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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The Evolution and Cultural Framing of Food Safety Management Systems—Where From and Where Next?
Manning, Louise ; Luning, Pieternel A. ; Wallace, Carol A. - \ 2019
Comprehensive Reviews in Food Science and Food Safety 18 (2019)6. - ISSN 1541-4337 - p. 1770 - 1792.
food safety - food safety culture - HACCP - private food safety and quality standards - risk assessment

The aim of this paper is to review the development of food safety management systems (FSMS) from their origins in the 1950s to the present. The food safety challenges in modern food supply systems are explored and it is argued that there is a need for a more holistic thinking approach to food safety management. The narrative review highlights that while the transactional elements of how FSMS are developed, validated, implemented, monitored, and verified remains largely unchanged, how organizational culture frames the operation and efficacy of FSMS is becoming more important. The evolution of a wider academic and industry understanding of both the influence of food safety culture (FS-culture) and also how such culture frames and enables, or conversely restricts the efficacy of the FSMS is crucial for consumer well-being. Potential research gaps worthy of further study are identified as well as recommendations given for the application of the research findings within the food industry.

Comparison of Pesticide Exposure in Honey Bees (Hymenoptera : Apidae) and Bumble Bees (Hymenoptera: Apidae): Implications for Risk Assessments
Gradish, Angela E. ; Steen, Jozef Van Der; Scott-Dupree, Cynthia D. ; Cabrera, Ana R. ; Cutler, G.C. ; Goulson, Dave ; Klein, Olaf ; Lehmann, David M. ; Lückmann, Johannes ; O'Neill, Bridget ; Raine, Nigel E. ; Sharma, Bibek ; Thompson, Helen - \ 2019
Environmental Entomology 48 (2019)1. - ISSN 0046-225X - p. 12 - 21.
bumble bee - honey bee - pesticide exposure - risk assessment

To date, regulatory pesticide risk assessments have relied on the honey bee (Apis mellifera L.) (Hymenoptera: Apidae) as a surrogate test species for estimating the risk of pesticide exposure to all bee species. However, honey bees and non-Apis bees may differ in their susceptibility and exposure to pesticides. In 2017, a workshop ('Pesticide Exposure Assessment Paradigm for Non-Apis Bees') was held to assess if honey bee risk assessment frameworks are reflective of non-Apis bee pesticide exposure. In this article, we summarize the workshop discussions on bumble bees (Bombus spp.). We review the life history and foraging behavior of bumble bees and honey bees and discuss how these traits may influence routes and levels of exposure for both taxa. Overall, the major pesticide exposure routes for bumble bees and honey bees are similar; however, bumble bees face additional exposure routes (direct exposure of foraging queens and exposure of larvae and adults to soil residues). Furthermore, bumble bees may receive comparatively higher pesticide doses via contact or oral exposure. We conclude that honey bee pesticide risk assessments may not always be protective of bumble bees, especially queens, in terms of exposure. Data needed to reliably quantify pesticide exposure for bumble bees (e.g., food consumption rates, soil residue levels) are lacking. Addressing these knowledge gaps will be crucial before bumble bee exposure can be incorporated into the pesticide risk assessment process. Because bumble bees exhibit appreciable interspecific variation in colony and behavioral characteristics, data relevant to pesticide exposure should be generated for multiple species.

Gene-Edited Crops : Towards a Harmonized Safety Assessment
Kleter, Gijs A. ; Kuiper, Harry A. ; Kok, Esther J. - \ 2019
Trends in Biotechnology 37 (2019)5. - ISSN 0167-7799 - p. 443 - 447.
crop biotechnology - gene editing - genetically modified crops - international harmonization - novel plant breeding techniques - regulation - risk assessment - safety assessment

Gene editing and other innovative plant breeding techniques are transforming the field of crop biotechnology. Divergent national regulatory regimes worldwide apply to crops bred with these techniques. A plea is made for international harmonization of the premarket assessment of their safety. Such harmonization has previously been achieved for genetically modified (GM) crops.

