Phytoplankton bioassays for evaluating toxicity of in situ sediment contaminants

Routine bulk chemical characterization of sediments does not provide useful information on toxicity of sediment bound contaminants. This study reviewed and evaluated the utility of phytoplankton bioassays for evaluation of toxicity of sediment bound contaminants, including state-of-the-art techniques. Several techniques such as Algal Fractionation Bioassays, microcomputer-based toxicity testing and in situ bioassays including plankton cages have been developed and successfully applied in our research at various contaminated sites in the St. Lawrence Great Lakes. These bioassay techniques are sensitive, rapid and inexpensive for screening contaminants. The use and application of such techniques, based on bioavailability and physiological response of micro-organisms, are essential for the detection of environmental perturbations of an ecosystem. Such an early warning system will facilitate the preservation and rehabilitation of the Great Lakes.     

Environmental Risk of Pesticides: Applying the DelAzulPestRisk Model to Freshwaters of an Agricultural Area of Argentina

DelAzulPestRisk is a risk-based chemical ranking model based on human and local biota toxicities that estimates the integrated risk of pesticides in water from their extensive (concentration, risk) and intensive (persistence, bioaccumulation) chemical properties. The model is built on two modules: human health risk factor (estimated based on the probabilistic cancer and non-cancer health risk by using U.S. Environmental Protection Agency models applied to a bathing exposure scenario) and biota health risk factor (quantified on the basis of the probabilistic toxicity exposure ratio –PEC/PNEC– for three local representatives of water biota multiplied by an amplification factor supported by the persistence and bioaccumulation potential). The model was applied to shallow creeks of Tres Arroyos County, Argentina, which flow across wheat and soybean agricultural lands, and in whose waters were detected many organochlorine pesticides (α, γ, y, δ-HCH, aldrin, heptachlor, γ-chlordane, endosulfan, endosulfan sulphate, dieldrin, and DDD). Dieldrin, aldrin, and heptachlor generated the worst potential effects—due mainly to the cancer and non-cancer dermal health risk—although this was not a significant environmental threat. DelAzulPestRisk is a screening assessment tool for water management purposes that become useful in countries lacking efficient water quality control systems.     

The Life-Cycle of Chlorine, Part IV

Some cyclic organo-chlorines share key characteristics to a significant degree, notably volatility, solubility in lipids, environmental persistence, a tendency to bioaccumulation, and toxicity to animals. A subset of this group has been designated "persistent organic pollutants" (POPs). Because of their volatility, persistence, and tendency to bioaccumulate, POPs are found in remote locations, such as the Arctic, far from the locations where they were initially used or produced.
Except PCDDs (dioxins) and PCDFs (furans), all are, or were, originally produced for use as such , mainly as pesticides or herbicides. PCDDs and PCDFs have never been produced for their own sake; they are unwanted contaminants of chemical intermediates that were passed on and incorporated in final products, notably herbicides; they are also generated spontaneously in most combustion processes and chlorine bleaching of paper. Most POPs have been sharply restricted or banned outright in most of the industrialized countries, but not in less developed countries.
The qualities of persistence and bioaccumulation give special urgency to monitoring not only point source emissions and local concentrations, but also the mobile environmental reservoirs and exposure routes of these chemicals. To conduct adequate risk analyses, far more detailed data is needed on quantities produced and used, quantities and location of storage, mode of use, location of use, and period of use. Such data are not collected consistently by government or international agencies.     

Terrestrial Metals Bioavailability: A Comprehensive Review and Literature-Derived Decision Rule for Ecological Risk Assessment

Interstudy variation among bioavailability studies is a primary deterrent to a universal methodology to assess metals bioavailability to soil-dwelling organisms and is largely the result of specific experimental conditions unique to independent studies. Accordingly, two datasets were established from relevant literature; one includes data from studies related to bioaccumulation (total obs = 520), while the other contains data from studies related to toxicity (total obs = 1264). Experimental factors that affected toxicity and bioaccumulation independent of the effect of soil chemical/physical properties were statistically apportioned from the variation attributed to soil chemical/physical properties for both datasets using a linear mixed model. Residual bioaccumulation data were then used to develop a non-parametric regression tree whereby bootstrap and cross-validation techniques were used to internally validate the resulting decision rule. A similar approach was employed with the toxicity dataset as an independent external validation. A validated decision rule is presented as a quantitative assessment tool that characterizes typical aerobic soils in terms of their potential to sequester common divalent cationic metal contaminants and mitigate their bioavailability to soil-dwelling biota.     

