Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Perspectieven voor de afzet van (fosfaat-verarmd) zuiveringsslib naar de landbouw
Regelink, Inge ; Ehlert, Phillip ; Römkens, Paul - \ 2017
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2819) - 75
afvalwater - rioolslib - besmetters - zware metalen - mest - fosfaten - landbouw - afvalhergebruik - waste water - sewage sludge - contaminants - heavy metals - manures - phosphates - agriculture - waste utilization
Het project heeft als doel om nieuwe afzetroutes te formuleren waarbij zuiveringsslib op een duurzame wijze wordt verwerkt tot meststoffen en bodemverbeteraars zodat waardevolle nutriënten en organische stof worden hergebruikt.
Overdracht van contaminanten van moeder naar jong en chemische profielen in bruinvissen gestrand langs de Nederlandse kust
Heuvel-Greve, M.J. van den; Kwadijk, C.J.A.F. ; Kotterman, M.J.J. - \ 2016
Wageningen Marine Research (Rapport / Wageningen Marine Research C096/16) - 30 p.
phocoena - besmetters - overdracht - pasgeboren dieren - polychloorbifenylen - toxische stoffen - toxicologie - contaminants - transfer - newborn animals - polychlorinated biphenyls - toxic substances - toxicology
Nederland heeft ten aanzien van de bruinvis een beschermingsplicht onder de Natuurbeschermingswet 1998. Om deze plicht goed te kunnen invullen is in 2011 het Bruinvisbeschermingsplan opgesteld. Dit beschermingsplan laat een aantal kennisleemten zien, o.a. ten aanzien van de rol die verontreinigingen spelen in de sterfte onder bruinvissen. In de afgelopen decennia is het aantal bruinvissen dat aanspoelt langs de Nederlandse kust toegenomen. Om te bepalen of aanwezigheid en gehalten van contaminanten in aangespoelde bruinvissen mogelijke effecten hebben gehad op hun gezondheid, zijn een aantal specifieke kennisvragen opgesteld die in dit rapport worden beantwoord. Er is in dit onderzoek gebruik gemaakt van monsters van aangespoelde bruinvissen gevonden in zowel Nederland als Denemarken.
Opname van struviet als categorie in het Uitvoeringsbesluit Meststoffenwet : advies
Ehlert, P.A.I. ; Dijk, T.A. van; Oenema, O. - \ 2016
Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-technical report 69) - 92
magnesiumammoniumfosfaat - kunstmeststoffen - wetgeving - afvalwater - fosfaten - besmetters - afvalwaterbehandelingsinstallaties - magnesium ammonium phosphate - fertilizers - legislation - waste water - phosphates - contaminants - waste water treatment plants
Only products, wastes and by-products designated by the Fertiliser Act can be freely traded as fertiliser in theNetherlands. Permitted fertilisers are listed in Regulation (EC) No 2003/2003 and wastes and by-products that canbe traded as fertiliser or as secondary raw material for fertiliser production are listed in Annex Aa of the implementingregulation of the Fertiliser Act. Wastes and by-products can be used as a fertiliser or a secondary raw materialif the criteria given in the Protocol for assessing the value and risks of waste used as fertiliser are met. Struvite is amagnesium ammonium phosphate (NH4MgPO4.6H2O) and is one of the forms in which phosphate can be recoveredfrom wastewater or process water. This origin means that struvite is classified as a waste, and as it is not listed inAnnex Aa the Fertiliser Act prohibits its use as a fertiliser. This publication reports on a study to formulate criteriafor lifting this waste status in accordance with the protocol. Depending on its quality, struvite acts as a fast-releaseor slow-release fertiliser. Due to the different techniques that are available for struvite formation, the differentwaste streams – municipal wastewater, effluent from manure processing, process water from the food manufacturingindustry – and different chemical polishing treatment processes, struvite can come in a range of qualities withdifferent concentrations of contaminants and may possibly contain pathogens. For the Ministry of Economic Affairs,the Scientific Committee on the Nutrient Management Policy has prepared an advice on including struvite in theFertiliser Act, with criteria. The study was based on literature research and consultation with stakeholders. Struviteis often co-precipitated with other phosphate minerals, such as phosphates of calcium, magnesium and iron, and anumber of these phosphates are present in struvite products. The advice covers this range of recovered phosphates
Impact of water quality and irrigation management on organic greenhouse horticulture
Dorais, M. ; Alsanius, B.W. ; Voogt, W. ; Pepin, S. ; Tuzel, Hakki ; Tuzel, Yuksel ; Möller, Kurt - \ 2016
[Netherlands] : BioGreenhouse - ISBN 9789462575387 - 97 p.
greenhouse horticulture - water management - biological techniques - organic farming - water supply - contaminants - glastuinbouw - waterbeheer - biologische technieken - biologische landbouw - watervoorziening - besmetters
Water quality and water supply are essential for organic greenhouse grown crops to prevent soil contamination by undesirable chemicals and microorganisms, while providing the correct amount of water required for plant growth. The absence of natural precipitation combined with higher evapotranspiration due to higher temperature and longer cropping period requires an adequate supply of water. Water quality is commonly defined by its chemical, physical, and biological attributes. It is closely linked to the soil/rock native components, surrounding environment and land use. The runoff from urban, industrial, farming, mining, and forestry activities also significantly affects the quality of water available for greenhouse horticulture. High water quality is particularly important to prevent soil salinization and ensure optimal soil biological activity. Indeed, unbalanced organic fertilizer inputs may contribute to soil salinity, while soil microbial activities responsible for nutrient mineralization, soil suppressiveness and plant health, are affected by soil pH, ions, and contaminants. Poor water quality can also result in drip and micro irrigation clogging, plant toxicity, and product contamination by human pathogens or illicit compounds.
Duplicaatvoedingsonderzoek bij kinderen 2014 : eerste resultaten
Wilson-van den Hooven, E.C. ; Alewijn, M. ; Top, H.J. van den; A, D.L. van der; Roos, A.M. ; Drijvers, J.J.M.M. ; Etemad, Z. ; Ocké, M.C. - \ 2015
Bilthoven : RIVM (RIVM Briefrapport 2015-0170) - 40 p.
voedselconsumptie - schadelijke stoffen - voeding en gezondheid - voedselveiligheid - kinderen - gezondheid van kinderen - besmetters - voedingsonderzoek - food consumption - noxious substances - nutrition and health - food safety - children - child health - contaminants - nutrition research
This report describes the consumption of children who participated in a
duplicate diet study. Furthermore it provides additional information on
the collected duplicate diets, for example if a child had followed a
specific diet. Duplicate diet studies are conducted periodically since 1976
in the Netherlands and provide the opportunity to monitor the quantities
of certain substances people ingest daily over time (chemicals,
