The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Kenneth M.y. Leung - One of the best experts on this subject based on the ideXlab platform.
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effects of unionised ammonia on tropical freshwater organisms implications on temperate to tropic extrapolation and water quality guidelines
Environmental Pollution, 2015Co-Authors: Zhen Wang, Kenneth M.y. LeungAbstract:Abstract Unionised ammonia (NH 3 ) is highly toxic to freshwater organisms. Yet, most of the available toxicity data on NH 3 were predominantly generated from temperate regions, while toxicity data on NH 3 derived from tropical species were limited. To address this issue, we first conducted standard acute toxicity tests on NH 3 using ten tropical freshwater species. Subsequently, we constructed a tropical species sensitivity distribution (SSD) using these newly generated toxicity data and available tropical toxicity data of NH 3 , which was then compared with the corresponding temperate SSD constructed from documented temperate acute toxicity data. Our results showed that tropical species were generally more sensitive to NH 3 than their temperate counterparts. Based on the ratio between temperate and tropical Hazardous Concentration 10% values, we recommend an extrapolation factor of four to be applied when surrogate temperate toxicity data or temperate water quality guidelines of NH 3 are used for protecting tropical freshwater ecosystems.
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Can we predict temperature-dependent chemical toxicity to marine organisms and set appropriate water quality guidelines for protecting marine ecosystems under different thermal scenarios?
Marine Pollution Bulletin, 2014Co-Authors: Guang-jie Zhou, Zhen Wang, Edward Tak Chuen Lau, Kenneth M.y. LeungAbstract:Temperature changes due to climate change and seasonal fluctuation can have profound implications on chemical toxicity to marine organisms. Through a comprehensive meta-analysis by comparing median lethal or effect Concentration data of six chemicals for various saltwater species obtained at different temperatures, we reveal that the chemical toxicity generally follows two different models: (1) it increases with increasing temperature and (2) it is the lowest at an optimal temperature and increases with increasing or decreasing temperature from the optimal temperature. Such observations are further supported by temperature-dependent Hazardous Concentration 10% (HC10) values derived from species sensitivity distributions which are constructed using the acute toxicity data generated at different temperatures. Considering these two models and natural variations of seawater temperature, we can scientifically assess whether applying an assessment factor (e.g. 10) to modify water quality guidelines of the chemicals can adequately protect marine ecosystems in tropics, subtropics and temperate regions, respectively.
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chronic toxicity of tributyltin to development and reproduction of the european freshwater snail lymnaea stagnalis l
Chemosphere, 2007Co-Authors: Kenneth M.y. Leung, Eric P. M. Grist, N J Morley, David Morritt, Mark CraneAbstract:Abstract Chronic toxicity, growth and reproduction were measured in the freshwater gastropod Lymnaea stagnalis exposed to waterborne bis(tri- n -butyltin) oxide (TBTO) over a range of four nominal Concentrations (0–10 μg TBT l −1 ). Egg development was completely inhibited at 10 μg TBT l −1 , whilst abnormal embryonic development was observed at 1 μg TBT l −1 . For the solvent control and the 0.01 μg TBT l −1 treatment group, normal development of L. stagnalis was observed. Survivorship of hatchlings was significantly reduced by TBT at 1 μg l −1 while inhibition of shell growth of L. stagnalis was also observed at this Concentration. The data were used to determine intrinsic growth rates ( r ) using two theoretical approaches (the Euler–Lotka equation and a Leslie Matrix). Both approaches showed that survival, fecundity and population growth rate were reduced at 1 μg TBT l −1 . Interestingly, at 0.01 μg TBT l −1 snails showed a higher fecundity and growth rate than in the solvent control. The TBT Concentration at which the r would equal zero (EC r 0 ) and the population NOEC (No Observed Effect Concentration) were estimated. The population NOEC was defined as either the lower 95% confidence or lower 95% pointwise percentile limit of the EC r 0 . Values obtained using the two different approaches were similar and thus a geometric mean was calculated to obtain a final representative population NOEC value for L. stagnalis of 2745 ng TBT l −1 . The present data together with chronic toxicity TBT data for freshwater organisms, obtained from peer-reviewed literature, were used to construct a species sensitivity distribution (SSD). A predicted no effect Concentration was then derived from the SSD (Hazardous Concentration at 5%, i.e., HC5 or 95% protection level). This SSD was compared with the SSD derived from saltwater species datasets. The HC5 value for saltwater species (3.55 ng TBT l −1 ; lower confidence limit: 1.93 ng TBT l −1 ) was significantly lower than that for freshwater species (30.13 ng TBT l −1 ; lower confidence limit: 9.23 ng TBT l −1 ), indicating that saltwater species are probably more susceptible to TBT than their freshwater counterparts.
