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The bioaccumulation behavior, including the uptake, internal distribution, depuration, and biotransformation rates, of three widely used linear methyl‐siloxanes was investigated in rainbow trout. Dietary uptake efficiencies of octamethyltrisiloxane (L3), decamethyltetrasiloxane (L4), and dodecamethylpentasiloxane (L5) were 15% (3.3% standard error [SE]), 8.6% (1.4% SE), and 15% (1.8% SE), respectively, and for L3 and L4 were well below those of nonmetabolizable reference chemicals with similar octanol–water partition coefficients, suggesting significant intestinal biotransformation of L3 and L4. Somatic biotransformation rate constants were 0.024 (0.003 SE) day–1 for L3 and 0.0045 (0.0053 SE) day–1 for L4 and could not be determined for L5. Lipid‐normalized biomagnification factors for L3, L4, and L5 were 0.24 (0.02 SE), 0.24 (0.01 SE), and 0.62 (0.05 SE) kg‐lipid kg‐lipid–1, respectively. Bioconcentration factors standardized to a 5% lipid content fish for water in Canadian oligotrophic lakes with a dissolved organic carbon content of 7.1 mg L–1 were 2787 (354 SE) for L3, 2689 (312 SE) for L4, and 1705 (418 SE) L kg‐wet weight–1, respectively, and 3085 (392 SE) for L3, 4227 (490 SE) for L4, and 3831 (938 SE) L kg‐wet weight–1 in water with a dissolved organic carbon content of 2.0 mg L–1. A comparison of 238 bioaccumulation profiles for 166 different chemicals shows that the bioaccumulation profiles for L3, L4, and L5 are vastly different from those of other very hydrophobic compounds found in the environment. Environ Toxicol Chem 2024;43:42–51. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Don Mackay, a pioneer in environmental organic chemistry, passed away in 2023. He was known for his contributions to understanding and quantifying the fate and transport of contaminants in the environment. Mackay's work, which applied principles from chemical engineering and physical chemistry, simplified complex concepts and made them accessible to a wide audience. His research was widely adopted and applied in regulatory practice, demonstrating its usefulness. Mackay was dedicated to translational research and believed in collaboration among academia, government, and industry to manage chemical risks. His work focused on understanding the properties of contaminants, their behavior in the environment, and developing models to assess their effects. Mackay's legacy highlights the importance of scientific collaboration and using knowledge to address environmental challenges. [Extracted from the article]

Abstract: To support the goals articulated in the vision for exposure and risk assessment in the twenty‐first century, we highlight the application of a thermodynamic chemical activity approach for the exposure and risk assessment of chemicals in the environment. The present article describes the chemical activity approach, its strengths and limitations, and provides examples of how this concept may be applied to the management of single chemicals and chemical mixtures. The examples demonstrate that the chemical activity approach provides a useful framework for 1) compiling and evaluating exposure and toxicity information obtained from many different sources, 2) expressing the toxicity of single and multiple chemicals, 3) conducting hazard and risk assessments of single and multiple chemicals, 4) identifying environmental exposure pathways, and 5) reducing error and characterizing uncertainty in risk assessment. The article further illustrates that the chemical activity approach can support an adaptive management strategy for environmental stewardship of chemicals where “safe” chemical activities are established based on toxicological studies and presented as guidelines for environmental quality in various environmental media that can be monitored by passive sampling and other techniques. Environ Toxicol Chem 2018;37:1235–1251. © 2018 The Authors. Published by Wiley Periodicals, Inc. on behalf of SETAC. [ABSTRACT FROM AUTHOR]

We document the development and application of a food web bioaccumulation model for polychlorinated biphenyls (PCBs) in San Francisco Bay, California, USA. The model calculates spatial distributions of PCB concentrations in a range of invertebrate, fish, avian, and mammalian organisms, including harbor seals, double-crested cormorants, and Forster's terns. The performance of the model is evaluated against independent empirical PCB concentrations and shows a mean deviation between observed and model-calculated concentrations of 36% for female harbor seals and 5% for benthic invertebrates and jack smelt. The model was applied to produce bay-wide PCB concentration distributions in fish and wildlife species, which were compared with threshold effect concentrations to determine ecological risks and human health risks of fish consumption. Because of their high trophic position in the food web, harbor seals exhibited the highest concentrations of ∑PCBs, which exceeded threshold concentrations for potential adverse effects. The model was also applied to derive bay-wide target sediment concentrations for remediation as part of an ongoing total maximum daily loading characterization. The model calculated bay-wide geometric mean concentrations of ∑PCB in sediments of 1.6 to 73 µg/kg dry weight to meet several ecological and human health risk objectives. The bay-wide geometric ∑PCB concentration in the sediments at the time of the study was 11.6 µg/kg dry weight. The model was developed for assessing the behavior and risks of bioaccumulative substances on an ecosystem level. Environ. Toxicol. Chem. 2010;29:1385–1395. © 2010 SETAC [ABSTRACT FROM AUTHOR]

The bioavailability of four sediment-spiked hydrophobic organic contaminants (HOCs; chrysene, benzo[a]pyrene, chlordane, and Aroclor 1254) was investigated by comparing bioaccumulation by the amphipod Corophium colo with uptake into a thin film of ethylene/vinyl acetate (EVA) copolymer. The EVA thin film is a solid-phase extraction medium previously identified as effective at measuring the bioavailable contaminant fraction in sediment. The present study presents the results of 11 separate treatments in which chemical uptake into EVA closely matched uptake into lipid over 10 d. For all compounds, the concentration in EVA was a good approximation for the concentration in lipid, suggesting that this medium would be an appropriate biomimetic medium for assessing the bioaccumulation of HOCs during risk assessment of contaminated sediment. For chrysene and benzo[a]pyrene, limitations on bioaccumulation and toxicity because of low aqueous solubility were observed. The fugacity of the compounds in lipid (flip) and in the EVA thin film (fEVA) also was determined. The ratio of flip to fEVA was greater than one for all chemicals, indicating that all chemicals biomagnified over the duration of the exposure and demonstrating the potential for EVA thin-film extraction to assess trophic transfer of HOCs. [ABSTRACT FROM AUTHOR]