The Challenges of Hazard Identification and Classification of Insoluble Metals and Metal Substances for the Aquatic Environment

The OECD is currently harmonizing procedures for aquatic hazard identification of substances. Such a system already exists in Europe where it is recognized that special consideration must be given to sparingly soluble metals and metal compounds (SSMMCs) because standard hazard testing procedures designed for organic chemicals do not accommodate the characteristics of SSMMCs. Current aquatic hazard identification procedures are based on persistence, bioaccumulation, and toxicity (PBT) measurements. Persistence measurements typically used for organic substances (biodegradation) do not apply to metals. Alternative measurements such as complexation and precipitation are more appropriate. Metal bioaccumulation is important in terms of nutritional sufficiency and potential food chain transfer and toxicity. Unlike organic substances, metal bioaccumulation potential cannot be estimated using log octanol-water partition coefficients. Further, bioaccumulation and bioconcentration factors are often inversely related to exposure concentration for most metals and organisms, and hence are not reliable predictors of chronic toxicity or food chain accumulation. Metal toxicity is due predominately to the free metal ion in solution. In order to assess the toxicity of SSMMCs, the rate and extent of transformation to a soluble form must be measured.     

Forecasting the effects of global change scenarios on bioaccumulation patterns in great lakes species

Climate change will have substantial impacts on biodiversity, particularly for aquatic species. Warming temperatures and changing weather patterns will also remobilize and modify chemical partitioning. Holding millions of cubic yards of sediments contaminated with persistent legacy chemicals such as polychlorinated biphenyls (PCBs) and dioxins, the Laurentian Great Lakes are a laboratory for observing interactions between biological and chemical responses to climate change. They provide a wide range of habitat to a variety of species, from littoral forage fish to deep‐water predators. In this paper, we couple bioenergetic and bioaccumulation models to investigate the biological and chemical effects of climate change in the Great Lakes. We consider three species: round goby, a warm‐water invasive forage fish; mottled sculpin, a cool‐water native forage fish; and lake trout, a cold‐water native predator. Using our coupled models, we calculate the accumulation of a representative persistent chemical, PCB‐77, under four climate scenarios for Lake Erie and Lake Superior. Predator–prey (lake trout–round goby) interactions and food availability (high–low) are incorporated into our simulations. For cool‐ to cold‐water species (sculpin, lake trout) we find that warm temperatures limit growth. For warm‐water species (round goby) cold temperatures limit growth. The impact of climate warming on growth depends on the winter lows as well as the summer highs of the scenario, in combination with the species' critical upper and lower thermal limits. We find conditions for high growth and consumption rates generally lead to high bioaccumulation. However, this can be confounded by predator–prey dynamics, as mismatches in the temperature preferences of predator and prey can lead to mismatches in relative growth and uptake rates. As predator–prey dynamics are expected to undergo substantial shifts with changing climate, these relative thermal sensitivities will be key in determining the implications of climate change for bioaccumulation, particularly in top predator species.     

Fish contamination in Lake Erie: An examination of temporal trends of organochlorine contaminants and a Bayesian approach to consumption advisories

