Evaluation of Sublethal Toxicity of Nitrite to a Suite of Aquatic Organisms in Support of the Derivation of a Chronic Environmental Water Quality Benchmark.

Nitrite is a naturally-occurring inorganic compound that occurs in aquatic environments as an intermediary between nitrate and ammonia in the nitrogen cycle. It is a contaminant of potential concern resulting from anthropogenic activities in some cases. While the acute toxicity of nitrite has been characterized in previous studies, its sublethal toxicity is less understood. To determine the sublethal toxicity of nitrite on freshwater organisms, a suite of organisms was tested including: two salmonids (Oncorhynchus mykiss and O. kisutch), an alga (Pseudokirchneriella subcapitata), an aquatic macrophyte (Lemna minor), and three invertebrates (Ceriodaphnia dubia, Chironomus dilutus, and Neocloeon triangulifer). Test organisms were exposed to nitrite concentrations ranging between 0.02 and 1.28 mg/L nitrite (NO2-N). The toxicity tests were conducted according to procedures specified in standardized methods, allowing for the estimation of multiple endpoints for each test species. Species sensitivity distributions (SSDs) were generated using endpoints from the toxicity testing results, as well as data from previous studies, from which water chemistry approximated that used in the tests (i.e., < 5 mg/L chloride, an important toxicity-modifying factor for nitrite). The mayfly, N. triangulifer, was the most sensitive species, followed by the two salmonids (which represented the second and third most sensitive species), although they were not as sensitive to nitrite exposure as reported in previous studies. The fifth percentile hazard concentration (HC5) generated from the SSD could be used for derivation of regulatory benchmarks and threshold values for site-specific aquatic risk assessments.

Implications of deep-seabed mining on marine ecosystems-Introduction to a special series of papers.

After more than 50 years of exploration and research that has intensified over the past decade, deep-seabed mining (DSM) remains a controversial subject, resulting mainly from legacy issues of other extractive industries. Moreover, our planet is environmentally challenged, with climate change as one of the major issues that we collectively face. Deep-seabed mining aims to collect metal resources lying on the deep seabed to help meet increased global demand caused by growth in population and urbanization, and clean energy, in a way that reduces pressures on land, such as deforestation and community relocation. The metals found on the seabed are those needed to address climate change through clean energy technologies. An important question facing us is: How do we, most responsibly, obtain the metals we need with the least impact on the planet we are trying to protect? DSM is one of the options to meet the demand. In this IEAM special series, we set out to present neutral and unbiased perspectives on the environmental implications of DSM. Our aim is to offer readers environmental management considerations learned by researchers around the world and working in diverse aspects of the field, including: population and community assessment, biota ecosystem services, environmental ethics, and rehabilitation and restoration. In consideration of the controversies, fundamental questions still remain: How can a new industry be given the opportunity to "do the right thing"? How do we make evidence-based decisions about where metals should come from when emotions and possibly fear often seem to drive the debate? Can we assume that decisions and policies are best achieved based on data and evidence? The papers presented in the series help address these questions and cover a range of diverse topics from ethical frameworks to biodiversity assessment to risk assessment to restoration. Integr Environ Assess Manag 2022;18:631-633. © 2021 SETAC.

Are current tissue-based selenium guidelines and criteria overly protective of freshwater fish populations? A critical review with recommendations.

Several decades after selenium impacts on wild fish populations were observed in freshwater reservoirs receiving fly ash effluents from electric power facilities at Belews Lake and Hyco Reservoir (North Carolina, USA), developments in selenium (Se) toxicology have led to a greater understanding of Se effects on freshwater fish. These latter advancements have allowed regulatory agencies in several jurisdictions to develop tissue-based toxicity benchmarks for the protection of aquatic life. These benchmarks were generally derived from datasets encompassing multiple fish species and designed to protect the most sensitive species (US Environmental Protection Agency [EPA] water quality criteria). Safety factors have been applied in the development of some Canadian guidelines (British Columbia [BC]), resulting in guidelines that appear to be overly conservative. The present study addresses the question, "Are current tissue-based selenium guidelines and criteria overly protective of freshwater fish populations?" A literature review was conducted of studies in which Se was the primary constituent of concern, to compare tissue concentrations and results of fish population metrics and deformity assessment studies with current regulatory thresholds for the protection of aquatic life in the United States and Canada. EPA fish tissue-based Se criteria were found to be protective of fish populations and, at times, overly protective. Canadian water quality guidelines for Se (BC Ministry of Environment and Climate Change Strategy [BCMOECCS], Environment and Climate Change Canada [ECCC]) were consistently found to be overly protective, especially for benchmarks in which safety factors were used to derive those guidelines. In addition to a synthesis of the results of these studies, various limitations of the reviewed studies are discussed, and recommendations for future studies are proposed. Integr Environ Assess Manag 2022;18:622-630. © 2021 SETAC.

Lentic, lotic, and sulfate-dependent waterborne selenium screening guidelines for freshwater systems.

