Environmental distribution of brominated flame retardants in Belgium = Verspreiding van gebromeerde vlamvertragers in het Belgische milieu

Brominated flame retardants [BFRs] are a diverse group of chemicals that are used to increase fire safety. They are incorporated into a wide range of products, such as TVs, computers, household appliances, textiles and upholstery. Some of them, such as polybrominated diphenyl ethers [PBDEs], hexabromocyclododecane [HBCD], and tetrabromobisphenol-A [TBBP-A], have led to both scientific and public concern since they have been found to accumulate in Man and wildlife. BFRs are linked to adverse physiological effects both in vitro and in vivo [e.g. interference in neurobehavioural development, foetal health and thyroid function]. Adequate data on the effects are currently still insufficient to fully understand their toxicology.This thesis presents analytical method development and measurements of BFRs in a wide range of environmental samples. Since concentrations of BFRs are low and since environmental pollution is not only restricted to these compounds, analysing these chemicals in environmental samples is a challenging task, necessitating severe quality control. Therefore, all methods that were developed and optimised in this work were finally validated through successful participation in inter-laboratory exercises.At the start of this PhD-work, environmental occurrence of BFRs was not yet studied in Belgium. This thesis provides insight into the environmental distribution of BFRs and into the analytical aspects involved. In the first part of this thesis, the presence of PBDEs was investigated in aquatic environments. Geographical distribution and levels of PBDEs in sediments and biological samples, such as invertebrates and fish, were studied. All investigated species showed measurable levels of all contaminants. In the second part of this thesis, the presence of PBDEs was investigated in terrestrial environments. Biological samples of representative wildlife avian and mammalian top predators were investigated for PBDEs. BDE 209, a compound that is supposedly not bioavailable, was detected in the majority of the samples, which contradicts previously published statements and which suggests that legislative action is recommended for this chemical. Based on PBDE data in the prey of the investigated terrestrial predators, it was shown that PBDEs are biomagnified. In the third part of this thesis, PBDEs were investigated in relation to Man. A method for the determination of PBDEs, including BDE 209, in [human] serum was developed. Additionally, human dietary exposure was assessed by means of a market-basket study. It could be concluded that levels in food are low and comparable to other European countries. Dietary intake of PBDEs should however not be neglected. The fourth and final part of this thesis focuses on HBCD, which was investigated in selected aquatic samples.BFR exposure to animals and humans will continue as long as these chemicals are a part of our daily life and as long as they are present as contaminants in the surrounding environment. Exposure to these compounds will not stop at the scheduled date of phase-out

Hexabromocyclododecane in marine species from the western Scheldt Estuary: diastereoisomer- and enantiomer-specific accumulation

Hexabromocyclododecane (HBCD) is a widely used brominated flame retardant, which is increasingly reported in the environment. Here, we report on the diastereomeric and, for the first time, on the enantiomeric composition of HBCD in muscle and liver of several fish species caught in the Western Scheldt Estuary (The Netherlands). The total HBCD content (sum of alfa-, béta- and gamma-diastereoisomers), as well as the distribution of diastereoisomers and enantiomers, varied between the species. The levels of total HBCD (9-1110 ng/g lipid weight) found in fish tissues were higher than those measured in fish from European rivers with no known point sources of HBCD but lower than in fish samples collected near factories producing or using HBCD. The concentrations of total HBCD expressed on a lipid weight basis were higher in liver than in muscle for bib and whiting, while in sole, HBCD had no preferential distribution between the tissues. A similar pattern for liver and muscle distribution was already observed for polybrominated diphenyl ethers (PBDEs) in these species. The alfa-HBCD diastereoisomer was most abundant in all fish samples with a higher contribution to the total HBCD levels in liver compared to muscle for bib and whiting. The gamma-HBCD diastereoisomer accumulated less in liver than in muscle of sole, bib, and whiting. For the first time, enantiomer fractions were determined for HBCD diastereoisomers in liver of three fish species and in muscle of two fish species. A significant enrichment of the (+) alfa-HBCD enantiomer was found in whiting and bib liver samples. A high enantioselectivity has also been seen for the gamma-HBCD diastereoisomer in whiting liver

