FIRE

RISK ASSESSMENT OF BROMINATED FLAME RETARDANTS AS SUSPECTED ENDOCRINE DISRUPTERS FOR HUMAN AND WILDLIFE HEALTH

Co-ordinator and partners

Objectives

The overall objective of this multi- and interdisciplinary project is to improve risk assessment of brominated flame retardants (BFRs) for human health and wildlife. BFRs, such as the high production volume chemicals polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDD) have been identified as potential endocrine disrupters. PBDE levels have been steadily increasing in biota over the last decades. Using in vitro cell systems of particular relevance for endocrine effects, BFRs will be selected for rodent and fish toxicity studies with emphasis on endocrine and immune system. After further selection, reproduction studies in the rat (with neurobehavioral and immune function tests) and partial life-cycle assays in zebrafish will be carried out. The exposure part includes congener specific identification, regional distribution and temporal trends of BFRs in tissue of wildlife and fish, human milk and diet within the EU. By integrating information on exposure, fate and toxicity this project aims a highly significant contribution to integrated risk assessment for humans and aquatic environment with respect to endocrine disruption by BFRs.

Scientific approach

For the prescreening of BFRs a battery of in vitro assays (human, rat and fish cell lines, WP2) and QSAR models (WP1) will be used, to: i) determine the endocrine disrupting potency; ii) to select the test compounds for testing in in vivo studies; and iii) to determine the appropriate test concentrations for in vivo studies (WPs 3, 4). TBBPA will be included as in vitro assays have shown that this compound can be a potent competitor with thyroxin for its plasma carrier protein transthyretin (TTR). The results of the prescreening study will also be used for the exposure assessment studies to define the compounds that will be determined in the human and aquatic wildlife samples.

Human and wildlife hazard identification and dose-response assessment

Based on the evaluation of the results of the prescreening study, WPs 3 and 5 will concentrate on the human hazard identification and dose-response assessment of the selected BFRs. A 2-generation reproduction study with rats (WP3) will be performed, including TBBPA. Information on the histopathology, sex steroidgenesis, thyroid activity, immune function, hepatic P450 enzymes, endocrine mediated neurobehavioral function, measurements of whole body and/of target tissues will be collected in the rat study (WP3).

In addition, the toxicokinetics of TBBPA will be studied in human volunteers, and physiologically-based pharmacokinetic (PBPK) modelling applied for humans and rats (WP5), because it is expected that the biliary elimination toxicokinetics of TBBPA may differ between rats and humans. Because of relatively rapid excretion, low toxicity and lack of genotoxicity, TBBPA will be administered to humans in low doses. Toxicokinetics are important determinants for endocrine disrupting activity, since they determine the amount of compound available for binding to the respective receptors and thus for biological responses. Moreover, metabolites formed by various biotransformation reactions may have increased or reduced receptor affinity. Therefore, toxicokinetic data are relevant for inclusion into the risk assessment process for endocrine disrupters.

For the aquatic wildlife hazard identification and dose-response assessment (WP4), the in vivo endocrine disrupting effects of the selected test BFR compound will be studied in a freshwater lower vertebrate model species (zebrafish) as well as in an estuarine wildlife species (flounder), a common indicator species in monitoring programmes. A rapid assay with transgenic reporter zebrafish will be used for the range finding tests before the start of a partial life-cycle assay with zebrafish (compounds selected following subacute testing). In this assay reproduction function will be assessed by fecundity and fertility parameters. In the flounder study the chronic effects of BFRs on endocrine and health status of adult fish at environmentally relevant concentrations will be investigated, after range finding tests have been performed. Fish studies include histopathology, with emphasis on endocrine and immune system, and measurements of whole body and/of target tissues. In the flounder steroid hormone and metabolism will also be investigated, and in the zebrafish a subsample will be used for toxicogenomic analysis as a potential new tool for hazard identification.

Human and aquatic wildlife exposure assessment

Human and aquatic wildlife exposure assessment will be studied in various European countries with different levels of BFRs exposure. To evaluate present and past human exposure to BFRs, composite food samples will be analysed (Czech Republic, The Netherlands, and Norway). To determine human body burdens of BFRs, breast milk (Czech Republic, The Netherlands, and Norway) and serum samples (Norway only) will be investigated (WP6). These countries were selected on the basis of different food consumption patterns (respectively low, medium and high consumption of fishery products) and levels of BFR contamination. In addition, temporal trends of human BFR exposure will be investigated in duplicate diets from 1978, 1984-1985 and 1994, and in serum samples from a time period of 20 years (WP6).

For the aquatic wildlife exposure assessment (WP7, 8, 10), information will be obtained on i) the food chain transfer of BFRs from water, sediment to invertebrates to predators (fish) and fish-eating top-predators (tern, seal and polar bear), ii) temporal trends, iii) environmental transformation (WP8). A predictive food web model will be developed (WP10). For the food chain transfer (WP7) samples will be collected at different levels of BFR pollution exposure in the marine environment, estuaries and freshwater locations. Reference sites will be Arctic and Froan (Norway) and more polluted locations will include The Netherlands (close to a BFR production plant as well as the Wadden Sea), UK (Clyde and Mersey), France (Seine estuary), Germany (Elbe) and Czech Republic (Elbe). BFRs (e.g. PBDEs, HBCD and TBBPA) will be determined and an interlaboratory study will be conducted between the laboratories that perform the BFRs analysis. Temporal trends of BFRs in aquatic wildlife will be investigated using harbour seal samples of a time period of the last 10 years, and dated sediment cores collected in one area of the fish-eating bird species (WP 7). In WP8 environmental transformation reactions of BFRs in the abiotic system (UV-irradiation) and biotic system (micro-organisms and microsomal systems of fish, birds, and marine mammals (e.g., harbour seals) will be studied. On the basis of the aquatic food chain transfer and environmental transformation data, a predictive food web model of BFRs in abiotic environment to the top-predators will be developed (WP10). WP9 is strongly linked to both human (WP6) and aquatic wildlife exposure (WP7, 8) and should provide information on the contribution of the levels of BFRs from human and wildlife samples to the total in vitro endocrine disrupter response.

Integrated risks assessment for humans and aquatic wildlife

Work package 11 will bring all information together for an integrated, comparative risk assessment of BFRs for human and aquatic wildlife. The integrated risk assessment combines the results on hazard identification, dose-response assessment and exposure assessment leading to risk characterisation. Risks of BFRs to ecological and human endpoints, the variability and uncertainty of these risks will be estimated, and is the input for the dissemination of results and risks in WP 12. The results of the hazard identification, dose-response assessment, exposure assessment, and risk characterisation will be compared with the EU risk assessments carried out under Reg. 793/93.

Dissemination and Cluster Activities

Finally, all information acquired during the FIRE project will be disseminated by Internet, newsletter and brochures via the CREDO cluster. In addition, results are disseminated by publication in scientific papers, and by a workshop (WP12) organised for legislation authorities, industries (CEFIC, BSEF), NGOs (green institutes, e.g. WWF), EU, IPCS, OECD, MEDPOL, ICES, OSPARCOM and HELCOM at month 42. A cluster workshop on exposure assessment will be organised around month 22.