Partition coefficients that are used to predict concentrations of hydrophobic organic chemicals in biota (e.g., the bioconcentration factor) often assume that the sorptive capacity of an organism or tissue is adequately represented by its lipid content. In lean organisms and tissues, however, theory suggests that partitioning may be strongly influenced by the sorptive capacity of nonlipid materials, such as protein. Little is known about the sorptive capacity of proteins for hydrophobic organic chemicals, and methods to include proteins in bioaccumulation models do not exist. Here, we present a compilation and meta-analysis of published data to estimate the relative sorptive capacities of animal proteins and lipids for neutral organic chemicals. We found that the estimated sorptive capacity of protein in solid animal tissues ranged from around 1 to 10% that of lipid for compounds with a log octanol/water partition coefficient (KOW) of greater than two. The sorptive capacity of blood protein (albumin) appeared to be substantially higher than this, especially for low-KOW chemicals. For modeling purposes, we recommend estimating the sorptive capacity of animal protein as 5% that of lipid. According to this estimate, the sorptive capacity of an animal or tissue will be dominated by the contribution from protein if the lipid content makes up less than 5% of the dry-weight organic content. In such situations, a consideration of the sorptive capacity of nonlipid constituents, such as protein, will permit more accurate predictions of chemical accumulation and distribution. [ABSTRACT FROM AUTHOR]

Mechanistic bioaccumulation models for fish and piscivorous food-webs are widely used to assess the environmental hazard and risk of commercial chemicals, develop water quality criteria and remediation objectives, and conduct exposure assessment of pesticides in aquatic systems. Similar models for mammals and terrestrial food-webs are largely absent. As a result, the hazards and risks of bioaccumulative substances in mammals, birds, and humans remain unrecognized by regulators, and current globally used criteria for identifying bioaccumulative substances only apply to water-breathing organisms and are inadequate for protecting air-breathing organisms including mammals, birds, and human beings. In this paper, we develop and test a modeling framework that can be used to estimate the biomagnification potential and the organism-soil bioaccumulation factor of organic commercial chemicals in terrestrial food-chains. We test the model for the soil-earthworm-shrew food-chain and apply the model to illustrate that (i) chemicals with an octanol-air partition coefficient (KOA) < 105.25 do not biomagnify even if the KOW is high and optimal for biomagnification in fish; (ii) chemicals with a KOA ≥ 105.25 and a KOW between 101.75 and 1012 have a biomagnification potential unless they are metabolized at a sufficiently rapid rate (e.g., in excess of 0.3 d-1 or a half-life time of 2.5 d for shrews). [ABSTRACT FROM AUTHOR]

It is well documented that the bioavailability of hydrophobic organic chemicals (HOCs) can vary substantially among sediments. This makes risk assessments based on total sediment concentrations problematic. The present study investigates the application of thin-film solid-phase extraction to measure bioavailable concentrations of phenanthrene in estuarine sediment by comparing concentrations of phenanthrene in the amphipod Corophium colo and in thin ethylene/vinyl acetate films at different concentrations in three geochemically different sediments. For all sediment types, concentrations of phenanthrene in sediments and thin films followed linear relationships, indicating first-order exchange kinetics. Organism/thin-film concentration ratios did not vary systematically among sediment types but dropped significantly with increasing phenanthrene concentration in the sediments. While at low phenanthrene concentrations in the sediment fugacities of phenanthrene in the amphipods approached the fugacities in the thin films, they were significantly lower than those in the sediments at higher concentrations. While phenanthrene concentrations in the three sediment types were identical, biota sediment accumulation factors and concentrations in amphipods and thin films were consistently lower in sediments enriched with black carbon than in sediments with sedimentary organic matter bearing a more diagenetic organic signature. It is concluded that, for the range of concentrations tested, thin-film solid-phase extraction can be a useful tool in the characterization of differences in bioavailability of HOCs among sediment types. [ABSTRACT FROM AUTHOR]

With farmed British Columbia (BC) oysters containing higher cadmium concentrations than wild oysters, long-term exposure to cadmium through consumption of oysters has the potential to cause health risks. This study reports on a risk assessment for cadmium intake resulting from the consumption of BC-cultured oyster. The study concludes that Health Canada's current recommended BC-cultured oyster consumption rate for Canadians of 12 oysters per month exceeds the Agency for Toxic Substances and Disease Registry chronic oral minimal risk levels (MRL) of 0.2 μ g·kg- 1·day- 1 by approximately 4-to 5-fold and reaches the Food and Agriculture Organization/World Health Organization (FAP/WHO) reference dose of 1 μg·kg-1·day-1 for cadmium consumption for Canadians. This suggests that although the current recommended maximum oyster consumption rates is consistent with the FAO/WHO and U.S. Environmental Protection Agency limits for acceptable risk, it leaves little or no room for error or uncertainty. This is noteworthy as recent studies demonstrate toxicological effects at cadmium intakes of 0.43 to 0.71 μ gCd·kg-1·day-1. This study indicates that a lower maximum BC-cultured oyster rate should be considered, particularly for high risk groups, including women with low iron stores, people with renal impairment, smokers, children, and indigenous people who consume organ meats of games and wildlife other than shellfish. [ABSTRACT FROM AUTHOR]