A systematic knowledge synthesis on the spatial dimensions of Q fever epidemics
Rooij, Myrna M.T. de; Leuken, Jeroen P.G. van; Swart, Arno ; Kretzschmar, Mirjam E.E. ; Nielen, Mirjam ; Koeijer, Aline A. de; Janse, Ingmar ; Wouters, Inge M. ; Heederik, Dick J.J. - \ 2019
Zoonoses and Public Health 66 (2019)1. - ISSN 1863-1959 - p. 14 - 25.
airborne exposure - Coxiella burnetii - epidemiology - Q fever - risk assessment - spatial analysis

From 2007 through 2010, the Netherlands experienced the largest Q fever epidemic ever reported. This study integrates the outcomes of a multidisciplinary research programme on spatial airborne transmission of Coxiella burnetii and reflects these outcomes in relation to other scientific Q fever studies worldwide. We have identified lessons learned and remaining knowledge gaps. This synthesis was structured according to the four steps of quantitative microbial risk assessment (QMRA): (a) Rapid source identification was improved by newly developed techniques using mathematical disease modelling; (b) source characterization efforts improved knowledge but did not provide accurate C. burnetii emission patterns; (c) ambient air sampling, dispersion and spatial modelling promoted exposure assessment; and (d) risk characterization was enabled by applying refined dose–response analyses. The results may support proper and timely risk assessment and risk management during future outbreaks, provided that accurate and structured data are available and exchanged readily between responsible actors.

