Assessing bioaccumulation with biomagnification factors from dietary bioaccumulation tests.

Despite the fact that the UN Stockholm Convention on persistent organic pollutants specifically acknowledges that Arctic ecosystems and Indigenous communities are particularly at risk due to biomagnification of contaminants in traditional foods, the bioconcentration factor (BCF) of substances in fish remains the preferred metric for identifying the biomagnification potential of organic substances. The BCF measures uptake of substances from water in water-breathing organisms, but not biomagnification of contaminants from food sources. The purpose of this study is to investigate how the biomagnification factor (BMF) can be used in bioaccumulation assessments.

Archetypes of Spatial Concentration Variability of Organic Contaminants in the Atmosphere: Implications for Identifying Sources and Mapping the Gaseous Outdoor Inhalation Exposome.

Whereas inhalation exposure to organic contaminants can negatively impact human health, knowledge of their spatial variability in the ambient atmosphere remains limited. We analyzed the extracts of passive air samplers deployed at 119 unique sites in Southern Canada between 2019 and 2022 for 353 organic vapors. Hierarchical clustering of the obtained data set revealed four archetypes of spatial concentration variability in the outdoor atmosphere, which are indicative of common sources and similar atmospheric dispersion behavior.

Development and Evaluation of Aquatic and Terrestrial Food Web Bioaccumulation Models for Per- and Polyfluoroalkyl Substances.

There is a need for reliable models to predict the food web bioaccumulation and assess ecological and human health risks of per- and polyfluoroalkyl substances (PFAS). This present study presents (i) the development of novel mechanistic aquatic and terrestrial food web bioaccumulation models for PFAS and (ii) an evaluation of model performance using available laboratory and field data. Model predictions of laboratory-measured bioconcentration factors and field-based bioaccumulation factors of PFAS in fish were in good agreement with observed data as measured by the mean model bias (MB), representing systematic over- or under-estimation and the standard deviation of the MB, representing general uncertainty.

Depletion rates of O-naphthenic acids from oil sands process-affected water in wetland microcosms.

Treatment wetland microcosms were constructed to evaluate the fate of O-naphthenic acids in microcosm reactors containing OSPW only (, natural attenuation), OSPW with peat soil (sorption and microbial degradation), and cattail microcosm reactors (plant-mediated uptake and biotransformation). Depletion in OSPW occurs by mechanisms of natural attenuation, sorption and microbial degradation, and plant-mediated uptake and biotransformation. The average rate of depletion for O-naphthenic acids was 0.

Low Dietary Uptake Efficiencies and Biotransformation Prevent Biomagnification of Octamethylcyclotetrasiloxane (D4) and Decamethylcyclopentasiloxane (D5) in Rainbow Trout.

With octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) being considered for evaluation under the UN Stockholm Convention on Persistent Organic Pollutants, which specifically acknowledges risks of biomagnification of persistent organic pollutants in traditional foods, a study into the mechanism of the biomagnification process of D4 and D5 in Rainbow trout was conducted by combining the absorption-distribution-metabolism-excretion for bioaccumulation (ADME-B) approach to determine intestinal and somatic biotransformation rates and radiochemical analyses to identify metabolite formation. High rates of intestinal biotransformation of D4 and D5 (i.e.

Sources and environmental fate of halomethoxybenzenes.

Halomethoxybenzenes are pervasive in the atmosphere at concentration levels that exceed, often by an order of magnitude, those of the persistent organic pollutants with which they share the attributes of persistence and potential for long-range transport, bioaccumulation, and toxic effects. Long ignored by environmental chemists because of their predominantly natural origin-namely, synthesis by terrestrial wood-rotting fungi, marine algae, and invertebrates-knowledge of their environmental pathways remains limited. Through measuring the spatial and seasonal variability of four halomethoxybenzenes in air and precipitation and performing complementary environmental fate simulations, we present evidence that these compounds undergo continental-scale transport in the atmosphere, which they enter largely by evaporation from water.

Bioaccumulation of Linear Siloxanes in Fish.

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.

Developing Methods for Assessing Trophic Magnification of Perfluoroalkyl Substances within an Urban Terrestrial Avian Food Web.

We investigated the trophic magnification potential of perfluoroalkyl substances (PFAS) in a terrestrial food web by using a chemical activity-based approach, which involved normalizing concentrations of PFAS in biota to their relative biochemical composition in order to provide a thermodynamically accurate basis for comparing concentrations of PFAS in biota. Samples of hawk eggs, songbird tissues, and invertebrates were collected and analyzed for concentrations of 18 perfluoroalkyl acids (PFAAs) and for polar lipid, neutral lipid, total protein, albumin, and water content. Estimated mass fractions of PFCA C-C and PFSA C-C predominantly occurred in albumin within biota samples from the food web with smaller estimated fractions in polar lipids > structural proteins > neutral lipids and insignificant amounts in water.

