Recent advances in recognition elements of food and environmental biosensors: a review

A sensitive monitoring of contaminants in food and environment, such as chemical compounds, toxins and pathogens, is essential to assess and avoid risks for both, human and environmental health. To accomplish this, there is a high need for sensitive, robust and cost-effective biosensors that make real time and in situ monitoring possible. Due to their high sensitivity, selectivity and versatility, affinity-based biosensors are interesting for monitoring contaminants in food and environment. Antibodies have long been the most popular affinity-based recognition elements, however recently a lot of research effort has been dedicated to the development of novel recognition elements with improved characteristics, like specificity, stability and cost-efficiency. This review discusses three of these innovative affinity-based recognition elements, namely, phages, nucleic acids and molecular imprinted polymers and gives an overview of biosensors for food and environmental applications where these novel affinity-based recognition elements are applied.

An integrated transcriptomic and proteomic approach characterizing estrogenic and metabolic effects of 17 alpha-ethinylestradiol in zebrafish (Danio rerio)

Nowadays there is much concern about the presence of endocrine disrupting compounds (EDCs) in the environment due to their ability to interfere with the endocrine system. In the presented study, adult zebrafish (Danio rerio) were exposed to 30 ng L(-1) 17alpha-ethinylestradiol (EE2) for 4 and 28 days. The underlying molecular mechanisms of EE2 were studied in the zebrafish liver by applying a combined transcriptomics and proteomics approach. In addition, we assessed the added value of such an integrated-omics approach. Oligo microarrays, spotted with 3479 zebrafish-specific oligos, were employed to generate differential gene expression levels. The proteomic responses were evaluated by means of differential in-gel electrophoresis (DiGE), combined with MALDI-tandem mass spectrometry. Assessment of the major biological functions of the differentially expressed transcripts and proteins illustrated that both individual platforms could profile a clear estrogenic interference, next to numerous metabolism-related effects and stress responses. Cross-comparison of both transcriptomics and proteomics datasets displayed limited concordance, though, thorough revision of the results illustrated that transcriptional effects were projected on protein level as downstream effects of affected signalling pathways. Overall, this study demonstrated that a proteomics approach can lift the biological interpretation of microarrays to a higher level, and moreover, opens a window for identification of possible new biomarkers.

Mixtures of similarly acting compounds in Daphnia magna: from gene to metabolite and beyond

Daphnia are an important and widely studied model species in ecological and toxicological studies throughout the world and an official (OECD) recommended test organism. Their small size, wide distribution and easy growth conditions make this organism ideal for functional genomics based studies, including metabolic profiling and transcriptomics. In this study we used an integrated systems approach in which transcriptomic, metabolomic and energetic responses of juvenile (4days old) daphnids were evaluated in response to exposure to two poly aromatic hydrocarbons (pyrene and fluoranthene) and binary mixtures thereof. In addition, these responses were linked to responses measured during chronic experiments (21days) assessing survival, growth and reproductive traits. Custom Daphnia magna microarrays were used to assess transcriptomic changes. Hierarchical cluster analysis did not result in a clear distinction between the single compounds suggesting similar molecular modes of action. Cluster analysis with both the single compounds and the binary mixture treatments resulted in a separation of treatments based on differences in toxic ratios rather than component differences. Changes in the metabolic profiles of the organisms were investigated using Nuclear Magnetic Resonance Spectroscopy and Gas and Liquid Chromatography Mass Spectrometry. These multivariate metabolomic datasets were analyzed with Principal Components Analysis and Partial Least Squares Discriminant Analysis. The major metabolite changes responsible for the differences observed indicated a disturbance in aminosugar metabolism in all cases. The study demonstrates the potential of 'omics' to provide screening tools for monitoring of the freshwater environment--in invertebrate species--which is reasonably rapid, cost-effective and has the potential to greatly increase the amount of information obtained from aquatic toxicology testing.