Bioaccumulation assessment is important in the scientific evaluation of risks that chemicals may pose to humans and the environment and is a current focus of regulatory effort. The status of bioaccumulation evaluations for organic chemicals in aquatic systems is reviewed to reduce uncertainty in bioaccumulation measurement, to provide quality data for assessment, and to assist in model development. A review of 392 scientific literature and database sources includes 5317 bioconcentration factor (BCF) and 1656 bioaccumulation factor (BAF) values measured for 842 organic chemicals in 219 aquatic species. A data quality assessment finds that 45% of BCF values are subject to at least one major source of uncertainty and that measurement errors generally result in an underestimation of actual BCF values. A case study of organic chemicals on the Canadian Domestic Substances List indicates that empirical data are available for less than 4% of the chemicals that require evaluation and of these chemicals, 76% have less than three acceptable quality BCF or BAF values. Field BAFs tend to be greater than laboratory BCFs emphasizing the importance of environmental measurement for reliable assessment; however, only 0.2% of current use organic chemicals have BAF measurements. Key parameters influencing uncertainty and variability in BCF and BAF data are discussed using reviewed data and models. A critical evaluation of representative BCF and BAF models in relation to existing measurements and regulatory criteria in Canada indicate the probability of Type II errors, i.e., false negatives or ``misses'', using BCF models for bioaccumulation assessment may be as high as 70.6% depending on the model. Recommendations for the selection of measured and modelled values used in bioaccumulation assessment are provided, and improvements for the science and regulatory criteria are proposed.Key words: bioconcentration, bioconcentration factor, bioaccumulation, bioaccumulation factor, octanol–water partition coefficient, fish. [ABSTRACT FROM AUTHOR]

Species vary greatly in the degree to which they accumulate dietary contaminants. Bioenergetic processes play a key role in chemical uptake and elimination, and interspecific variation in bioaccumulation can be attributed in large part to variation in how species feed, digest, and allocate energy. We present a quantitative treatment of this relationship for the entire animal kingdom. We derive a model to predict the biomagnification factor for nonmetabolizable, slowly eliminated chemicals, BMFmax. We test the model with observed biomagnification factors and independently derived bioenergetic parameters for a diverse suite of species, including herbivores and carnivores, heterotherms and homeotherms, vertebrates and invertebrates, adults and juveniles, domestic/laboratory animals and wild individuals from freshwater, marine, and terrestrial environments. The model successfully predicts species- specific BMFmax values across this range of taxa, with values ranging from less than 1 in caterpillars to nearly 100 in some carnivores. In addition, we make novel predictions of BMFmax for several taxa for which no measured bioaccumulation data are available. Our analysis provides new insights into the role of ecology in chemical dynamics across the animal kingdom, providing a general framework for understanding how characteristics of an organism and its ecological context influence the degree to which that organism accumulates chemicals present in its diet. [ABSTRACT FROM AUTHOR]

Methods for the regulatory assessment of the bioaccumulation potential of organic chemicals are founded on empirical measurements and mechanistic models of dietary absorption and biomagnification. This study includes a review of the current state of knowledge regarding mechanisms and models of intestinal absorption and biomagnification of organic chemicals in organisms of aquatic and terrestrial food chains and also includes a discussion of the implications of these models for assessing the bioaccumulation potential of organic chemicals. Four mechanistic models, including biomass conversion, digestion or gastrointestinal magnification, micelle-mediated diffusion, and fat-flush diffusion, are evaluated. The models contain many similarities and represent an evolution in understanding of chemical bioaccumulation processes. An important difference between the biomagnification models is whether intestinal absorption of an ingested contaminant occurs solely via passive molecular diffusion through serial resistances or via facilitated diffusion that incorporates an additional advective transport mechanism in parallel (i.e., molecular ferrying within gastrointestinal micelles). This difference has an effect on the selection of physicochemical properties that best anticipate the bioaccumulative potential of commercial chemicals in aquatic and terrestrial food chains. Current regulatory initiatives utilizing KOW threshold criteria to assess chemical bioaccumulation potential are shown to be unable to identify certain bioaccumulative substances in air-breathing animals. We urge further research on dietary absorption and biomagnification of organic chemicals to develop better models for assessing the bioaccumulative nature of organic chemicals. [ABSTRACT FROM AUTHOR]

The present study examines a new bioaccumulation model for hydrophobic organic chemicals in aquatic food webs. The purpose of the model is to provide site-specific estimates of chemical concentrations and associated bioconcentration factors, bioaccumulation factors, and biota--sediment accumulation factors in organisms of aquatic food webs using a limited number of chemical, organism, and site-specific data inputs. The model is a modification of a previous model and incorporates new insights regarding the mechanism of bioaccumulation derived from laboratory experiments and field studies as well as improvements in model parameterization. The new elements of the model include: A model for the partitioning of chemicals into organisms; kinetic models for predicting chemical concentrations in algae, phytoplankton, and zooplankton; new allometric relationships for predicting gill ventilation rates in a wide range of aquatic species; and a mechanistic model for predicting gastrointestinal magnification of organic chemicals in a range of species. Model performance is evaluated using empirical data from three different freshwater ecosystems involving 1, 019 observations for 35 species and 64 chemicals. The effects of each modification on the model's performance are illustrated. The new model is able to provide better estimates of bioaccumulation factors in comparison to the previous food web bioaccumulation model while the model input requirements remain largely unchanged. [ABSTRACT FROM AUTHOR]

The present study examined the metabolic pathways of pyrene in dungeness crabs (Cancer magister) in the laboratory and the potential of using synchronous fluorescence spectrometry (SFS) to determine pyrene metabolite concentrations in the hemolymph of crabs exposed to polycyclic aromatic hydrocarbons (PAHs) in the field. Pyrene was metabolized by crabs mainly to 1-hydroxypyrene and pyrene-1-glucoside. Both pyrene metabolites could be detected by SFS in the hemolymph of crabs. A nondestructive hemolymph collection procedure was developed and used in conjunction with the SFS assay to assess the exposure of crabs to PAHs in Kitimat Arm (British Columbia, Canada). Our results showed that crabs obtained near the source of PAH contamination had the highest level of pyrene-related fluorescence in the hemolymph, whereas concentrations were lower at other sites downstream from the pollution source. In a separate study, the hepatopancreases of crabs were analyzed for parent PAHs by using gas chromatography-mass spectrometry. Pyrene-associated fluorescent responses of the hemolymph were found to correlate positively with the concentration of total PAHs in the hepatopancreas (r = 0.39, p < 0.05). [ABSTRACT FROM AUTHOR]

Deals with a study that estimated the effects of zebra mussels on the trophodynamics of polychlorinated biphenyl (PCB) through their effects on food web structure and particulate organic carbon (POC) levels. Experimental procedure; Results and discussion.

