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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Potatoes, pathogens and pests : effects of genetic modifi cation for plant resistance on non-target arthropods
Lazebnik, Jenny - \ 2017
University. Promotor(en): Joop van Loon; Marcel Dicke. - Wageningen : Wageningen University - ISBN 9789463431620 - 151
solanum tuberosum - potatoes - oomycetes - phytophthora infestans - genetic engineering - transgenic plants - disease resistance - risk assessment - nontarget organisms - arthropods - insect pests - herbivores - trophic levels - ecological risk assessment - greenhouse experiments - field experimentation - aardappelen - oömyceten - genetische modificatie - transgene planten - ziekteresistentie - risicoschatting - niet-doelorganismen - geleedpotigen - insectenplagen - herbivoren - trofische graden - ecologische risicoschatting - kasproeven - experimenteel veldonderzoek

Currently, fungicides are necessary to protect potato crops against late blight, Phytophthora infestans, one of the world’s most damaging crop pathogens. The introgression of plant resistance genes from wild potato species targeted specifically to the late blight pathogen into susceptible potato varieties may alleviate the environmental impact of chemical control. Genetically modified plants are subject to an environmental risk assessment, and this includes testing for risks to the non-target arthropod community associated with the crop. The thesis begins with a review about the main plant defense responses and their role in influencing sequential interactions between herbivores and plant pathogens. The experimental chapters each focus on different aspects of the interaction between potato plants (both resistant and susceptible), the target pathogen (P. infestans) and several non-target insects. With each chapter, the scope widens: from the molecular gene expression in potato leaves in response to sequential attacks, to field scale biodiversity analyses. At the molecular level, one of the main findings was that the genomic position of the Rpi-vnt1 insertion conferring resistance to P. infestans influenced potato gene expression measured in leaves, when interacting with the non-target insect pests Myzus persicae (Green peach aphid) and Leptinotarsa decemlineata (Colorado potato beetle). Insect performance differed between the resistant GM and susceptible non-GM comparator. In the following chapter, the differences in insect performance were tested across a range of conventionally bred cultivars varying in resistance to P. infestans. Differences in M. persicae performance between several cultivars greatly outweighed the differences previously detected between the GM and non-GM comparator. These results are crucial in shaping the way risk is assessed in the context of GM crops, and these results are supported in our experiments assessing effects on biodiversity with pitfall traps in the field. The third trophic level was also addressed by comparing the performance of the parasitoid Aphidius colemani reared on GM and non-GM fed aphids, both with an without exposure to P. infestans. Differences in parasitoid performance were only found on the susceptible cultivar when inoculated with P. infestans. In the last experimental chapter the risk assessment is taken to the field comparing pitfall trap catches over two years and in two countries. Different methods for statistical analysis of biodiversity data were compared to arrive at recommendations for such analysis in the framework of environmental risk assessments. Drawing on these lessons, the discussion ends with ideas for the development of protocols for environmental risk assessments in the light of expected scientific progress in agricultural biotechnology.

Integrated strategy for the assessment of kidney toxicity : the case of aristolochic acids
Abdullah, Rozaini - \ 2017
University. Promotor(en): Ivonne Rietjens, co-promotor(en): Ans Punt; Sebas Wesseling; Jochem Louisse. - Wageningen : Wageningen University - ISBN 9789463430807 - 207
animal testing alternatives - in vitro - toxicity - models - risk assessment - toxins - carboxylic acids - alternatieven voor dierproeven - toxiciteit - modellen - risicoschatting - toxinen - carbonzuren

This PhD thesis aimed to provide additional evidence to demonstrate the potential of an integrated testing strategy using in vitro assays with physiologically based kinetic (PBK) modeling based-reverse dosimetry to predict in vivo toxicity without animal testing. Kidney toxicity was chosen as the toxicity endpoint and aristolochic acids (AAs) were selected as model chemicals. AAs are natural nephrotoxic, genotoxic and carcinogenic chemicals present in Aristolochia species. PBK models for rat, mouse and human were developed for aristolochic acid I (AAI) based on kinetic parameter values derived from in vitro incubations using relevant tissue fractions. Then, in vitro concentration-response curves for cytotoxicity of AAI were obtained in kidney cell lines and translated to in vivo dose-response curves for kidney toxicity using PBK modeling-based reverse dosimetry. The points of departure (PODs) obtained from these predicted in vivo dose-response curves generally fell within the range of PODs derived from in vivo literature data on kidney toxicity of AAI. The same PBK models were subsequently used to translate the in vitro concentration-response curves for AAI-DNA adduct formation to in vivo dose-response curves for kidney AAI-DNA adduct formation. The predicted in vivo AAI-DNA adduct formation in the rat, mouse and human kidney varied within an order of magnitude compared to the in vivo values reported in the literature. The PBK models were also used to predict the dose level that would be required in humans to obtain the level of DNA adducts in rats at the BMD10 (the benchmark dose causing a 10% extra risk above background level) value for AAI-induced tumor formation in the rat kidney. This analysis revealed that the dose level required to induce the level of DNA adduct formation that equals the DNA adduct level at the BMD10 were similar to AA doses estimated to be taken in Belgian patients that developed urinary tract cancer. Given that the exposure to AAI is often accompanied by the presence of AAII, in a next study the relative formation of DNA adducts by these two major AA congeners was investigated. The results revealed that the relative higher formation of AAI-DNA adducts as compared to AAII-DNA adducts observed in vitro was not reflected in vivo where the levels formed upon exposure to equal dose levels were relatively similar. PBK model based translation of the in vitro data to the in vivo situation revealed that PBK model based prediction of in vivo DNA adduct formation is feasible. However, predicted AAI-DNA adduct levels were higher than predicted AAII-DNA adduct levels, indicating that the difference between the in vitro and in vivo AAI-/AAII-DNA adduct ratios could only in part be explained by differences in in vivo kinetics of AAI compared to AAII. The discrepancy between the difference in DNA adduct formation of AAI and AAII in the in vitro and the in vivo situation is an issue that needs further investigation to also adequately predict the relative differences between the two AAs. In a final chapter this thesis aimed to investigate the possible risks associated with exposure to AAs based on AA levels measured in plant food supplements (PFS) and herbal products. This is of interest given the restrictions on the presence of AAs in food, installed in various countries including The Netherlands, after the incidences with induction of Aristolochic Acid Nephropathy upon use of herbal weight loss preparations that accidentally contained AAs. The risk assessment of PFS and herbal products containing AAs purchased via online markets revealed that consumers can still be exposed to AA-containing PFS and herbal products and that the corresponding levels of exposure raise concern especially for people who frequently use the products. Altogether, this thesis presented further support for the use of combined in vitro-PBK modeling based alternative tools for risk assessment and revealed the continued risks posed by AAs present in PFS and herbal products.

