropods, mammals and birds when exposed to RAs. This review summarizes sources, concentrations, adverse effects and ecological risks of RAs and 4-oxo-RAs in aquatic environments. An interim, predicted no-effect concentration (PNEC) of RAs (in terms of at-RA) for freshwater environments was determined to be 3.93 ng/L at-RA equivalents. Based on limited data on concentrations of RAs in freshwater ecosystems, their hazard quotients were found to range from zero to 16.41, depending on the environmental conditions of receiving waters. Ecological risks of RAs in marine environments are yet to be explored due to the paucity of data related to both their concentrations in marine environment and toxic potencies to marine species. This review updates current knowledge of RAs and 4-oxo-RAs in aquatic environments and calls for more studies on their concentrations and fate in aquatic environments, especially estuarine and coastal marine environments with a view to enabling a comprehensive assessment of their ecological risks around the globe.

Ecological risk assessment of fifty pharmaceuticals and personal care products (PPCPs) in Chinese surface waters: A proposed multiple-level system

Interest in the risks posed by trace concentrations of pharmaceuticals and personal care products (PPCPs) in surface waters is increasing, particularly with regard to potential effects of long-term, low-dose exposures of aquatic organisms. In most cases, the actual studies on PPCPs were risk assessments at screening-level, and accurate estimates were scarce. In this study, exposure and ecotoxicity data of 50 PPCPs were collected based on our previous studies, and a multiple-level environmental risk assessment was performed. The 50 selected PPCPs are likely to be frequently detected in surface waters of China, with concentrations ranging from the ng L^-1 to the low-g L^-1, and the risk quotients based on median concentrations ranged from 2046 for nonylphenol to 0 for phantolide. A semi-probabilistic approach screened 33 PPCPs that posed potential risks to aquatic organisms, among which 15 chemicals (nonylphenol, sulfamethoxazole, di (2-ethylhexyl) phthalate, 17β-ethynyl estradiol, caffeine, tetracycline, 17β-estradiol, estrone, dibutyl phthalate, ibuprofen, carbamazepine, tonalide, galaxolide, triclosan, and bisphenol A) were categorized as priority compounds according to an optimized risk assessment, and then the refined probabilistic risk assessment indicated 12 of them posed low to high risk to aquatic ecosystem, with the maximum risk products ranged from 1.54% to 17.38%. Based on these results, we propose that the optimized risk assessment was appropriate for screening priority contaminants at national scale, and when a more accurate estimation is required, the refined probability risk assessment is useful. The methodology and process might provide reference for other research of chemical evaluation and management for rivers, lakes, and sea waters.

Development and use of interspecies correlation estimation models in China for potential application in water quality criteria

Establishment of numerical water quality criteria (WQC) has brought increasing interest in China. However, toxicity data to develop robust WQC values (number of toxicity data ≥8) of contaminants based solely on endemic and indigenous species are insufficient. In this study, interspecies correlation estimation (ICE) models were developed using a combination of North American ICE models supplemented with China-specific species to resolve this problem. A total of 207 significant surrogate-predicted models (p < 0.05, F-test) were derived: 119, 66 and 22 models for vertebrates, invertebrates and plant surrogate species, respectively. Model cross-validation success rate (≥80%), mean square error (MSE, ≤ 0.54), R² (≥0.78) and taxonomic distance (≤4, within the same class) were selected as guiding criteria to screen the resulted ICE models. The differences of 5th percentile hazard concentrations (HC₅s) for 6 chemicals (2,4-dichlorophenol, triclosan, tetrabromobisphenol A, nitrobenzene, perfluorooctane sulfonate and octabromodiphenyl ether) calculated from ICE-based and measured toxicity-based SSDs were within 3-fold among models. Although the number of derived ICE models was not comprehensive and continues to be improved, they can already be used in the development of WQC targeting protection of aquatic life and environmental risk assessments for chemicals lacking toxicity data.

Development of aquatic life criteria for tonalide (AHTN) and the ecological risk assessment

AHTN (tonalide) is a polycyclic musk that is widely used as fragrance additive in numerous consumer products. AHTN is of great worldwide concern owing to its adverse effects on aquatic organisms and frequent detection in both domestic and foreign aquatic environments. Therefore, derivation of the aquatic life criteria for AHTN exposure is urgently needed. In this work, AHTN toxicity data for eight Chinese native freshwater organisms were used to derive a criterion maximum concentration of 59.39 μg/L and a criterion continuous concentration of 22.43 μg/L using United States Environmental Protection Agency guidelines. Toxicity tests showed that the annelid L. hoffmeisteri and the amphibian R. nigromaculata were the least and most sensitive species to AHTN, respectively. The sensitivity of the planktonic crustacean D. magna to AHTN obviously differed from that of the benthic crustacean M. nipponense. The AHTN and HHCB correlation analysis exhibited a strong positive linear correlation (R² = 0.8622) in water. The ecological risk assessment showed that AHTN and HHCB posed a higher risk in foreign surface waters than Chinese waters, but a lower risk in foreign wastewater treatment plant effluent than in China. The ecological risks of AHTN and HHCB in most surveyed water bodies of various countries were at acceptable levels, with a few exceptions.