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Better bootstrap estimation of Hazardous Concentration thresholds for aquatic assemblages.
Environmental toxicology and chemistry, 2002Co-Authors: Eric P. M. Grist, Kenneth M.y. Leung, James R. Wheeler, Mark CraneAbstract:The introduction of species sensitivity distribution (SSD) approaches to ecological risk assessment offers the potential for a more transparent scientific basis for the derivation of predicted no-effect Concentrations. However, conventional SSD methodologies have relied on standard distributions (e.g., log logistic, log normal) that are not necessarily based on sound ecological or statistical grounds. More recently, bootstrap resampling techniques that do not rely on distributional assumptions have been applied to the problem. Here we describe how a more advanced bootstrap methodology may be applied to derive better point estimates and confidence intervals for SSD estimates of safe environmental Concentrations. Motivated by the fact that the true SSD may not fit any standard model category, we go on to consider a hybrid bootstrap regression approach. This can yield a substantially different estimate for the SSD when compared with both the basic bootstrap and the more frequently used parametric curve approaches. With increasing use of SSDs in ecological risk assessment, it is now imperative that the scientific community develops agreement over appropriate methods for their derivation.
Karel De Schamphelaere - One of the best experts on this subject based on the ideXlab platform.
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acute and chronic toxicity of cobalt to freshwater organisms using a species sensitivity distribution approach to establish international water quality standards
Environmental Toxicology and Chemistry, 2020Co-Authors: William A Stubblefield, Colin R. Janssen, Eric Van Genderen, Allison S Cardwell, Dagobert G Heijerick, Karel De SchamphelaereAbstract:: Water quality standards for cobalt (Co) have not been developed for the European Union or United States. The objective of the present study was to produce freshwater Co toxicity data that could be used by both the European Union and the United States to develop appropriate regulatory standards (i.e., environmental quality standards or predicted-no-effect Concentrations in Europe and ambient water quality criteria or state water quality standards in the United States). Eleven species, including algae, an aquatic plant, and several invertebrate and fish species, were used in the performance of acute and chronic Co toxicity tests. Acute median lethal or median effective Concentration (LC50 or EC50) values ranged from 90.1 µg Co/L for duckweed (Lemna minor) to 157 000 µg Co/L for midges (Chironomus tentans). Chronic 10% effect Concentration (EC10) values ranged from 4.9 µg Co/L for duckweed to 2170 µg Co/L for rainbow trout (Oncorhynchus mykiss). Chronic 20% effect Concentration (EC20) values ranged from 11.1 µg Co/L for water flea (Ceriodaphnia dubia) to 2495 µg Co/L for O. mykiss. Results indicated that invertebrate and algae/plant species are more sensitive to chronic Co exposures than fish. Acute-to-chronic ratios (derived as acute LC50s divided by chronic EC20s) were lowest for juvenile O. mykiss (0.6) and highest for the snail Lymnaea stagnalis (2670). Following the European-based approach and using EC10 values, species sensitivity distributions (SSDs) were developed and a median Hazardous Concentration for 5% of the organisms of 1.80 µg Co/L was derived. Chronic EC20 values were used, also in an SSD approach, to derive a US Environmental Protection Agency-style final chronic value of 7.13 µg Co/L. Environ Toxicol Chem 2020;39:799-811. © 2020 SETAC.