mycotoxins). Moreover, it can be assessed if these quantities remain
within the safety limits.
This duplicate diet study was conducted during the spring and autumn of
2014 by RIVM and RIKILT and was commissioned by the Dutch Food and
Consumer Product Safety Authority (NVWA). Parents/ carers of 126
children aged 2 to 6 years in the region of Wageningen participated in
the study. They collected duplicate portions (duplicate diet) of all foods
and beverages their child consumed over a 24-hour period. They also
kept food diaries to record what the child had consumed during the day.
The duplicate diets were processed into freeze-dried samples and stored
at RIKILT.
The results of this study showed that for many children less duplicate
diet was collected than what they probably consumed. This should be
taken into account when interpreting the results of dietary exposure to
harmful substances.
Species interactions and chemical stress combined effects of intraspecific and interspecific interactions and pyrene n Daphnia magna populations dynamics
Viaene, K.P.J. ; Laender, F. de; Rico, A. ; Brink, P.J. van den; Guardo, A. Di; Morselli, M. ; Janssen, C.R. - \ 2015
Environmental Toxicology and Chemistry 34 (2015)8. - ISSN 0730-7268 - p. 1751 - 1759.
ecological risk-assessment - competition delays recovery - dry-weight estimate - modeling approach - exposure - sensitivity - water - ecotoxicology - contaminants - zooplankton
Species interactions are often suggested as an important factor when assessing the effects of chemicals on higher levels of biological organization. Nevertheless, the contribution of intraspecific and interspecific interactions to chemical effects on populations is often overlooked. In the present study, Daphnia magna populations were initiated with different levels of intraspecific competition, interspecific competition, and predation and exposed to pyrene pulses. Generalized linear models were used to test which of these factors significantly explained population size and structure at different time points. Pyrene had a negative effect on total population densities, with effects being more pronounced on smaller D. magna individuals. Among all species interactions tested, predation had the largest negative effect on population densities. Predation and high initial intraspecific competition were shown to interact antagonistically with pyrene exposure. This was attributed to differences in population structure before pyrene exposure and pyrene-induced reductions in predation pressure by Chaoborus sp. larvae. The present study provides empirical evidence that species interactions within and between populations can alter the response of aquatic populations to chemical exposure. Therefore, such interactions are important factors to be considered in ecological risk assessments. Environ Toxicol Chem 2015;34:1751-1759. (c) 2015 SETAC
Duplicaatvoedingsonderzoek bij kinderen 2014: opzet en uitvoering
Wilson-van den Hooven, E.C. ; Top, H.J. van den; A, D.L. van der; Roos, A.M. ; Drijvers, J. ; Ocké, M.C. - \ 2015
Bilthoven : RIVM (RIVM Briefrapport 2015-0053) - 31
voedselconsumptie - schadelijke stoffen - besmetters - voeding en gezondheid - voedselveiligheid - kinderen - food consumption - noxious substances - contaminants - nutrition and health - food safety - children
Sinds 1976 wordt in Nederland periodiek gemeten in welke mate mensen via voeding schadelijke stoffen binnenkrijgen, zoals metalen en gewasbeschermingsmiddelen. Hiervoor verzamelt een representatieve groep deelnemers in een gekoelde box de equivalenten van alles wat zij gedurende een etmaal hebben gegeten en gedronken (duplicaatvoeding). Het RIVM en het RIKILT voeren dit zogeheten duplicaatvoedingsonderzoek uit in opdracht van de Nederlandse Voedsel-en Warenautoriteit (NVWA). In dit rapport is beschreven hoe het onderzoek in 2014 is opgezet en uitgevoerd.
Tagetes, ook rendabel voor de akkerbouw!
Visser, J.H.M. ; Molendijk, L.P.G. ; Korthals, G.W. - \ 2015
groenbemesters - waardplanten - gewasbescherming - ziektebestrijdende teeltmaatregelen - tagetes - aaltjesdodende eigenschappen - plantenparasitaire nematoden - aardappelen - lelies - planten met knollen - penen - daucus carota - besmetters - veldgewassen - green manures - host plants - plant protection - cultural control - nematicidal properties - plant parasitic nematodes - potatoes - lilies - tuberous species - carrots - contaminants - field crops
De teelt van Tagetes heeft de besmetting met wortellesieaaltjes zeer sterk verlaagd. Na de teelt in 2006 tot minder dan 20 aaltjes/100 ml grond en na de tweede teelt in 2009 naar een nog lager niveau (<2 wortellesieaaltjes/ 100 ml grond). Ondanks de teelt van gewassen die dit aaltje sterk kunnen vermeerderen (goede waardgewassen) als aardappel en lelie en na 2009 van aardappel en peen blijft de besmetting zeer laag. Deze resultaten bevestigen het duur-effect van Tagetes dat in eerder onderzoek is waargenomen.
Polyfluorinated substances in abiotic standard reference materials
Reiner, J.L. ; Blaine, A.C. ; Higgins, C.P. ; Kwadijk, C.J.A.F. - \ 2015
Analytical and Bioanalytical Chemistry 407 (2015)11. - ISSN 1618-2642 - p. 2975 - 2983.
alkyl acid concentrations - perfluorinated compounds - temporal trends - perfluorooctane sulfonate - spatial trends - human plasma - house-dust - perfluorochemicals - contaminants - china
The National Institute of Standards and Technology (NIST) has a wide range of Standard Reference Materials (SRMs) which have values assigned for legacy organic pollutants and toxic elements. Existing SRMs serve as homogenous materials that can be used for method development, method validation, and measurement for contaminants that are now of concern. NIST and multiple groups have been measuring the mass fraction of a group of emerging contaminants, polyfluorinated substances (PFASs), in a variety of SRMs. Here we report levels determined in an interlaboratory comparison of up to 23 PFASs determined in five SRMs: sediment (SRMs 1941b and 1944), house dust (SRM 2585), soil (SRM 2586), and sludge (SRM 2781). Measurements presented show an array of PFASs, with perfluorooctane sulfonate being the most frequently detected. SRMs 1941b, 1944, and 2586 had relatively low concentrations of most PFASs measured while 23 PFASs were at detectable levels in SRM 2585 and most of the PFASs measured were at detectable levels in SRM 2781. The measurements made in this study were used to add values to the Certificates of Analysis for SRMs 2585 and 2781.
Use of electron ionization and atmospheric pressure chemical ionization in gas chromatography coupled to time-of-flight mass spetrometry for screening and identification of organic pollutants in waters
Portoles, T. ; Mol, J.G.J. ; Sancho, J.V. ; Hernandez, F. - \ 2014
Journal of Chromatography. A, Including electrophoresis and other separation methods 1339 (2014). - ISSN 0021-9673 - p. 145 - 153.
urban waste-water - pesticide-residues - ms analysis - qtof-ms - tof-ms - contaminants - metabolites - quantification - elucidation - vegetables