There is consensus that fish are the most sensitive aquatic organisms to selenium (Se) and that Se concentrations in fish tissue are the most reliable indicators of potential toxicity. Differences in Se speciation, biological productivity, Se concentration, and parameters that affect Se bioavailability (e.g., sulfate) may influence the relationship between Se concentrations in water and fish tissue. It is desirable to identify environmentally protective waterborne Se guidelines that, if not exceeded, reduce the need to directly measure Se concentrations in fish tissue. Three factors that should currently be considered in developing waterborne Se screening guidelines are 1) differences between lotic and lentic sites, 2) the influence of exposure concentration on Se partitioning among compartments, and 3) the influence of sulfate on selenate bioavailability. Colocated data sets of Se concentrations in 1) water and particulates, 2) particulates and invertebrates, and 3) invertebrates and fish tissue were compiled; and a quantile regression approach was used to derive waterborne Se screening guidelines. Use of a regression-based approach for describing relationships in Se concentrations between compartments reduces uncertainty associated with selection of partitioning factors that are generally not constant over ranges of exposure concentrations. Waterborne Se screening guidelines of 6.5 and 3.0 µg/L for lotic and lentic water bodies were derived, and a sulfate-based waterborne Se guideline equation for selenate-dominated lotic waters was also developed. Environ Toxicol Chem 2017;36:2503-2513. © 2017 SETAC.

Evaluation of the effect of water type on the toxicity of nitrate to aquatic organisms.

A suite of acute and chronic toxicity tests were conducted to evaluate the sensitivity of freshwater organisms to nitrate (as sodium nitrate). Acute exposures with rainbow trout (Onchorhynchus mykiss) and amphipods (Hyalella azteca), as well as chronic exposures with H. azteca (14-d survival and growth), midges (Chironomus dilutus; 10-d survival and growth), daphnids (Ceriodaphnia dubia; 7-d survival and reproduction), and fathead minnows (Pimephales promelas; 7-d survival and growth) were used to determine sublethal and lethal effect concentrations. Modification of nitrate toxicity was investigated across a range of ionic strengths, created through the use of very soft water, and standard preparations of synthetic soft, moderately-hard and hard dilution waters. The most sensitive species tested were C. dubia and H. azteca, in soft water, with reproduction and growth IC25 values of 13.8 and 12.2 mg/L NO3-N, respectively. All of the organisms exposed to nitrate demonstrated significantly reduced effects with increasing ionic strength associated with changes in water type. Possible mechanisms responsible for the modifying effect of increasing major ion concentrations on nitrate toxicity are discussed.

Species sensitivity distribution evaluation for selenium in fish eggs: considerations for development of a Canadian tissue-based guideline.

A freshwater Se guideline was developed for consideration based on concentrations in fish eggs or ovaries, with a focus on Canadian species, following the Canadian Council of Ministers of the Environment protocol for developing guideline values. When sufficient toxicity data are available, the protocol recommends deriving guidelines as the 5th percentile of the species sensitivity distribution (SSD). When toxicity data are limited, the protocol recommends a lowest value approach, where the lowest toxicity threshold is divided by a safety factor (e.g., 10). On the basis of a comprehensive review of the current literature and an assessment of the data therein, there are sufficient egg and ovary Se data available for freshwater fish to develop an SSD. For most fish species, Se EC10 values (10% effect concentrations) could be derived, but for some species, only no-observed-effect concentrations and/or lowest-observed-effect concentrations could be identified. The 5th percentile egg and ovary Se concentrations from the SSD were consistently 20 µg/g dry weight (dw) for the best-fitting distributions. In contrast, the lowest value approach using a safety factor of 10 would result in a Se egg and ovary guideline of 2 µg/g dw, which is unrealistically conservative, as this falls within the range of egg and ovary Se concentrations in laboratory control fish and fish collected from reference sites. An egg and ovary Se guideline of 20 µg/g dw should be considered a conservative, broadly applicable guideline, as no species mean toxicity thresholds lower than this value have been identified to date. When concentrations exceed this guideline, site-specific studies with local fish species, conducted using a risk-based approach, may result in higher egg and ovary Se toxicity thresholds.

An aquatic toxicological evaluation of sulfate: the case for considering hardness as a modifying factor in setting water quality guidelines.

Elevated concentrations of sulfate occur commonly in anthropogenically impacted and natural waters. However, water quality guidelines (WQG) have not been developed in many jurisdictions, and chronic toxicity data are scarce for this anion. A variety of test organisms, including species of invertebrate, fish, algae, moss, and an amphibian, were tested for chronic toxicity to develop a robust dataset that could be used to develop WQGs. As an example of how these data might be used to establish guidelines, calculations were performed using two standard procedures: a species sensitivity distribution (SSD) approach, following methods employed in developing Canadian WQGs, and a safety factor approach, according to procedures typically used in the development of provincial WQGs in British Columbia. The interaction of sulfate toxicity and water hardness was evaluated and incorporated into the calculations, resulting in separate values for soft (10-40 mg/L), moderately hard (80-100 mg/L) and hard water (160-250 mg/L). The resulting values were 129, 644, and 725 mg/L sulfate, respectively, following the SSD approach, and 75, 625, and 675 mg/L sulfate, following the safety factor approach.

A new quality assurance system for the evaluation of ecotoxicity studies submitted under the New Substances Notification Regulations in Canada.

New substances destined for import into, or manufacture in, Canada must be reported to Environment Canada and Health Canada under the New Substances Notification Regulations (Chemicals and Polymers) (NSNR). With the use of information provided by the notifier, and other complementary information available to the 2 departments, the New Substances Program conducts ecological and human health risk assessments. Over the past 10 y, more than 750 ecotoxicity studies have been submitted to the New Substances Program of Environment Canada under the NSNR. Most of these experimental studies are not publicly available but are useful in the ecological risk assessment of new substances and for the development of Quantitative Structure-Activity Relationships (QSARs). In this paper, we describe the development and validation of a computer-based scoring system and our approach in the development of scoring methods used to assess the quality and usability of ecotoxicity studies with fish, Daphnia spp., and green algae. Results of ranking exercises conducted with these methods are described and discussed, together with the potential use of these results in a regulatory context. In addition, the methods are discussed in comparison with other similar evaluation schemes described in the literature.