Effect assessment of the herbicide paraquat on a green alga using differential gene expression and biochemical biomarkers

Effects of the herbicide paraquat were assessed on the green freshwater alga Chlamydomonas reinhardtii using different endpoints of toxicity. Cell concentration and growth rate were monitored, whereas flow cytometry was applied to determine changes in chlorophyll content, viability and presence of reactive oxygen species. Furthermore, a transcriptomics approach using microarray hybridizations was applied to elucidate the mechanisms of toxicity. The results reveal that paraquat concentrations above 0.25 microM induce toxic effects in C. reinhardtii, reflected in a significantly reduced growth rate and cell concentration with a corresponding median effective concentration (EC50) value of 0.26 microM. With increasing paraquat concentrations, an increase in cell volume was registered with a particle counter as well as in the forward scattering signal of flow cytometric measurements, which is a measure of cell size. Flow cytometry, moreover, showed an increase in reactive oxygen species with increasing exposure concentration, corroborating the general knowledge that this herbicide exerts its toxicity through the generation of oxidative stress. At the same time, several genes involved in oxidative stress defense mechanisms, such as L-ascorbate peroxidase, glutaredoxin, and a possible glutathione-S-transferase were differentially expressed, demonstrating the value of microarrays for elucidating possible mechanisms of toxicity. The fact that several genes were differentially expressed at paraquat concentrations that caused no adverse effects on higher levels of biological organization indicates that a transcriptomics approach allows for the detection of early effects, even before they become manifest at higher levels.

Phage display as a novel screening tool for primary toxicological targets

In the present study the use of phage display as a screening tool to determine primary toxicological targets was investigated. These primary toxicological targets are the targets in the cell with which a chemical compound initially interacts and that are responsible for consecutive (toxic) effects. Nickel was used as model compound for the present study. By selection of Ni-binding peptides out of a 12-mer peptide phage library, it was possible to identify primary toxicological targets of Ni (and other metals). The selected Ni-binding peptides showed similarities to important primary toxicological targets of Ni, such as the hydrogenase nickel incorporation protein (hypB) and the Mg/Ni/Co transporter (corA). This shows that phage display, which is already widely used in other research fields, also has potential in ecotoxicology, as a novel screening tool with which to determine primary toxicological targets of chemical compounds.

Understanding the gap between the estrogenicity of an effluent and its real impact into the wild

To study the reliability between in vitro and in vivo data collected downstream 2 sewage treatment plants (STP) as well as from bleached kraft mill industry (BKME), 5 rivers (3 impacted and 2 references) were investigated in the Walloon region (southern of Belgium). For the in vitro part of the work, water samples were collected to measure the estrogenicity of the 'out' effluent compared to reference sample point by MCF-7 assay. Results indicated significant estrogenicity of effluents from STP and BKME and a weak estrogenicity in reference sites. However, estradiol equivalents (EEQ) estimated into rivers were probably too low to impact wild population. Chemical analysis of 13 compounds of interest indicated that extraction procedure used in this study gave low recoveries of estrogen-like xenobiotics, leading to probably under-estimated MCF-7 responses. Surprisingly, a full scan mode has revealed an unexpected compound in the sample of BKME which was: 7-isopropyl-1,1,4a-trimethyl-1,2,3,4a,9,10,10a-octahydrophenanthrene, a product of pulp mill manufacture. In parallel to in vitro, in vivo assessment of estrogenic impact of effluent was followed on the gudgeon (Gobio gobio). Samples were achieved during 2 different periods of the reproductive cycle, resting period (RP) and pre-spawning period (pSP). Unspecific physiological parameters to estrogenic exposure (gonadosomatic index and systematic testis cell counting) displayed no significant differences related to endocrine disruption of the reproductive tract, only differences were correlated with the reproductive state of fish (RP versus pSP). Concerning the potent biomarker of estrogen exposure, vitellogenin (vtg), only basal induction was revealed but not related to estrogenic exposure. Nevertheless, vtg over-expression was found for male fish presenting a feminization of the reproductive tract captured downstream the STP station of Wégnez in the Vesdre River. Intersexuality, another indicator of the estrogenicity impact in fish, was observed in every site. Actually, ovotestis was systematically formed by protoplasmic oocyte observed in low percentage in every group analysed (impacted and references). Moreover, in fish captured in Wégnez, oocyte diameter was significantly higher compared to the other groups. In this study, only moderate to none impact in population of gudgeon was noticed. Moreover, in this case no discrepancy between in vitro and vivo was viewed although both approaches revealed gaps in monitoring effluent incidence into the environment. We should remain careful in the interpretation when only partial approaches are used in order to characterize impact in the aquatic milieu.