A new approach has been developed for multiclass screening of organic contaminants in water based on the use of gas chromatography coupled to hybrid quadrupole high-resolution time-of-flight mass spectrometry with atmospheric pressure chemical ionization (GC–(APCI)QTOF MS). The soft ionization promoted by the APCI source allows effective and wide-scope screening based on the investigation of the molecular ion and/or protonated molecule. This is in contrast to electron ionization (EI) where ionization typically results in extensive fragmentation, and diagnostic ions and/or spectra need to be known a priori to facilitate detection of the analytes in the raw data. Around 170 organic contaminants from different chemical families were initially investigated by both approaches, i.e. GC-(EI)TOF and GC-(APCI)QTOF, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and a notable number of pesticides and relevant metabolites. The new GC–(APCI)QTOF MS approach easily allowed widening the number of compounds investigated (85 additional compounds), with more pesticides, personal care products (UV filters, musks), polychloronaphthalenes (PCNs), antimicrobials, insect repellents, etc., most of them considered as emerging contaminants. Both GC-(EI)TOF and GC-(APCI)QTOF methodologies have been applied, evaluating their potential for a wide-scope screening in the environmental field.
Identification of Unknown Microcontaminants in Dutch River Water by Liquid Chromatography-High Resolution Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy.
Leerdam, J.A. van; Vervoort, J.J.M. ; Stroomberg, G. ; Voogt, P. de - \ 2014
Environmental Science and Technology 48 (2014)21. - ISSN 0013-936X - p. 12791 - 12799.
accurate-mass - degradation-products - phenolic resins - waste-water - transformation products - polar pesticides - surface-water - catalyst type - contaminants - formaldehyde
In the past decade during automated surface water monitoring in the river Meuse at border station Eijsden in The Netherlands, a set of unknown compounds were repeatedly detected by online liquid chromatography-diode-array detection in a relatively high signal intensity. Because of the unknown nature of the compounds, the consequently unknown fate of this mixture in water treatment processes, the location being close to the water inlet of a drinking water supply company and their possible adverse public health effects, it was deemed necessary to elucidate the identity of the compounds. No data are available for the occurrence of these unknowns at downstream locations. After concentration and fractionation of a sample by preparative Liquid Chromatography, identification experiments were performed using Liquid Chromatography-High Resolution Mass Spectrometry (LC-HR-MS) combined with High Resolution Nuclear Magnetic Resonance Spectroscopy (HR-NMR). Accurate mass determination of the unknown parent compound and its fragments obtained in MS/MS provided relevant information on the elemental composition of the unknown compounds. With the use of NMR techniques and the information about the elemental composition, the identity of the compounds in the different sample fractions was determined. Beside some regularly detected compounds in surface water, like caffeine and bisphenol-S, five dihydroxydiphenylmethane isomers were identified. The major unknown compound was identified as 4,4'-dihydroxy-3,5,3',5'-tetra(hydroxymethyl)diphenylmethane. This compound was confirmed by analysis of the pure reference compound. This is one of the first studies that employs the combination of high resolution MS with NMR for identification of truly unknown compounds in surface waters at the µg/L level. Five of the seven identified compounds are unexpected and not contained in the CAS database, while they can be presumed to be products generated during the production of resins.
Trendanalyse van contaminanten in diervoeders : mogelijkheden en problemen bij het gebruik van historische monitoringsgegens
Adamse, P. ; Boer, W.J. de; Nijs, W.C.M. de - \ 2014
Wageningen : RIKILT Wageningen UR (RIKILT report 2014.007) - 53
besmetters - diervoeding - historische verslagen - tendensen - statistische analyse - gevalsanalyse - voedselveiligheid - voedingsnormen - gegevensverwerking - analytische methoden - contaminants - animal nutrition - historical records - trends - statistical analysis - case studies - food safety - feeding standards - data processing - analytical methods
Voor het verkrijgen van inzicht in het basisniveau van een contaminant in een diervoeder kan gebruik worden gemaakt van monitoringsgegevens. Zowel de gegevens als de te gebruiken technieken moeten wel aan bepaalde voorwaarden voldoen. In een vorig rapport (Adamse, 2014) staat beschreven hoe met redelijk eenvoudige statistische basistools analyses kunnen worden uitgevoerd. In het huidige rapport staan meer complexe statistische analyses beschreven met daarbij de mogelijkheden en potentiele problemen.
Trendanalyse van historische gegevens : handleiding voor het gebruik van monitoringsgegevens
Adamse, P. - \ 2014
Wageningen : RIKILT Wageningen UR (RIKILT report 2014.001) - 22
tendensen - historische verslagen - monitoring - analytische methoden - statistische analyse - diervoeding - besmetters - voedselveiligheid - voedingsnormen - gegevensverwerking - voederveiligheid - trends - historical records - analytical methods - statistical analysis - animal nutrition - contaminants - food safety - feeding standards - data processing - feed safety
Het doel van dit rapport is om aan te geven welke technieken gebruikt kunnen worden om inzicht te krijgen in het achtergrondniveau van contaminanten in diervoeders en diervoederproducten. Beschreven is tevens met welke factoren rekening gehouden moet worden bij het gebruik van historische monitoringsgegevens. Deze gegevens zijn verzameld in het kader van monitoringsprogramma’s.
Bronnen van Aardappelvirus Y
Vlugt, R.A.A. van der; Bekkum, P.J. van; Raaij, H.M.G. van; Piron, P.G.M. ; Verbeek, M. ; Topper, C.G. ; Bus, C.B. ; Wustman, R. - \ 2014
Wageningen : Kennisakker
akkerbouw - aardappelen - proeven op proefstations - gewasbescherming - virussen - aardappelvirus y - ziekten overgebracht door vectoren - onkruiden - besmetters - arable farming - potatoes - station tests - plant protection - viruses - potato virus y - vector-borne diseases - weeds - contaminants
Gedurende het groeiseizoen 2011, tussen begin april en eind augustus, heeft Plant Research International, samen met PPO-AGV, onderzoek uitgevoerd naar de mogelijke bronnen van besmettingen met het aardappelvirus Y (PVY) in aardappelen. Er is vooral gekeken naar de rol van bladluizen als belangrijkste overbrengers (‘vectoren’) van PVY en naar mogelijke bronnen van het virus in andere planten (met name onkruiden).
Protein biomarker-based screening for detection of recombinant bovine somatotropin abuse in dairy cows
Ludwig, S.K.J. - \ 2014
Wageningen University. Promotor(en): Michel Nielen, co-promotor(en): Leen van Ginkel. - Wageningen : Wageningen University - ISBN 9789462570146 - 248
somatotropine - melkvee - besmetters - biomarkers - recombinant eiwitten - toxicologie - detectie - somatotropin - dairy cattle - contaminants - biomarkers - recombinant proteins - toxicology - detection