When examining environmental levels of organic contaminants, much of our focus has been placed on fish due to their greater potential to bioaccumulate and their direct linkage with human as a staple of their diet. Contaminant levels in Great Lakes fish communities have been closely monitored over the last few decades, and the resulting information has been indispensable in guiding consumption advisories. In this study, we first conducted an analysis of temporal trends of three organochlorines (hexachlorobenzene, octachlorostyrene, and α-hexachlorocyclohexane) in five Lake Erie fish species using dynamic linear modeling, while explicitly considering fish length and lipid content as covariates. Our results indicate that the levels of the three compounds have been steadily decreasing during the late 1970s to 2007, although there were instances in which the fish organochlorine contents exhibited fluctuations through time. The second part of our analysis focused on the development of a Bayesian framework to update fish consumption advisories. We present a methodology that incorporates the uncertainty in contaminant predictions and the natural variability in fish length and lipid content, while remaining flexible for different human weights and diet patterns. We then illustrate our Bayesian framework for two important contaminants in the Great Lakes region, mercury and PCBs. We established thresholds for each contaminant based on the tolerable daily intake (TDI) values and made predictive statements about the probability of exceedance of these critical levels. Our study also discusses how failure to account for model uncertainty/error can have profound implications for the credibility of the predictive risk assessment statements derived. The proposed Bayesian approach to fish consumption advisories can serve as a valuable framework for year-specific, highly customizable risk assessment statements that also account for the inherent variability in natural systems.     

A method for evaluating the impact of navigationally induced suspended sediments from the Upper Great Lakes Connecting Channels on the primary productivity

The impact of navigationally induced suspended sediments from the Upper Great Lakes Connecting Channels on the size-fractionated primary productivity was evaluated by the Carbon-14 technique. The method applied was on-site, rapid, sensitive, inexpensive, and provided dynamic-toxicological information essential for hazard assessment. Both enhancement and inhibition of the primary productivity was observed in various parts of the Upper Great Lakes Connecting Channels. These responses appear to depend on the type of natural plankton and their exposure to various contaminant/nutrient complexes generated by the disturbance of the bottom sediments during the passage of ships. Traditionally, only the inhibition of primary productivity has been monitored from a toxicity point of view, but it is important also to evaluate the implications of enhancement since it may result in increased eutrophication, propagation of nuisance blooms, and change of intricate food-web interactions. The procedure adopted in this study for the first time appears to possess considerable potential for a simple and rapid screening of environmental perturbations resulting from navigational activities.     

Integrated use of biomarkers and bioaccumulation data in Zebra mussel (Dreissena polymorpha) for site-specific quality assessment.

One of the useful biological tools for environmental management is the measurement of biomarkers whose changes are related to the exposure to chemicals or environmental stress. Since these responses might vary with different contaminants or depending on the pollutant concentration reached in the organism, the support of bioaccumulation data is needed to prevent false conclusions. In this study, several persistent organic pollutants -- 23 polychlorinated biphenyl (PCB) congeners, 11 polycyclic aromatic hydrocarbons (PAHs), six dichlorodiphenyltricholroethane (DDT) relatives, hexachlorobenzene (HCB), chlorpyrifos and its oxidized metabolite -- and some herbicides (lindane and the isomers alpha, beta, delta; terbutilazine; alachlor; metolachlor) were measured in the soft tissues of the freshwater mollusc Zebra mussel (Dreissena polymorpha) from 25 sampling sites in the Italian portions of the sub-alpine great lakes along with the measure of ethoxyresorufin dealkylation (EROD) and acetylcholinesterase (AChE) activity. The linkage between bioaccumulation and biomarker data allowed us to create site-specific environmental quality indexes towards man-made chemicals. This classification highlighted three different degrees of xenobiotic contamination of the Italian sub-alpine great lakes: a high water quality in Lake Lugano with negligible pollutant levels and no effects on enzyme activities, an homogeneous poor quality for Lakes Garda, Iseo and Como, and the presence of some xenobiotic point-sources in Lake Maggiore, whose ecological status could be jeopardized, also due to the heavy DDT contamination revealed since 1996.     