Influence of Hardness and Dissolved Organic Carbon on the Acute Toxicity of Copper to Zebrafish (Danio rerio) at Different Life Stages

Copper (Cu) bioavailability varies under water conditions. In the present study, the whole life of zebrafish was divided into three different life stages (larvae, juvenile and adult) based on the growth curve, then the influences of water hardness and dissolved organic carbon (DOC) concentration on the acute toxicity of zebrafish were respectively investigated. The results indicated that the life stages had significant effects on Cu toxicity. The larvae stage was less sensitive to Cu than both the juvenile and adult stages. With the increase of water hardness, the toxicity of Cu on zebrafish was decreased, a linear relationship was observed between water hardness and Cu toxicity, and the same was true for DOC concentration. The results showed that taking the 24 days juvenile zebrafish to study the water quality criteria of Cu was stable, sensitive and economical.

Probabilistic ecological risk assessment of heavy metals using the sensitivity of resident organisms in four Korean rivers

The environment has been continuously exposed to heavy metals by various routes, from both natural and artificial sources. In particular, heavy metals in water can affect aquatic organisms adversely, even at very low concentrations, and can lead to the disturbance of the ecosystem balance and biodiversity. Ecological risk assessments are conducted to protect the environment from such situations, primarily by deriving the predicted no-effect concentration (PNEC) from the species sensitivity distribution (SSD). This study developed the SSDs based on the species living in Korean freshwater for four heavy metals including cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). The species compositions of the SSDs were examined, and three types of PNECs were derived by applying different assessment factors (AF). In addition, the occurrence and concentrations of heavy metals in Korean rivers were investigated, and the ecological risk assessment was carried out to compare the SSDs with the environmental concentrations. The SSDs were developed using a sufficient number of species, but the missing data of plants and insects provided an incomplete species composition. The results show that Cd and Pb in the environmental concentrations of rivers would not cause any risk to aquatic organisms from the derived PNEC. However, some organisms might be adversely affected by the concentrations of Zn, and a small amount of risk was expected under the conservative PNEC. The distribution of Cu in the rivers was not considered to be safe for aquatic organisms because the average environmental concentrations potentially affected the proportion of the SSD, and the environmental concentrations exceeded the PNECs. The concentrations of Cu and Zn in industrial waters indicated a considerable risk to aquatic organisms, and the probability of exceeding the PNECs appeared to be quite high. Therefore, this study indicates that additional actions and parallel field studies are required based on the risk posed to aquatic organisms by Cu and Zn in four Korean rivers.

Study of aquatic life criteria and ecological risk assessment for triclocarban (TCC)

Triclocarban (TCC) is used as a broad-spectrum antimicrobial agent, the intensive detection of TCC in aquatic environments and its potential risks to aquatic organisms are concerned worldwide. In this study, 8 Chinese resident aquatic organisms from 3 phyla and 8 families were used for the toxicity tests, and four methods were employed to derive the aquatic life criteria (ALC). A criterion maximum concentration (CMC) of 1.46 μg/L and a criterion continuous concentration (CCC) of 0.21 μg/L were derived according to the USEPA guidelines. The acute predicted no effect concentrations (PNECs) derived by species sensitivity distribution (SSD) methods based on log-normal, log-logistic and Burr Type Ⅲ models were 2.64, 1.88 and 3.09 μg/L, respectively. The comparisons of ALCs derived with resident and non-resident species showed that the CMC and CCC of TCC derived with Chinese resident species could provide a sufficient protection for non-resident species. The higher toxicity of TCC on aquatic organisms was found compared with other antimicrobial agents (except for Clotrimazole) in aquatic environment. The strong positive linear correlation was observed between the TCC and TCS concentrations in aquatic environment with a correlation coefficient (R²) of 0.8104, it is of great significance in environmental monitoring and risk assessment for TCC and TCS. Finally, the ecological risk assessment showed that the TCC in Yellow River basin and Pearl River basin had higher risk with the mean potential affected fractions (PAFs) of 9.27% and 7.09%, and 22.10% and 15.00% waters may pose potential risk for 5% aquatic organisms, respectively. In general, the risk of TCC in Asian waters was higher than that in Europe and North America.