Recombinant bovine somatotropin (rbST) is a 22 kDa proteohormone, which can be used to increase milk production in dairy cows. It has been marketed since 1994 and while its use in food production is approved in several countries, such as the US, it is banned in the EU since 2000. To enforce the ban on rbST in the EU and to control for ‘rbST-free’ –labelling in the US, detection methods are required that identify whether rbST has been used. Existing rbST detection methods focus on the detection of rbST itself in bovine serum. The recombinant form of the hormone has one amino acid exchanged at the N-terminus of the protein. RbST can therefore be potentially discriminated from the endogenous bST by mass spectrometric methods. Other methods employ sandwich enzyme-linked immunosorbent assays (ELISAs) with antibodies having a higher affinity to rbST than bST. These methods, however mainly lack sensitivity, reproducibility or selectivity for rbST and are therefore not widely applied. Hence, no method has been implemented so far to monitor rbST abuse in dairy farming. Screening methods developed for veterinary drug residue control in the EU have to perform according to Commission Decision 2002/657/EC and have to identify at least 95 % of the treated animals.

An alternative approach for rbST abuse detection is the analysis of rbST-dependent biomarkers. A biomarker is defined as an indicator of normal physiological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention. Therefore, the levels of rbST-dependent protein biomarkers are either up- or downregulated after administration of rbST and rbST-specific biomarker profiles can be used to detect its abuse. RbST exerts similar physiological actions in the cow’s body as the endogenous bST. Therefore, proteins involved in the regulatory circuit of bST have been chosen as candidate biomarkers, such as insulin-like growth factor-1 (IGF-1), IGF binding protein 2 (IGFBP2) and osteocalcin. Additionally to that, the administration of rbST induces anti-rbST antibodies in the cow’s body, which can be detected as biomarkers. This approach is according to the growth hormone (GH) abuse detection in sports doping control, where solely protein biomarker profiles are used to identify the abuse.