Integrated use of biomarkers and bioaccumulation data in Zebra mussel (Dreissena polymorpha) for site-specific quality assessment

One of the useful biological tools for environmental management is the measurement of biomarkers whose changes are related to the exposure to chemicals or environmental stress. Since these responses might vary with different contaminants or depending on the pollutant concentration reached in the organism, the support of bioaccumulation data is needed to prevent false conclusions. In this study, several persistent organic pollutants — 23 polychlorinated biphenyl (PCB) congeners, 11 polycyclic aromatic hydrocarbons (PAHs), six dichlorodiphenyltricholroethane (DDT) relatives, hexachlorobenzene (HCB), chlorpyrifos and its oxidized metabolite — and some herbicides (lindane and the isomers α, β, δ; terbutilazine; alachlor; metolachlor) were measured in the soft tissues of the freshwater mollusc Zebra mussel (Dreissena polymorpha) from 25 sampling sites in the Italian portions of the sub-alpine great lakes along with the measure of ethoxyresorufin dealkylation (EROD) and acetylcholinesterase (AChE) activity. The linkage between bioaccumulation and biomarker data allowed us to create site-specific environmental quality indexes towards man-made chemicals. This classification highlighted three different degrees of xenobiotic contamination of the Italian sub-alpine great lakes: a high water quality in Lake Lugano with negligible pollutant levels and no effects on enzyme activities, an homogeneous poor quality for Lakes Garda, Iseo and Como, and the presence of some xenobiotic point-sources in Lake Maggiore, whose ecological status could be jeopardized, also due to the heavy DDT contamination revealed since 1996.     

Evaluation and application of aquatic toxicity tests: use of the Microtox test for the prediction of toxicity based upon concentrations of contaminants in soil

The quality control for the reuse of cleaned soil from a contaminated site consisted in the determination of the main contaminants by analytical chemical methods such as GC and HPLC. Since it is not possible to analyze for all contaminants a toxicity test should be used to detect large concentrations of not routinely analyzed chemicals. The aim of the study was to develop a system for toxicity testing, which should be able to predict the toxicity of soil samples based on the concentration of chemicals in the soil and to detect toxic chemicals not analyzed by the routinely conducted soil analysis.Based upon the relative sensitivity to various contaminants as well as practical aspects such as test duration and costs the Microtox® test was favoured over the bioassays with Daphnia magna and Scenedesmus subspicatus. The Microtox® test was used to measure the toxicity of various pesticides and their major metabolites. The toxicity data of the pure compounds were used to predict the toxicity (EC₅₀ and % inhibition of the bioluminescence reaction) of defined mixtures of chemicals in water by applying two different mathematical appriaches which are based on the additivity of the effects of the single chemicals. The predicted values were compared with the experimental data and showed good agreement.In order to be able to predict the toxicity of soil samples using the Microtox® test the soil/water partition coefficient (K _d) was measured for the main contaminants. The toxicity of soil samples was predicted by calculating the concentration of the contaminants in the leachate by using the corresponding concentration in the soil and applying the K _d values determined. From the calculated composition of the leachate the expected toxicity was estimated. This value was compared with the toxicity experimentally determined in the Microtox® test.     

Evaluation of “Classic” and Emerging Contaminants Resulting from the Application of Biosolids to Agricultural Lands: A Review

The presence of detectable amounts of contaminants in treated sewage sludge (concentrations μg/kg – mg/kg) has led to concerns that land applications of biosolids may result in an accumulation of contaminants in the soil and their subsequent translocation through the food chain. Despite advances in wastewater management (e.g., anaerobic, thermophilic, and mesophilic digestion), many compounds and their metabolites remain intact following treatment. This review looks at the main risk factors relating to the occurrence of “classic” (persistent organic pollutants [POPs]) and emerging pollutants (pharmaceuticals and personal care products) in biosolids. Relevant EU legislation and risk assessment strategies for the control of emerging contaminants are also considered. Organic pollutants regulated under the Stockholm Convention on POPs along with PPCPs were identified as contaminants of concern based on the risk factors: persistence, bioaccumulation, and toxicity (PBT). PPCPs were recognized as being of particular concern as their high transformation/removal rates are compensated by their continuous introduction into the environment. This study highlights the growing concern in relation to emerging contaminants in biosolids and highlights risk assessment strategies that can be used to characterize potential human/environmental risks.     