Deriving water quality criteria for China for the organophosphorus pesticides dichlorvos and malathion

Organophosphorus pesticides are effective, cheap, and used extensively but can harm aquatic organism and human health. Here, water quality criteria (WQCs) for dichlorvos (DDVP) and malathion (MAL) were derived. Nine aquatic organisms native to China were used in toxicity tests. Published toxicity data for aquatic organisms native and non-native to China were also analyzed. DDVP and MAL WQCs were derived using (log-normal model) species sensitivity distributions. Species sensitivity distribution curves indicated native and non-native species have different sensitivities to DDVP. The sensitivities of native and non-native species to MAL were not different because non-native species data for fewer than eight genera were available, so further research is required. The results indicated that native species need to be considered when deriving WQCs. The criteria maximum concentration (CMC) and criteria continuous concentration (CCC) were 1.33 and 0.132 μg/L, respectively, for DDVP, and 0.100 and 0.008 μg/L, respectively, for MAL. The CMCs for DDVP and MAL derived using ETX 2.0 software and species sensitivity ranks were different from the CMCs obtained using the SSD method because of parameter uncertainties. The DDVP and MAL WQCs were significantly lower than Chinese surface water quality standard thresholds. The results provide basic data for revising these thresholds.

Management principles for heavy metal contaminated farmland based on ecological risk-A case study in the pilot area of Hunan province, China

A pilot project for farmland soil remediation was carried out in the Changsha-Zhuzhou-Xiangtan (CZX) area of Hunan province, China. However, the pilot project focused mainly on the risk of exposure to heavy metals on grain safety, and little attention was paid to the risk to ecosystem quality. The study selected three areas in counties of in the CZX, and focused on five high toxicity heavy metals-Cd (cadmium), Cr (chromium), Pb (lead), As (arsenic), Hg (mercury) to explore the potential ecological risks of the soil. Probabilistic ecological risk assessment (new method) and traditional methods were introduced to quantitatively evaluate the ecological risk. Two target criteria levels (LC/EC/IC₅₀ and NOEC/LOEC) were employed. Through constructing species sensitivity distribution (SSD) models and joint probability curves (JPC), the predicted no effect concentrations (PNECs) derived from the SSD models were 0.21, 1.57, 3.05, 0.86 and 0.16 mg/kg for Cd, Cr, Pb, As and Hg, respectively. Compared with the ecological risk assessment results of the traditional methods, the new method reached a different conclusion, Cr showed the highest risk, at 84.3%, which signified that there was an 84.3% probability that 5% of the species with their NOEC/LOECs exceeded in County C. Despite differences among the risk assessment approaches, all methods indicated that County C was the most contaminated. The case study signifies that traditional methods underestimated the soil ecological risk of exposure to heavy metals and there should be a strong focus on farmland ecosystem security. At the same time, this study provided a scientific basis for goal-setting in species protection and prioritizing ecosystem protection as a management principle for heavy metal contaminated farmland from the perspective of ecological risk.

Deriving aquatic life criteria for galaxolide (HHCB) and ecological risk assessment

The polycyclic musk galaxolide (HHCB) is widely used as fragrances in personal care products (PCPs) and has been detected in various environmental media. There is an urgent need to derive aquatic life criteria (ALC) of HHCB for the protection of aquatic organisms. Toxicity tests with 8 Chinese resident aquatic organisms from 3 phyla and 8 families were conducted, and three methods were used for deriving the ALC. A criterion maximum concentration (CMC) of 8.33 μg/L and a criterion continuous concentration (CCC) of 2.20 μg/L were derived according to the USEPA guidelines. The acute predicted no effect concentrations (PNECs) values derived by log-normal species sensitivity distribution (SSD) and log-logistic SSD method were 77.41 and 66.47 μg/L, respectively. In addition, a significant sensitivity difference was observed between the planktonic crustacean and benthic crustacean, and there was no significant difference (p > 0.05) among SSDs based on resident and non-resident species. A comparison of chronic SSDs between HHCB, tonalide (AHTN) and musk ketone (MK) showed that nitro musk (MK) was more toxic to aquatic organisms than polycyclic musks (HHCB and AHTN). Finally, an assessment of risk to aquatic organisms in surface waters and effluents of wastewater treatment plants (WWTPs) worldwide showed that potential risk may exist at several locations. HHCB concentrations in 4.08 and 46.17% of the WWTP effluents in China and 1.71 and 16.13% of the WWTP effluents in other countries exceed the hazard concentration for 5% and 1% aquatic species.

Development of interspecies correlation estimation (ICE) models to predict the reproduction toxicity of EDCs to aquatic species

Endocrine disrupting chemicals (EDCs) threaten the reproductive fitness of aquatic organisms at concentrations lower than those associated with longevity and development. However, the small number of aquatic species assessed for reproductive toxicity has limited the ecological risk assessment of EDCs, making sensible decisions more difficult. In response to this, interspecies correlation estimation (ICE) models were established for EDCs to enable the estimation of reproduction toxicity values to a wider range of organisms. A total of 16 ICE models of EDCs for 6 surrogate species were statistically significant. Of the 16 models, 37.5% (6 models) had a cross-validation success rate > 60%, with a relatively small model squared error, indicating that the model fit is robust. These model results implied that the action of EDCs for each species pair might involve the same mechanisms, and taxonomic relationships did not influence the prediction precision. The cross-validation success rate corroborated the consistency between the projected and experimental values for the EDC ICE models. Sixty-seven percent of the projected values fell within a 10-fold difference of the experimental data. The results indicated that a proven ICE model can greatly increase the amount of EDCs chronic toxicity data for predicted species, without the need for extensive animal experiments, thus providing substitute chronic toxicity data for rapid assessment of EDCs ecological risks.