Chapter 2 introduces protein biomarkers and how biomarkers can be used in sports doping and veterinary control to detect the abuse of illegal substances. The advantages of using biomarkers are that the biological effect of a substance usually lasts longer than the substance itself can be detected and therewith, the window of detection is expanded. Moreover, since different substances exert similar effects on physiological machineries for growth or production enhancement, biomarker-based-detection methods have the potential to detect a whole class of substances. Furthermore, low-dose mixtures of different banned substances, which might escape from direct detection of each individual substance used, could be still detected by the combined effect they exert. In this chapter, protein biomarker-based detection strategies are discussed against generic challenges in biomarker discovery and method development.

Part I of the thesis concerns biomarker analysis in serum and plasma samples from cattle, which are analysed using laboratory-based equipment.A triplex flow cytometric immunoassay (FCIA), which combines the detection of three rbST-dependent biomarkers, viz. IGF-1, IGFBP2 and anti-rbST antibodies is demonstrated in Chapter 3. Serum samples from treated and untreated dairy cows from a single animal study were analysed using this triplex FCIA. Characteristic treatment-dependent responses for all three individual biomarkers were shown. These results were combined using the statistical model k-nearest neighbours (kNN). This model discriminated rbST-treated from untreated cows with a truepositive rate of 89.1 % and a true-negative rate of 97.7 %.

This triplex FCIA was further extended with the biomarker osteocalcin and the resulting fourplex FCIA was used for biomarker profiling in serum samples from rbST-treated and untreated cows from two independent rbST treatment studies. In Chapter 4, different data analysis approaches were tested with the aim to detect the highest possible number of true-positive samples. The statistical model kNN was used on all 11 possible biomarker combinations and the combination of the biomarkers osteocalcin and endogenously produced antibodies against rbST proved to be very reliable and correctly predicted 95 % of the samples of treated cows starting from the second rbST injection until the end of the treatment period and even thereafter. With the same biomarker combination, only 12 % of the samples of untreated animals appeared false-positive. This reliability meets the requirements of Commission Decision 2002/657/EC for screening methods in veterinary control.

It can be expected that rbST-dependent biomarkers also show a response upon other treatments. Therefore in Chapter 5, the fourplex FCIA for rbST abuse detection was applied to bovines treated with steroids, such as estradiol, dexamethasone and prednisolone. Each treatment resulted in a specific plasma biomarker profile for IGF-1, IGFBP2, osteocalcin and anti-rbST antibodies, which could be distinguished from the profile of untreated animals. Therefore, the fourplex biomarker FCIA is, apart from rbST, also capable of detecting treatment with other growth-promoting agents and clearly shows the potential of biomarker profiling as a screening method in veterinary control.

Part II of the thesis focusses on protein biomarker analysis in milk samples and the change from laboratory-based to on-site analysis. In Chapter 6, the detection of anti-rbST antibodies in raw milk samples was demonstrated, which discriminated rbST-treated from untreated cows with a 67 % true-positive and 94 % true-negative rate. The laboratory-based assay was also applied to simulated tank milk and pasteurized milk samples. Using milk as a sample matrix for detection has the advantages of non-invasive sampling, and for tank milk analysis at the farm only one milk sample is needed to screen the whole farm for rbST (ab)use.