Risicobeoordeling van contaminanten in afval- en reststoffen bestemd voor gebruik als covergistingsmateriaal
Ehlert, P.A.I. ; Wijnen, H.J. van; Struijs, J. ; Dijk, T.A. van; Schöll, L. van; Poorter, L.R.M. de - \ 2016
Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-technical report 70) - 158
biogas - co-vergisting - arsenicum - residuen - zware metalen - verontreinigende stoffen - pesticiden - biociden - mestbeleid - landbouwbeleid - organische verontreinigende stoffen - risicoschatting - co-fermentation - arsenic - residues - heavy metals - pollutants - pesticides - biocides - manure policy - agricultural policy - organic pollutants - risk assessment
A number of wastes and by-products were reviewed for their suitability as substrates for co-digestion with animalmanure to produce biogas and a digestate for use as a fertiliser. The review included 21 substances proposed byLTO Noord (Dutch Farmers Union – Northern Netherlands) and Biogas Branche Organisatie (BBO, the Dutch BiogasIndustry Association) for inclusion in Annex Aa of the Fertiliser Act. At the request of the Ministry of EconomicAffairs a further 6 substances were added (21+6). In addition, 119 substances were re-reviewed in connection witha change to the reference composition for animal manure. The review focused on the possible adverseenvironmental effects of using the digestate as a fertiliser and followed the protocol for assessing the value andrisks of waste used as a fertiliser, version 2.1. The risk assessment included the inorganic contaminants (Cd, Cr, Cu,Hg, Ni, Pb, Zn, As) and organic contaminants (dioxine, PCBs, PAHs, mineral oil, residues of crop protectionproducts) as required by the Fertiliser Act. For all the wastes and by-products, data on composition were collectedfrom the literature and from analyses provided by stakeholders. Expert judgment was used where data were notavailable or were insufficient to conduct a risk assessment as prescribed by the protocol. Criteria for expertjudgment were developed for such situations. Two alternative risk assessment methods were developed for theresidues of pesticides and biocides, based partly on expert judgement. These methods were compared with themethod prescribed by the protocol. These three methods reflect different policy judgements; the protection level setby policymakers will determine which method should be used. The 21+6 substances were evaluated in accordancewith the protocol and using the three methods for evaluating the residues of pesticides and biocides. The resultswere compared with registered co-digestion materials in Flanders, Denmark and Germany. Recommendations aregiven to support policy decisions on the choice of alternative risk assessment method to be used to permit the codigestionof wastes and by-products in biogas production that produce an agronomically and environmentallyacceptable digestate for fertiliser use
Statistical modelling of variability and uncertainty in risk assessment of nanoparticles
Jacobs, R. - \ 2016
University. Promotor(en): Cajo ter Braak, co-promotor(en): Hilko van der Voet. - Wageningen : Wageningen University - ISBN 9789462578197 - 205 p.
modeling - statistics - particles - risk assessment - uncertainty - uncertainty analysis - nanotechnology - probabilistic models - modelleren - statistiek - deeltjes - risicoschatting - onzekerheid - onzekerheidsanalyse - nanotechnologie - waarschijnlijkheidsmodellen

Engineered nanoparticles (ENPs) are used everywhere and have large technological and economic potential. Like all novel materials, however, ENPs have no history of safe use. Insight into risks of nanotechnology and the use of nanoparticles is an essential condition for the societal acceptance and safe use of nanotechnology.

Risk assessment of ENPs has been hampered by lack of knowledge about ENPs, their environmental fate, toxicity, testing considerations, characterisation of nanoparticles and human and environmental exposures and routes. This lack of knowledge results in uncertainty in the risk assessment. Moreover, due to the novelty of nanotechnology, risk assessors are often confronted with small samples of data on which to perform a risk assessment. Dealing with this uncertainty and the small sample sizes are main challenges when it comes to risk assessment of ENPs. The objectives of this thesis are (i) to perform a transparent risk assessment of nanoparticles in the face of large uncertainty in such a way that it can guide future research to reduce the uncertainty and (ii) to evaluate empirical and parametric methods to estimate the risk probability in the case of small sample sizes.

To address the first objective, I adapted an existing Integrated Probabilistic Risk Assessment (IPRA) method for use in nanoparticle risk assessment. In IPRA, statistical distributions and bootstrap methods are used to quantify uncertainty and variability in the risk assessment in a two-dimensional Monte Carlo algorithm. This method was applied in a human health (nanosilica in food) and an environmental (nanoTiO2 in water) risk context. I showed that IPRA leads to a more transparent risk assessment and can direct further environmental and toxicological research to the areas in which it is most needed.

For the second objective, I addressed the problem of small sample size of the critical effect concentration (CEC) in the estimation of R = P(ExpC > CEC), where ExpC is the exposure concentration. First I assumed normality and investigated various parametric and non-parametric estimators. I found that, compared to the non-parametric estimators, the parametric estimators enable us to better estimate and bound the risk when sample sizes and/or small risks are small. Moreover, the Bayesian estimator outperformed the maximum likelihood estimators in terms of coverage and interval lengths. Second, I relaxed the normality assumption for the tails of the exposure and effect distributions. I developed a mixture model to estimate the risk, R = P(ExpC > CEC), with the assumption of a normal distribution for the bulk data and generalised Pareto distributions for the tails. A sensitivity analysis showed significant influence of the tail heaviness on the risk probability, R, especially for low risks.

In conclusion, to really be able to focus the research into the risks of ENPs to the most needed areas, probabilistic methods as used and developed in this thesis need to be implemented on a larger scale. With these methods, it is possible to identify the greatest sources of uncertainty. Based on such identification, research can be focused on those areas that need it most, thereby making large leaps in reducing the uncertainty that is currently hampering risk assessment of ENPs.