Investigating the variance of edge-of-field deposits of spray drift
Holterman, H.J. ; Michielsen, J.M.G.P. ; Stallinga, H. ; Velde, P. van; Zande, J.C. van de - \ 2018
pesticide - statistics - risk assessment - systems analysis
Spray applications in arable crops often lead to off-target spray deposits downwind from the treated field. Throughout several decades, many experiments have been carried out by different researchers to quantify the downwind spray deposits. Relations between downwind spray deposits and parameters like sprayer settings, field conditions and environmental conditions were investigated. Still, there is a large variance in the observed data that cannot be explained satisfactorily by the experimental and environmental conditions. Sprayer boom movements and local fluctuations in driving speed, wind speed and wind direction are the most likely factors affecting variance in downwind spray deposits.
In this study variations in downwind deposits of spray drift caused by sprayer boom movements are investigated both experimentally and based on simulations using the spray drift model IDEFICS. Downwind deposits of spray drift were measured alongside a treated potato field, at 2 m and 5 m off the edge. Wind speed and direction were recorded during the experiments. Horizontal and vertical movements of the sprayer boom were recorded as well. Variance of spray deposits at 2 m downwind from the field edge was about 50%. At 5 m downwind variance was about 30%.
A quasi-dynamic model was developed based on the IDEFICS spray drift model. In the new model the effect of both horizontal and vertical boom movements on downwind spray deposits was studied. From the above mentioned experiments, the most important frequencies and amplitudes of boom movements were derived. Using these frequencies, the model simulations resulted in variances of spray drift deposits similar to those established experimentally. Effects of fluctuating wind directions are to be investigated in the near future.
Exposure assessment for edge-of-field watercourses next to tree nurseries regarding spray drift deposits
Holterman, H.J. ; Zande, J.C. van de - \ 2018
pesticide - statistics - risk assessment - systems analysis - surface water - spatial
Spray applications in arable crops often lead to off-target spray deposits downwind from the treated field. Throughout several decades, many experiments have been carried out by different researchers to quantify the downwind spray deposits. Relations between downwind spray deposits and parameters like sprayer settings, field conditions and environmental conditions were investigated. Still, there is a large variance in the observed data that cannot be explained satisfactorily by the experimental and environmental conditions. Sprayer boom movements and local fluctuations in driving speed, wind speed and wind direction are the most likely factors affecting variance in downwind spray deposits.
In this study variations in downwind deposits of spray drift caused by sprayer boom movements are investigated both experimentally and based on simulations using the spray drift model IDEFICS. Downwind deposits of spray drift were measured alongside a treated potato field, at 2 m and 5 m off the edge. Wind speed and direction were recorded during the experiments. Horizontal and vertical movements of the sprayer boom were recorded as well. Variance of spray deposits at 2 m downwind from the field edge was about 50%. At 5 m downwind variance was about 30%.
A quasi-dynamic model was developed based on the IDEFICS spray drift model. In the new model the effect of both horizontal and vertical boom movements on downwind spray deposits was studied. From the above mentioned experiments, the most important frequencies and amplitudes of boom movements were derived. Using these frequencies, the model simulations resulted in variances of spray drift deposits similar to those established experimentally. Effects of fluctuating wind directions are to be investigated in the near future.
UV-filters and musk fragrances in seafood commercialized in Europe Union: Occurrence, risk and exposure assessment
Cunha, S.C. ; Trabalón, L. ; Jacobs, S. ; Castro, M. ; Fernandez-Tejedor, M. ; Granby, K. ; Verbeke, W. ; Kwadijk, C. ; Ferrari, F. ; Robbens, J. ; Sioen, I. ; Pocurull, E. ; Marques, A. ; Fernandes, J.O. ; Domingo, J.L. - \ 2018
Environmental Research 161 (2018). - ISSN 0013-9351 - p. 399 - 408.
fish - UV-filters - Musk fragrances - Occurrence - risk assessment - GC-MS/MS
In the framework of the FP7 ECsafeSeafood project, 62 seafood samples commercialized in Europe Union from several representative species – mackerel, tuna, salmon, seabream, cod, monkfish, crab, shrimp, octopus, perch
and plaice – were analysed for residues of 21 personal care products (PCPs), including 11 UV-filters (UV-Fs) and 10 musk fragrances (musks). PCPs analysis were performed by Quick, Easy, Cheap, Effective Rugged, Safe (QuEChERS), combined with liquid-liquid extraction (LLE) or dispersive solid-phase extraction (dSPE), followed by gas chromatography-tandem mass spectrometry (GC-MS/MS). The results showed the presence in a wide range of samples of nine out of eleven UV-Fs compounds analysed, namely 2-ethylhexyl salicylate (EHS), 2-
ethylhexyl,4-methoxycinnamate (EHMC), 4-methylbenzylidenecamphor (4-MBC), benzophenone-1 (BP1), benzophenone- 3 (BP3), isoamyl-4-methoxycinnamate (IMC), 2,2′-dihydroxy-4,4′-dimethoxybenzophenone (DHMB), homosalate (HS), and octocrylene (OC), whereas galaxolide (HHCB), galaxolide lactone (HHCB-lactone), and tonalide (AHTN) were the most found musks. The potential risks to human health associated with the exposure to eight of the more prevalent PCPs – EHS, EHMC, 4-MBC, BP1, BP3, IMC, HHCB, and AHTN - through seafood
consumption were assessed for consumers from five European countries (Belgium, Ireland, Italy, Portugal and Spain). Results showed that the human exposure to UV-Fs and musks estimated from the concentration values
found in seafood and the daily consumption of concerned seafood species, were far below toxicological reference values.
Application of Bayesian networks for hazard ranking of nanomaterials to support human health risk assessment
Marvin, H.J.P. ; Bouzembrak, Y. ; Janssen, E.M. ; Zande, M. van der; Murphy, Finbarr ; Sheehan, Barry ; Mullins, Martin ; Bouwmeester, H. - \ 2017
Bayesian networks - metal nanomaterials - scenario studies - risk assessment - expert elicitation
In this study, a Bayesian Network (BN) was developed for the prediction of the hazard potential and biological effects with the focus on metal- and metal-oxide nanomaterials to support human health risk assessment. The developed BN captures the (inter) relationships between the exposure route, the nanomaterials physicochemical properties and the ultimate biological effects in a holistic manner and was based on international expert consultation and the scientific literature (e.g., in vitro/in vivo data). The BN was validated with independent data extracted from published studies and the accuracy of the prediction of the nanomaterials hazard potential was 72% and for the biological effect 71%, respectively. The application of the BN is shown with scenario studies for TiO2, SiO2, Ag, CeO2, ZnO nanomaterials. It is demonstrated that the BN may be used by different stakeholders at several stages in the risk assessment to predict certain properties of a nanomaterials of which little information is available or to prioritize nanomaterials for further screening.
The Regulatory Framework Across International Jurisdictions for Risks Associated with Consumption of Botanical Food Supplements
Low, Teng Yong ; Wong, Kwok Onn ; Yap, Adelene L.L. ; Haan, Laura H.J. De; Rietjens, Ivonne M.C.M. - \ 2017
Comprehensive Reviews in Food Science and Food Safety 16 (2017)5. - ISSN 1541-4337 - p. 821 - 834.
botanical food supplements - botanicals - regulatory challenges - regulatory framework - risk assessment