As a next step in Chapter 7, this assay was translated to an on-site pre-screening platform including a cellphone. Using this on-site platform, samples can be tested at the point where they were taken. Only samples that are suspect are transported to a laboratory for further analysis. To this end, a cellphone-based fluorescence imaging platform for the detection of anti-rbST antibodies in milk extracts was developed, which is based on a microsphere fluorescence immunoassay. After performing the assay, the fluorescence is excited by UV LEDs embedded in a dedicated cellphone attachment and the emitted fluorescence light is imaged by the cellphone camera. The fluorescence micro-images were analysed using a custom-developed Android application running on the same cellphone and milk samples from rbST-treated and untreated cows were discriminated.

Also in milk samples, the simultaneous detection of several biomarkers is advantageous as they can increase the confidence of a positive finding. Therefore in Chapter 8, a protein microarray-based platform for multiple rbST biomarker detection on a cellphone is presented, which detects anti-rbST antibodies and IGF-1 in milk samples. The 48 microspots on the microarray were labelled with Quantum Dots depending on the biomarker levels in the sample. Quantum Dot fluorescence was detected by the cellphone camera and the same opto-mechanical attachment as in Chapter 7 and images were analysed by custom software. RbST-treated clearly showed a treatment-dependent biomarker profile in milk that could be discriminated from the profile of untreated cows.

Future research should focus on the simultaneous detection of different targets of interest in milk samples, such as hormones, allergens, antibiotics, contaminants and other substances, all at the same time using the microarray platform on the cellphone. Moreover, sample handling can be facilitated by the use of pre-fabricated microfluidic devices including all required assay reagents. With the work presented in this thesis, screening for rbST abuse in serum and milk becomes possible: in the laboratory and on-site. The future implementation of these testing platforms for rbST abuse detection is a major leap forward concerning the enforcement of the rbST ban in the EU and concerning the value of protein biomarker-based approaches in veterinary control.

Contaminants in food supplements and associated health risks
Reeuwijk, N.M. - \ 2014
Wageningen University. Promotor(en): Ivonne Rietjens, co-promotor(en): Ron Hoogenboom; M.J. Martena. - Wageningen : Wageningen University - ISBN 9789461739438 - 160
voedselsupplementen - besmetters - voedselbesmetting - risicoschatting - food supplements - contaminants - food contamination - risk assessment

Summary

Through the increasing use and availability of food supplements on the market, safety Aconcerns relating to the safety of these food supplements are growing as well. The aim of the present PhD thesis was to investigate the presence and actual levels of contaminants of concern in selected food supplements on the Dutch market and to estimate the associated health risks.

First, in chapter 1, an overview is provided on the food supplements selected for the studies, which are clay products for oral use, herbal food supplements used to enhance sexual potency and herbal food supplements used for weight loss. Furthermore, an overview is given on the Dutch en European legal provisions for food supplements.

In the first study described in chapter 2 of this theses data are presented on the occurrence of metals such as lead, mercury and cadmium and the metalloid arsenic in clay products which are used via the oral route by pregnant and lactating women. For lead, the use of 34 of the 36 traditional clays and two of the 27 health clays would result in intake levels exceeding the selected health based guidance values, by up to 20-fold. In the case of inorganic arsenic, the use of 15 of the 35 traditional clays and 11 of the 27 health clays would result in intake levels exceeding the health based guidance values by up to 19-fold.

The second study, described in chapter 3 of the thesis, reports data on the presence of dioxins in 33 clay products, which were collected on the Dutch market and in some African countries. Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) were detected in clay products from the Dutch market, in concentrations ranging from 66 to 103 pg TEQ g-1, whereas PCDD/F concentrations in the suspected clay products from African countries varied from 24 to 75 pg TEQ g-1. Furthermore, in this study congener patterns in African clay products were compared with those of pooled human milk samples collected by WHO in eight African countries, to investigate a possible relation between PCDD/Fs in human milk with contaminated clay used for consumption. From the similarity between the patterns in clays and the human milk samples from the Democratic Republic of The Congo and Côte d’Ivoire, it can be concluded that there is probably a relationship with the consumption of contaminated clay.

The aim of the third study, described in chapter 4 of this thesis, was to determine whether herbal food supplements on the Dutch market contain active pharmacological ingredients (APIs) known to inhibit phosphodiesterase type 5 (PDE-5), such as sildenafil and other known analogous PDE-5 inhibitors. Therefore, herbal food supplements intended to enhance sexual potency (n=71), and two soft drinks, were analysed. In 23 herbal supplements, nine different PDE-5 inhibitors were identified, in a few cases (n=3) more than one. The presence of these APIs was however not stated on the label. Subsequently, it was estimated whether intake of the supplements with the detected PDE-5 inhibitors could result in pharmacological effects. It was concluded that 18 of the 23 herbal food supplements with PDE-5 inhibitors, when used as recommended, would have pharmacological effects due to the added APIs.