Health-Based Criteria for Sediment Disposal Options: A Case Study of the Port of New York/New Jersey

Approximately 4 million cubic yards of sediment are dredged annually from the Port of New York and New Jersey in order to maintain navigable channels. In many cases, the sediments contain elevated levels of numerous contaminants. The New York District of the U.S. Army Corps of Engineers and U.S. Environmental Protection Agency Region II employ a framework of sediment quality evaluation to determine whether contaminated sediments are suitable for open ocean disposal (i.e., do not pose a health risk from bioaccumulation in human food chain) or whether more extensive and costly disposal methods are required. The degree to which chemicals can bioaccumulate from sediments into benthic invertebrates is a key determinant in the permitting decision. The maximally “acceptable” levels of bioaccumulation (bioaccumulation criteria) have been developed over a period of several years, using a variety of different methods. We reviewed the technical bases of these criteria and found that, while some values can be considered “risk-based,” others are based on historical background concentrations, Food and Drug Administration Action Levels, limits of detection, and other non-“risk-based” methodologies. Hence, the degree of uncertainty and health protection (or lack thereof) in the criteria varies considerably among the chemicals. We also reviewed the outcomes of several permit applications and found that the bioaccumulation criteria were not applied consistently. We propose the following refinements to the decision-making process: (1) bioaccumulation screening values based only upon risk-based criteria, using a single method that is applied for all chemicals; (2) increased consistency in decision-making and considerations of site-specific information where appropriate; and (3) assured availability of testing results for review and analysis by interested parties.     

C8- and C9-Alkylphenols and Ethoxylates: II. Assessment of Environmental Persistence and Bioaccumulation Potential

C8- and C9-alkylphenols and their ethoxylates (APE) are widely used commercial products mainly used in industrial applications, in the formulation of crop protection chemicals, and in industrial and household cleaners. Recent regulatory focus on these compounds has included an assessment of their potential to meet criteria for persistent, bioaccumulative, and toxic compounds (PBT). To fully evaluate either the relative persistence or bioaccumulation potential of any APE, degradation intermediates and metabolic by-products of these compounds should also be considered. To facilitate the evaluation of the ultimate fate of APE in the environment, a review of the degradation pathways and identification of degradation intermediates was performed (part I of a two-part series). In part II of this series, the relative persistence of APE as indicated by degradation half-lives was examined based on a review of abiotic and biological degradation data. To assess the bioaccumulation potential of APE, the relevant literature was also reviewed. The available data for C8- and C9-APE show that the commercial products and their degradation intermediates do not meet any national or international criteria for identifying these compounds as PBT substances.     

A Probabilistic Analysis of Regional Mercury Impacts on Wildlife

We investigate the uncertainties associated with modeling the potential health effects on piscivorous animals of mercury released to the atmosphere. The multimedia modeling system combines an atmospheric fate and transport model, an aquatic cycling model, and a terrestrial food web model. First, the modeling system is used to calculate point values of the animals' hazard quotients (i.e., measures of toxic dose). Next, we use a simplified version of the modeling system to conduct a probabilistic analysis for the Great Lakes region that takes into account input uncertainty, variability, and uncertainty and variability combined. The use of two different software packages for the combined uncertainty/variability analysis led to similar results except for high values (>90th percentile) where some differences were evident. A sensitivity study was performed on the combined uncertainty and variability analysis. Regional variability caused more than 70% of the variance in the results, with the fish bioaccumulation factor accounting for the majority of the variability. The major sources of uncertainty were the speciation of the mercury emissions, the lake pH, and the sediment burial rate.     

