Sublethal Toxicity Testing of Canadian Metal Mining Effluents: National Trends and Site-Specific Uses

As part of the Canadian Environmental Effects Monitoring program under the National Metal Mining Effluent Regulation, there is a requirement to conduct sublethal toxicity tests twice per year for the first three years. These first three years (2003 to 2005) were considered a period of initial monitoring and resulted in test endpoints for each of the required standardized methods on a fish, an aquatic plant, an invertebrate, and an algal species. On a national level (based on 1648 valid results), the test from most to least sensitive was: the inhibition of reproduction with Ceriodaphnia dubia, the growth inhibition (frond number) with Lemna minor, the inhibition of cell yield with Pseudokirchneriella subcapitata, the growth inhibition (dry weight) with Lemna minor, the growth inhibition of fathead minnows, and the effect on embryo viability with rainbow trout. This sensitivity ranking changed when tests were further evaluated on a geographical region and mine-type basis (e.g., base metal, precious metal, uranium, iron ore). Site-specific examples show how sublethal toxicity data are being used to track changes in effluent quality, choosing a final discharge point, monitoring multiple discharges to the same watercourse, and to identify study design weaknesses by comparing laboratory results to field survey conclusions.     

A Conceptual Framework for Using Mussels as Biomonitors in Whole Effluent Toxicity

As a main source of direct and continuous input of pollutants in the aquatic ecosystem, studying the effects of effluents on receiving ecosystems has a high ecological relevance. While ecological risk assessment procedures are usually based on a chemical-based single component approach, their application for complex mixtures and effluents is less straightforward. A chemical-based approach has to rely on the knowledge of what chemicals are present in effluents, their potential toxicity, how all of these individual chemicals interact and what their individual and combined contribution to the mixture is. Whole effluent toxicity (WET) testing, however, is an integrative tool that measures the toxic effect of an effluent as a whole and accounts for uncharacterized sources of toxicity and for interactions. This paper addresses the use of transplanted bivalves, i.e., caged mussels, as a biomonitoring tool in WET testing with special reference to field situations in both freshwater and marine environments. We indicate how endpoints at different levels of biological organization within exposed mussels can give an integrative overview of effects. Finally, we will provide a framework for future research using mussels and discuss a multitude of instream responses for routine, efficient and cost-effective active biomonitoring applications.     

Effect of hardness on bioavailability and toxicity of cadmium to rainbow trout

Abstract

Water quality characteristics affecting toxicity of metals to aquatic life include pH, inorganic and organic ligands (negatively charged ions and molecules), and water hardness. Ligands control the ability of natural waters to bind metals which could adversely affect aquatic life. Bioavailability of metals in natural waters is primarily controlled by alkalinity. Hardness does not affect metal complexation but can reduce acute toxicity through antagonistic mechanisms. In most natural waters, concentrations of alkalinity and hardness are similar, but they may be very different in some waters.

Most toxicity studies have not distinguished between reduced toxicity resulting from effects of hardness and that resulting from complexation of metals by ligands. A series of acute and long-term experiments were conducted to assess these relationships while exposing rainbow trout (Oncorhynchus mykiss) to cadmium (Cd) in waters of low alkalinity (30 mg L^?1) and hardnesses of 400, 200, and 50 mg L^?1 adjusted with magnesium sulfate (MgSO⁴). These tests did not show a strong antagonistic influence of Mg hardness on Cd toxicity. At Mg hardnesses of 50, 200, and 400 mg L^?1, 96-h LC50s were 3.02, 6.12, and 5.70 μg Cd L^?1, differing by a factor of only 1.8. Similarly, chronic values derived from 100-day experiments in waters with the same range of hardness were 1.47, 3.57, and 3.64 μg L^?1, respectively. With an eight-fold difference in Mg hardness, chronic values differed by a factor of only 2.5. Antagonistic properties of hardness are primarily controlled by Ca with Mg playing a minor role. The long-term role of Ca in reducing metal toxicity will require further investigation.     

Invited Debate/Commentary: Selenium — A Potential Time Bomb or Just Another Contaminant?