Dietary supplements, including those containing botanical ingredients and botanical-derived compounds, have been marketed to consumers globally for many decades. However, the legislative framework for such products remains inconsistent across jurisdictions internationally. This study aims to compare the regulatory framework of botanical food supplements in the EU, USA, Canada, Australia, New Zealand, India, Japan, and China. The study also aims to investigate and describe safety assessment criteria for botanical food supplements where they are present in the above said jurisdictions, and attempts to analyze whether these criteria are suitable for addressing the toxicological risks associated with the use of botanical food supplement products, based on the evaluation of reported adverse effects related to botanical food supplement use as examples. Finally, this study discusses some future issues that need further attention, such as the consideration of less than lifetime exposures, potential for misidentification, and adulteration of botanical supplements by pharmacologically active substances. It is concluded that the regulatory approaches towards botanical food supplements differ significantly across jurisdictions. In addition, national authorities are increasingly considering having more regulatory oversight for such products. Further consideration of the actual impact of adverse events arising from botanical food supplement usage will be helpful in guiding such decisions.

Risk assessment of combined exposure to alkenylbenzenes through consumption of plant food supplements containing parsley and dill
Alajlouni, Abdalmajeed M. ; Al-Malahmeh, Amer J. ; Wesseling, Sebastiaan ; Kalli, Marina ; Vervoort, Jacques ; Rietjens, Ivonne M.C.M. - \ 2017
Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 34 (2017)12. - ISSN 1944-0049 - p. 2201 - 2211.
alkenylbenzenes - estimated daily intake - margin of exposure - Parsley- and dill-based plant food supplements (PFS) - risk assessment - toxic equivalency approach
A risk assessment was performed of parsley- and dill-based plant food supplements (PFS) containing apiol and related alkenylbenzenes. First, the levels of the alkenylbenzenes in the PFS and the resulting estimated daily intake (EDI) resulting from use of the PFS were quantified. Since most PFS appeared to contain more than one alkenylbenzene, a combined risk assessment was performed based on equal potency or using a so-called toxic equivalency (TEQ) approach based on toxic equivalency factors (TEFs) for the different alkenylbenzenes. The EDIs resulting from daily PFS consumption amount to 0.74–125 µg kg–1 bw for the individual alkenylbenzenes, 0.74–160 µg kg–1 bw for the sum of the alkenylbenzenes, and 0.47–64 µg kg–1 bw for the sum of alkenylbenzenes when expressed in safrole equivalents. The margins of exposure (MOEs) obtained were generally below 10,000, indicating a priority for risk management if the PFS were to be consumed on a daily basis. Considering short-term use of the PFS, MOEs would increase above 10,000, indicating low priority for risk management. It is concluded that alkenylbenzene intake through consumption of parsley- and dill-based PFS is only of concern when these PFS are used for long periods of time.
Potatoes, pathogens and pests : effects of genetic modifi cation for plant resistance on non-target arthropods
Lazebnik, Jenny - \ 2017
Wageningen University. Promotor(en): J.J.A. Loon; M. 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 - solanum tuberosum - aardappelen - oömyceten - phytophthora infestans - 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
Wageningen 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 - in vitro - 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.

Application of Bayesian networks for hazard ranking of nanomaterials to support human health risk assessment
Marvin, Hans J.P. ; Bouzembrak, Yamine ; Janssen, Esmée M. ; Zande, Meike van der; Murphy, Finbarr ; Sheehan, Barry ; Mullins, Martin ; Bouwmeester, Hans - \ 2017
Nanotoxicology 11 (2017)1. - ISSN 1743-5390 - p. 123 - 133.
Bayesian networks - expert elicitation - metal nanomaterials - risk assessment - scenario studies
In this study, a Bayesian Network (BN) was developed for the prediction of the hazard potential and biological effects with the focus on metal- and metal-oxide nanomaterials to support human health risk assessment. The developed BN captures the (inter) relationships between the exposure route, the nanomaterials physicochemical properties and the ultimate biological effects in a holistic manner and was based on international expert consultation and the scientific literature (e.g., in vitro/in vivo data). The BN was validated with independent data extracted from published studies and the accuracy of the prediction of the nanomaterials hazard potential was 72% and for the biological effect 71%, respectively. The application of the BN is shown with scenario studies for TiO2, SiO2, Ag, CeO2, ZnO nanomaterials. It is demonstrated that the BN may be used by different stakeholders at several stages in the risk assessment to predict certain properties of a nanomaterials of which little information is available or to prioritize nanomaterials for further screening.
Occurrence and diversity of fungal pathogens associated with water hyacinth and their potential as biocontrol agents in the Rift Valley of Ethiopia
Gebregiorgis, Firehun ; Struik, P.C. ; Lantinga, E.A. ; Tessema, Taye - \ 2017
International Journal of Pest Management 63 (2017)4. - ISSN 0967-0874 - p. 355 - 363.
Biological control - Eichhornia crassipes - fungal pathogens - multivariate analysis - native bio-agents - pathogenicity - risk assessment - water hyacinth