Methods for assessing the bioaccumulation of hydrocarbons and related substances in terrestrial organisms: A critical review.

This study investigates and reviews methods for the assessment of the terrestrial bioaccumulation potential of hydrocarbons and related organic substances. The study concludes that the unitless biomagnification factor (BMF) and/or the trophic magnification factor (TMF) are appropriate, practical, and thermodynamically meaningful metrics for identifying bioaccumulative substances in terrestrial food chains. The study shows that various methods, including physical-chemical properties like the K and K , in vitro biotransformation assays, quantitative structure-activity relationships, in vivo pharmacokinetic and dietary bioaccumulation tests, and field-based trophic magnification studies, can inform on whether a substance has the potential to biomagnify in a terrestrial food chain as defined by a unitless BMF exceeding 1.

Bioaccumulation Screening of Neutral Hydrophobic Organic Chemicals in Air-Breathing Organisms Using In Vitro Rat Liver S9 Biotransformation Assays.

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.

Treatment of naphthenic acids in oil sands process-affected waters with a surface flow treatment wetland: mass removal, half-life, and toxicity-reduction.

This study is the first to investigate the removal of naphthenic acids in a full-scale constructed wetland within the Alberta Oil Sands region. The average mass-removal efficiency for all O-naphthenic acids measured in three separate deployments in the wetland ranged from 7.5% to 68.

A food web bioaccumulation model for the accumulation of per- and polyfluoroalkyl substances (PFAS) in fish: how important is renal elimination?

Per- and polyfluoroalkyl substances (PFAS) are a large class of highly fluorinated anthropogenic chemicals. Some PFAS bioaccumulate in aquatic food webs, thereby posing risks for seafood consumers. Existing models for persistent organic pollutants (POPs) perform poorly for ionizable PFAS.

Fugacity-Based Trophic Magnification Factors Characterize Bioaccumulation of Cyclic Methyl Siloxanes within an Urban Terrestrial Avian Food Web: Importance of Organism Body Temperature and Composition.

Trophic magnification of cyclic volatile methyl siloxanes (cVMS) in a terrestrial food web was investigated by measuring concentrations of octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) and two reference chemicals within air and biota samples from an avian food web located in a mixed urban-agricultural landscape. Terrestrial trophic magnification factors derived from lipid normalized concentrations (TMFs) for D5 and D6 were 0.94 (0.

Bioaccumulation of dodecamethylcyclohexasiloxane (D6) in fish.

To investigate the bioaccumulation behavior of dodecamethylcyclohexasiloxane (D6, CAS number: 540-97-6) in fish, an OECD-305 style dietary bioaccumulation study of D6 in rainbow trout was conducted in the presence of non-metabolizable reference chemicals. The dietary uptake absorption efficiency of D6 was 14 (3 SE) % and lower than that of the reference chemicals which ranged between 22 (2 SE) to 60 (8 SE) %. The concentration of D6 in the body of the fish showed a rapid 40% drop during the first day of the depuration phase, followed by a slower decline during the remainder of the depuration period.

Deconvoluting Thermodynamics from Biology in the Aquatic Food Web Model.

Bioaccumulation of hydrophobic pollutants in an aquatic food web is governed by exposure concentrations in sediment and water phases and by complex trophic interactions among the various species. We demonstrate that biological interactions and exposure from the chemical environment can be deconvoluted for aquatic food webs to allow clearer assessments of the role of thermodynamic drivers from the sediment and surface water phases. We first demonstrate the feasibility of this deconvolution mathematically for hypothetical food webs with 3 and 4 interacting species and for more realistic real-world food webs with >10 species of aquatic organisms (i.

Normalizing the Biomagnification Factor.

Following a recent proposal of normalizing the experimentally derived biomagnification factor (BMF) to a 5% lipid content in fish, we explore the normalization of the BMF of lipophilic chemicals in fish. We illustrate with theoretical models and experimental data that the BMF of lipophilic chemicals is a function of the lipid content of the diet and that poorly metabolizable, lipophilic chemicals biomagnify in organisms to a greater degree when present in higher-lipid content food. The proposed normalization of the laboratory BMF to the lipid content of the fish and subsequent standardization to a 5% fish lipid content, which is numerically identical to normalizing the BMF to a 5% dietary lipid content, has the potential to underestimate the biomagnification potential of lipophilic substances in aquatic food webs.

In vitro-in vivo extrapolation of hepatic and gastrointestinal biotransformation rates of hydrophobic chemicals in rainbow trout.