Environmental issues related to selenium are complex and not universally understood. This paper provides detailed information regarding selenium and associated aquatic environmental issues, and then introduces and comments on five debate/commentary papers discussing selenium in the context of the title of this paper. Selenium has a complex and not fully understood biogeochemistry in the aquatic environment as well as an unusual mode of toxicity (acute via water column exposure; chronic via food chain exposure). It has the narrowest range between nutritional requirements and toxicity of any essential element, and chronic toxicity is not readily predictable. Selenium contamination of waters or even of tissues does not necessarily indicate a ticking time bomb; there are no generally accepted or universally accepted threshold values for chronic toxicity. Assessing risk must be done site-specifically in a risk assessment framework, focusing on reproductive effects to sensitive exposed fish and waterfowl and on “worst case” hydrologic units. Unless selenium inputs decrease or site-specific biogeochemistry can be shown not to change, continued biological monitoring and testing are required. Provided the necessary investigative and monitoring studies are done, any potential selenium time bombs can be defused.     

Investigation of the sublethal effects of some petroleum refinery effluents

In Canada, environmental regulations for protection of the biota from the adverse effects of effluents from petroleum refineries have tended to focus on acute toxicity. There is concern those effluents may have other subtle, but still deleterious, long-term effects on aquatic ecosystems. We have used a battery of toxicity tests to assess the acute toxicity, genotoxicity, and chronic toxicity of effluent samples from two Ontario refineries. The test organisms included representatives of the bacterial, algal, plant, cladoceran, and fish communities. The results of our preliminary study indicate that the effluent samples had little acute toxicity to the test organisms. There were indications of some sublethal toxicity to Ceriodaphnia dubia, Panagrellus redivivus, and Pimephales promelas. One of the effluents inhibited the growth of Selanastrum capricornutum (IC₅₀ of 59.9%) and Lemna gibba (IC₂₅ of 73.3%) and also caused a 15 percent reduction in the germination of Lactuca sativa seeds. The SOS-Chromotest, a commercially available test that measures the activity of a bacterial DNA repair system, detected genotoxic effects in a single effluent that had been concentrated ten fold. There was no apparent relationship between several chemical parameters and the observed sublethal effects. Further research is needed to establish whether or not the observed toxic effects are typical of effluents from Ontario refineries.     

Exploration of structure-antifouling relationships of capsaicin-like compounds that inhibit zebra mussel (Dreissena polymorpha) macrofouling

Abstract

Macrofouling of aquatic man-made structures by zebra mussels (Dreissena polymorpha) poses significant economic burdens on commercial freshwater shipping and facilities utilising raw water. The negative environmental impact of some current antifouling technologies has limited their use and prompted investigation of non-organometallic and non-oxidising antifoulants as possible environment-friendly alternatives. The plant-derived natural product capsaicin and 18 other compounds with one or more capsaicin-like structural features were tested for their potential to inhibit zebra mussel byssal attachment at a single high concentration of 30 μM. Of these, three compounds displaying the highest levels of attachment inhibition where selected for further concentration-response testing. This testing revealed that capsaicin (8-methyl-N-vanillyl-trans-6-nonenamide), N-vanillylnonanamide, and N-benzoylmonoethanolamine benzoate all inhibited byssal attachment with potency values (EC₅₀) in the micromolar range. None of these compounds were lethal to adult specimens of the water flea, Daphnia magna, at concentrations that inhibited mussel byssal attachment.     

Feeding and nutritional considerations in aquatic toxicology

The nutritional status of an aquatic organism, both prior to and during testing, can significantly modify the apparent toxicity of a chemical. In order to decrease the variability of toxicity test results, both within and between laboratories, feeding regimes, feed types and proximate composition of diets should be routinely reported. The advantages and metabolic effects of various feeding practices currently used in toxicity testing (fasting, starvation, feeding as a percentage of body weight, feeding ad libitum and pair feeding) are discussed. The disadvantages of monitoring nutritional status of test organisms are also reviewed and suggestions are offered as to how best to monitor nutritional status.     