The article focuses on investigating the sources and environmental fate of halomethoxybenzenes (HMBs), compounds with attributes of persistence and potential for long-range transport, bioaccumulation, and toxic effects. It is discussed that the study reveals the widespread atmospheric dispersal of HMBs, emphasizing their continent-scale transport primarily through evaporation from water sources, shedding light on their origins and environmental pathways.

The article introduces several articles about the contributions of Don Mackay to the study of the behavior and effects of chemical substances in the environment.

To advance methods for bioaccumulation assessment of organic substances in air‐breathing organisms, the present study developed an in vitro approach for screening neutral hydrophobic organic substances for their bioaccumulation potential in air‐breathing organisms consisting of (1) depletion assays for chemicals in rat liver S9 subcellular fractions, (2) in vitro–in vivo extrapolation, and (3) whole‐organism bioaccumulation modeling to assess the biomagnification potential of neutral organic substances in the rat. Testing of the in vitro method on 14 test chemicals of potentially biomagnifying substances showed that the bioassays could be conducted with a high level of reproducibility and that in vitro–derived elimination rate constants were in good agreement with in vivo–determined elimination rate constants in the rat. Exploring the potential of the in vitro approach for screening organic chemicals for bioaccumulation in air‐breathing organisms indicated that chemical substances that exhibit a depletion rate constant in the S9 in vitro bioassay ≥0.3 h−1 are not expected to biomagnify in rats independent of their octanol–water partitioning coefficient (KOW) or octanol–air partitioning coefficient (KOA). The high level of reproducibility achieved in the test, combined with the good agreement between in vitro–derived and in vivo–determined depuration rates, suggests that the in vitro approach in combination with a KOA‐ and KOW‐based screening approach has good potential for screening chemicals in commerce for their bioaccumulation potential in air‐breathing organisms in a cost‐effective and expedient manner, especially if the bioassay can be automated. Environ Toxicol Chem 2022;41:2565–2579. © 2022 SETAC [ABSTRACT FROM AUTHOR]

Investigations into the biodegradation potential of perfluorooctane sulfonate (PFOS)-precursor candidates have focused on low molecular weight substances (e.g., N-ethyl perfluorooctane sulfonamido ethanol (EtFOSE)) in wastewater treatment plant sludge. Few data are available on PFOS-precursor biodegradation in other environmental compartments, and nothing is known about the stability of high-molecular-weight perfluorooctane sulfonamide-based substances such as the EtFOSE-based phosphate diester (SAmPAP diester) in any environmental compartment. In the present work, the biodegradation potential of SAmPAP diester and EtFOSE by bacteria in marine sediments was evaluated over 120 days at 4 and 25 °C. At both temperatures, EtFOSE was transformed to a suite of products, including N-ethyl perfluorooctane sulfonamidoacetate, perfluorooctane sulfonamidoacetate, N-ethyl perfluorooctane sulfonamide, perfluorooctane sulfonamide, and perfluorooctane sulfonate. Transformation was significantly more rapid at 25 °C (t1/2 = 44 ± 3.4 days; error represents standard error of the mean (SEM)) compared to 4 °C (t1/2 = 160 ± 17 days), but much longer than previous biodegradation studies involving EtFOSE in sludge (t1/2 ∼0.7-4.2 days). In contrast, SAmPAP diester was highly recalcitrant to microbial degradation, with negligible loss and/or associated product formation observed after 120 days at both temperatures, and an estimated half-life of >380 days at 25 °C (estimated using the lower bounds 95% confidence interval of the slope). We hypothesize that the hydrophobicity of SAmPAP diester reduces its bioavailability, thus limiting biotransformation by bacteria in sediments. The lengthy biodegradation half-life of EtFOSE and recalcitrant nature of SAmPAP diester in part explains the elevated concentrations of PFOS-precursors observed in urban marine sediments from Canada, Japan, and the U.S, over a decade after phase-out of their production and commercial application in these countries. [ABSTRACT FROM AUTHOR]

The environmental occurrence of perfluorooctane sulfonate (PFOS) can arise from its direct use as well as from transformation of precursors ((N-alkyl substituted) perfluorooctane sulfonamides; FOSAMs). Perfluorooctane sulfonamidoethanol-based phosphate (SAmPAP) esters are among numerous potential PFOS-precursors which have not been previously detected in the environment and for which little is known about their stability. Based on their high production volume during the 1970s-2002 and widespread use in food contact paper and packaging, SAmPAP esters may be potentially significant sources of PFOS. Here we report for the first time on the environmental occurrence of SAmPAP diester in marine sediments from an urbanized marine harbor in Vancouver, Canada. SAmPAP diester concentrations in sediment (40-200 pg/g dry weight) were similar to those of PFOS (71-180 pg/g). A significant (p < 0.05) correlation was observed between SAmPAP diester and N-ethyl perfluorooctane sulfonamido acetate (an anticipated degradation product of SAmPAP diester). ΣPFOS-precursor (FOSAM) concentrations in sediment (120-1100 pg/g) were 1.6-24 times greater than those of PFOS in sediment. Although SAmPAP diester was not detected in water, PFOS was observed at concentrations up to 710 pg/L. Among the per- and polyfluoroalkyl substances monitored in the present work, mean log-transformed sediment/water distribution coefficients ranged from 2.3 to 4.3 and increased with number of CF2 units and N-alkyl substitution (in the case of FOSAMs). Overall, these results highlight the importance of FOSAMs as potentially significant sources of PFOS, in particular for urban marine environments. [ABSTRACT FROM AUTHOR]