Exposure and ecological risk of phthalate esters in the Taihu Lake basin, China

The environmental spatial distribution and exposure risk of 6 phthalate esters (PAEs) including dimethyl phthalate (DMP), diethyl phthalate (DEP), butyl benzyl phthalate (BBP), di-n-octyl phthalate (DnOP), bis(2-ethylhexyl) phthalate (DEHP), and dibutyl phthalate (DBP), in surface water and sediment of Taihu Lake basin, China, were investigated at 65 sites. The exposure concentrations of 6 PAEs (∑6PAEs) detected in the samples spanned a range of 0.740-13.0 μg/L in surface water and 5.15-20.9 mg/kg in sediment. DBP and DEHP were the predominant compounds in surface water, with mean concentrations of 1.59 μg/L and 1.29 μg/L, respectively. DnOP was the predominant compound in sediment with mean concentration of 7.41 mg/kg. Ecological risk assessment was conducted by the hazard quotient method in which the predicted no effect concentration (PNEC) was derived from the species sensitivity distribution (SSD) curve. The results showed that DEHP in water phase posed a higher environmental risk than the other PAEs, while the DEP in sediment posed a high risk to the aquatic system. The study contributed to better understanding the presence of PAEs in Taihu Lake basin and provided valuable information for managing and controlling PAEs pollution.

Derivation of aquatic life criteria for four phthalate esters and their ecological risk assessment in Liao River

As a critical family of endocrine disruptors, phthalate esters (PAEs) attracted considerable attentions due to increasingly detected worldwide. Aquatic life criteria (ALC) for PAEs are crucial for their accurate ecological risk assessment (ERA) and have seldom been derived before. Given this concern, the purpose of the present study is to optimize the ALCs of four priority PAEs to estimate their ecological risks in Liao River. Reproductive endpoint was found to be more sensitive than other endpoints. Thus, reproduction related toxicity data were screened to derive ALCs applying species sensitivity distribution (SSD) method. ALCs of DEHP, DBP, BBP and DEP were calculated to be 0.04, 0.62, 4.71 and 41.9 μg L^-1, which indicated decreased toxicity in sequence. Then, the derived ALCs of the four PAEs were applied to estimate their ecological risks in Liao River. A total of 27 sampling sites were selected to detect and analyze the exposure concentrations of PAEs. ERA using the hazard quotient (HQ) method was conducted. The results demonstrated that DEHP exhibited higher risks at 92.6% of sampling sites, and risks posed by DBP were moderate at 63.0% sampling sites. However, risks posed by BBP were low at 70.4% of sampling sites, and there were no risks posed by DEP at 96.3% of sampling sites. The results of probabilistic ecological risk assessment (PERA) indicated that probabilities of exceeding effects thresholds on 5% of species were 60.41%, 0%, 0.12%, 14.28% for DEHP, DEP, BBP and DBP, respectively. The work provides useful information to protect aquatic species in Liao River.

Probabilistic ecological risk assessment of heavy metals in western Laizhou Bay, Shandong Province, China

Considering the serious land-based pollution and the weak water exchange ability of western Laizhou Bay, it is essential to conduct an ecological risk assessment of the pollutants in this area. In this study, the ecological risk caused by heavy metals deposited in the surface sediments and those resuspended in the seawater of western Laizhou Bay was evaluated using probabilistic approaches. First, the concentrations of seven heavy metals, namely As, Cd, Cr, Cu, Hg, Pb, and Zn, in the surface sediments and seawater of western Laizhou Bay were detected during the spring and autumn of 2016. The concentrations of As, Cd, Cr, Cu, and Pb were found to be at levels comparable to those in the other global coastal systems, while those of Hg and Zn were lower than those in other coastal areas. Next, an ecological risk assessment of heavy metals in the surface sediments was performed using a typical potential ecological risk index and refined by using a Monte Carlo simulation. The results suggested low risk for the heavy metals detected in the sediments of western Laizhou Bay, with the exception of Hg in September 2016, which showed a probability (0.03%) of moderate risk. Meanwhile, the aquatic ecological risk assessment of the heavy metals was performed by applying a combination of hazard quotient (HQ) and joint probability curve. While the ecological risk of Cd, Hg, and Pb was found to be acceptable, the HQs for Cr, Cu, and Zn were greater than 1, and the overall risk probability of their adverse effects was higher than 0.05, suggesting certain ecological risk. Specifically, in the case of As, the overall risk probability was lower than 0.05, suggesting that its ecological risk was acceptable, although its HQ was greater than 1. Thus, by applying the probabilistic approaches, the ecological risk of the heavy metals in western Laizhou Bay was better characterized in this study, avoiding both overestimation and underestimation of ecological risk.

