In vitro screening of the endocrine disrupting potency of brominated flame retardants and their metabolites

DEVELOPMENTAL AND REPRODUCTIVE TOXICITY vitro screening the endocrine disrupting potency brominated flame retardants and their metabolites Timo Hamers Jorke Kamstra Edwin Sonneveld Albertinka Murk Bart Zegers Jan Boon Abraham Brouwer Institute for Environmental Studies IVM Amsterdam BioDetection Systems BDS Amsterdam Wageningen University Toxicology Group Wageningen Royal Netherlands Institute for Sea Research NIOZ Den Burg Ume University Ume Introduction Substantial evidence recently becoming available that brominated flame retardants BFRs are potential endocrine disruptorsi The toxicological profile BFRs however too incomplete and insufficient perform human and ecological risk assessment fill these gaps the funded research program FIREii was started December This program aims the identification and toxicological characterization the most potent and environmentally relevant BFRs and their possible risk for human and wildlife health part hazard identification approach twentyseven BFRs have been selected within the framework FIRE for pre screening their endocrinedisrupting potencies Selection test compounds was based maximal variation physicochemical characteristics BFRs within the test set allowing the establishment quantitative structure activity relationships QSARs iii addition environmental relevance high production volumes and persistence and availability for testing were used selection criteria BFRs were tested seven different vitro bioassays for their potency interfer

In vitro profiling of the endocrine-disrupting potency of brominated flame retardants

Over the last years, increasing evidence has become available that some brominated flame retardants (BFRs) may have endocrine disrupting (ED) potencies. The goal of the current study was to perform a systematic in vitro screening of the ED potencies of BFRs (1) to elucidate possible modes of action of BFRs in man and wildlife, and (2) to classify BFRs with similar profiles of ED potencies. A test set of twenty-seven individual BFRs was selected, consisting of nineteen polybrominated diphenylethers (PBDE) congeners, tetrabromobisphenol-A (TBBPA), hexabromocyclododecane (HBCD), 2,4,6-tribromophenol (246-TBP), ortho-hydroxylated BDE-47 (6OH-BDE-47), and TBBPA-bis(2,3)dibromopropylether (TBBPA-DBPE). All BFRs were tested for their potency to interact with the arylhydrocarbon receptor (AhR), androgen receptor (AR), progesterone receptor (PR), and estrogen receptor (ER). In addition, all BFRs were tested for their potency to inhibit estradiol (E2) sulfation by E2-sulfotransferase (E2SULT), to interfere with thyroid hormone 3,3`,5-triiodothyronine (T3) mediated cell proliferation, and to compete with T3-precursor thyroxine (T4) for binding to the plasma transport protein transthyretin (TTR). The results of the in vitro screening indicated that BFRs have ED potencies, some of which had not or only marginally been described before (AR-antagonism, PR-antagonism, E2SULT inhibition, and potentiation of T3-mediated effects). For some BFRs, the potency to induce AR-antagonism, E2SULT inhibition and TTR competition was higher than for natural ligands or clinical drugs used as positive controls. Based on their similarity in ED profiles, BFRs were classified into five different clusters. These findings support further investigation of the potential endocrine disrupting effects of these environmentally relevant BFRs in man and wildlife

Levels of hexabromocyclododecane in harbor porpoises and common dolphins from Western European seas, with evidence for stereoisomer-specific biotransformation by cytochrome P450

Commercial hexabromocyclododecane (HBCD) is a high-production-volume flame-retardant applied in polystyrene foams. It contains three stereoisomers, of which γ-HBCD always dominates. Here we report on the levels of HBCD in blubber of harbor porpoise and common dolphin from different European seas. The highest total (Σ)-HBCD levels were measured in harbor porpoises stranded on the Irish and Scottish coasts of the Irish Sea (median concentration 2.9 μg (g of lipid