The depletion of lipids associated with pre-spawning migration of Pacific salmon has the potential to magnify concentrations of hydrophobic organic contaminants (HOCs), which elevates risk of toxic effects. We present data from a field study of sockeye salmon (Oncorhynchus nerka) migrating to spawn in Great Central Lake, BC, which demonstrate that pre-spawning migration causes a magnification of PCB, PCDD, and PCDF concentrations in female gonads (1.9-2.5-fold), female soma (3.4-5.6-fold), and male soma (5.6-9.7-fold). We further develop a model of pre- spawning migration chemical magnification for sockeye salmon stocks as a function of migration distance. This model is shown to be consistent with available empirical data on pre-spawning magnification and predicts magnification factors ranging between 1.4 and 7.9 in gonad and between 1.6 and 10.4 in soma in seven Pacific salmon stocks in British Columbia. Post-migration (pre- spawning) toxic equivalent dioxin concentrations in roe were measured to be approximately 3 pg/g lipid in salmon from the Great Central Lake sockeye stock and estimated to range between 1.5 pg/g lipid for the shortest- migrating stocks and 7 pg/g lipid for the longest-migrating stocks. Concentrations in certain stocks approach or exceed the concentration of 3 pg/g lipid associated with 30% egg mortality in Oncorhynchus mykiss. This indicates the potential for population-level effects of current contaminant levels. It also suggests that historic contaminant concentrations, which were greater than current concentrations, may have contributed significantly to the decline of certain Pacific salmon stocks in British Columbia. [ABSTRACT FROM AUTHOR]

An aluminum smelter situated at the head of Kitimat Arm (BC, Canada) has discharged polycyclic aromatic hydrocarbons (PAHs) into the receiving waters since 1954. The purpose of the present study was to examine the distribution of PAHs contaminants in dungeness crabs (Cancer magister) collected in Kitimat Armand Douglas Channel (BC, Canada) by determining the concentrations of PAHs in the hepatopancreas and muscle tissues of crabs by using gas chromatography--mass spectrometry. Crabs were collected at specific sites down the Arm from the smelter on four separate occasions over a three-year period. Hepatopancreas and muscle tissues of the crabs were analyzed for 10 of the 16 PAH priority pollutants recommended by the U.S. Environmental Protection Agency. Results of the studies showed that the crabs had detectable levels of PAHs in hepatopancreas and muscle tissues. The highest concentrations of PAHs in the tissues were found at a site near the aluminum smelter, the alleged point source of PAH discharge. The concentrations of PAH analytes were high in crabs collected close to the smelter and at lower levels in crabs collected throughout Douglas Channel. These results show that PAHs discharged by the smelter were bioavailable to the crabs. The concentration of each PAH analyte in the hepatopancreas was found to be strongly related to its water solubility. However, the PAH analyte concentrations in the hepatopancreas and muscle did not appear to correlate highly with each other. [ABSTRACT FROM AUTHOR]

In vivo dietary bioaccumulation experiments for 85 hydrophobic organic substances were conducted to derive the in vivo gastrointestinal biotransformation rates, somatic biotransformation rates, bioconcentration factors (BCF), and biomagnification factors (BMF) for improving methods for bioaccumulation assessment and to develop an in vivo biotransformation rate database for QSAR development and in vitro to in vivo biotransformation rate extrapolation. The capacity of chemicals to be biotransformed in fish was found to be highly dependent on the route of exposure. Somatic biotransformation was the dominant pathway for most chemicals absorbed via the respiratory route. Intestinal biotransformation was the dominant metabolic pathway for most chemicals absorbed via the diet. For substances not biotransformed or transformed exclusively in the body of the fish, the BCF and BMF appeared to be closely correlated. For substances subject to intestinal biotransformation, the same correlation did not apply. We conclude that intestinal biotransformation and bioavailability in water can modulate the relationship between the BCF and BMF. This study also supports a fairly simple rule of thumb that may be useful in the interpretation of dietary bioaccumulation tests; i.e., chemicals with a BMFL of <1 tend to exhibit BCFs based on either the freely dissolved (BCFWW,fd) or the total concentration (BCFWW,t) of the chemical in the water that is less than 5000. [ABSTRACT FROM AUTHOR]

The development of an area-based polychlorinated biphenyl (PCB) food-web bioaccumulation model enabled a critical evaluation of the efficacy of sediment quality criteria and prey tissue residue guidelines in protecting fish-eating resident killer whales of British Columbia and adjacent waters. Model-predicted and observed PCB concentrations in resident killer whales and Chinook salmon were in good agreement, supporting the model's application for risk assessment and criteria development. Model application shows that PCB concentrations in the sediments from the resident killer whale's Critical Habitats and entire foraging range leads to PCB concentrations in most killer whales that exceed PCB toxicity threshold concentrations reported for marine mammals. Results further indicate that current PCB sediment quality and prey tissue residue criteria for fish-eating wildlife are not protective of killer whales and are not appropriate for assessing risks of PCB-contaminated sediments to high trophic level biota. We present a novel methodology for deriving sediment quality criteria and tissue residue guidelines that protect biota of high trophic levels under various PCB management scenarios. PCB concentrations in sediments and in prey that are deemed protective of resident killer whale health are much lower than current criteria values, underscoring the extreme vulnerability of high trophic level marine mammals to persistent and bioaccumulative contaminants. [ABSTRACT FROM AUTHOR]