Mutual promotion of apoptosis and autophagy in prepubertal rat testes induced by joint exposure of bisphenol A and nonylphenol

BPA and NP are both typical endocrine disruptors, the exposed populations are widespread, and the health risks mustn't be ignored. However, the interactions between them on spermatogenesis are rarely mentioned. And the underlying mechanism is unclear yet. In the present study, prepubertal SD rats were exposed to different low doses of BPA and NP separately or jointly for 4 weeks. The results indicate that the joint exposure induced excessive apoptosis and autophagy in the testes, as proved by a series of characteristics such as chromatin condensation and autophagosomes formation. Besides, endocrine disorders and oxidative stress were also caused by the exposure. Apoptosis was mediated by the mitochondrial apoptosis pathway, since the Bax and Caspase-3 gene expressions significantly increased with a prominent decrease of Bcl-2. While autophagy was caused by the inhibition of the Akt/mTOR pathway, as the expressions of the downstream genes Beclin-1, Atg5, Atg12 and the split of LC3 protein increased altogether. Worse yet, autophagy and apoptosis might reinforce each other and make the situation more severe in the joint group. What's more, remarkable histopathological changes such as spermatogenic epithelium atrophy, germ cell loss, and various ultrastructural modifications were strongly related to the apoptosis and autophagy. In aggregate, this study shows the enormous risk on male reproductive system brought by the interactions between BPA and NP. The findings provide a broader vision to understand the roles of apoptosis and autophagy induced by the joint exposure in the aggravation of spermatogenesis impairment, which could be a reference for the situation of complex EDCs exposure-induced male reproductive toxicity, and possibly inspire us to find new ideas for preventive and therapeutic treatments.

Integrated regional ecological risk assessment of multiple metals in the soils: A case in the region around the Bohai Sea and the Yellow Sea

Methodology to quantify and distinguish the spatial distribution of the risks from multiple pollutants within the region was developed in this paper. An integrated quantitative risk assessment was conducted by utilizing a large amount of information available to explore spatial distribution of risk by single and multiple pollutants, and the magnitude of the overall risk from multiple pollutants based on the current concentrations of pollutants and toxicity data. Two target criteria levels - level I (NOEC/LOEC based) and level II (LC/EC/IC₅₀ based) - were employed, and thus, the regional and sub-regional risks were evaluated according to these two levels. The risk of multiple toxic metals (As, Cd, Cr, Hg and Pb) to a terrestrial ecosystem for the region around the Bohai Sea and the Yellow Sea were evaluated as a case. The total overall ecological risks from heavy metals in the region for level I and level II were 21.73% and 12.53%, respectively. The risks were ranked in the order of Cr > As > Pb > Cd > Hg with Cr posing the greatest ecological risk, which was 61.12% for level I. The top three cities according to the level II ecological risk were Cangzhou > Lianyungang > Panjin, while the top three cities of level I ecological risk were Cangzhou > Panjin > Lianyungang. This method provides a quantitative risk assessment with multiple and clear protection levels for risk management.

Predicted no-effect concentration (PNEC) and assessment of risk for the fungicide, triadimefon based on reproductive fitness of aquatic organisms

Triadimefon, a broad-spectrum, systemic fungicide used to protect agricultural crops is popular in China. However, sub-lethal effects of triadimefon on aquatic organisms remained poorly understood, and its risks to aquatic organisms were unclear. In the current study, thresholds for chronic toxicity to five aquatic organisms were determined and a PNEC based on reproductive fitness of nine aquatic organisms was derived through use of a species sensitivity distribution (SSD). NOECs, based on reproduction or inhabitation of growth, for Oryzias latipes, Daphnia magna, Brachionus calyciflorus, Heterocypris incongruens and Soirodela polyrhiza were 5, 25, 80, 320 and 500 μg L^-1, respectively, and the final PNEC derived was 3.66 μg L^-1. A screening-level hazard assessment of surface water based on both measured environment concentrations (ND∼5.22 μg L^-1) in 3 lakes, 2 reservoirs and 1 river and predicted environment concentrations (0.36-65 μg L^-1) in a simulated river and pond, identified unacceptable hazard to aquatic organisms posed by triadimefon, with maximum hazard quotients (HQs) of 1.43 and 17.8, respectively. Potential deleterious effects and hazards or risks of exposure of aquatic organisms from current patterns of use of triadimefon in surface water if of concern. Since HQs were relatively small and the benefits large, it is suggested that mitigations be applied to allow use while minimizing potential for adverse effects on aquatic organisms.