Comparative Study between CalTOX and Soil Screening Levels Modeling Approaches

A comparison was made between two different approaches to environmental modeling and risk assessment, specifically the one-medium approach of the USEPA Soil Screening Levels (SSL) and the multimedia approach in the CalEPA (CalTOX). Eleven priority pollutants were selected to represent different classes of chemicals as per their toxicity, physical and chemical properties, and persistence in the environment. Benzene, dioxin, PCB, B(a)P, chlo-rdane, chloroform, and TCE represent carcinogens, while xylene, toluene, phenol, chlordane, pyrene, TCE, and chloroform represent noncarcinogens. The highly volatile contaminants, including benzene, chloroform, xylene, toluene, and TCE, were selected to compare the volatilization from soil and the significance of inhalation pathways of the two models. The contaminants with strong sorption to soil and dust particles (dioxin, B(a)P, PCB, and chlordane) exhibited a preferential soil ingestion pathway. In contrast with CalTOX, inhalation was not considered as the dominant pathway for all the volatile contaminants in SSL. Furthermore, the risk assessment component of CalTOX accounts for multiple pathways as a consequence of its multimedia representation. Because the two models were based on different approaches, it is expected that the results would be different. For example, the results of the SSL were more conservative compared with CalTOX for all 11 chemicals. This observation still holds when considering the total risk from CalTOX vs. the risk based on the dominant pathway in SSL. Finally, the cancer slope factors and references doses were not the same for all the chemicals used in this study and resulted in different risk estimates.     

Sediment-associated contaminants — an overview of scientific bases for developing remedial options

The review article covers three major aspects of scientific research on sediment-associated contaminants during the last 20 years: (i) identification and monitoring of sources and distribution (sampling; sample preparation; analyses, mainly of non-residual fractions; estimation of pollution potential); (ii) study of processes and mechanisms of pollutant transfer (interactions between dissolved and particulate element species; particle environments; transport and diagenesis: colloids; surface microlayers; particle related processes; bioturbation; dredging operations; remobilization of toxic elements; bioaccumulation of organic chemicals: solid/dissolved distribution of contaminants); (iii) assessment of the environmental impact of particle-bound pollutations (chemical extraction sequence; sediment bioassay; combined chemical/biological test procedures). Enstead, empirical tests developed from multi-disciplinary research on biological, chemical and physical factors are applied for assessing the reactivity, mobility and bioavailability of sediment-bound pollutations and for estimating the validity of remedial measures.     

Challenges in constructing statistically based structure-activity relationship models for developmental toxicity

Regulatory agencies are increasingly called upon to review large numbers of environmental contaminants that have not been characterized for their potential to pose a health risk. Additionally, there is special interest in protecting potentially sensitive subpopulations and identifying developmental toxicants that may be present in the environment. Thus, there is an urgent need for efficient methods to screen large numbers of chemicals for their potential to pose a developmental hazard. One potential screening method involves the use of statistically based structure-activity relationship (SAR) tools to predict activity of untested chemicals. Such systems rely on statistical analyses to discern relationships between structure and activity for a training set of substances. Predictions can then be made for an untested substance as long as its structural features are encompassed by chemicals of the training set. In theory, such systems could assist regulatory agencies in their screening efforts; however, to date, there has been little independent evaluation of these tools for this use. To contribute to such an evaluation, the International Life Sciences Institute Risk Science Institute (ILSI RSI) convened a Working Group to examine methodology used to construct statistically based SAR systems for developmental toxicity. This document reports on the deliberations of the Working Group, which concluded that an improved process is needed for utilizing developmental toxicity data in the construction of statistically based SAR models. The process must be objective, reproducible, rational and transparent. Moreover, it must be informed by the expertise of developmental toxicologists and biologists and must be subject to peer review.     

A Decision Analytic Approach to Exposure-Based Chemical Prioritization

The manufacture of novel synthetic chemicals has increased in volume and variety, but often the environmental and health risks are not fully understood in terms of toxicity and, in particular, exposure. While efforts to assess risks have generally been effective when sufficient data are available, the hazard and exposure data necessary to assess risks adequately are unavailable for the vast majority of chemicals in commerce. The US Environmental Protection Agency has initiated the ExpoCast Program to develop tools for rapid chemical evaluation based on potential for exposure. In this context, a model is presented in which chemicals are evaluated based on inherent chemical properties and behaviorally-based usage characteristics over the chemical’s life cycle. These criteria are assessed and integrated within a decision analytic framework, facilitating rapid assessment and prioritization for future targeted testing and systems modeling. A case study outlines the prioritization process using 51 chemicals. The results show a preliminary relative ranking of chemicals based on exposure potential. The strength of this approach is the ability to integrate relevant statistical and mechanistic data with expert judgment, allowing for an initial tier assessment that can further inform targeted testing and risk management strategies.