Use of aquatic macrophytes as a bioassay method to assess relative toxicity,uptake kinetics and accumulated forms of trace metals

Floating aquatic macrophytes such as the Lemnaceae have many attributes which commend their use in laboratory and field investigations to assess both the toxicity of substances and the quality of freshwater systems. As well as their more well known advantages of small size, relative structural simplicity, rapid growth and vegetative reproduction and genetically homogenous populations, they are also excellent accumulators of a number of metallic elements. This raises the possibility of the use of these aquatic macrophytes in water quality monitoring and also as laboratory bioassays for toxicity and uptake studies. Results are presented of a study of the comparative toxicity, uptake kinetics and accumulated forms of thallium and cadmium in the duckweed, Lemna minor and the role of this methodology in water quality monitoring and hazard evaluation are discussed.     

伊维菌素在环境中的降解及其对七种水生生物的急性毒性研究

伊维菌素作为一种高效的抗寄生虫兽药,在畜禽业有着广泛的应用。但药物随着畜禽动物的代谢产物的排放而进入自然生态系统也成为逐渐显现的环境问题。由于药物具有在自然环境中难以快速降解和对水生枝角类高毒性的特点,因此流入天然水体的伊维菌素存在着影响水生态平衡的风险。为了比较全面评估药物对水生动物潜在的毒害作用,研究模拟天然河道环境,对药物在底质中的降解速率进行了测定,并选取7种占据不同生态位的水生生物作为试验对象,通过关于急性毒性的国家标准试验方法来初步评价药物对水生态系统的风险。结果显示伊维菌素在自然水体中降解缓慢,在泥水混合25℃恒温条件下,70d的降解率仅为28.3%。急性毒性试验结果显示伊维菌素对发光细菌(Photobacterium)并不表现出毒性,对淡水小球藻(Chlorella vulgaris)的96h EC50=19.80 mg/L,属中毒;而对其他实验生物则表现出了较高的毒性,伊维菌素对斑马鱼(Brachydanio rerio)、食蚊鱼(Gambusia affinis)和鲫鱼鱼苗(Carassius carassius)的96h LC50分别为40.48、34.81和13.79μg/L,对罗氏沼虾(Macrobrachium rosenbergii)的96h LC50=7.87μg/L,对大型溞(Daphniamagna)的24h LC50=4.81 ng/L,均属极高毒。因此残留在天然水体的伊维菌素对水生态中的生物有较大影响,对含伊维菌素的废弃物排放进行监控和科学管理非常必要。     

Sensitivity of various parameters in Euglena gracilis to short-term exposure to industrial wastewaters

Due to the presence of various potential pollutants industrial wastewaters pose considerable threats to natural waters and make it unfit for the aquatic biota. Analysis of wastewaters by chemical methods is a common practice; however, it does not reflect the toxic effects on living organism. Therefore, bioassessment is necessary for monitoring of wastewater quality. In the present study, the toxic effects of wastewater samples from different industries were evaluated using Euglena gracilis as a biotest organism. Various parameters of the freshwater flagellate E. gracilis like motility, swimming velocity, cell shape, gravitactic orientation (using the automatic biotest ECOTOX) and photosynthetic efficiency (using a pulse amplitude modulated fluorometer) were used as end points for toxicity assessment. In addition, the samples were analysed for some ecologically important physicochemical properties. With some exceptions, most of the physicochemical properties of the tested samples were within the acceptable range of national environmental quality standards for municipal and industrial effluents. However, all the water samples adversely affected different parameters in E. gracilis. This study led to the conclusion that different toxic substances present in wastewater, even at low concentrations, can be a possible threat to aquatic biota. The results of this study prove that ECOTOX is a sensitive, easy, and fast bioassay for monitoring of water and wastewater quality. Gravitactic orientation and cell compactness of E. gracilis were the most sensitive parameters to wastewater toxicity.     