Perfluorinated substances in human food and other sources of human exposure

The widespread distribution and degradation of PFCs in the environment results in a very complex exposure pattern, which makes it difficult to define the relative contribution to human exposure from different exposure pathways. The present review is designed to provide an overview of the existing data on levels of PFCs measured in the human diet and in drinking water. Data on levels of PFCs in the human diet are rather scarce, but the level in the fish appear to be well documented. Among PFCs, PFOS and PFOA are the best studied compounds in fish from both experimental and monitoring studies. Recently, the number of publications that address other PFCs has increased, but the total number available is still limited. In general, we discovered that care should be exercised when using the reviewed data, because, in the majority of publications, quality control and/or details on analysis are, at least partly, lacking. It has been well documented that PFOA and PFOS have the potential to accumulate in fish and concentrations up to 7 and 170 ng/g wwt, respectively in edible fish species have been found. PFOS is the most crucial and prominent compound identified, followed by the PFOA. Also, in aquatic invertebrate such as shrimps, mussels, clams, and oysters, high PFOS levels have been reported (up to 387 ng/g wwt). However in most publications PFC level reported in molluscs were less than 1 ng/g wwt. Positive correlations were found between PFC body burden and self reported fish consumption. In recognition of the potential for human exposure to PFCs via fish consumption, the Minnesota Department of Health has recently issued fish consumption advisories for contaminated sections of the Mississippi River. It is interesting to note that 79% of the reviewed publications on PFCs in the whole fish homogenates exceed the that threshold. Moreover, five of the PFC concentration reported in muscles tissue exceeded the advisory level of 38 ng/g wwt. Even though several authors concluded that consumption of contaminated food and drinking water constitutes the major exposure pathway for humans, only a few reports on PFCs in composite food exist. Food can be contaminated in an indirect way, because PFCs are widely used in food-packaging coatings and cooking materials. On the other hand, PFCs can also enter food organisms via environmental routes such as inhalation or adsorption from air. In a few studies, composite samples, duplicate diet samples, or other food items were analyzed for several PFCs, PFOS and PFOA, PFHpA, PFHxA, and PFHxS were meAsured and displayed concentrations ranging from-detected up to 15 ng/g wwt. In one study, a very high PFOA concentration of 118 ng/g were reported, but overall, PFC levels are below 10 ng/g wwt. It is important to note that, among all studies reviewed, PFCs were found in a maximum of 50% of the analyzed samples and generally only in 10% or less of samples analyzed. In contrast to what is observed in fish and other food items PFOA levels in drinking water (ND - 50 ng/L) and other PFCs (1-3 ng/L). In one study, extremely high values (519 ng/L) were measured in drinking water of a contaminated area in the Ruhr region. In Spain, bottled water was analyzed and four PFCs (PFOA, PFNA,PFDA and PFHpA) were found at low levels (<1 ng/L). Because of higher levels found in drinking water at several locations, some provisional drinking water guideline values for PFOS and PFOA have already been established, e.g., in the UK, Bavaria, and Minnesota. Since PFCs are present both in food and drinking water, Tolerable Daily Intake values for PFOS and PFOA have also been proposed by several institutes in Europe and in the USA. The ingestion of dust through hand-to-mouth transfer from indoor house dust can also be a potential source of PFC exposure, especially for toddlers and children. In publications on PFCs in indoor dust, the mean PFOS and PFOA levels varied between 39 and 1,200 ng/g and between 11 and 220 ng/g, respectively. Overall, it is clear that there is still lack of PFC exposure data for food and beverages, which renders the assessment of the contribution of the diet to total human PFC exposure uncertain. It is, therefore, appropriate that several scientific projects have recently been launched that addresses the assessment of human exposure to PFCs and related compounds from dietary sources.