Methods for rapid and cost-effective assessment of the biotransformation potential of very hydrophobic and potentially bioaccumulative chemicals in mammals are urgently needed for the ongoing global evaluation of the environmental behavior of commercial chemicals. We developed and tested a novel solvent-free, thin-film sorbent-phase in vitro dosing system to measure the in vitro biotransformation rates of very hydrophobic chemicals in male Sprague-Dawley rat liver S9 homogenates and compared the rates to those measured by conventional solvent-delivery dosing. The thin-film sorbent-phase dosing system using ethylene vinyl acetate coated vials was developed to eliminate the incomplete dissolution of very hydrophobic substances in largely aqueous liver homogenates, to determine biotransformation rates at low substrate concentrations, to measure the unbound fraction of substrate in solution, and to simplify chemical analysis by avoiding the difficult extraction of test chemicals from complex biological matrices. Biotransformation rates using sorbent-phase dosing were 2-fold greater than those measured using solvent-delivery dosing. Unbound concentrations of very hydrophobic test chemicals were found to decline with increasing S9 and protein concentrations, causing measured biotransformation rates to be independent of S9 or protein concentrations. The results emphasize the importance of specifying both protein content and unbound substrate fraction in the measurement and reporting of in vitro biotransformation rates of very hydrophobic substances, which can be achieved in a thin-film sorbent-phase dosing system. [ABSTRACT FROM AUTHOR]

The article discusses the increasing health risk of Galapagos sea lions because of Dichlorodiphenyltrichloroethane (DDT) pesticide contamination. It states that DDT concentrations in Galapagos sea lions are expected to be associated with impacts on the immune system. It mentions that Persistent Organic Pollutants (POPs) can have a bioaccumulation in oceanic and coastal-marine food chains of the Galapagos sea lions, wherein it compromises its reproductive status and health.

Methylmercury (MeHg) bioaccumulation in marine food webs poses risks to fish-consuming populations and wildlife. Here we develop and test an estuarine mercury cycling model for a coastal embayment of the Bay of Fundy, Canada. Mass budget calculations reveal that MeHg fluxes into sediments from settling solids exceed losses from sediment-to-water diffusion and resuspension. Although measured methylation rates in benthic sediments are high, rapid demethylation results in negligible net in situ production of MeHg. These results suggest that inflowing fluvial and tidal waters, rather than coastal sediments, are the dominant MeHg sources for pelagic marine food webs in this region. Model simulations show water column MeHg concentrations peaked in the 1960s and declined by almost 40% by the year 2000. Water column MeHg concentrations respond rapidly to changes in mercury inputs, reaching 95% of steady state in approximately 2 months. Thus, MeHg concentrations in pelagic organisms can be expected to respond rapidly to mercury loading reductions achieved through regulatory controls. In contrast, MeHg concentrations in sediments have steadily increased since the onset of industrialization despite recent decreases in total mercury loading. Benthic food web MeHg concentrations are likely to continue to increase over the next several decades at present-day mercury emissions levels because the deep active sediment layer in this system contains a large amount of legacy mercury and requires hundreds of years to reach steady state with inputs. [ABSTRACT FROM AUTHOR]

This study presents results of an analytical method developed for the quantification of monoalkyl phthalate esters (MPEs) in seawater, sediments, and biota. The method uses accelerated solvent extraction, solid-phase extraction, and liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). Results show the method is robust and can provide trace measurement of several MPE analytes at low parts per trillion levels in water and low parts per billion levels in sediments and biological tissues. Analyte recoveries varied between 70% and 110%. Method detection limits (MDLs) varied between 0.19 and 3.98 ng/L in seawater and between 0.024 and 0.99 ng/g in sediment and biota, which is approximately 10-50 times lower than previously reported MDLs using gas chromatography mass spectrometry. We applied the method to field collected samples of seawater, sediments, and tissues of mussels, crabs, and fish from False Creek, an urbanized marine inlet near Vancouver, Canada. The results indicate residues of several MPEs can be found in surface waters, sediments, and organism tissues of this marine system. Monoethyl phthalate (MEP), mono-n-butyl phthalace (MnBP), and msno-(2-ethylhexyl)- phthalate (MEHP) were frequently detected in all matrices. MnBP generally exhibited the highest concentrations among MPEs analyzed. Detectable concentrations of MPEs varied from 1 to 600 ng/L in seawater, 0.1 to 20 ng/g dry wt in sediments, and 0.1 to 600 ng/g wet wt in biota. Observed concentrations of low molecular weight MPEs in mussels were found to be significantly higher (P < 0.05) than those of corresponding parent DPEs (e.g., MnBP > DBP). Mono-iso-nonyl-phthalate (MoC9) and mono-iso-decyl phthalate (MoC10), which were routinely detected in water and sediments, were not detected in False Creek bista, indicating negligible uptake and/or in vivo bioformation of these high molecular weight MPEs. The ability to measure MPEs in complex environmental samples provided by this LC/ESI-MS/MS method expands the capability for future biomonitoring and risk assessment of phthalate plasticizers. [ABSTRACT FROM AUTHOR]