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a microcosm study to support aquatic risk assessment of nickel community level effects and comparison with bioavailability normalized species sensitivity distributions
Environmental Toxicology and Chemistry, 2016Co-Authors: Udo Hommen, Karel De Schamphelaere, Burkhard Knopf, Heinz Rudel, Christoph Schafers, Chris Schlekat, Emily R GarmanAbstract:The aquatic risk assessment for nickel (Ni) in the European Union is based on chronic species sensitivity distributions and the use of bioavailability models. To test whether a bioavailability-based safe threshold of Ni (the Hazardous Concentration for 5% of species [HC5]) is protective for aquatic communities, microcosms were exposed to 5 stable Ni treatments (6-96 μg/L) and a control for 4 mo to assess bioaccumulation and effects on phytoplankton, periphyton, zooplankton, and snails. Concentrations of Ni in the periphyton, macrophytes, and snails measured at the end of the exposure period increased in a dose-dependent manner but did not indicate biomagnification. Abundance of phytoplankton and snails decreased in 48 μg Ni/L and 96 μg Ni/L treatments, which may have indirectly affected the abundance of zooplankton and periphyton. Exposure up to 24 μg Ni/L had no adverse effects on algae and zooplankton, whereas the rate of population decline of the snails at 24 μg Ni/L was significantly higher than in the controls. Therefore, the study-specific overall no-observed-adverse-effect Concentration (NOAEC) is 12 μg Ni/L. This NOAEC is approximately twice the HC5 derived from a chronic species sensitivity distribution considering the specific water chemistry of the microcosm by means of bioavailability models. Thus, the present study provides support to the protectiveness of the bioavailability-normalized HC5 for freshwater communities.
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An approach to assess the regulatory relevance of microevolutionary effects in ecological risk assessment of chemicals: A case study with cadmium
Environmental toxicology and chemistry, 2013Co-Authors: Dieter De Coninck, Colin R. Janssen, Karel De SchamphelaereAbstract:The authors suggest an approach to assess the regulatory relevance of microevolutionary effects of chemicals based on a comparison of Concentrations at which microevolutionary effects have been reported in the literature and conventionally derived ecotoxicological threshold Concentrations. The authors found reports of microevolutionary effects of cadmium in freshwater organisms at hardness-normalized Concentrations between 0.5 µg Cd L−1 and 6290 µg Cd L−1 (normalized to a hardness of 50 mg CaCO3 L−1). These Concentrations were at least 1.5 times higher than the hardness-normalized Hazardous Concentration for 5% of the organisms of 0.34 µg Cd L−1. This suggests that there is no immediate need to consider microevolutionary effects of Cd in environmental risk assessments of freshwater environments. However, some other aspects should be kept in mind as well. First, microevolutionary effects have so far only been investigated at few, relatively high Concentrations of Cd and not encompassing the 5% Hazardous Concentration. Second, different types of microevolutionary effects or investigated ecotoxicological end points may influence the conclusions of the suggested comparative approach. Finally, factors influencing the bioavailability of Cd were not commonly reported in the literature, which made normalization of Concentrations at which evolutionary effects occurred impossible and affected the number of studies that could be evaluated in the suggested approach. Environ Toxicol Chem 2014;33:453–457. © 2013 SETAC
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Ecological significance of Hazardous Concentrations in a planktonic food web.
Ecotoxicology and environmental safety, 2009Co-Authors: Frederik De Laender, Karel De Schamphelaere, Karline Soetaert, Jack J. Middelburg, Colin R. JanssenAbstract:Abstract Species sensitivity distributions (SSDs) are statistical distributions that are used to estimate the potentially affected fraction (PAF) of species at a given toxicant Concentration, the Hazardous Concentration for that fraction of species (HCPAF). Here, we use an aquatic food web model that includes 14 phytoplankton and 6 zooplankton species to estimate the number of species experiencing a biomass reduction when the food web is exposed to the HCPAF and this for 1000 hypothetical toxicants and for PAF=5–30%. When choosing a 20% decrease as a cut-off to categorize a species’ biomass as affected, 0–1 and 2–5 out of the 20 species were affected at the HC5 and HC30, respectively. From this, it can be concluded that the PAF is a relatively good estimator of the number of affected species. However, when phytoplankton species experiencing ≥20% biomass increase were also classified as affected, the number of affected species predicted by the food web model varied strongly among toxicants for PAF >5, with 2–16 out of 20 species affected at the HC30. Phytoplankton species with extreme (both high and low) values for uptake rates and light limitation constants experienced smaller effects on their biomass than phytoplankton species with more average parameter values. We conclude that, next to measures of toxicity, ecological characteristics of species may help understanding ecological effects occurring in ecosystems also.