Habitat type-based bioaccumulation and risk assessment of metal and As contamination in earthworms, beetles and woodlice

The present study investigated the contribution of environmental factors to the accumulation of As, Cd, Cu, Pb and Zn in earthworms, beetles and woodlice, and framed within an exposure assessment of the European hedgehog. Soil and invertebrate samples were collected in three distinct habitat types. Results showed habitat-specific differences in soil and invertebrate metal concentrations and bioaccumulation factors when normalized to soil metal concentration. Further multiple regression analysis showed residual variability (habitat differences) in bioaccumulation that could not be fully explained by differences in soil metal contamination, pH or organic carbon (OC). Therefore, the study demonstrated that in bioaccumulation studies involving terrestrial invertebrates or in risk assessment of metals, it is not sufficient to differentiate habitat types on general soil characteristics such as pH and/or OC alone. Furthermore, simple generic soil risk assessments for Cd and Cu showed that risk characterization was more accurate when performed in a habitat-specific way.

Omics in algae: paving the way for a systems biological understanding of algal stress phenomena?

The last decade, the biological and biomedical scientific landscape has seen the increase in use and applications of "omics" technologies. These technologies provide methods that allow for a comprehensive description of nearly all components within the cell. Microalgae not only play an important ecological role, but are also of commercial importance and therefore call for an in depth knowledge of basic biological functions. Knowledge of separate algal subsystems has gradually become available, but the challenge remains to integrate data obtained from these subsystems and from different levels of biological organization. Systems biology is a discipline that aims at this integration. In this paper, the current status of "omics" in algae is reviewed. At the lowest level, genome studies and the use of microarrays seem to have found widespread acceptance in algal research. At higher level such as the proteome and metabolome, however, very few omic studies have been carried out in algae so far. Moreover, the need arises for the construction of computer databases to store obtained information in a systematic way. To illustrate the use and especially the future needs of algal "omics" in a systems biological context, a case study is presented in which a freshwater alga was subjected to heavy metal stress and toxicity endpoints were monitored on different levels of biological organization.

Nickel and binary metal mixture responses in Daphnia magna: molecular fingerprints and (sub)organismal effects

The recent development of a custom cDNA microarray platform for one of the standard organisms in aquatic toxicology, Daphnia magna, opened up new ways to mechanistic insights of toxicological responses. In this study, the mRNA expression of several genes and (sub)organismal responses (Cellular Energy Allocation, growth) were assayed after short-term waterborne metal exposure. Microarray analysis of Ni-exposed daphnids revealed several affected functional gene classes, of which the largest ones were involved in different metabolic processes (mainly protein and chitin related processes), cuticula turnover, transport and signal transduction. Furthermore, transcription of genes involved in oxygen transport and heme metabolism (haemoglobin, delta-aminolevilunate synthase) was down-regulated. Applying a Partial Least Squares regression on nickel fingerprints and biochemical (sub)organismal parameters revealed a set of co-varying genes (haemoglobin, RNA terminal phosphate cyclase, a ribosomal protein and an "unknown" gene fragment). An inverse relationship was seen between the mRNA expression levels of different cuticula proteins and available energy reserves. In addition to the nickel exposure, daphnids were exposed to binary mixtures of nickel and cadmium or nickel and lead. Using multivariate analysis techniques, the mixture mRNA expression fingerprints (Ni2+ + Cd2+, Ni2+ + Pb2+) were compared to those of the single metal treatments (Ni2+, Cd2+, Pb2+). It was hypothesized that the molecular fingerprints of the mixtures would be additive combinations of the gene transcription profiles of the individual compounds present in the mixture. However, our results clearly showed additionally affected pathways after mixture treatment (e.g. additional affected genes involved in carbohydrate catabolic processes and proteolysis), indicating interactive molecular responses which are not merely the additive sum of the individual metals. These findings, although indicative of the complex nature of mixture toxicity evaluation, underline the potential of a toxicogenomics approach in gaining more mechanistic information on the effects of single compounds and mixtures.