Hepatic in vitro biotransformation assays, in combination with in vitro-in vivo extrapolation (IVIVE) and bioaccumulation modeling, can be used to support regulatory bioaccumulation assessments. In most applications, however, these methods ignore the possibility of extrahepatic metabolism. Here we evaluated intestinal biotransformation in rainbow trout using S9 fractions prepared from the upper intestinal (GIT) epithelium.

Trophic magnification of legacy persistent organic pollutants in an urban terrestrial food web.

Legacy persistent organic pollutants (POPs), including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), persist for generations in the environment and often negatively impact endocrine functions in exposed wildlife. Protocols to assess the bioaccumulation potential of these chemicals within terrestrial systems are far less developed than for aquatic systems. Consequently, regulatory agencies in Canada, the United States, and the European Union rely primarily on aquatic information for the bioaccumulation assessment of chemicals.

Dietary Bioaccumulation and Biotransformation of Hydrophobic Organic Sunscreen Agents in Rainbow Trout.

The present study investigated the dietary bioaccumulation and biotransformation of hydrophobic organic sunscreen agents, 2-ethylhexyl-4-methoxycinnamate (EHMC) and octocrylene (OCT), in rainbow trout using a modified Organisation for Economic Co-operation and Development 305 dietary bioaccumulation test that incorporated nonbiotransformed reference chemicals. Trout were exposed to 3 dietary concentrations of each chemical to investigate the relationship between dietary exposure concentration and observed accumulation and depuration. Both EHMC and OCT were significantly biotransformed, resulting in mean in vivo whole-body biotransformation rate constants (k ) of 0.

A Toxicokinetic Framework and Analysis Tool for Interpreting Organisation for Economic Co-operation and Development Guideline 305 Dietary Bioaccumulation Tests.

The Organisation for Economic Co-operation and Development guideline 305 for bioaccumulation testing in fish includes the option to conduct a dietary test for assessing a chemical's bioaccumulation behavior. However, the one-compartment toxicokinetic model that is used in the guidelines to analyze the results from dietary bioaccumulation tests is not consistent with the current state of the science, experimental practices, and information needs for bioaccumulation and risk assessment. The present study presents 1) a 2-compartment toxicokinetic modeling framework for describing the bioaccumulation of neutral hydrophobic organic chemicals in fish and 2) an associated toxicokinetic analysis tool (absorption, distribution, metabolism, and excretion [ADME] B calculator) for the analysis and interpretation of dietary bioaccumulation test data from OECD-305 dietary tests.

Growth-Correcting the Bioconcentration Factor and Biomagnification Factor in Bioaccumulation Assessments.

We illustrate that the Organisation for Economic Co-operation and Development guideline 305 (OECD-305) for growth-correcting bioconcentration factors (BCFs) and biomagnification factors (BMFs) violates the mass-balance assumption underlying the definition of BCFs and BMFs and provides unrealistic estimates of BCFs and BMFs of chemicals in nongrowing fish. We present and test alternative methods for growth-correcting BCFs and BMFs that maintain mass balance. We conclude that the OECD-305-recommended growth correction of BCFs and BMFs causes error, is unnecessary, and should be revisited.

Development and evaluation of a mechanistic model to assess the fate and removal efficiency of hydrophobic organic contaminants in horizontal subsurface flow treatment wetlands.

A mechanistic model for assessing the fate and removal efficiency of hydrophobic organic contaminants in horizontal subsurface flow treatment wetlands was developed and evaluated using empirical concentration data from Singapore's Lorong Halus Treatment Wetland. This treatment wetland consists of a series of horizontal subsurface flow reed beds. The model, calibrated for the Lorong Halus Treatment Wetland, provided an adequate description of the concentrations of nine neutral organic substances in water, rhizomes and emergent vegetation in the wetland.

Concentration dependence of in vitro biotransformation rates of hydrophobic organic sunscreen agents in rainbow trout S9 fractions: Implications for bioaccumulation assessment.

In vitro biotransformation studies were performed to support the bioaccumulation assessment of 3 hydrophobic organic ultraviolet filters (UVFs), 4-methylbenzylidene camphor (4-MBC), 2-ethylhexyl-4-methoxycinnamate (EHMC), and octocrylene. In vitro depletion rate constants (k ) were determined for each UVF using rainbow trout liver S9 fractions. Incubations performed with and without added cofactors showed complete (4-MBC) or partial (EHMC and octocrylene) dependence of k on addition of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH), suggesting that hydrolysis of EHMC and octocrylene by NADPH-independent enzymes (e.

AGRO-2014: A time dependent model for assessing the fate and food-web bioaccumulation of organic pesticides in farm ponds: Model testing and performance analysis.

A time-dependent environmental fate and food-web bioaccumulation model is developed to improve the evaluation of the behaviour of non-ionic hydrophobic organic pesticides in farm ponds. The performance of the model was tested by simulating the behaviour of 3 hydrophobic organic pesticides, i.e.