Ecological risks posed by ammonia nitrogen (AN) and un-ionized ammonia (NH3) in seven major river systems of China

Previous studies showed that continuous exposure to ammonia nitrogen (AN) contributed to regional losses of benthic invertebrate diversity in China. Yet, the overall ecological risk of AN to aquatic organisms in major riverine systems of China has not been appropriately studied. Our research then investigated temporal (seasonally/yearly) and spatial distributions of AN and un-ionized ammonia (NH₃) in major Chinese river basins using historic data generated between 2007 and 2014, and developed risk assessment criteria. Our results showed that the highest average AN concentrations occurred during winter (0.82-2.76 mg/L) and the lowest during summer (0.36-0.78 mg/L). NH₃ exhibited the opposite trend with the highest average concentrations mostly observed during spring (15.13-92.84 μg/L) and the lowest concentrations mainly during winter (10.53-45.43 μg/L). Both AN and NH₃ concentrations steadily increased and reached maximum levels in 2008 (AN: 1.22 mg/L and NH₃: 50.65 μg/L), and then decreased. Temporal trends showed that the Yellow, Hai, and Huai river basins had the highest AN and NH₃ concentrations. Subsequently, conventional (hazard quotients) and probabilistic (joint probability curves) methods were applied to assess the hazards and risks posed by AN and NH₃. The results showed that the probability of exceeding the acute toxicity threshold for 5% of species (exposed to AN or NH₃) was less than 13.3% and gradually decreased over time. To protect aquatic organisms, an acute criterion of 51.4 μg NH₃/L and a chronic criterion of 1.14 mg AN/L at pH = 7.5, 20 °C were developed and are recommended for future risk assessment studies.

The ecological competition and grazing reverse the effects of sulfamethoxazole on plankton: a case study on characterizing community-level effect

The toxic effects of sulfamethoxazole (SMX) on densities of two algae, Platymonas helgolandica var. tsingtaoensis, Isochrysis galbana, and of a rotifer, Brachionus plicatilis, were tested by the population and community experiments. Two endpoints, the carrying capacity and the densities array of community in steady state (DACS), were used to characterize the toxic effects at a population level and a community one, respectively. The results showed that the carrying capacity of P. helgolandica var. tsingtaoensis and B. plicatilis did not decline significantly in population test when the concentration of SMX was lower than 6.0 mg L^-1 and 12.0 mg L^-1, respectively. However, I. galbana was sensitive to SMX and had presented toxic effect at 3.0 mg L^-1. By extrapolation of toxic effect at a population level to a community one, a derived community-NOEC was 3.0 mg L^-1, representing an inference from data of toxic effects at population level. In community experiment, when the customized community was in steady state, the density of I. galbana increased as a whole with SMX concentration in the range of tested concentration (0-144 mg L^-1), while that of P. helgolandica var. tsingtaoensis assumed the trend of a reversed "v" in this range. Only the density of B. plicatilis decreased with SMX concentration. With the DACS as endpoint, a NOEC for the customized community was determined to be 6.0 mg L^-1. This indicates that interspecific interactions can reverse the toxic effects of SMX on phytoplankton. The DACS was reliable and stable, serving as the endpoints in assessment of the effects of the pollutants on the ecosystems.

Derivation of aquatic predicted no-effect concentration (PNEC) for ibuprofen and sulfamethoxazole based on various toxicity endpoints and the associated risks

For pharmaceuticals, the ecological risk assessment based on traditional endpoints of toxicity could not be properly protective in the long run since the mode of action could vary because they are intended for different therapeutic uses. In this study, the predicted no-effect concentrations (PNECs) of two selected pharmaceuticals, ibuprofen (IBU) and sulfamethoxazole (SMX), were derived based on either traditional endpoints of survival and growth data or some nonlethal endpoints such as reproduction, biochemical and molecular data. The PNECs of IBU based on biochemical-cellular and reproduction data were 0.018 and 0.026 μg L^-1 that were significantly lower than those derived from other endpoints, while the lowest PNEC for SMX derived from growth data with the concentration of 0.89 μg L^-1. Ecological risk assessment was performed for IBU and SMX to the aquatic environment by applying hazard quotient and probabilistic distribution based quotient (DBQs) methods. The results showed that the probability of DBQs of IBU exceeding 0.1 was 11.2%, while for SMX the probability was 0.9% that could be neglected.

Amendment of water quality standards in China: viewpoint on strategic considerations

Water quality standards (WQS) are the most important tool for protection of quality of aquatic environments in China and play a decisive role in the management of China's aquatic environments. Due to limited scientific information available previously, WQS were developed largely based on water quality criteria (WQC) or WQS recommended by developed countries, which may not be suitable for current circumstances in China. The Chinese government recently initiated the revision of Environmental Quality Standards for Surface Water (EQSSW) (GB3838-2002) to meet the challenge of environmental protection. This review analyzed how the WQS developed and applied in China differ from those of more developed countries and pointed out that the lack of strong scientific bases for China's WQC pose major limitations of current WQS. We focus on discussing the six aspects that require high attention on how to establish a national WQC system to support the revision of WQS (Table 1) such as development of methodology, refining water function zoning, establish priority pollutants list, improving protection drinking water sources, development of site-specific water quality criteria, and field toxicity test. It is essential that China and other developing countries established a relatively mature system for promulgating, applying, and enforcing WQC and to implement a dynamic system to incorporate most recent research results into periodically updated WQS.