Behaviour of damselfly larvae (Enallagma cyathigerum) (Insecta, Odonata) after long-term exposure to PFOS

Perfluorooctane sulfonic acid (PFOS) is a persistent and ubiquitous environmental contaminant that has been detected in organisms worldwide. Here, we evaluate whether long-term (1 and 4 months) exposure to PFOS contamination affects the behavioural performance of freshwater larvae of the damselfly Enallagma cyathigerum (Insecta: Odonata). Our results show reduced behavioural performance with increasing PFOS concentration. In 1 month exposed larvae, no observed effect concentrations (NOECs) were 100 microg/L for general activity. In 4 months exposed larvae, NOECs were 10 microg/L, for each behavioural trait, except swimming acceleration of male larvae where the NOEC was 100 microg/L. When faced with PFOS concentrations above the NOEC, E. cyathigerum larvae were less active, less capable to escape a simulated predator attack and less efficient in foraging. Together, our results show that damselfly larvae suffer reduced survival-related behavioural performance.

Relevance of hair and spines of the European hedgehog (Erinaceus europaeus) as biomonitoring tissues for arsenic and metals in relation to blood

Hair has been proven to be suitable for non-destructive and non-invasive exposure assessments in human and mammal populations. A previous study with European hedgehog (Erinaceus europaeus) showed that, for some metals, hair and spine metal concentrations were positively correlated to levels in liver, kidney and muscle. Although blood has been studied in a wide variety of species, the relationship between hair and blood metal concentrations has yet to be quantified in many mammalian species. Tissue concentrations from hedgehogs residing in a park with known metal pollution were compared with those from a reference park and correlations between contaminant levels in hair and blood, and spines and blood were studied. Moreover, the relative distribution of arsenic and metals in hair, spines and blood was determined. Elevated concentrations were found in hedgehogs residing in the polluted site for As (8.2 microg/g, 6.3 microg/g, 3.6 microg/ml), Cd (0.48 microg/g, 0.17 microg/g, 0.02 microg/ml) and Pb (7.6 microg/g, 7.3 microg/g, 54 microg/ml), in hair, spines and blood respectively. Positive correlations were identified for exposure levels between hair and blood as well as between spines and blood for three elements (As, Cd, and Pb), whereas a negative correlation was found between Cr concentrations in spines and blood. In conclusion, hair and spines can be used to monitor blood concentrations of some metals, although more data are needed on uptake from the food chain and on the incorporation dynamics of these contaminants.

Molecular targets of TBBPA in zebrafish analysed through integration of genomic and proteomic approaches

Tetrabromobisphenol-A (TBBPA) is nowadays one of the most frequently used brominated flame retardants (BFRs) and can be considered as a high production volume chemical. Over the last decade, numerous reports of increasing concentrations of BFRs in the environment and humans have been published. However, the toxicological knowledge on TBBPA, and more specifically its molecular mode of action, is rather fragmentary. In this study two populations of adult zebrafish (Danio rerio) were exposed for 14 days to 0.75 microM and 1.5 microM TBBPA. Subsequently, we employed a combined transcriptomic and proteomic approach to evaluate the molecular effects of TBBPA in zebrafish liver. Oligonucleotide microarrays were used to study the effects on gene expression levels. These results were validated through real-time PCR. The proteome of the liver was analysed by means of differential in-gel electrophoresis (DiGE), an innovative application of traditional 2D-PAGE. Combination of the extracted datasets allowed reassembling of individual molecular responses into a comprehensive overview of affected molecular pathways. Interpretation of the results depicted an interference of thyroid and Vitamin A homeostasis in the exposed zebrafish, TBBPA also elicited responses indicating onset of oxidative stress and general stress responses. Additionally, numerous differentially expressed transcripts could be associated with defence mechanisms or corresponded to metabolizing enzymes. Furthermore, cellular metabolism was clearly affected, illustrated as disturbance of e.g. lipid, carbohydrate, and organic acid metabolic processes. Summarizing, these results enabled us to hypothesize several working mechanisms of TBBPA and demonstrated the potential of a combined genome and proteome approach to generate detailed mechanistic toxicological information.