Colin R. Janssen - One of the best experts on this subject based on the ideXlab platform.
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acute and chronic toxicity of cobalt to freshwater organisms using a species sensitivity distribution approach to establish international water quality standards
Environmental Toxicology and Chemistry, 2020Co-Authors: William A Stubblefield, Colin R. Janssen, Eric Van Genderen, Allison S Cardwell, Dagobert G Heijerick, Karel De SchamphelaereAbstract:: Water quality standards for cobalt (Co) have not been developed for the European Union or United States. The objective of the present study was to produce freshwater Co toxicity data that could be used by both the European Union and the United States to develop appropriate regulatory standards (i.e., environmental quality standards or predicted-no-effect Concentrations in Europe and ambient water quality criteria or state water quality standards in the United States). Eleven species, including algae, an aquatic plant, and several invertebrate and fish species, were used in the performance of acute and chronic Co toxicity tests. Acute median lethal or median effective Concentration (LC50 or EC50) values ranged from 90.1 µg Co/L for duckweed (Lemna minor) to 157 000 µg Co/L for midges (Chironomus tentans). Chronic 10% effect Concentration (EC10) values ranged from 4.9 µg Co/L for duckweed to 2170 µg Co/L for rainbow trout (Oncorhynchus mykiss). Chronic 20% effect Concentration (EC20) values ranged from 11.1 µg Co/L for water flea (Ceriodaphnia dubia) to 2495 µg Co/L for O. mykiss. Results indicated that invertebrate and algae/plant species are more sensitive to chronic Co exposures than fish. Acute-to-chronic ratios (derived as acute LC50s divided by chronic EC20s) were lowest for juvenile O. mykiss (0.6) and highest for the snail Lymnaea stagnalis (2670). Following the European-based approach and using EC10 values, species sensitivity distributions (SSDs) were developed and a median Hazardous Concentration for 5% of the organisms of 1.80 µg Co/L was derived. Chronic EC20 values were used, also in an SSD approach, to derive a US Environmental Protection Agency-style final chronic value of 7.13 µg Co/L. Environ Toxicol Chem 2020;39:799-811. © 2020 SETAC.
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An approach to assess the regulatory relevance of microevolutionary effects in ecological risk assessment of chemicals: A case study with cadmium
Environmental toxicology and chemistry, 2013Co-Authors: Dieter De Coninck, Colin R. Janssen, Karel De SchamphelaereAbstract:The authors suggest an approach to assess the regulatory relevance of microevolutionary effects of chemicals based on a comparison of Concentrations at which microevolutionary effects have been reported in the literature and conventionally derived ecotoxicological threshold Concentrations. The authors found reports of microevolutionary effects of cadmium in freshwater organisms at hardness-normalized Concentrations between 0.5 µg Cd L−1 and 6290 µg Cd L−1 (normalized to a hardness of 50 mg CaCO3 L−1). These Concentrations were at least 1.5 times higher than the hardness-normalized Hazardous Concentration for 5% of the organisms of 0.34 µg Cd L−1. This suggests that there is no immediate need to consider microevolutionary effects of Cd in environmental risk assessments of freshwater environments. However, some other aspects should be kept in mind as well. First, microevolutionary effects have so far only been investigated at few, relatively high Concentrations of Cd and not encompassing the 5% Hazardous Concentration. Second, different types of microevolutionary effects or investigated ecotoxicological end points may influence the conclusions of the suggested comparative approach. Finally, factors influencing the bioavailability of Cd were not commonly reported in the literature, which made normalization of Concentrations at which evolutionary effects occurred impossible and affected the number of studies that could be evaluated in the suggested approach. Environ Toxicol Chem 2014;33:453–457. © 2013 SETAC
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Ecological significance of Hazardous Concentrations in a planktonic food web.