In the fourth study, described chapter 5 of in this thesis, another group of herbal food supplements, claiming to reduce weight, was investigated for the presence of APIs that can be used for the treatment of overweight and obesity. To this end, 30 herbal food supplements for weight loss on the Dutch market were collected and analysed for the presence of APIs with weight loss properties. In 24 samples the APIs sibutramine, desmethylsibutramine (DMS), didesmethylsibutramine (DDMS), rimonabant, sildenafil, and/or the laxative phenolphthalein were identified 41 times. The potential pharmacological effects of the detected APIs were estimated, and use of 20 of the 24 herbal food supplements, may result in potential pharmacological effects. Furthermore, a risk assessment of phenolphthalein regarding its carcinogenic effects, resulted in Margin of Exposure (MOE) values of 96-30,000. MOE values lower than the minimum required 10,000 (96-220) were calculated for the daily intake levels of four out of the ten supplements in which phenolphthalein was found. However, taking into account that weight loss preparations may be used for only a few weeks or months rather than during lifetime, MOE values may be two to three orders of magnitude higher. This study shows that the use of food supplements with sibutramine, DMS, DDMS, and/or phenolphthalein could result in both pharmacological but also other health effects.

From the studies described in this thesis it can be concluded (chapter 6) that, in addition to concerns over naturally occurring endogenous toxins present in herbal supplements, the presence of exogenous contaminants in herbal supplements can pose a health concern. Furthermore, the results of the present thesis also lead to the conclusion that in order to refine the risk assessment on the presence of contaminants such as metals, metalloids, dioxins and APIs in (herbal) food supplements more precise data are required on bioaccessibility of contaminants of concern from the food matrix. Also information on groups at increased risk may need to be increased. Additionally, the presence of APIs in herbal supplements, which may originate from drop outs in the drug development process, is of concern. In order to screen for unknown APIs the use of effect-based bioassays should be considered more often, as they have been shown to be successful in detecting unexpected and as yet unknown active ingredients. From the results obtained for the food supplements included in our studies it can be concluded that consumers should be aware that food supplements may not be without risks. The overall conclusion from the work described in this thesis is that for food supplements ‘natural’ does not equal ‘safe’.

Leaching of Plastic Additives to Marine Organisms
Koelmans, A.A. ; Besseling, E. ; Foekema, E.M. - \ 2014
Environmental Pollution 187 (2014). - ISSN 0269-7491 - p. 49 - 54.
bisphenol-a - environment - water - bioaccumulation - wildlife - pellets - fish - microplastics - accumulation - contaminants
It is often assumed that ingestion of microplastics by aquatic species leads to increased exposure to plastic additives. However, experimental data or model based evidence is lacking. Here we assess the potential of leaching of nonylphenol (NP) and bisphenol A (BPA) in the intestinal tracts of Arenicola marina (lugworm) and Gadus morhua North Sea cod.). We use a biodynamic model that allows calculations of the relative contribution of plastic ingestion to total exposure of aquatic species to chemicals residing in the ingested plastic. Uncertainty in the most crucial parameters is accounted for by probabilistic modelling. Our conservative analysis shows that plastic ingestion by the lugworm yields NP and BPA concentrations that stay below the lower ends of global NP and BPA concentration ranges, and therefore are not likely to constitute a relelvant exposure pathway. For cod, plastic ingestion appears to be a negligible pathway for exposure to NP and BPA.
Evaluation of solid polymeric organic materials for use in bioreactive sediment capping to stimulate the degradation of chlorinated aliphatic hydrocarbons
Atashgahi, S. ; Maphosa, F. ; Vrieze, J. de; Haest, P.J. ; Boon, N. ; Smidt, H. ; Springael, D. ; Dejonghe, W. - \ 2014
Applied Microbiology and Biotechnology 98 (2014)5. - ISSN 0175-7598 - p. 2255 - 2266.
reductive dechlorination - trichloroethylene tce - natural attenuation - groundwater plume - vinyl-chloride - hydrogen - tetrachloroethene - river - contaminants - communities
In situ bioreactive capping is a promising technology for mitigation of surface water contamination by discharging polluted groundwater. Organohalide respiration (OHR) of chlorinated ethenes in bioreactive caps can be stimulated through incorporation of solid polymeric organic materials (SPOMs) that provide a sustainable electron source for organohalide respiring bacteria. In this study, wood chips, hay, straw, tree bark and shrimp waste, were assessed for their long term applicability as an electron donor for OHR of cis-dichloroethene (cDCE) and vinyl chloride (VC) in sediment microcosms. The initial release of fermentation products, such as acetate, propionate and butyrate led to the onset of extensive methane production especially in microcosms amended with shrimp waste, straw and hay, while no considerable stimulation of VC dechlorination was obtained in any of the SPOM amended microcosms. However, in the longer term, short chain fatty acids accumulation decreased as well as methanogenesis, whereas high dechlorination rates of VC and cDCE were established with concomitant increase of Dehalococcoides mccartyi and vcrA and bvcA gene numbers both in the sediment and on the SPOMs. A numeric simulation indicated that a capping layer of 40 cm with hay, straw, tree bark or shrimp waste is suffice to reduce the groundwater VC concentration below the threshold level of 5 µg/l before discharging into the Zenne River, Belgium. Of all SPOMs, the persistent colonization of tree bark by D. mccartyi combined with the lowest stimulation of methanogenesis singled out tree bark as a long-term electron donor for OHR of cDCE/VC in bioreactive caps
Transport and degradation of propylene glycol in the vadose zone: model development and sensitivity analysis
Schotanus, D. ; Meeussen, J.C.L. ; Lissner, H. ; Ploeg, M.J. van der; Wehrer, M. ; Totsche, K.U. ; Zee, S.E.A.T.M. van der - \ 2014
Environmental Science and Pollution Research 21 (2014)15. - ISSN 0944-1344 - p. 9054 - 9066.
in-situ bioremediation - soil respiration - biodegradation - groundwater - diffusion - water - denitrification - contaminants - simulation - aggregate
Transport and degradation of de-icing chemical (containing propylene glycol, PG) in the vadose zone were studied with a lysimeter experiment and a model, in which transient water flow, kinetic degradation of PG and soil chemistry were combined. The lysimeter experiment indicated that aerobic as well as anaerobic degradation occurs in the vadose zone. Therefore, the model included both types of degradation, which was made possible by assuming advection-controlled (mobile) and diffusion-controlled (immobile) zones. In the mobile zone, oxygen can be transported by diffusion in the gas phase. The immobile zone is always water-saturated, and oxygen only diffuses slowly in the water phase. Therefore, the model is designed in a way that the redox potential can decrease when PG is degraded, and thus, anaerobic degradation can occur. In our model, manganese oxide (MnO2, which is present in the soil) and NO 3 - - 3 (applied to enhance biodegradation) can be used as electron acceptors for anaerobic degradation. The application of NO 3 - - 3 does not result in a lower leaching of PG nor in a slower depletion of MnO2. The thickness of the snowcover influences the leached fraction of PG, as with a high infiltration rate, transport is fast, there is less time for degradation and thus more PG will leach. The model showed that, in this soil, the effect of the water flow dominates over the effect of the degradation parameters on the leaching at a 1-m depth.
Bioaffinity mass spectrometry for screening and identification of contaminants
Aqai, P. - \ 2013
Wageningen University. Promotor(en): Michel Nielen, co-promotor(en): Willem Haasnoot. - Wageningen : Wageningen UR - ISBN 9789461738042 - 199
besmetters - massaspectrometrie - analytische scheikunde - contaminants - mass spectrometry - analytical chemistry