Environmental risk assessment of pesticides in Ethiopia : a case of surface water systems
Teklu, B.M. - \ 2016
University. Promotor(en): Paul van den Brink. - Wageningen : Wageningen University - ISBN 9789462578104 - 152 p.
surface water - water systems - water pollution - risk assessment - ecological risk assessment - pesticides - aquatic ecology - aquatic organisms - irrigation systems - ethiopia - oppervlaktewater - watersystemen - waterverontreiniging - risicoschatting - ecologische risicoschatting - pesticiden - aquatische ecologie - waterorganismen - irrigatiesystemen - ethiopië

The current increase in application rate and usage frequency of application of pesticides in Ethiopia pose direct risks to surface water aquatic organisms and humans and cattle using surface water as a source of drinking water in rural parts of the country. A model based risk assessment as currently being used in Europe and elsewhere in the world is tailored to the Ethiopian situation to quantify the risks. Suitability of toxicity data used as an input for risk assessment usually taken from the temperate world was checked through simple toxicity testing of Ethiopian aquatic macroinvertebrates. Subsequent monitoring activities to see the actual residue levels of pesticides in rivers and temporary ponds adjacent to extensive farming activities was also done and results compared with model prediction values. Combining all this knowledge is believed to bring the current pesticide registration system in Ethiopia one step closer to be a more reliable method, protecting non-target organisms as well as the health of humans at risk.

Dermal absorption and toxicological risk assessment : pitfalls and promises
Buist, H. - \ 2016
University. Promotor(en): Ruud Woutersen; Ivonne Rietjens, co-promotor(en): J.J.M. van de Sandt. - Wageningen : Wageningen University - ISBN 9789462577275 - 200 p.
skin - absorption - permeability - in vitro - experiments - exposure assessment - risk assessment - toxicology - biocides - rodenticides - preservatives - disinfection - huid - absorptie - permeabiliteit - experimenten - blootstellingsbepaling - risicoschatting - toxicologie - biociden - rodenticiden - conserveermiddelen - desinfectie

Absorption of toxic substances via the skin is an important phenomenon in the assessment of the risk of exposure to these substances. People are exposed to a variety of substances and products via the skin, either directly or indirectly, while at work, at home or in public space. Pesticides, organic solvents and metalworking fluids are seen to be important contributors to adverse health effects due to occupational exposure via the skin. In daily life, cosmetics, clothing and household products are the most relevant commodities with respect to exposure via the skin.

Given the importance of skin exposure in the assessment of the risk of toxic substances, the objective of this thesis was to further develop, evaluate and improve methods for including skin absorption data this assessment.

In this thesis, four factors influencing dermal absorption, namely dermal loading (chapters 3 and 6), irritative/corrosive potential (chapters 3 and 4), frequency of exposure (chapters 3, 4 and 5) and the vehicle used (chapter 5), were investigated in more detail. Furthermore, a model to extrapolate infinite dose absorption data to finite dose conditions, baptized Dermal Absorption Model for Extrapolation (DAME), was developed and tested.

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n chapter 2 of this thesis, the relationship between relative dermal absorption and dermal loading was investigated. Hundred-and-thirty-eight dermal publicly available absorption experiments with 98 substances were evaluated. The results obtained revealed that dermal loading ranged mostly between 0.001 and 10 mg/cm2. In 87 experiments (63%), an inverse relationship was observed between relative dermal absorption and dermal loading. On average, relative absorption at high dermal loading was 33 times lower than at low dermal loading. Known skin irritating and volatile substances less frequently showed an inverse relationship between dermal loading and relative absorption. It was concluded that when using relative dermal absorption in regulatory risk assessment, its value should be determined at or extrapolated to dermal loadings relevant for the exposure conditions being evaluated.

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n chapter 3 of this thesis, a literature search was presented with the aim to investigate whether neglecting the effects of repeated exposure may lead to an incorrect estimate of dermal absorption. The results demonstrated that the effect of repeated versus single exposure does not demonstrate a unique trend. Nevertheless, an increase in daily absorption was frequently observed upon repeated daily exposure. The little information available mostly concerned pharmaceuticals. However, consumers and workers may be repeatedly exposed to other types of chemicals, like disinfectants and cleaning products, which often contain biocidal active substances that may decrease the barrier function of the skin, especially after repeated exposure. These biocidal products, therefore, may present a safety risk that is not covered by the current risk assessment practice since absorption data are usually obtained by single exposure experiments. Consequently, it was decided to investigate the importance of this issue for biocide safety evaluation. As the literature search revealed that hardly any data on absorption upon repeated dermal exposure to biocides are available, it was concluded that data need to be generated by testing.

To cover the entire range of biocidal products in such testing, a representative series of biocidal substances should be tested, making in vitro testing of dermal absorption the preferred choice over in vivo testing. Based on an inventory made, it appeared that the 16 product types represented among the biocidal products authorised in the Netherlands could be clustered into 6 more or less homogeneous categories based on similarity in active substances. This result could facilitate experimental testing by providing a basis for selection of a limited number of representative compounds to be evaluated.

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n chapter 4 of this thesis, the importance of the effect of repeated dermal exposure on skin permeability for biocide safety evaluation was investigated, using a selection of nine representative biocides from the inventory made in chapter 3. The in vitro dermal penetration of tritiated water and [14C]propoxur was chosen as a measure of the permeability and integrity of human abdominal skin after single and repeated exposure. The results indicated that single and repeated exposure to specific biocidal products (e.g. the quaternary ammonium chlorides DDAC and ADBAC) may significantly increase skin permeability, especially when the compounds are applied at high concentrations, while a substance like formaldehyde may reduce skin permeability under specific conditions.

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n chapter 5 of this thesis, the in vitro dermal absorption kinetics of the quaternary ammonium compound didecyldimethylammonium chloride (DDAC) during single and repeated exposure was studied in more detail. In addition, the influence of biocidal formulations on the absorption of DDAC was investigated, because it was expected that formulation characteristics may be another factor influencing its dermal absorption. The analysis of biocidal products on the Dutch market, reported in chapter 3, indicated that DDAC is often used in combination with other active ingredients. DDAC was most frequently combined with formaldehyde, glutaraldehyde and/or alkyldimethylbenzyl­ammo­nium chloride (ADBAC). Consequently, commercial formulations containing one or more of these additional active ingredients were selected, in addition to one formulation containing only DDAC as an active ingredient. The selected commercial formulations tended to reduce skin penetration of DDAC. This was most pronounced with the formulation containing the highest concentration of formaldehyde (196 mg/mL) and glutaraldehyde (106 mg/mL), which reduced the flux of DDAC across the skin by 95%. The reduction caused by the only tested formulation containing no other active ingredients than DDAC, and thus incorporating no aldehydes, was smallest, and did not reach statistical significance.

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n chapter 6 of this thesis, a simple in silico model to predict finite dose dermal absorption from infinite dose data (kp and lag time) and the stratum corneum/water partition coefficient (KSC,W) was developed. This model was tentatively called Dermal Absorption Model for Extrapolation (DAME). As dermal exposure may occur under a large variety of conditions leading to quite different rates of absorption, such a predictive model using simple experimental or physicochemical inputs provides a cost-effective means to estimate dermal absorption under different conditions.