To better understand the bioaccumulation behavior of perfluoroalkyl contaminants (PFCs), we conducted a comparative analysis of PFCs and lipophilic organohalogens in a Canadian Arctic marine food web. Concentrations of perfluorooctane sulfonic acid (PFOS), perfluorooctansulfoamide (PFOSA), and C7-C14 perfluorocarboxylic acids (PFCAs) ranged between 0.01 and 0.1 ng·g-1 dry wt in sediments and 0.1 and 40 ng·g-1 wet wt in biota, which was equivalent to or higher than levels of PCBs, PBDEs, and organochlorine pesticides. In beluga whales, PFOS and PFCA concentrations were higher (P < 0.05) in protein-rich compartments (liver and blood), compared to other tissues/fluids (milk, blubber, muscle, and fetus). In the marine mammalian food web, concentrations of PFOSA and lipophilic organochlorines (ng·g-1 lipid equivalent) and proteinophilic substances (i.e., PFOS and C8-C14 PFCAs, ng·g-1 protein) increased significantly (P < 0.05) with trophic level. Trophic magnification factors (TMFs) of organochlorines ranged between 5 and 14 and exhibited significant curvilinear relationships (P < 0.05) with octanol-water and octanol-air partition coefficients (KOW, KOA). TMFs of perfluorinated acids (PFAs) ranged between 2 and 11 and exhibited similar correlation (P < 0.05) with protein-water and protein-air partition coefficients (KPW, KPA). PFAs did not biomagnify in the aquatic piscivorous food web (TMF range: 0.3-2). This food web specific biomagnification behavior was attributed to the high aqueous solubility and low volatility of PFAs. Specifically, the anticipated phase-partitioning of these proteinophilic substances, represented by their protein-water (KPW) and protein-air (KPA) partition coefficients, likely results in efficient respiratory elimination in water-respiring organisms but very slow elimination and biomagnification in air-breathing animals. Lastly, the results indicate that PFOS exposure in nursing Hudson Bay beluga whale calves (CI95 range = 2.7 × 10-5 to 1.8 × 10-4 mg·kg bw-1·d-1), exceeds the oral reference dose for PFOS (7.5 × 10-5 mg·kg bw-1·d-1), which raises concern for potential biological effects in these and other sensitive Arctic marine wildlife species. [ABSTRACT FROM AUTHOR]

Differences in bioavailability among sediments are a source of variability and uncertainty in sediment quality assessment. We present three sets of studies designed to test a thin-film solid phase extraction technique for characterizing the bioavailability of organic chemicals in sediments. Laboratory studies with spiked natural sediments reveal highly reproducible thin-film extractions for chemicals with octanol-water partition coefficients between 104.5 and 108.5, with 95% equilibration times between 1 and 600 h. Studies with field-collected sediments illustrate that method detection limits are sufficiently low for field application at contaminated sites. Bioaccumulation studies with clams (Macoma balthica) show excellent correlations between thin-film and animal tissue concentrations. We conclude that thin-film extraction provides an ecologically relevant, fugacity-based measure of chemical exposure that can be expected to improve sediment quality assessments. [ABSTRACT FROM AUTHOR]

Residues of hydroxylated (OH-) and methoxylated (MeO-) polybrominated diphenyl ethers (PBDEs) have been previously detected in precipitation, surface waters, wildlife, and humans. We report measured concentrations of OH-PBDEs, MeO- PBDEs, and Br3-Br7 PBDEs in sediments and biota from a Canadian Arctic marine food web. PBDEs exhibited very low trophic magnification factors (TMFs between 0.1-1.6), compared to recalcitrant PCBs (TMFs between 3 and 11), indicating biotransformation via debromination and/or cytochrome P450 mediated metabolism. OH-PBDEs were not detectable in samples of blood, muscle, and/or liver offish and marine wildlife. Five OH-PBDEs were detected at very low concentrations (range: 0.01-0.1 ng·g-1 lipid equivalent) in beluga whale blubber and milk. The dataindicate negligible formation/retention of OH-PBDEs in these Arctic marine organisms. Appreciable levels of several MeO-PBDEs were observed in bivalves, Arctic cod, sculpin, seaducks, and beluga whales (mean range 0.1-130 ng·g-1 lipid equivalent). 2'-MeO-BDE-68 and 6-MeO-BDE-47 exhibited the highest concentrations among the brominated compounds studied (including BDE-47 and BDE-99) and biomagnified slightly in the food web, with TMFs of 2.3 and 2.6, respectively. OH- and MeO-PBDEs in this Arctic marine food web may occur via metabolic transformation of PBDEs or bioaccumulation of PBDE degradation products and/or natural marine products. We observed no evidence of a local natural source of OH- or MeO-PBDEs, as no measurable quantities of those compounds were observed in ambient environmental media (i.e., sediments) or macroalgae. Further investigations of PBDEs and their hydroxylated and methoxylated analogues would be useful to better understand sources, fate, and mechanisms governing biotransformation and bioaccumulation behavior of these compounds. [ABSTRACT FROM AUTHOR]

Substances that accumulate to hazardous levels in living organisms pose environmental and human-health risks, which governments seek to reduce or eliminate. Regulatory authorities identify bioaccumulative substances as hydrophobic, fat-soluble chemicals having high octanol-water partition coefficients (KOW) (⩾100,000). Here we show that poorly metabolizable, moderately hydrophobic substances with a KOW between 100 and 100,000, which do not biomagnify (that is, increase in chemical concentration in organisms with increasing trophic level) in aquatic food webs, can biomagnify to a high degree in food webs containing air-breathing animals (including humans) because of their high octanol-air partition coefficient (KOA) and corresponding low rate of respiratory elimination to air. These low KOW-high KOA chemicals, representing a third of organic chemicals in commercial use, constitute an unidentified class of potentially bioaccumulative substances that require regulatory assessment to prevent possible ecosystem and human-health consequences. [ABSTRACT FROM AUTHOR]