Ecotoxicology and environmental safety, 2009Co-Authors: Frederik De Laender, Karel De Schamphelaere, Karline Soetaert, Jack J. Middelburg, Colin R. JanssenAbstract:Abstract Species sensitivity distributions (SSDs) are statistical distributions that are used to estimate the potentially affected fraction (PAF) of species at a given toxicant Concentration, the Hazardous Concentration for that fraction of species (HCPAF). Here, we use an aquatic food web model that includes 14 phytoplankton and 6 zooplankton species to estimate the number of species experiencing a biomass reduction when the food web is exposed to the HCPAF and this for 1000 hypothetical toxicants and for PAF=5–30%. When choosing a 20% decrease as a cut-off to categorize a species’ biomass as affected, 0–1 and 2–5 out of the 20 species were affected at the HC5 and HC30, respectively. From this, it can be concluded that the PAF is a relatively good estimator of the number of affected species. However, when phytoplankton species experiencing ≥20% biomass increase were also classified as affected, the number of affected species predicted by the food web model varied strongly among toxicants for PAF >5, with 2–16 out of 20 species affected at the HC30. Phytoplankton species with extreme (both high and low) values for uptake rates and light limitation constants experienced smaller effects on their biomass than phytoplankton species with more average parameter values. We conclude that, next to measures of toxicity, ecological characteristics of species may help understanding ecological effects occurring in ecosystems also.
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Relevance of generic and site-specific species sensitivity distributions in the current risk assessment procedures for copper and zinc.
Environmental toxicology and chemistry, 2005Co-Authors: Bart T.a. Bossuyt, Brita T.a. Muyssen, Colin R. JanssenAbstract:Species sensitivity distributions (SSD) were constructed using acute toxicity data of various cladoceran species collected in five different aquatic systems. The aim of this research was to study the relative acute cladoceran community sensitivity in different aquatic systems. Current risk assessment procedures are based upon hypothetical communities and do not take into account variation in species composition and tolerance between aquatic communities. Two metals, copper and zinc, were used as model toxicants. To establish comparative sensitivity, a standard medium (International Organization for Standardization [ISO]) was used. The generic SSD (log-normal distribution) based on toxicity data obtained in this standard medium for all species (collected at all sites) resulted in a Hazardous Concentrations that protects 95% of the species occurring in a (hypothetical) ecosystem (i.e., Hazardous Concentration protecting 95% of the species of the hypothetical ecosystem [HC5]) of 6.7 microg Cu L(-1) (90% confidence limits: 4.2-10.8) and 559 microg Zn L(-1) (375-843). This generic SSD was not significantly different from the site-specific SSDs (i.e., constructed with species only occurring at a specific site). Mean community sensitivity (the geometric mean of 48-h 50% effective Concentration [EC50] values of species within a community) among sites varied within a factor of 2 (between 17.3 and 23.6 microg Cu L(-1) for Cu and between 973 and 1,808 microg Zn L(-1) for Zn), and HC5s varied within a factor of 4 for copper (between 4.5 and 17.3 microg Cu L(-1)) and 7 for zinc (between 194 and 1,341 microg Zn L(-1)). For copper, the HC50 of our generic SSD was significantly lower than the one based on literature toxicity data of cladoceran species (which were recalculated to the hardness of our standard medium). In contrast, no significant differences were observed between the generic SSD and the literature-based SSD for zinc. It is suggested that the community sensitivity of different cladoceran populations is similar among aquatic systems and is not dependent on the species composition.
Rongxue Cui - One of the best experts on this subject based on the ideXlab platform.