To evaluate the DAME, a series of in vitro dermal absorption experiments was performed under both infinite and finite dose conditions using a variety of different substances. The kp’s and lag times determined in the infinite dose experiments were entered into DAME to predict relative dermal absorption value under finite dose conditions. For six substances, the predicted relative dermal absorption under finite dose conditions was not statistically different from the measured value. For all other substances, measured absorption was overpredicted by DAME, but most of the overpredicted values were still lower than 100%, the European default absorption value for the tested compounds.

In conclusion, our finite dose prediction model (DAME) provides a useful and cost-effective estimate of in vitro dermal absorption, to be used in risk assessment for non-volatile substances dissolved in water at non-irritating concentrations.

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n chapter 7 of this thesis, the results of the research reported in chapters 2 to 6 were put into perspective, the pitfalls and promises emanating from them discussed and general conclusions drawn. The possible influence of vehicles on absorption and the possible impact of irritative or corrosive vehicles or chemicals on the skin barrier have been demonstrated in this thesis. An in silico predictive model tentatively called DAME was developed, which enables the user to evaluate a variety of dermal exposure scenarios with limited experimental data (kp and lag time) and easy to obtain physicochemical properties (MW and log KOW). The predictions of our experiments reported in chapter 6 were compared to those of the Finite Dose Skin Permeation (FDSP) model published on the internet by the US Centers for Disease Control and Prevention (CDC). DAME outperformed FDSP (R2 of the correlation predicted/measured potential absorption 0.64 and 0.12, respectively). At present, the applicability domain of DAME is limited to non-volatile substances dissolved in aqueous solvents. However, in future the model will be adapted to include volatile substances as well.

Altogether, it is concluded that dermal exposure can be an important factor in risks posed by chemicals and should be taken into account in risk assessment. The methods to actually do this are still open for further improvement to better account for the various factors influencing skin penetration and to develop adequate combinations of in vitro and in silico models that can accurately predict human dermal absorption.

Pesticide use and off-site risk assessment : a case study of glyphosate fate in Chinese Loess soil
Yang, X. - \ 2016
University. Promotor(en): Coen Ritsema; Violette Geissen, co-promotor(en): Hans Mol; Fei Wang. - Wageningen : Wageningen University - ISBN 9789462576759 - 152 p.
pesticides - risk assessment - pesticide residues - glyphosate - loess soils - soil pollution - erosion - china - pesticiden - risicoschatting - pesticidenresiduen - glyfosaat - lössgronden - bodemverontreiniging - erosie

Pesticide use and off-site risk assessment: a case study of glyphosate fate in Chinese Loess soil

Xiaomei Yang

Abstract: Repeated applications of pesticide may contaminate the soil and water, threatening their quality within the environmental system and beyond it through water erosion related processes and leaching. Taking into account the situation of intense farming, pesticide use and erosion in China, and in the loess area in particular, this study aims to further the science of pesticide risk assessment by increasing the understanding of the fate of glyphosate and its main metabolite AMPA while also assessing their risks related to soil erosion in Chinese loess soil. Four main objectives are conducted:

1) Assessment of farmers’ knowledge and awareness of pesticide use in the Wei River catchment

In this study, we presented the information for the knowledge and awareness of pesticide risks via face-to-face interview among farmers (209) and retailers (20) in two rural regions (Qianyang County (S1) and Chencang County (S2)) of the Wei River catchment in China where the modes of farming and the state of erosion are very different. The results showed that farmers learned about the use and risk related to of pesticide use mainly by oral communication (p<0.01), rather than by introduction labelled on pesticide package bag/bottle and media tools (TV/newspaper/Internet/books). Protective measures were inadequate and washing hands (>70%) was the most common mode of personal hygiene after spraying, comparing to wearing masks, showering, and changing clothes. Regarding to dealing with the packages or containers of pesticide, farmers dumped them directly onto the land or into water, and over 85% of farmers claimed to use illegal pesticides. Compared to farmers, pesticide retailers were well-informed and highly conscious of their responsibility for the safe use of pesticides. Educational programmes targeted to age groups, proper disposal of pesticide waste, and sufficient supervision from authorities should consequently be considered for improving the levels of knowledge and awareness of the dangers of pesticides to human health and environmental pollution in the Wei River catchment, China.

2) Investigation of off-site transport of glyphosate and AMPA by runoff and erosion in Chinese loess soil

In this study, we assessed the short-term transport (1h duration, 1 mm min-1 rainfall) of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) related to erosion and runoff on bare loess soil with different slopes (10° and 20°)and application rates (3.6 kg ha-1 and 7.2 kg ha-1) in hydraulic flumes. Significant power and exponent function described a significantly negative relation between rainfall duration and the content of glyphosate and AMPA (p<0.01) in runoff and suspended load, respectively. The transport rate of glyphosate (including AMPA) by runoff and suspended load was approximately 4% and 10% of the applied amount, respectively indicating that it mainly underlies particulate transport. The glyphosate and AMPA content in the flume soil at the end of the experiment (after 1h) decreased significantly with depth (p<0.05), and 72, 2, and 3% of the applied glyphosate (including AMPA) remained in the 0-2, 2-5, and 5-10 cm soil layers, respectively. Thus, the risk of leaching was low. In view of loss of 14 % of the initially applied glyphosate after 1 h, “buffer zone”, referred as the protection area for ecosystem discharge between farming land and public rivers, is strongly recommended, especially in regions where rain-induced soil erosion is common.

3) Investigation of the on-site fate of glyphosate and AMPA formation in Chinese loess soil

In this study, we observed glyphosate decay, erosion and runoff related transport of glyphosate and AMPA at different slopes (10° and 20°) and application rates (3.6 kg ha-1 and 7.2 kg ha-1) under field condition during 35 d, September-October in 2012 (16.8±2.1°C with 35 mm rainfall in total) and July-August in 2013 (27 ± 2.3°C with 74 mm rainfall in total). The initial glyphosate decayed rapidly (half-life of 3.5 d) in the upper 2 cm of soil following a first-order rate of decay. AMPA content in the 0-2 cm soil layer correspondingly peaked 3 d after glyphosate application and then gradually decreased. The residues of glyphosate and AMPA decreased significantly with soil depth (p<0.05) independently of the slope inclination and application rate. About 0.36% of the glyphosate initially applied was transported off-site plots after one erosive rain 2 days after the application. Glyphosate and AMPA concentration in runoff were low while the contents in the sediment was much higher than in the upper 2 cm of the soil. This suggested that even though the transported glyphosate is limited, the off-site risk of glyphosate and AMPA is high. Consequently, a realistic erosion-pesticide model should be developed that can simulate the particulate-facilitated transport of glyphosate and its off-site risks involving decay processes.