Effects of Chronic Waterborne and Dietary Metal Exposures on Gill Metal-Binding: Implications for the Biotic Ligand Model

The biotic ligand modeling (BLM) approach has gained recent widespread interest among the scientific and regulatory communities because of its potential for developing ambient water quality criteria (AWQC), which are site-specific, and in performing aquatic risk assessment for metals. Currently, BLMs are used for predicting acute toxicity (96?h LC50 for fish) in any defined water chemistry. The conceptual framework of the BLM has a strong physiological basis because it considers that toxicity of metals occurs due to the binding of free metal ions at the physiologically active sites of action (biotic ligand, e.g., fish gill) on the aquatic organism, which can be characterized by conditional binding constants (log K) and densities (B_max). At present, these models assume that only water chemistry variables such as competing cations (e.g., Na⁺, Ca²⁺, Mg²⁺, and H⁺), inorganic ligands (e.g., hydroxides, chlorides, carbonates), and organic ligands (dissolved organic matter) can influence the bioavailability of free metal ions and thereby the acute toxicity of metals. Current BLMs do not consider the effects of chronic history of the fish in modifying gill-metal binding characteristics and acute toxicity. Here, for Cu, Cd, and Zn, we review a number of recent studies on the rainbow trout that describe significant modifying effects of chronic acclimation to waterborne factors (hardness and chronic metal exposure) and dietary composition (metal and essential ion content) on gill metalbinding characteristics (on both log K and B_max) and on acute toxicity. We conclude that the properties of gill-metal interaction and toxicological sensitivity appear to be dynamic rather than fixed, with important implications for further development of both acute and chronic BLMs. Now that the initial framework of the BLM has been established, future research needs a more integrative approach with additional emphasis on the dynamic properties of the biotic ligand to make it a successful tool for ecological risk assessment of metals in the natural environment.     

MASS MORTALITY OF MARINE AND ESTUARINE FISH IN THE SWARTVLEI AND WILDERNESS LAKE SYSTEMS,SOUTHERN CAPE.

Summary

Two incidences of mass mortality of fish were recorded in two saline waterbodies (Swartvlei estuary and Rondevlei) in the Wilderness National Park. Species affected were the Knysna seahorse (Hippocampus capensis) and longsnout pipefish (Syngnathus acus) in the Swartvlei estuary, and Cape stumpnose (Rhabdosargus holubi) and white steenbras (Lithognathus lithognathus) in Rondevlei. Comparison of water quality parameters during fish mortalities to past ranges and reported species tolerances indicated that the probable causes for the mortalities were high water temperature in the Swartvlei estuary, and low dissolved oxygen concentration in Rondevlei.     

THE USE OF BENZOCAINE HYDROCHLORIDE AS FISH TRANQUILLIZER AND ANAESTHETIC IN SALINE WATERS

SUMMARY

The anaesthetic effects of various concentrations of benzocaine hydrochloride were tested on Liza macrolepis and Sarotherodor mossambicus in sea water and diluted sea water, respectively. Induction time for anaesthesia was negatively correlated with increasing anaesthetic concentrations in L. macrolepis.

In S. mossambicus, however, operculum clamping appeared to be responsible-f or induction times increasing with increased anaesthetic concentration.

The tranquillizing effects of low concentrations of benzocaine hydrochloride on L. macrolepis was also studied.     

Effects of water hardness and Cu and Zn on LC50 in Gambusia holbrooki

Abstract

The aim of this study was to determine by static bioassay whether water hardness affects the toxicity of Zn and Cu to a fish, Gambusia holbrooki Girard, 1859. The acute toxicity of selected heavy metals to G. holbrooki was determined in soft, hard and very hard water (25, 125 and 350 mg L^?1 as CaCO₃). Results showed that water hardness had a significant effect on Cu and on Zn toxicity on fish. Toxicity of Cu and of Zn increased with decreasing water hardness. The 96 hours LC₅₀ values for G. holbrooki were higher in the hard and very hard water compared with soft water. Water hardness had a much smaller effect upon the acute toxicity of Cu than that of Zn. It was observed that the 96 hours LC50 for Cu at the soft, hard and very hard water was found to be 0.017, 0.17 and 0.65 mg L^?1, respectively, while the 96 hours LC₅₀ for Zn at the soft, hard and very hard water was found to be 0.46, 48.1 and 121.6 mg L^?1, respectively.     