A major route of exposure to hydrophobic organic contaminants (HOCs), such as benzo[a]pyrene (BaP), is ingestion. Matrix-bound HOCs may become bioavailable after mobilization by the gastrointestinal fluids followed by sorption to the intestinal epithelium. The purpose of this research was to measure the bioavailability of [14C]-BaP bound to pristine soils or field-contaminated sediment using an in vitro model of gastrointestinal digestion followed by sorption to human enterocytes (Caco-2 cells) or to a surrogate membrane, ethylene vinyl acetate (EVA) thin film. Although Caco-2 cells had a twofold higher lipid-normalized fugacity capacity than EVA, [14C]-BaP uptake by Caco-2 lipids and EVA thin film demonstrated a linear relationship within the range of BaP concentrations tested. These results suggest that EVA thin film is a good membrane surrogate for passive uptake of BaP. The in vitro system provided enough sensitivity to detect matrix effects on bioavailability; after 5 h, significantly lower concentrations of [14C]-BaP were sorbed into Caco-2 cells from soil containing a higher percentage of organic matter compared to soil with a lower percentage of organic matter. The [14C]-BaP desorption rate from Caco-2 lipids consistently was twofold higher than from EVA thin film for all matrices tested. The more rapid kinetics observed with Caco-2 cells probably were due to the greater surface area available for absorption/desorption in the cells. After 5 h, the uptake of BaP into Caco-2 lipid was similar in live and metabolically inert Caco-2 cells, suggesting that the primary route of BaP uptake is by passive diffusion. Moreover, the driving force for uptake is the fugacity gradient that exists between the gastrointestinal fluid and the membrane. [ABSTRACT FROM AUTHOR]

Accurate estimates for the oral bioavailability of hydrophobic contaminants bound to solid matrices are challenging to obtain because of sorption to organic matter. The purpose of this research was to measure the bioavailability of [14C]chrysene sorbed to soil using an in vitro model of gastrointestinal digestion and absorption to a surrogate intestinal membrane, ethylene vinyl acetate (EVA) thin film. The [14C]chrysene moved rapidly from soil into the aqueous compartment and reached steady state within 2 h. Equilibrium was reached in the EVA film within 32 h. Aging the spiked soil for 6 or 12 months had no effect on chrysene mobilization. This was supported by the finding that the data best fit a one-compartment model. Despite significant decreases in [14C]chrysene mobilization when water or nonneutralized gastrointestinal fluids were used in place of the complete medium, the equilibrium concentration of [14C]chrysene in EVA film remained the same in all conditions. Thus, the driving force for uptake was the fugacity gradient between the aqueous phase and the EVA film. Cultured human enterocytes (human colorectal carcinoma cell line [Caco-2 cells]) had a higher lipid-normalized fugacity capacity than EVA film, but the elimination rate constants were the same, suggesting that the rate was controlled by the resistance of the unstirred aqueous layer at the membrane-water interface. [ABSTRACT FROM AUTHOR]

Dialkyl phthalate esters (DPEs) are widely used industrial chemicals with octanol-seawater partition coefficients ranging between 101.80 for dimethyl phthalate to 1010.0 for di- iso-decyl phthalate, indicating a propensity to sorb strongly to particulate matter in aquatic environments. Sorption plays a key role in controlling the long-term fate of DPEs in aquatic systems and exposure to organisms in aquatic food-webs. However, field observations of the sorption of many commercial DPEs do not exist. To characterize the sorptive nature of DPEs in a real-world aquatic ecosystem, we measured concentrations of DPEs congeners, commercial DPE mixtures, and 10 polychlorinated biphenyls (PCBs) in water, suspended sediments, and bottom sediments of a marine inlet. Sorption coefficients of spiked and native DPEs and PCBs between suspended sediments and water indicate that the apparent sorptive nature of DPEs and PCBs is substantially greater than expected from Kow-based sorption models. Particulate and dissolved organic matter showed similar (i.e., not statistically different) sorption affinities for native analytes. The apparent fraction of the total aqueous concentration of DPEs that is freely dissolved and absorbable via the respiratory tract of aquatic organisms varied from virtually 100% for DMP to 0.0003% for C10. The observed decline in concentration of most DPEs between suspended and bottom sediments, compared to an increase in the concentration of high Kow PCBs, suggests that the rate of desorption and degradation of DPEs exceeds that of organic carbon mineralization and contributes to the previously observed lack of biomagnification of DPEs in the aquatic food-web of this system. [ABSTRACT FROM AUTHOR]

High-volume air samples collected over the period Aug. 14-30, 2001, in the Lower Fraser Valley, BC, Canada, were used to assess urban/rural differences of organochlorine pesticides (OCPs) for ground level samples and to attempt to directly measure events of trans-Pacific inputs through the mid-troposphere. Hexachiorocyclohexanes (α- and γ-isomers; 2-25 pg m-3) and endosulfan1 and -2(5-150 pg m-3) were detected in all ground level samples. Seven air samples were collected during mid-troposphere flights (∼4400 m altitude) over the Lower Fraser Valley. These flights occurred concurrently with ground level sampling. Trajectory analysis identified three events of substantial mid-troposphere, trans-Pacific flow where 10- day back trajectories stemmed from potential source regions in Asia. These events were also characterized by higher air concentrations of α-HCH at 4400 m as compared to the ground level stations. This represents the first event- based, aircraft measurement of advection inputs of OCPs in the mid-troposphere of the west coast of North America. [ABSTRACT FROM AUTHOR]

Dialkyl phthalate esters (DPEs) are widely used as plasticizers in, poly vinyl chloride cellulosics, and polyurethanes, and as nonpiasticizers in products such as lubricating oils, automobile parts, paints, glues, insect repellents, photographic films, perfumes, and food packaging. Current NorthAmerican production of phthalate esters is approximately 0.65 million tonnes/year. The global production level is approximately 4.3 million tonnes/year. DPEs have been detected throughout the world, particularly in sediments in North America and Western Europe. In several jurisdictions, DPEs are currently being evaluated for their ability to bioaccumulate, exert toxicity, and persist in the environment following the 1999 UNEP Protocol on Long-Range Transboundary Air Pollution.

The article presents a response by researcher Barry C. Kelly and colleagues regarding comments about their report "Perfluoroalkyl Contaminants in an Arctic Marine Food Web: Trophic Magnification and Wildlife Exposure" within the issue. They outline the purpose of their study, including the investigation of perfluoroalkyl contaminants (PFCs) throughout the Arctic food chain, provide details regarding their research methodology, and note areas where they agree and disagree with their critics.