4) Off-site risk assessment of particle-facilitated pesticide transport related to erosion

In this study, we have developed a parsimonious integrative model of pesticide displacement by runoff and erosion that explicitly accounts for water infiltration, erosion, runoff, and pesticide transport and degradation in soil. The conceptual framework was based on broadly accepted assumptions such as the convection-dispersion equation and lognormal distributions of soil properties associated with transport, sorption, degradation, and erosion. To illustrate the concept, a few assumptions are made with regard to runoff in relatively flat agricultural fields: dispersion is ignored and erosion is modelled by a functional relationship. A sensitivity analysis indicated that the total mass of pesticide associated with soil eroded by water scouring increased with slope, rain intensity, and water field capacity of the soil. The mass of transported pesticide decreased as the micro-topography of the soil surface became more distinct. The timing of pesticide spraying and rate of degradation before erosion negatively affected the total amount of transported pesticide. The mechanisms involved in pesticide displacement, such as runoff, infiltration, soil erosion, and pesticide transport and decay in the topsoil, were all explicitly accounted for, so the mathematical complexity of their description can be high, depending on the situation.

Overall, the outcome of this study indicates that it is urgent to improve farmers knowledge and awareness on pesticide use in order to reduce pesticide risks before they are applied in environmental system. The rapid decay of glyphosate to AMPA in loess soil suggests that on-site risks of glyphosate is mainly related to AMPA, especially under warmer climatic conditions. The off-site transport of glyphosate in our study was about 14% of the applied dose after 1 h of rainfall indicating that the off-site risks of glyphosate should be taken into account in regions highly prone to soil erosion. The concept of particulate transport elaborated in objective 4 should be incorporated in existing erosion models, such as LISEM, to predict off-site effects of glyphosate applications.

Alternative testing strategies for predicting developmental toxicity of antifungal compound
Li, H. - \ 2016
University. Promotor(en): Ivonne Rietjens; Bennard van Ravenzwaay, co-promotor(en): Jochem Louisse. - Wageningen : Wageningen University - ISBN 9789462576780 - 197 p.
toxicity - fetal development - transfer - infant development - adolescent development - child development - pregnancy - in vivo experimentation - modeling - placenta - in vitro - risk assessment - tebuconazole - conazole fungicides - antifungal agents - alternative methods - toxiciteit - foetale ontwikkeling - overdracht - zuigelingenontwikkeling - adolescentenontwikkeling - kinderontwikkeling - zwangerschap - in vivo experimenten - modelleren - risicoschatting - tebuconazool - conazoolfungiciden - antimycotica - alternatieve methoden

Determination of safe human exposure levels of chemicals in toxicological risk assessments largely relies on animal toxicity data. In these toxicity studies, the highest number of animals are used for reproductive and developmental toxicity testing. Because of economic and ethical reasons, there is large interest in the development of in vitro and/or in silico test systems as alternatives for the animal studies. The aim of the present thesis was to evaluate the applicability of combined in vitro approaches taking toxicokinetic and toxicodynamic aspects into account, as well as of an integrated in vitro and in silico approach for prediction of developmental toxicity using a series of antifungal compounds as the model compounds.

Transplacental transfer of compounds is highly likely to play an important role in developmental toxicity, so we developed and validated an in vitro placental barrier model using BeWo b30 cells to predict placental transfer. Then we investigated the applicability of the ES-D3 cell differentiation assay combined with the in vitro BeWo transport model to predict the relative in vivo developmental toxicity potencies of two sets of selected antifungal compounds. The data obtained show that the combined in vitro approach provided a correct prediction for the relative in vivo developmental toxicity, whereas the ES-D3 cell differentiation assay as stand-alone did not. In order to detect specific structural alterations induced by chemicals, we investigated the applicability of the ex ovo assay of chicken embryos to predict the specific alterations induced by the antifungal compounds. Data revealed that the ex ovo assay of chicken embryos is able to assess the teratogenic potential of antifungal compounds, and, when combined with the in vitro BeWo transport model, is able to better predict relative in vivo prenatal developmental toxicity potencies.

Subsequently, we translated in vitro concentration–response data of the antifungal compound tebuconazole, obtained in the ES-D3 cell differentiation assay and the ex ovo assay of chicken embryos, into predicted in vivo dose–response data using physiologically based kinetic (PBK) modelling-facilitated reverse dosimetry. The results show that the BMD10 values from predicted dose–response data from both assays are in concordance with BMD10 values derived from in vivo data (within 5-fold difference). This revealed that PBK modeling is a promising tool to predict in vivo dose-response curves based on the results of in vitro toxicity assays, and may therefore be used to set a point of departure for deriving safe exposure limits in risk assessment.

It is concluded the combined in vitro approaches and the integrated in vitro-in silico approaches appear to be promising for the screening and prioritization of chemicals and to provide reference values, such as BMD10 values, without using animals, therefore contributing to the 3R principle of animal testing.