Egg Selenium Concentrations as Predictors of Avian Toxicity

Aquatic birds are exposed to selenium through their diet by ingesting aquatic invertebrates that have accumulated selenium from water and the food chain. However, dietary composition is highly variable among species, over time, and across sites, making it difficult to provide accurate estimations of dietary exposure for particular species at specific locations. Selenium accumulates in the egg, resulting in embryo malformation, embryonic death, and decreased survival of juveniles. If the relationship between egg concentration and these reproductive parameters can be defined with sufficient certainty, then risk assessments can be performed through analysis of egg selenium concentrations. Other researchers have proposed egg toxicity thresholds that lead to conclusions of widespread selenium toxicoses in waterbirds. However, we believe these values are overly conservative and that it is unlikely that selenium is posing a significant risk to wild birds in areas where the current water quality criterion is being met. Through the use of simple statistical models (logit, probit, and Weibull functions) we are able to express mortality and teratogenicity relationships for mallards (Anas platyrhynchos) in such a manner that the risk manager can be presented with information about the probability of reduced duckling survival if mean egg selenium (MES) concentrations are known. Data analysis indicates that the two endpoints (mortality and teratogenesis) cannot be distinguished statistically. Commonly used effects thresholds (the EC₁₀ and EC₂₀) correspond to 16 and 21?mg/kg dw MES using the most sensitive endpoint, chick mortality. Both of these values are higher than the 6?mg/kg dw level proposed by Skorupa (1998) who based his estimate on field-observational data potentially confounded by other environmental stress factors. The mortality and teratogenicity endpoints presented here relate selenium exposure to risk to individuals within a population and do not provide information about the probability of selenium causing changes in population growth rates, either at the local or regional levels.     

An effect factor approach for quantifying the impact of plastic additives on aquatic biota in life cycle assessment

Purpose

Plastic pervades now almost every aspect of our daily lives, but this prosperity has led to an increasing amount of plastic debris, which is now widespread in the oceans and represents a serious threat to biota. However, there is a general lack of consideration regarding marine plastic impacts in life cycle assessment (LCA). This paper presents a preliminary approach to facilitate the characterization of chemical impacts related to marine plastic within the LCA framework.

Methods

A literature review was carried out first to summarize the current state of research on the impact assessment of marine plastic. In recent years, efforts have been made to develop LCA-compliant indicators and models that address the impact of marine littering, entanglement, and ingestion. The toxicity of plastic additives to marine biota is currently a less understood impact pathway and also the focus of this study. Relevant ecotoxicity data were collected from scientific literature for a subsequent additive-specific effect factor (EF) development, which was conducted based on the USEtox approach. Extrapolation factors used for the data conversion were also extracted from reliable sources.

Results and discussion

EFs were calculated for six commonly used additives to quantify their toxicity impacts on aquatic species. Triclosan shows an extremely high level of toxicity, while bisphenol A and bisphenol F are considered less toxic according to the results. Apart from additive-specific EFs, a generic EF was also generated, along with the species sensitivity distribution (SSD) illustrating the gathered data used to calculate this EF. Further ecotoxicity data are expected to expand the coverage of additives and species for deriving more robust EFs. In addition, a better understanding of the interactive effect between polymers and additives needs to be developed.

Conclusions

This preliminary work provides a first step towards including the impact of plastic-associated chemicals in LCA. Although the toxicity of different additives to aquatic biota may vary significantly, it is recommended to consider additives within the impact assessment of marine plastic. The generic EF can be used, together with a future EF for adsorbed environmental pollutants, to fill a gap in the characterization of plastic-related impacts in LCA.

     

Environmental improvement of lead refining: a case study of water footprint assessment in Jiangxi Province,China

Purpose

China is currently facing water scarcity due to its large national population and rapid economic development. Lead is a typical non-ferrous metal. The lead industry is one of the top 10 water-consuming industries in China and suffers from the heavy burden of properly managing discharged wastewater containing heavy metals and organic pollutants. Accordingly, a water footprint analysis of lead refining was conducted in this study to enhance the water management in China’s lead industry. This study is part 2 of the environmental improvement for lead-refining series.

Methods

In accordance with the ISO 14046 standard, life cycle assessment-based water footprint analysis was applied to a lead-refining enterprise in Jiangxi Province, China. Five midpoint (i.e., water scarcity, aquatic eutrophication, carcinogens, non-carcinogens, and freshwater ecotoxicity) and two endpoint (i.e., human health and ecosystem quality) indicators are utilized to assess the water footprint impact results.