PBDEs in marine and freshwater sediments from Belgium: levels, profiles and relations with biota

Sediments from the Belgian North Sea (BNS), the Western Scheldt Estuary (SE) and freshwater watercourses from the Scheldt basin were analysed for eight PBDE congeners, namely BDEs 28, 47, 99, 100, 153, 154, 183 and 209. Previously analysed biological samples from the same locations in the BNS and the SE have been shown to contain large amounts of PBDEs. Surprisingly, PBDE concentrations in the sediments were below the LOQ for samples from the BNS (except BDE 209), while in those from the SE the sum of PBDEs (not including BDE 209) were higher and ranged from 0.20 to 0.41 ng g-1 dw. BDE 209 could be detected in 83% of the samples from the BNS and in all the samples from the SE. Concentrations up to 1200 ng g-1 were hereby measured in the SE. Compared to the marine and estuarine locations, the sediments from the freshwater watercourses were relatively more polluted with the lower brominated PBDEs (-1 dw). BDE 209 concentrations up to 320 ng g-1 dw were measured in those sediments. However, the contribution of BDE 209 to the total amount of PBDEs varied much more at the freshwater locations than in the SE, which suggests a different input of pollutants. PBDE profiles observed in biological samples do not match the profiles of the sediments. BDE 183 and 209 could not be quantified in biota, although these congeners were undoubtedly present in the sediments. This raises questions about the bioavailability of these congeners in the environment

Inferring choice criteria with mixture IRT models: A demonstration using ad hoc and goal-derived categories

Whether it pertains to the foods to buy when one is on a diet, the items to take along to the beach on one’s day off or (perish the thought) the belongings to save from one’s burning house, choice is ubiquitous. We aim to determine from choices the criteria individuals use when they select objects from among a set of candidates. In order to do so we employ a mixture IRT (item-response theory) model that capitalizes on the insights that objects are chosen more often the better they meet the choice criteria and that the use of different criteria is reflected in inter-individual selection differences. The model is found to account for the inter-individual selection differences for 10 ad hoc and goal-derived categories. Its parameters can be related to selection criteria that are frequently thought of in the context of these categories. These results suggest that mixture IRT models allow one to infer from mere choice behavior the criteria individuals used to select/discard objects. Potential applications of mixture IRT models in other judgment and decision making contexts are discussed

Norms of age of acquisition and concreteness for 30,000 Dutch words

Abstract not availableMarc Brysbaert, Michaël Stevens, Simon De Deyne, Wouter Voorspoels, Gert Storm

When cheating is an honest mistake

Dishonesty is an intriguing phenomenon, studied extensively across various disciplines due to its impact on people’s lives as well as society in general. To examine dishonesty in a controlled setting, researchers have developed a number of experimental paradigms. One of the most popular approaches in this regard, is the matrix task, in which participants receive matrices wherein they have to find two numbers that sum to 10 (e.g., 4.81 and 5.19), under time pressure. In a next phase, participants need to report how many matrices they had solved correctly, allowing them the opportunity to cheat by exaggerating their performance in order to get a larger reward. Here, we argue, both on theoretical and empirical grounds, that the matrix task is ill-suited to study dishonest behavior, primarily because it conflates cheating with honest mistakes. We therefore recommend researchers to use different paradigms to examine dishonesty, and treat (previous) findings based on the matrix task with due caution

Accounting for graded structure in adjective categories with valence-based opposition relationships

In contrast to noun categories, little is known about the graded structure of adjective categories. In this study, we investigated whether adjective categories show a similar graded structure and what determines this structure. The results show that adjective categories like nouns exhibit a reliable graded structure. Similar to nouns, we investigated whether similarity is the main determinant of the graded structure. We derived a low-dimensional similarity representation for adjective categories and found that valence differences in adjectives constitute an important organising principle in this similarity space. Valence was not implicated in the categories’ graded structure, however. A formal similarity-based model using exemplars accounted for the graded structure by effectively discarding the valence differences between adjectives in the similarity representation through dimensional weighting. Our results generalise similarity-based accounts of graded structure and highlight a closely knit relationship between adjectives and nouns on a representational level.Simon De Deyne, Wouter Voorspoels, Steven Verheyen, Daniel J. Navarro and Gert Storm