Scenarios for exposure of aquatic organisms to plant protection products in the Netherlands : soilless cultivations in greenhouses
Linden, A.M.A. van der; Os, E.A. van; Wipfler, E.L. ; Cornelese, A.A. ; Ludeking, Daniel ; Vermeulen, T. - \ 2015
Bilthoven : RIVM (RIVM report 2015-0128) - 78
greenhouse horticulture - pesticides - water pollution - authorisation of pesticides - leaching - risk assessment - protected cultivation - emission - surface water - glastuinbouw - pesticiden - waterverontreiniging - toelating van bestrijdingsmiddelen - uitspoelen - risicoschatting - teelt onder bescherming - emissie - oppervlaktewater
Als door het gebruik van gewasbeschermingsmiddelen in kassen restanten van deze middelen in het nabijgelegen oppervlaktewater terechtkomen, kan dat het waterleven aantasten. Hiermee wordt te weinig rekening gehouden bij de huidige risicobeoordeling van het gebruik van een gewasbeschermingsmiddel voor gewassen die in kassen op substraat, bijvoorbeeld steenwol, worden geteeld. Daarom zijn voor deze toepassingen nieuwe methoden voor de risicobeoordeling ontwikkeld waarin dat wel is ingecalculeerd.
Evaluation of the Dutch leaching decision tree with the substances bentazone, MCPA and mecoprop
Linden, A.M.A. van der; Beltman, W.H.J. ; Boesten, J.J.T.I. ; Pol, J.W. - \ 2015
Bilthoven : RIVM (RIVM report 2015-0095) - 78
pesticides - groundwater - drinking water - water quality - water pollution - degradation - risk assessment - sorption - decision models - leaching - bentazone - mcpa - pesticiden - grondwater - drinkwater - waterkwaliteit - waterverontreiniging - degradatie - risicoschatting - sorptie - beslissingsmodellen - uitspoelen - bentazon
Sinds 2004 wordt een beslismodel (beslisboom) gebruikt om te beoordelen in welke mate een gewasbeschermingsmiddel uitspoelt naar het grondwater. Uit een evaluatie van het RIVM, het College voor de toelating van gewasbeschermingsmiddelen en biociden (Ctgb) en onderzoekinstituut Alterra blijkt dat de beslisboom goed werkt en state of the art is. Wel laten de stofgegevens waarmee wordt gerekend te wensen over. Om de kwaliteit van het grondwater te waarborgen moeten deze gegevens zorgvuldiger worden afgeleid.
Sediment toxicity testing and prospective risk assessment of organic chemicals
Diepens, N.J. - \ 2015
University. Promotor(en): Bart Koelmans, co-promotor(en): Paul van den Brink. - Wageningen : Wageningen University - ISBN 9789462574991 - 346
sediment - toxiciteit - testen - sedimenttest - verontreinigde sedimenten - chemicaliën - risicoschatting - ecotoxicologie - toxicity - testing - sediment test - contaminated sediments - chemicals - risk assessment - ecotoxicology

While providing an option for development in coastal areas, shrimp farming is usually associated with high environmental cost due to the loss of mangrove forest and high social cost as farmers suffer heavy financial losses due to disease outbreaks. Planning shrimp farming requires to integrate risk as well as social and environmental cost. This thesis, using the Mekong Delta as a case, presents an approach to investigate, with local stakeholders, options to plan a resilient and sustainable shrimp farming sector. First, Olivier Joffre analyzed the different shrimp production systems from economic point of view before analyzing farmer’s strategies and providing insights on drivers that will push or, at the opposite, constraint farmers to choose integrated mangrove shrimp systems. This knowledge was integrated in an Agent Based Model (ABM) that was calibrated using Role Playing Games (RPG).

The effect of future scenarios and different policies on the farmers’ decisions was tested using a combination of RPG and ABM. For one coastal district of the Mekong Delta, the results showed that promotion of intensification of shrimp production has a high social cost and decreases the total production in the study area after 10 years. Policies for supporting the spread of integrated mangrove-shrimp systems, such as Payment for Ecosystem Services, or access to an organic value chain, are not strong enough to influence farmers’ decision toward adopting these systems. Without any adaptation to climate change a sharp decrease of the production is expected. The approach brought local farmers’ knowledge to the attention of decision makers.

Development of probabilistic models for quantitative pathway analysis of plant pests introduction for the EU territory
Douma, J.C. ; Robinet, C. ; Hemerik, L. ; Mourits, M.C.M. ; Roques, A. ; Werf, W. van der - \ 2015
European Food Safety Authority - 435
gewasbescherming - landen van de europese unie - plantgezondheid - siergewassen - stochastische modellen - bouwhout - vermeerderingsmateriaal - invasieve exoten - plantaardige producten - waarschijnlijkheid - risicoschatting - risicovermindering - plantenplagen - plant protection - european union countries - plant health - ornamental crops - stochastic models - building timbers - propagation materials - invasive alien species - plant products - probability - risk assessment - risk reduction - plant pests
The aim of this report is to provide EFSA with probabilistic models for quantitative pathway analysis of plant pest introduction for the EU territory through non-edible plant products or plants. We first provide a conceptualization of two types of pathway models. The individual based PM simulates an individual consignment (or a population of such consignment) by describing the stochastic change in the state of the individual consignment over time and space. The flow-based PM, simulates the flow of infested product over time and space, without distinguishing individual consignments. We show how these two conceptualisations are mathematically related, and present, as a show case, both models for cut flowers. Second, we developed PMs for five product groups: round wood, sawn wood, cut flowers, plants for planting and seeds. For each product group we have developed a case-study (combination of product, origin and pest) to illustrate the use of the pathway models: (1) oak wood from the USA and Ceratocystis fagacearum, (2) Coniferous sawn wood from China and Bursaphelenchus xylophilus, (3) Cut orchids from Thailand and Thrips palmi, (4) Pot orchids from Thailand and Thrips palmi, and (5) Tomato seeds and Clavibacter michiganensis subsp. michiganensis from outside the European Union. An uncertainty analysis on the models shows that the pest species-specific parameters appear to be sensitive and uncertain. Third, a practical guidance is provided on i) how to develop a PM, ii) the application of PMs in @Risk (a plugin for MS Excel), and iii) application in R. Finally, future research topics are defined. Further work is needed on interpretation of results, linking quantitative outcomes of pathway modelling to pest risk scoring guidance, and evaluation of management options using pathway models.
Ontwikkeling emissietoetswaarden voor het beoordelen van duurzaam stortbeheer op pilotstortplaatsen : fase 2: Voorstellen voor emissietoetswaarden (Nederlandstalige verkorte versie van RIVM-rapport 607710002)
Brand, E. ; Nijs, T. de; Claessens, J. ; Dijkstra, J. ; Comans, R.N.J. ; Lieste, R. - \ 2015
Bilthoven : Rijksinstituut voor Volksgezondheid en Milieu - 105
dumping - afvalstortplaatsen - emissie - grondwater - risicoschatting - diffusiemodellen - waterverontreiniging - grondwaterverontreiniging - modelleren - waterkwaliteit - waste disposal sites - emission - groundwater - risk assessment - diffusion models - water pollution - groundwater pollution - modeling - water quality
Sinds de jaren negentig wordt internationaal onderzoek verricht naar ‘duurzaam stortbeheer’. Het idee hierachter is dat de bron, de stortplaats zelf, schoner wordt, zodat er minder verontreinigingen uit de stortplaatsen kunnen weglekken. Op deze manier worden de bodem en het nabijgelegen grondwater beschermd. Tot nu toe zijn er nog geen technieken beschikbaar waarvan het effect op grote schaal bewezen is. In dat verband heeft het RIVM, in samenwerking met het Energieonderzoek Centrum Nederland (ECN), onderzoek gedaan voor drie vuilstortlocaties in Nederland. Voor deze locaties zijn ‘emissietoetswaarden’ afgeleid, waarmee kan worden vastgesteld hoeveel schadelijke stoffen er maximaal in het water afkomstig van de stortplaats mag zitten.
Overweight and obesity in primary-school children: a surveillance system for policy-making in Europe from 2007 onwards
Wijnhoven, T.M.A. - \ 2015
University. Promotor(en): Pieter van 't Veer, co-promotor(en): Joop van Raaij. - Wageningen - ISBN 9789462574656 - 265
overgewicht - obesitas - quetelet index - lichaamsgewicht - schoolkinderen - kinderen - kwantitatieve analyse - who - gezondheid van kinderen - risicoschatting - kindervoeding - lichamelijke activiteit - kleding - overweight - obesity - body mass index - body weight - school children - children - quantitative analysis - child health - risk assessment - child nutrition - physical activity - clothing

Trudy M.A. Wijnhoven

Overweight and obesity in primary-school children: a surveillance system for policy-making in Europe from 2007 onwards.