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ecological hazard assessment of methyl ethyl ketone using the species sensitivity distribution approach in a soil ecosystem
Journal of Hazardous Materials, 2018Co-Authors: Yooeun Chae, Rongxue Cui, Jongmin MoonAbstract:Abstract Methyl ethyl ketone (MEK) is a common and widely used industrial solvent. However, few studies have investigated its toxicity, or its effects as a contaminant in soil ecosystems. In this study, acute and chronic toxicity data for MEK were generated, and ecological risk based on a species sensitivity distribution was assessed. Seven soil organisms from six taxonomic groups were used for acute toxicity tests and five soil organisms from four taxonomic groups were used for chronic toxicity tests. Acute and chronic soil HC5 (Hazardous Concentration for 5% of species) values for MEK were estimated as 53.04 and 2.593 mg MEK/kg dry soil, respectively. This is the first study to conduct battery testing for MEK; it specifies Hazardous Concentrations, warns of the need for accident preparedness, and points to serious potential hazards of MEK at various levels of the soil ecosystem which can translate into greater environmental damage with implications for human health. The specific sensitivity levels determined may serve as a benchmark for establishing soil standards and strategies for ecosystem protection in the face of accidental contamination.
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Estimation of the soil Hazardous Concentration of methylparaben using a species sensitivity approach.
Environmental pollution (Barking Essex : 1987), 2018Co-Authors: Dokyung Kim, Jin Il Kwak, Jongmin Moon, Rongxue Cui, Shin Woong Kim, Dasom KimAbstract:Abstract Methylparaben, which is known to be an endocrine-disrupting chemical, is added to various personal care products, including cosmetics, and is also used as a food preservative and in pharmaceuticals. However, information on the toxicity of methylparaben in soil ecosystems is limited. Furthermore, unlike other substances such as metals and pesticides, there is no regulation of levels or safe Concentrations of methylparaben in soil ecosystems. Therefore, the aims of this study were to evaluate the toxicity of methylparaben on soil species and to derive Hazardous Concentration (HC) values with respect soil ecosystem protection. We conducted acute bioassays on eight species within six taxonomic groups and chronic bioassays on five species within four taxonomic groups. On the basis of the results obtained, we derived an acute HC5 value of 44 mg/kg soil and a corresponding chronic value of 27 mg/kg soil for methylparaben using species sensitivity distribution methodology following Australian and New Zealand guidelines. Given that there has been no proposed standard value for methylparaben in soil in any country, it was not possible to compare the HC values calculated in this study with regulation standard levels. Nevertheless, to our knowledge, this study is first to assess the toxicity of methylparaben against soil-inhabiting species and to estimate acute and chronic HCs for soil fauna and flora. The results of this study will provide valuable fundamental data for the establishment of acceptable levels of methylparaben in soil.
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Species Sensitivity Distributions for Nonylphenol to Estimate Soil Hazardous Concentration
Environmental science & technology, 2017Co-Authors: Jin Il Kwak, Jongmin Moon, Dokyung Kim, Rongxue CuiAbstract:Nonylphenol is an endocrine-disrupting chemical that mimics estrogenic activity. Few studies have investigated the soil ecotoxicity of nonylphenol in the environment, based on probabilistic approaches. The present study generated soil toxicity data for nonylphenol through bioassays that determined the acute and chronic species sensitivity distributions and estimated the Hazardous Concentrations of nonylphenol in soil in order to protect soil ecosystems. We used eight soil-based organisms from six taxonomic groups for acute assays and five soil-based organisms from four taxonomic groups for chronic assays. The Hazardous Concentration values of nonylphenol in soil, based on acute and chronic species sensitivity distributions, were estimated using compiled data from the present study, as well as previous studies. This is the first study that generated sufficient data to develop species sensitivity distributions for nonylphenol in soil, and to determine Hazardous Concentrations of nonylphenol for soil environments.
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Determination of the soil Hazardous Concentrations of bisphenol A using the species sensitivity approach
Journal of hazardous materials, 2017Co-Authors: Jin Il Kwak, Jongmin Moon, Dokyung Kim, Rongxue CuiAbstract:Abstract This study describes the determination of the species sensitivity distribution (SSD)-based soil Hazardous contamination of bisphenol A for environmental risk assessment. We conducted a battery of bioassays, including acute assays using eight species from six different taxonomic groups and chronic assays using five species from four different taxonomic groups. We determined that our dataset satisfied Australia & New Zealand’s guidelines for applying the SSD methodology. Finally, the chronic soil HC5 and HC50 values for bisphenol A were estimated to be 13.7 and 74.7 mg/kg soil, respectively, for soil ecosystem protection against chronic exposure using the data generated from this and previous studies. Because the soil standard values of bisphenol A for protection of the soil ecosystem are not currently available, the HC values of bisphenol A that we suggested based on the SSD approach would be applied as fundamental data to establish soil standards of bisphenol A for soil ecosystem protection. To our knowledge, this is the first study reporting the soil Hazardous Concentration of bisphenol A for environmental risk assessment.