Toxic potency and effects of diffuse air pollution

Diffuse air pollution consists of an omnipresent complex mixture of pollutants that is emitted from many widely dispersed sources as traffic, industries, households, energy plants, waste incinerators, and agriculture. It can be deposited in relatively remote areas as a result of (long-range) airborne transport. It has a heterogeneous composition in time and space and consists of many known and unknown compounds. Given the unknown chemical identity and toxicity of many constituents of this mixture, it is virtually impossible to make a toxicological characterization of diffuse air pollution based on evaluations of the individual compounds. Alternatively, in the present thesis the integrated toxic potency and the subsequent effects have been studied of the air polluting mixture as a whole. Three objectives were defined:to determine the overall exposure to diffuse air pollution by measuring biomarker responses to relevant environmental samples;to determine possible (early-warning) effects of diffuse air pollution by analyzing biomarkers in ecologically relevant exposed organisms;to develop a strategic research concept for a toxicological risk characterization of diffuse air pollution based on overall exposure and effect assessments.To meet these objectives, the integrated toxic potency has been qualified and quantified in small-scale in vitro bio-assays (exposure assessment) and the possible changes in biochemical and physiological endpoints have been quantified by measuring biomarkers in organisms exposed to airborne pollution in the field (effect assessment). Biomarkers were selected based on their specific response to toxicants with a specific mode of action. Selected toxicants were [1] genotoxic compounds, including PAHs, [2] arylhydrocarbon receptor (AhR) agonists including dioxin-like compounds, [3] estrogenic compounds, and [4] esterase inhibitors. Most of these toxicants were known to be relevant airborne pollutants, except for the estrogenic compounds, of which the atmospheric presence had hardly been studied yet. Exposure and effects of diffuse air pollution have been compared between background locations and locations with notoriously exposure to traffic or to pesticide emissions. Genotoxic and AhR-activating potency was demonstrated for almost any of the of airborne particulate matter (APM) samples studied. APM collected at a relatively ghway, but differences were amply within one order of magnitude. In general, genotoxic potency could mainly be attributed to direct genotoxicants, rather than to compounds that first need to be metabolized to become genotoxic. However, during easterly wind conditions some APM samples contained relatively high indirect genotoxic potency with little differences between a highway and a background location. Trajectory analysis suggested that the different composition of pollutants in these samples is due to industrial pollutants that have been transported over long distances through the atmosphere. The AhR activating potency of APM was completely attributed to readily biodegradable compounds such as polycyclic aromatic hydrocarbons (PAHs), and not to stable congeners as dioxins or polychlorinated biphenyls (PCBs). Differences among toxic potencies of APM collected next to a highway and in a background location were too small to be reflected in biomarker responses in small mammals. Actually, relatively high levels of aromatic DNA adduct in heart, lung, and liver and relatively low hepatic retinyl-palmitate levels were found in herbivorous bank voles ( Clethrionomys glareolus ) from the background location compared to the sampling locations closer to the highway. As these differences were not found in carnivorous common shrews ( Sorex araneus ), they were attributed to oral exposure to an actual deposition of airborne pollutants on the vegetation. Esterase inhibiting potency was demonstrated in rainwater using a specially adapted bio-assay. Esterase inhibition correlated with analyzed concentrations of organophosphate and carbamate insecticides in rainwater and significantly depended on sampling location, with highest potency in an area with intense horticultural practice (greenhouses). Maximum concentrations of individually analyzed pesticides and maximum esterase inhibiting potencies (expressed as dichlorvos equivalent concentrations) incidentally exceeded EC 50 -values for Daphnia and maximum permissible concentrations (MPCs) set for surface water in The Netherlands. Estrogenic potency was observed in all rainwater samples tested and differed significantly with sampling season. Highest estrogenic potency was found in spring, and correlated significantly with the presence of organochlorine compounds in the rainwater, although it could not be explained by the analyzed concentrations of these compounds. Incidentally, estrogenic potency (expressed as estradiol equivalent concentrations ) exceeded lowest observed effect concentrations reported in literature for vitellogenesis in male rainbow trout. In conclusion, rainwater was frequently polluted with estrogenic and esterase inhibiting compounds at concentrations above MPCs for surface water and incidentally at effect levels for aquatic organisms, also in relatively remote and seemingly unpolluted areas. Because rainwater pollutants are diluted by surface water and adsorbed by particles after deposition, aquatic ecosystems will be exposed to lower concentrations and are probably not directly at risk. Possibly, shallow and mainly rainwater-fed water pools are an exception, and further studies should focus on such pools, especially in remote areas. Based on the experiences gained in the present study,a strategic research concept is proposed for the risk characterization of diffuse air pollution. The strategy includes several steps: [1] Relevant environmental samples are collected and adequately processed and their toxic potency is tested in bio-assays. [2] Bio-assay responses are compared to threshold levels for toxic effects. [3] For active environmental samples, a Toxicity Identity and Evaluation (TIE) procedure is proposed to identify the compounds that contribute most to its toxic potency. [4] In vivo responses should be studied in indicative organisms that are exposed via relevant routes of exposure to those compounds or groups of pollutants that exceeded thresholds levels in the bio-assays. [5] A risk assessment of diffuse air pollution can be made, based on the outcome of the exposure and effect assessments

Substrate-dependent bioavailability of Deltamethrin for the epigeal spider Oedothorax apicatus (Blackwall) (Aranaea, Erigonidae).

Terrestrial arthropods are mainly exposed to pesticides by uptake from the substrate e.g. “residual” uptake, which depends on the bioavailability of the pesticide. The residual uptake of deltamethrin by female Oedothorax apicatus (Blackwall), a linyphiid spider, was studied in relation to dependence on soil cover, soil moisture, walking behaviour, time after spraying and deposition rate. C14-labelled deltamethrin was used to quantify the uptake processes. Data were analysed using multiple regression analysis.Uptake was markedly higher from soil covered with fungi or moss than from uncovered soil. From uncovered soils with moisture contents varying from 7 to 49% dry weight, low uptake was measured, while at 63% moisture, the uptake was high. The bioavailability half-life was 157 min. The rate of uptake decreased with distance walked. The possible consequences of these results for field experiments are discussed

Risk assessment of metals and organic pollutants for herbivorous and carnivorous small mammal food chains in a polluted floodplain (Biesbosch, The Netherlands)

A risk assessment was made for a carnivorous and a herbivorous food chain in a heavily polluted natural estuary (Biesbosch), by determining the most critical pollutants and the food chain most at risk. Exposure of food chains to metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) was assessed by analyzing dietary concentrations, internal concentrations, and biomarkers of exposure. Common shrew (Sorex araneus) and bank vole (Clethrionomys glareolus) were selected as representative small mammal species for the carnivorous and herbivorous food chain, respectively, and earthworms (Lumbricus rubellus) and snails (Cepaea nemoralis) as representative prey species for the carnivorous food chain. Metals contributed most to the total risk for small mammals and earthworms. PCBs, but not PAHs, contributed to the overall risk for S. araneus at regularly flooded locations. The carnivorous food chain appeared most at risk given the higher exposure levels and bioaccumulating potency found for contaminants in S. araneus