Our environment is constantly threatened by large amounts and variations of man-made chemicals and natural substances. Parts of these substances accumulate and contaminate soil and surface water, affecting the organisms living in it and eventually contaminate the food chain. The European Union (EU) has imposed regulations and obliged EU member states to monitor for possible contaminants in the environment and food. For this, highly sophisticated mass spectrometry (MS) techniques, which can nowadays screen >100 contaminants in a single run, are applied. For rapid and inexpensive screening of contaminants, bioactivity-based screening assays are applied, however, identification of compounds based on their chemical-physical properties is not possible. As both methods cannot identify emerging and unknown bioactive contaminants, there is a need for new tools and concepts. In this thesis, new bioaffinity MS (BioMS) concepts, using an antibody, transport proteins and a receptor, are presented for the screening and identification of contaminants. In the first concept, monoclonal antibodies (Mabs) against ochratoxins were coupled to fluorescent labeled paramagnetic microbeads for high-throughput flow cytometric screening of ochratoxins in wheat and cereal. The identification of ochratoxins with nano-ultra performance liquid chromatography-quadrupole-time-of-flight-MS (nano-UPLC-Q-ToF-MS) was achieved in full scan accurate mass mode. In the second BioMS approach, the flow cytometer was replaced by UPLC-triple quadrupole (QqQ)-MS for rapid screening of thyroid transporter ligands. For this, thyroid transport protein transthyretin (TTR) was immobilized onto inexpensive non-colored paramagnetic microbeads and a stable isotopic thyroid hormone was used as label in the competitive inhibition format. For the identification of TTR-binding endocrine disrupting chemicals (EDCs) in process water and urine, nano-UPLC-Q-ToF-MS was used. In order to perform high-throughput screening, a microtiter plate-based high-throughput BioMS approach was developed with the same beads but coupled with recombinant human sex hormone-binding globulin (rhSHBG) for the detection of designer steroids in dietary supplements. Following the screening with rhSHBG-based BioMS using LC-QqQ-MS, the rhSHBG bioaffinity extracts were injected onto chip-UPLC-Q-ToF-MS operated in full scan mode and a wide range of steroids were identified. The same approach was applied with the estrogen receptor α (ERα) in which LC-QqQ-MS, instead of the commonly applied GC-MS, was used for the screening of estrogens with a suitable LC-MS-compatible label. The identification of estrogens in ERα-purified supplement extracts was achieved with UPLC-ion mobility (IM)-Q-ToF-MS. These new BioMS concepts present new tools for the screening and identification of emerging yet unknown food and environmental contaminants to ensure consumer’s health and fair play in sports.

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