Applying adverse outcome pathways and species sensitivity-weighted distribution to predicted-no-effect concentration derivation and quantitative ecological risk assessment for bisphenol A and 4-nonylphenol in aquatic environments: A case study on Tianjin City, China

Adverse outcome pathways (AOPs) are a novel concept that effectively considers the toxic modes of action and guides the ecological risk assessment of chemicals. To better use toxicity data including biochemical or molecular responses and mechanistic data, we further developed a species sensitivity-weighted distribution (SSWD) method for bisphenol A and 4-nonylphenol. Their aquatic predicted-no-effect concentrations (PNECs) were derived using the log-normal statistical extrapolation method. We calculated aquatic PNECs of bisphenol A and 4-nonylphenol with values of 4.01 and 0.721 µg/L, respectively. The ecological risk of each chemical in different aquatic environments near Tianjin, China, a coastal municipality along the Bohai Sea, was characterized by hazard quotient and probabilistic risk quotient assessment techniques. Hazard quotients of 7.02 and 5.99 at 2 municipal sewage sites using all of the endpoints were observed for 4-nonylphenol, which indicated high ecological risks posed by 4-nonylphenol to aquatic organisms, especially endocrine-disrupting effects. Moreover, a high ecological risk of 4-nonylphenol was indicated based on the probabilistic risk quotient method. The present results show that combining the SSWD method and the AOP concept could better protect aquatic organisms from adverse effects such as endocrine disruption and could decrease uncertainty in ecological risk assessment. Environ Toxicol Chem 2018;37:551-562. © 2017 SETAC.

Criteria for assessing the ecological risk of nonylphenol for aquatic life in Chinese surface fresh water

The typical environmental endocrine disruptor nonylphenol is becoming an increasingly common pollutant in both fresh and salt water; it compromises the growth and development of many aquatic organisms. As yet, water quality criteria with respect to nonylphenol pollution have not been established in China. Here, the predicted "no effect concentration" of nonylphenol was derived from an analysis of species sensitivity distribution covering a range of species mainly native to China, as a means of quantifying the ecological risk of nonylphenol in surface fresh water. The resulting model, based on the log-logistic distribution, proved to be robust; the minimum sample sizes required for generating a stable estimate of HC₅ were 12 for acute toxicity and 13 for chronic toxicity. The criteria maximum concentration and criteria continuous concentration were, respectively 18.49 μg L^-1 and 1.85 μg L^-1. Among the 24 sites surveyed, two were associated with a high ecological risk (risk quotient >1) and 12 with a moderate ecological risk (risk quotient >0.1). The potentially affected fraction ranged from 0.008% to 24.600%. The analysis provides a theoretical basis for both short- and long-term risk assessments with respect to nonylphenol, and also a means to quantify the risk to aquatic ecosystems.

Derivation of predicted no-effect concentration and ecological risk for atrazine better based on reproductive fitness

Atrazine (ATZ) is an herbicide most commonly used in China and other regions of the world. It is reported toxic to aquatic organisms, and frequently occurs at relatively high concentrations. Currently, ATZ has been proved to affect reproduction of aquatic species at much lower levels. So it is controversial to perform ecological risk assessment using predicted no-effect concentrations (PENCs) derived from traditional endpoints, which fail to provide adequate protection to aquatic organisms. In this study, PNECs of ATZ were derived based on six endpoints of survival, growth, behavior, biochemistry, genetics and reproduction. The PNEC derived from reproductive lesion was 0.044μg ATZ L^-1, which was obviously lower than that derived from other endpoints. In addition, a tiered ecological risk assessment was conducted in the Taizi River based on six PNECs derived from six categories of toxicity endpoints. Results of these two methods of ecological risk assessment were consistent with each other, and the risk level of ATZ to aquatic organisms reached highest as taking reproductive fitness into account. The joint probability indicated that severe ecological risk rooting in reproduction might exist 93.9% and 99.9% of surface water in the Taizi River, while 5% threshold (HC₅) and 1% threshold (HC₁) were set up to protect aquatic organisms, respectively. We hope the present work could provide valuable information to manage and control ATZ pollution.