Metallothioneins (MTs) and delta-aminolevulinic acid dehydratase (ALAd) as biomarkers of metal pollution in great tits (Parus major) along a pollution gradient

Biomonitoring allows an integrated evaluation of different aspects of exposure, accumulation and effects to environmental pollution, simultaneously accounting for the natural variety between individuals in an ecosystem. In this study, the effects of increased metal accumulation were evaluated at the biochemical level in terms of two biomarker responses in the great tit (Parus major), a small insectivorous songbird, along an established metal pollution gradient. Metal concentrations in internal tissues (liver and kidney) and blood indicated that lead and cadmium were the most important metals in the pollution gradient under study. At the biochemical level, induction of metal binding protein metallothionein (MT) in liver and kidney reflected cadmium concentrations in these tissues (R(2)=0.42 and R(2)=0.94 respectively, n=19), although in kidney, MT induction was not sufficient to complex all cadmium present. Secondly, the activity of the enzyme delta-aminolevulinic acid dehydratase (ALAd) in blood decreased exponentially in response to increased lead accumulation (R(2)=0.70, n=18) and represents therefore a specific effect marker for lead exposure. In the highest polluted area, an ALAd inhibition of 85% was reported. Since a higher metal exposure resulted in an increased metal accumulation and subsequent biomarker responses in a dose-dependent way, this study indicates the applicability of ALAd and MT levels in great tits for biomonitoring responses to heavy metal pollution.

Linking molecular and population stress responses in Daphnia magna exposed to cadmium

DNA microarrays can be used to measure environmental stress responses. If they are to be predictive of environmental impact, we need to determine if altered gene expression translates into negative impacts on individuals and populations. A large cDNA microarray (14000 spots) was created to measure molecular stress responses to cadmium in Daphnia magna,the mostwidely used aquatic indicator species, and relate responses to population growth rate (pgr). We used the array to detect differences in the transcription of genes in juvenile D. magna (24 h old) after 24 h exposure to a control and three cadmium concentrations (6, 20, and 37 microg Cd2+ L(-1)). Stress responses at the population level were estimated following a further 8 days exposure. Pgr was approximately linear negative with increasing cadmium concentration over this range. The microarray profile of gene expression in response to acute cadmium exposure begins to provide an overview of the molecular responses of D. magna, especially in relation to growth and development. Of the responding genes, 29% were involved with metabolism including carbohydrate, fat and peptide metabolism, and energy production, 31% were involved with transcription/translation, while 40% of responding genes were associated with cellular processes like growth and moulting, ion transport, and general stress responses (which included oxidative stress). Our production and application of a large Daphnia magna microarray has shown that measured gene responses can be logically linked to the impact of a toxicant such as cadmium on somatic growth and development, and consequently pgr.

Mixture toxicity and gene inductions: can we predict the outcome?

As a consequence of the nature of most real-life exposure scenarios, the last decade of ecotoxicological research has seen increasing interest in the assessment of mixture ecotoxicology. Often, mixtures are considered to follow one of two models, concentration addition (CA) or response addition (RA), both of which have been described in the literature. Nevertheless, mixtures that deviate from either or both models exist; they typically exhibit phenomena like synergism, ratio or concentration dependency, or inhibition. Moreover, both CA and RA have been challenged and evaluated mainly for acute responses at relatively high levels of biological organization (e.g., whole-organism mortality), and applicability to genetic responses has not received much attention. Genetic responses are considered to be the primary reaction in case of toxicant exposure and carry valuable mechanistic information. Effects at the gene-expression level are at the heart of the mode of action by toxicants and mixtures. The ability to predict mixture responses at this primary response level is an important asset in predicting and understanding mixture effects at different levels of biological organization. The present study evaluated the applicability of mixture models to stress gene inductions in Escherichia coli employing model toxicants with known modes of action in binary combinations. The results showed that even if the maximum of the dose-response curve is not known, making a classical ECx (concentration causing x% effect) approach impossible, mixture models can predict responses to the binary mixtures based on the single-toxicant response curves. In most cases, the mode of action of the toxicants does not determine the optimal choice of model (i.e., CA, RA, or a deviation thereof).