Background

As a follow-up to the European Ministerial Conference on Counteracting Obesity convened in 2006 in Turkey, the European Childhood Obesity Surveillance Initiative (COSI) was launched by the Regional Office for Europe of the World Health Organization (WHO). COSI, a collaboration between WHO and interested Member States, aims to monitor the magnitude of overweight and obesity among primary-school children in European countries, to allow intercountry comparisons and to identify regional differences for informed policy-making. It collects at regular intervals data on weight and height of primary-school children and on their nutrition and physical activity behaviours, as well as on school environmental characteristics supportive to healthy nutrition and physical activity.

Methods

The research described in this PhD thesis is based on the data collected in the first two COSI rounds by 12 European countries in school year 2007/2008 and by 13 European countries in school year 2009/2010. Nationally representative samples of children aged 6–9 years were drawn, whereby a majority of the countries applied a two-stage school-based cluster sampling approach.

A total of 168 832 children in school year 2007/2008 and 224 920 children in school year 2009/2010 were included in the anthropometric intercountry data analyses. Children's weight and height were measured by trained examiners using standardized procedures. Participating countries were allowed to adhere to their local legal requirements by specified deviations from standardized procedures, such as in types of clothing worn by the children during weight and height measurements. For each country, the prevalence of overweight and obesity, as well as mean Z-scores of anthropometric indices of height, weight and body mass index (BMI) were computed.

The characteristics included in the analyses on the school environment referred to the frequency of physical education lessons, the availability of school playgrounds, the possibility to obtain food items and beverages on the school premises, and the organization of school initiatives to promote a healthy lifestyle. The school form was usually completed by the school principal or the teachers involved with the sampled classes. Data from 1831 schools in school year 2007/2008 and from 2045 schools in school year 2009/2010 were used. For each school, a school nutrition environment score (range: 0–1) was determined whereby higher scores correspond to higher support for a healthy school nutrition environment and the mean of the children's BMI-for-age Z-scores calculated.

Five countries in school year 2007/2008 provided children's data on 13 health-risk behaviours related to breakfast and food consumption frequency, physical activity, screen time and sleep duration (n = 15 643). These data were reported by the caregivers alone or jointly with their child. For each country, the prevalence of the risk behaviours was estimated, and associations between them and overweight and obesity examined by multilevel logistic regression analyses.

Results

In both school years, a wide range in overweight and obesity prevalence estimates was found that differed significantly by country, as well as by European region. In all countries, the percentage of overweight children was about 20% or more (range: 18–57%), and the percentage of obese children was 5% or more (range: 5–31%). The findings suggest the presence of a north–south gradient with the highest overweight and obesity prevalence estimates found in southern European countries. Furthermore, changes in mean BMI-for-age Z-scores (range: from –0.21 to +0.14) and prevalence of overweight (range: from –9.0% to +6.2%) from school year 2007/2008 to school year 2009/2010 varied significantly among countries, whereas a period of two years is considered too short to identify these developments. The clothes-adjusted overweight prevalence estimates were lower by as much as 12% than the unadjusted estimates. Monthly BMI-for-age Z-score values within countries did not show systematic seasonal effects.

Large between-country differences were observed in both school years in the availability of food items or beverages on the school premises (e.g., fresh fruit could be obtained in 12–95% of schools) and in the organization of initiatives to promote a healthy lifestyle in the selected classes (range: 42–97%). The provision of physical education lessons and the availability of school playgrounds were more uniformly present across the countries (range: 76–100%). A large variation was also seen in school nutrition environment scores (range: 0.30–0.93) whereby countries with a low score (< 0.70) graded less than three out of five characteristics as supportive. High-score countries showed more often than low-score countries a combined absence of cold drinks containing sugar, sweet snacks and salted snacks on the school premises.

The prevalence of all 13 health-risk behaviours differed significantly across countries. For instance, the percentage of children who ate ‘foods like candy bars or chocolate’ > 3 days/week ranged from 2.2% to 63.4%; this figure ranged from 1.1% to 46.5% for those who ate ‘foods like potato chips (crisps), corn chips, popcorn or peanuts’ > 3 days/week. The range for children who did not have breakfast every day was between 4.4% and 32.5%, and from 4.8% to 35.0% for those who did not play outside ≥ 1 hour/day. Not having breakfast daily and spending screen time ≥ 2 hours/day were clearly positively associated with obesity. The same was true for eating ‘foods like pizza, French fries, hamburgers, sausages or meat pies’ > 3 days/week and playing outside < 1 hour/day. While a combination of multiple less favourable physical activity behaviours was clearly positively associated with obesity, a combination of the presence of multiple unhealthy eating behaviours did not lead to higher odds of obesity.

Conclusions

The results found in both COSI school years show that overweight and obesity among 6–9-year-old children are a serious public health concern, especially in southern European countries, and show the need for accelerated efforts to prevent excess body weight early in life by all participating countries. It was possible to detect relevant changes within a period of two years but to identify clear trends within countries, a longer time interval is necessary. The data on the school nutrition environment and the children's health-risk behaviours may assist policy-makers in monitoring their national policies targeting school settings and childhood obesity. In particular, promoting physical activity-related and discouraging sedentary behaviours among schoolchildren in the context of obesity preventive interventions seem to be essential.