Results and discussion

Direct pollutant emissions are a major contributor to ecosystem quality and freshwater ecotoxicity, whereas indirect processes (i.e., industrial hazardous waste landfill, transport, and chemicals) contribute considerably to human health, aquatic eutrophication, and carcinogen categories. Chromium, copper, arsenic, and zinc were the key substances in the lead production chain, and their emissions exerted a significant impact on human health and ecosystem quality.

Conclusions

Reducing direct copper emission was the most important key to minimizing ecosystem quality decline in China’s lead industry, and optimizing indirect processes was effective in mitigating the impact on human health. Enhancing wastewater treatment, increasing chemical consumption efficiency, optimizing transport and industrial hazardous waste disposal, improving supervision, issuing relevant governmental regulations, and adopting advanced wastewater treatment technologies are urgently needed to control the water footprint.

     

Analysis of CYP450 gene allelic variants can predict ifosfamide toxicity in Mexican paediatric patients

Abstract

Context: Ifosfamide (IFA) is an effective antineoplastic for solid tumours in children, although it is associated with high levels of systemic toxicity and causes death in some cases.

Objective: The aim of this study was to determine whether the presence of certain allelic variants of genes CYP2B6, CYP2C9, CYP3A4 and CYP3A5 increases the risk of toxicity in children with solid tumours treated with ifosfamide.

Materials and methods: A total of 131 DNA samples were genotyped by real-time polymerase chain reaction (RT-PCR) using TaqMan probes. Toxicity was assessed using WHO criteria, and survival analysis was performed using Kaplan–Meier curves.

Results: The rs3745274 allelic variant in CYP2B6 was associated with haematological toxicity, affecting neutrophils; CYP3A4 variant rs2740574 was also associated with toxicity, affecting both leukocytes and neutrophils. Additionally, the CYP3A5 gene variant rs776746 was found to affect haemoglobin.

Conclusions: Our results show that allelic variants rs3745274 (CYP2B6), rs2740574 (CYP34) and rs776746 (CYP3A5) increase the risk for high haematological toxicity.

Clinical trial registration: 068/2013     

乙腈的水生态基准

本文参照美国国家环保局推荐的“推导保护水生生物及其用途的国家水质基准的技术指南”,根据我国水生生物区系特点,通过水生生物毒性试验研究和制定石油化工废水中重要污染物—乙腈的水生态基准。试验动物涉及到4个门、6个纲、8个科、13属和13个种。文中根据乙腈对13种水生动物的急性毒性试验,对水生动物的慢性毒性试验以及对水生植物浮萍的生长抑制试验,推导出乙腈的基准连续浓度为413mg／L,基准最大浓度为1145mg／L。     

Limnology of the Green Lakes Valley: phytoplankton ecology and dissolved organic matter biogeochemistry at a long-term ecological research site

ABSTRACT

Background: Surface waters are the lowest points in the landscape, and therefore serve as excellent integrators and indicators of changes taking place in the surrounding terrestrial and atmospheric environment.

Aims: Here we synthesise the findings of limnological studies conducted during the past 15 years in streams and lakes in the Green Lakes Valley, which is part of the Niwot Ridge Long Term Ecological Research (LTER) Site.

Methods: The importance of these studies is discussed in the context of aquatic ecosystems as indicators, integrators, and regulators of environmental change. Specifically, investigations into climatic, hydrologic, and nutrient controls on present-day phytoplankton, and historical diatom, community composition in the alpine lake, Green Lake 4, are reviewed. In addition, studies of spatial and temporal patterns in dissolved organic matter (DOM) biogeochemistry and reactive transport modelling that have taken place in the Green Lakes Valley are highlighted.

Results and conclusions: The findings of these studies identify specific shifts in algal community composition and DOM biogeochemistry that are indicative of changing environmental conditions and provide a framework for detecting future environmental change in the Green Lakes Valley and in other alpine watersheds. Moreover, the studies summarised here demonstrate the importance of long-term monitoring programmes such as the LTER programme.