Mode of action clustering of chemicals and environmental samples on the bases of bacterial stress gene inductions

Over the years, environment and the human population have seen an increasing exposure to both existing and newly developed chemicals. It is generally accepted that at least some of those are toxic, albeit as pure compound or in combination with others. In response to a growing public awareness and scientific data, the new European chemicals legislation (Registration, Evaluation and Authorization of Chemicals) is under implementation at the moment. As a consequence, during the coming years about 30,000 chemicals have to be assessed on their potential hazard for man and biota. Part of this assessment will be done using existing and new in vitro tests offering insight into the toxicity of chemicals and into their toxicological mode of action. This study presents data on a battery of 14 bacterial reporter gene assay allowing mode of action determination and statistical grouping of chemicals based on their induction profile. Gene induction results are used to group reference chemicals in a statistical cascade employing hierarchical tree and k-means clustering for initial grouping. Both complementary, yet mathematically different, algorithms are consequently confirmed by principal component analysis (PCA). The gene induction profiles of an environmental extract with documented in vivo effects and a chemical with limited toxicological are data available and projected in the PCA vector space. The projection allows correct mode of action grouping and indicates that effect predictions based on the known toxicological effects of the reference compounds can be made.

Ecotoxicological risk assessment using DNA chips and cellular reporters

Ecotoxicological risk assessment has long been based on (acute) effective concentration and lethal concentration (EC/LC50) endpoints in organisms from different trophic levels. These tests are insufficient adequately to assess the risk associated with many chemical classes. The introduction of advanced molecular techniques is leading to improved risk assessment and is also providing an alternative to the massive use of animal testing. Transcriptional profiling and DNA chips are highly informative and are among the most promising novel techniques for environmental risk assessment. Moreover, information discerned from these chips enables the identification of new discriminative biomarker genes. Based on these biomarker genes, cellular reporters can be constructed. These can be used in a high-throughput set-up and can facilitate ecotoxicological risk assessment significantly. Some important technical and interpretative hurdles still need to be overcome before a full implementation of ecotoxicogenomics in regulatory settings will occur.

PFOS levels in the blood and liver of a small insectivorous songbird near a fluorochemical plant

Perfluorooctane sulfonate (PFOS) is the stable end product of the degradation of various perfluorinated compounds and is the predominant compound found in the environment and biota. PFOS is a widespread environmental contaminant that is found in a great diversity of wildlife species with more elevated tissue concentrations in animals from populated and industrialized areas. In this study we determined the PFOS accumulation in blood and livers of a small songbird, the great tit (Parus major), in the vicinity of a large fluorochemical plant in Antwerp, Belgium. PFOS concentrations ranged from 553 ng/g to 11359 ng/g in liver and ranged from 24 to 1625 ng/ml in blood, which are among the highest ever reported in free-living animals, and exceeded in almost all birds the hepatic benchmark concentrations for the protection of avian species [Beach SA, Newsted JL, Coady K, Giesy JP. Ecotoxicological evaluation of perfluorooctanesulfonate (PFOS). Rev Environ Contam Toxicol 2006;186:133-174]. Although PFOS concentrations in liver and blood decreased significantly within approximately 5.5 km of the plant, differences were smaller than previously described for wood mice (Apodemus sylvaticus) and nestling great tits. PFOS concentrations in liver and blood were higher in young birds (<one-year old) than in older birds (>one-year old). No significant sex differences were found. A highly significant correlation between liver and blood concentrations indicates the usefulness of blood as a non-destructive matrix for biomonitoring purposes.

Non-destructive pollution exposure assessment in the European hedgehog (Erinaceus europaeus): IV. Hair versus soil analysis in exposure and risk assessment of organochlorine compounds

Few ecotoxicological studies on mammals use non-destructive methodologies, despite the growing ethical concern over the use of destructive sampling methods. In the present study we assessed exposure of hedgehogs (Erinaceus europaeus) to polychlorinated biphenyls (PCBs), dichloro-diphenyl-trichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB), by investigating concentrations of these compounds in soils and hedgehog hair from seven study sites around the urban area of Antwerp, Belgium. No relationships were observed between organochlorine compound concentrations in soils and hair from the different study areas. Furthermore, the individual variation of contamination levels in hair within study sites was high, especially for HCHs and HCB, and hair and soil had different relative profiles for PCBs, DDTs and HCHs. Our results show that concentrations of organochlorine compounds in soils alone are not predictive of the risk of these pollutants to hedgehogs and that tissue analyses are preferred to soil analyses in exposure and risk assessment studies.