Omgaan met bodemverontreiniging in het landelijk gebied
Waarde, J.J. van der; Boels, D. ; Hopman, M. - \ 2015
De Levende Natuur 105 (2015)3. - ISSN 0024-1520 - p. 110 - 114.
bodemverontreiniging - bodembiologie - herstel - natuurbescherming - ecologie - risicoschatting - bodemkwaliteit - soil pollution - soil biology - rehabilitation - nature conservation - ecology - risk assessment - soil quality
Bodemverontreiniging kan leiden tot ecologische effecten en risico's voor plant en dier. Soms moeten er daarom maatregelen worden getroffen. In de praktijk van natuurbeheer en natuurontwikkeling is er nog veel onduidelijkheid over hoe deze effecten bepaald moeten worden. Daartoe is door VROM, LNV, RIZA, RIVM en Bioclear (mede gefinancierd door SKB) PERISCOOP opgezet (Platform Ecologische Risicobeoordeling)
Phosphorus leaching from soils: process description, risk assessment and mitigation
Schoumans, O.F. - \ 2015
Wageningen : Alterra, Wageningen-UR (Alterra scientific contributions 46) - ISBN 9789462573666 - 261
nutrient leaching - leaching - soil chemistry - adsorption - phosphorus - phosphate leaching - risk assessment - water quality - eutrophication - nutriëntenuitspoeling - uitspoelen - bodemchemie - adsorptie - fosfor - fosfaatuitspoeling - risicoschatting - waterkwaliteit - eutrofiëring
Extensive literature searches soil and growing media inventories : (RC/EFSA/PLH/2013/01-SC1)
Bremmer, J. ; Holeva, M. ; Breukers, M.L.H. ; Brouwer, J.H.D. - \ 2015
Brussels : IBF International Consulting (EFSA supporting publication 2015- EN-834) - 49
bodem - groeimedia - basisproducten - plantenziekteverwekkers - plantenplagen - onkruiden - gastheerreeks - inventarisaties - risicoschatting - soil - growing media - commodities - plant pathogens - plant pests - weeds - host range - inventories - risk assessment
In this project two inventories by means of extensive literature searches have been executed: Inventory 1 of all types of soil and growing media (if relevant components thereof) to be elaborated considering (i) the soil and growing medium imported as commodities (i.e. not in association with plants intended for planting), (ii) the soil and growing medium attached to plants for planting, and (iii) the soil and growing medium attached as a contaminant to imported goods (ranging from ware potatoes to agricultural machinery). Inventory 2, based on interceptions data and scientific and technical literature, of plant pests, plant diseases and weeds that can be associated with soil and growing medium (if relevant components thereof). Execution of Inventory 1 resulted in a list of 956 soils and growing media. Execution of Inventory 2 resulted in Excel tables for each taxonomic group separately in which the pests and diseases are linked to the soil and growing media. Additional information has been provided for processes applied to produce growing media and the impact on harmful organisms and private certification schemes applied in Europe to control the trade and use of growing media.
Phosphorus leaching from soils: process description, risk assessment and mitigation
Schoumans, O.F. - \ 2015
University. Promotor(en): Sjoerd van der Zee, co-promotor(en): Wim Chardon. - Wageningen : Wageningen University - ISBN 9789462572997 - 261
nutriëntenuitspoeling - uitspoelen - bodemchemie - adsorptie - fosfor - fosfaatuitspoeling - risicoschatting - waterkwaliteit - eutrofiëring - nutrient leaching - leaching - soil chemistry - adsorption - phosphorus - phosphate leaching - risk assessment - water quality - eutrophication
Er zijn succesvolle management strategieën voor P nodig om de waterkwaliteit te verbeteren en daarvoor is allereerst kwantitatieve informatieve nodig over de ruimtelijke verdeling van de fosfaatbelasting van het oppervlaktewater vanuit landbouwgronden. In Nederland is een protocol fosfaatverzadigde gronden ontwikkeld om het potentiële risico van verhoogde fosfaatconcentraties in het bovenste grondwater (op termijn) te voorspellen voor kalkarme zandgronden, omdat in deze gebieden veel intensieve veehouderij voorkomt. Voor deze grondsoort zijn de parameters voor het protocol vastgesteld. Echter, voor de overige grondsoorten is geen informatie verzameld, waardoor er voor Nederland als geheel geen ruimtelijke beeld bestaat van de mate van fosfaatverzadiging en van het potentiële risico van verhoogde fosfaatconcentraties in het bovenste grondwater. Daarnaast is er behoefte aan eenvoudige methoden om het (huidige) actuele risico van de fosfaatbelasting van het oppervlaktewater in kaart te brengen, zodat inzichtelijk gemaakt kan worden welke gebieden nu al substantieel de oppervlaktewaterkwaliteit en de eutrofiestatus beïnvloeden.
Crop protection and pesticide risk assessment Myanmar : towards sustainable agricultural and export of high value crops
Peeters, F.M. ; Meggelen, J. van; Schepers, H.T.A.M. - \ 2015
Wageningen : Alterra, Wageningen-UR (Alterra-report 2621) - 81
gewasbescherming - pesticiden - risicoschatting - myanmar - plant protection - pesticides - risk assessment
Development of an integrated in vitro model for the prediction of oral bioavailability of nanoparticles
Walczak, A.P. - \ 2015
University. Promotor(en): Ivonne Rietjens, co-promotor(en): Hans Bouwmeester; Peter Hendriksen. - Wageningen : Wageningen University - ISBN 9789462572201 - 153
nanotechnologie - deeltjes - in vitro - inname - biologische beschikbaarheid - voedingsonderzoek bij de mens - risicoschatting - nanotechnology - particles - ingestion - bioavailability - human nutrition research - risk assessment

Title of the PhD thesis: Development of an integrated in vitro model for the prediction of oral bioavailability of nanoparticles

The number of food-related products containing nanoparticles (NPs) increases. To understand the safety of such products, the potential uptake of these NPs following consumption needs to be assessed. In normal safety assessment studies this is investigated using animal models. For scientific, ethical and economical reasons, there is a demand to refine, reduce and replace animal testing by developing in vitro alternatives for hazard characterization. In this thesis an in vitro model for the prediction of the uptake of NPs in the human body after consumption was developed. The model consists of two parts. The first part is a laboratory incubation model mimicking human digestion in mouth, stomach and intestine. For the second part, human intestinal wall cells are used to assess the uptake of nanoparticles. The two models were combined into the integrated in vitro model to take into consideration the potential effect of digestion on nanoparticle uptake in the gut. The main outcome of the work is that the cell-based integrated in vitro model can be used to evaluate which NPs are likely taken up by the body at the highest rate. The size of NPs and the type of chemical groups on their surface greatly influenced the uptake of NPs. The developed model can be used to prioritize the NPs for additional investigations. Using this model in the safety assessment of NPs would reduce the number of animals used in safety assessment.

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