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Multispecies toxicity test for silver nanoparticles to derive Hazardous Concentration based on species sensitivity distribution for the protection of aquatic ecosystems.
Nanotoxicology, 2015Co-Authors: Jin Il Kwak, Rongxue Cui, Shin Woong Kim, Sun-hwa Nam, Yooeun ChaeAbstract:With increasing concerns about the release of silver nanoparticles (AgNPs) into the environment and the risks they pose to ecological and human health, a number of studies of AgNP toxicity to aquatic organisms have been conducted. USEPA and EU JRC have published risk assessment reports for AgNPs. However, most previous studies have focused on the adverse effects of AgNPs on individual species. Hazardous Concentration (HC) of AgNPs for protection of aquatic ecosystems that are based on species sensitivity distributions (SSDs) have not yet been derived because sufficient data have not been available. In this study, we conducted multispecies toxicity tests, including acute assays using eight species from five different taxonomic groups (bacteria, algae, flagellates, crustaceans and fish) and chronic assays using six species from four different taxonomic groups (algae, flagellates, crustaceans and fish). Using the results of these assays, we used a SSD approach to derive an AgNP aquatic HC5 (Hazard Concentrations at the 5% species) of 0.614 μg/L. To our knowledge, this is the first report of a proposed HC of AgNPs for the protection of aquatic ecosystems that is based on SSDs and uses chronic toxicity data.
Zhen Wang - One of the best experts on this subject based on the ideXlab platform.
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effects of unionised ammonia on tropical freshwater organisms implications on temperate to tropic extrapolation and water quality guidelines
Environmental Pollution, 2015Co-Authors: Zhen Wang, Kenneth M.y. LeungAbstract:Abstract Unionised ammonia (NH 3 ) is highly toxic to freshwater organisms. Yet, most of the available toxicity data on NH 3 were predominantly generated from temperate regions, while toxicity data on NH 3 derived from tropical species were limited. To address this issue, we first conducted standard acute toxicity tests on NH 3 using ten tropical freshwater species. Subsequently, we constructed a tropical species sensitivity distribution (SSD) using these newly generated toxicity data and available tropical toxicity data of NH 3 , which was then compared with the corresponding temperate SSD constructed from documented temperate acute toxicity data. Our results showed that tropical species were generally more sensitive to NH 3 than their temperate counterparts. Based on the ratio between temperate and tropical Hazardous Concentration 10% values, we recommend an extrapolation factor of four to be applied when surrogate temperate toxicity data or temperate water quality guidelines of NH 3 are used for protecting tropical freshwater ecosystems.
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Can we predict temperature-dependent chemical toxicity to marine organisms and set appropriate water quality guidelines for protecting marine ecosystems under different thermal scenarios?
Marine Pollution Bulletin, 2014Co-Authors: Guang-jie Zhou, Zhen Wang, Edward Tak Chuen Lau, Kenneth M.y. LeungAbstract:Temperature changes due to climate change and seasonal fluctuation can have profound implications on chemical toxicity to marine organisms. Through a comprehensive meta-analysis by comparing median lethal or effect Concentration data of six chemicals for various saltwater species obtained at different temperatures, we reveal that the chemical toxicity generally follows two different models: (1) it increases with increasing temperature and (2) it is the lowest at an optimal temperature and increases with increasing or decreasing temperature from the optimal temperature. Such observations are further supported by temperature-dependent Hazardous Concentration 10% (HC10) values derived from species sensitivity distributions which are constructed using the acute toxicity data generated at different temperatures. Considering these two models and natural variations of seawater temperature, we can scientifically assess whether applying an assessment factor (e.g. 10) to modify water quality guidelines of the chemicals can adequately protect marine ecosystems in tropics, subtropics and temperate regions, respectively.