Spatial and temporal ecological risk assessment of unionized ammonia nitrogen in Tai Lake, China (2004-2015)

Ammonia toxicity varies largely due to its pH- and temperature-dependent speciation (unionized ammonia nitrogen, NH₃-N). The seasonal and long-term trend of ammonia risk in ecologically significant sections of Tai Lake, China was unknown. In this study, a two-level (deterministic and quantitative) method was developed to assess the special ecological risks posed by NH₃-N at 37 sites during two seasons (February and September) of 2014 in Tai Lake. The long-term temporal (2004-2015) risk posed by NH₃-N was also assessed by comparing annual quantitative risk values (probability of exceeding acute or chronic threshold values) in three key sections of Tai Lake. The results indicated the species living in the Tai Lake were at a 0.04% and 32.45% chance of risk due to acute exposure, and a 1.97% and 92.05% chance of risk due to chronic exposure in February and September of 2014, respectively. Alarmingly, the chronic ecological risks of NH₃-N in the Lanshanzui section of the Tai Lake remained >30% from 2004 to 2011. The chronic risk of NH₃-N in all three key sections of Tai Lake started to decrease in 2011. This was likely the consequence of the control practice of eutrophication implemented in the Tai Lake. A significant decline in diversity of the benthic invertebrate community of the Tai Lake could be associated with continuous exposure to ammonia over decades given different sensitivity of taxa to ammonia. The results laid a scientific foundation for risk assessment and management of ammonia in Tai Lake, China, and the developed two-level risk assessment approach can also be applied to other similar aquatic regions.

Deriving water quality criteria for trivalent and pentavalent arsenic

Arsenic (As) is a common trace element whose oxidation states mainly include four types (-3, 0, +3, and +5), and inorganic As(III) and As(V) are regarded as the most commonly existing forms in aqueous environments. Generally, As(III) has a higher toxicity than As(V) due to the different mechanisms in arsenic toxicity. However, there are few studies about the water quality criteria (WQC) of As(III) and As(V) respectively because of the deficiency of arsenic toxicity data coming from diverse taxonomic groups. In this research, eight native Chinese aquatic organisms were adopted to conduct toxicity tests for As(III) and As(V) to supplement the published toxicity data. The species sensitivity distribution (SSD) method on the basis of the Log-normal model which was the most optimal among eight models was applied to derive WQCs of As(III) and As(V). Results showed that crustaceans were the most sensitive to As(III) and As(V) among all tested species, thus they could be a biological indicator, and the influence of pH values on arsenic toxicity was complex and species-specific. Besides, the sensitivity differences between native and non-native species were observed. Finally, a criterion maximum concentration (CMC) of 167 and 384μg/L for As(III) and As(V), and a criterion continuous concentration (CCC) of 42 and 44μg/L for As(III) and As(V) were derived using native species, regardless of pH values. The WQCs were also verified by other two methods of ETX 2.0 and species sensitivity rank.

Tiered probabilistic assessment of organohalogen compounds in the Han River and Danjiangkou Reservoir, central China

Occurrence of organohalogen contaminants (OCs) including 12 organochlorine pesticides (OCPs), 7 polychlorinated biphenyl congeners (PCBs) and 7 polybrominated diphenyl ethers (PBDEs) were investigated in the Han River, which is the largest tributary of the Yangtze River, and Danjiangkou Reservoir, the source of water for China's South-to-North Water Diversion Project. OCPs were found to be dominant in water, with concentrations of 0.14-11 and 2.9-59ngL^-1during winter and summer, respectively. In sediment, OCPs were also predominant contaminants during summer (5.0-1.7×10²ngg^-1), whereas during winter PCBs (4.3-2.3×10²ngg^-1) were dominant. Concentrations of OCs observed during this study were generally less or comparable to those from other locations in the world. Concentrations of OCPs were significantly greater in lower reaches of the Han River, during winter. This observation might be due to proximity of this location to more developed areas. Distributions of OCs between water and sediment were not at steady state except for PBDEs during winter. This disequilibrium is likely due to continuing inputs of pollutants. A tiered assessment of risks to aquatic organisms was conducted for OCs. Initially species sensitivity distributions (SSD) were employed to determine predicted no effect concentration (PNEC), followed by evaluation based on hazard quotients (HQ). In subsequent tiers, a probabilistic approach was used to develop joint probability distributions, where species sensitivity distributions were compared to distributions of measured concentrations of OCs. Consistent results were obtained by use of all methods, which suggested endosulfans and heptachlors could pose risk to local aquatic organisms. Furthermore, heptachlors and PCBs might also cause potential adverse effect to health of humans through consumption of water.

Deriving freshwater safety thresholds for hexabromocyclododecane and comparison of toxicity of brominated flame retardants

Hexabromocyclododecane (HBCD) is a brominated flame retardant used throughout the world. It has been detected in various environmental media and has been shown toxic to aquatic life. The toxic effects of HBCD to aquatic organisms in Chinese freshwater ecosystems are discussed here. Experiments were conducted with nine types of acute toxicity testing and three types of chronic toxicity testing. After comparing a range of species sensitivity distribution models, the optimal model of Bull III was used to derive the safety thresholds for HBCD. The acute safety threshold and the chronic safety threshold of HBCD for Chinese freshwater organisms were found to be 2.32mg/L and 0.128mg/L, respectively. Both values were verified by the methods of the Netherlands and the United States. HBCD was found to be less toxic compared to other widely used brominated flame retardants. The present results provide valuable information for revision of the water quality standard of HBCD in China.