Water hyacinth poses serious socio-economic and environmental problems in Ethiopia. To integrate fungal pathogens into water hyacinth management, a survey was conducted in the Rift Valley of Ethiopia. Based on morphological characterization and DNA sequencing, 25 fungal species were identified that belong to nine genera. Alternaria tenuissima, A. alternata, Aspergillus niger, Phoma sp., Curvularia trifolii, Mucor fragilis, M. racemosus, A. fumigatus, Fusarium oxysporum, and F. equiseti were the most common fungi detected. However, their occurrence was influenced by water wave action, temperature, season, and altitude. Among the fungal pathogens, A. alternata, A. tenuissima, F. oxysporum, F. equiseti, and Neofisicoccum parvum were highly pathogenic to water hyacinth. Alternaria alternata and A. tenuissima did not cause disease symptoms on ecologically important plant species (e.g. Noug, Tef, and Coffee). Application of the fungal pathogens on water hyacinth plants also showed 11%–67%, 22%–72%, 15%–55%, and 12%–50% reduction in fresh weight, dry weight, plant height, and root length of water hyacinth, respectively. This study suggests that fungal species have the potential to control water hyacinth biologically and provides baseline data for biological control efforts in the future.

Risk assessment of plant food supplements and other herbal products containing aristolochic acids using the margin of exposure (MOE) approach
Abdullah, Rozaini ; Diaz, Leolean Nyle ; Wesseling, Sebas ; Rietjens, Ivonne M.C.M. - \ 2017
Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 34 (2017)2. - ISSN 1944-0049 - p. 135 - 144.
Aristolochic acids - margin of exposure - plant food supplements - risk assessment - safety assessment
After the incidences of induction of aristolochic acid nephropathy after consumption of herbal weight loss preparations that accidentally contained aristolochic acids (AAs), several countries defined national restrictions on the presence of AAs in food, including plant food supplements (PFS) and herbal products. This study investigates whether the risks associated with exposure to AAs via PFS and herbal products are at present indeed negligible. Data reported in literature on AA levels in PFS and other herbal products and also obtained from a new series of PFS in the present study were used to calculate the estimated daily intakes (EDIs) and corresponding margins of exposure (MOEs). Available literature data revealed that 206 out of 573 samples were found to contain aristolochic acid I (AAI) and/or aristolochic acid II (AAII). The results obtained from recently collected PFS revealed that both AAI and AAII were detected in three out of 18 analysed PFS at levels up to 594.8 and 235.3 µg g–1, respectively, being in line with the levels reported in literature. The EDIs resulting from intake of these PFS resulted in MOEs that were generally below 10,000, corroborating the priority for risk management. Although these results refer to PFS collected by targeted sampling strategies, the data reveal that AA-containing PFS are still freely available. When considering that the use of these samples may be limited to shorter periods of time, the EDIs might be lower, but MOE values would still be lower than 10,000 for more than 50% of the AA-containing PFS and herbal products. In conclusion, the presence of AAs in PFS and herbal products even several years after instalment of the legal restrictions still raises concern, especially for people who frequently use the respective PFS and herbal products.
Level of Alkenylbenzenes in Parsley and Dill Based Teas and Associated Risk Assessment Using the Margin of Exposure Approach
Alajlouni, Abdul ; Al-Malahmeh, Amer J. ; Isnaeni, Farida Nur ; Wesseling, Sebas ; Vervoort, Jacques ; Rietjens, Ivonne M.C.M. - \ 2016
Journal of Agricultural and Food Chemistry 64 (2016)45. - ISSN 0021-8561 - p. 8640 - 8646.
alkenylbenzenes - estimated daily intake - margin of exposure - parsley and dill based teas - risk assessment - toxic equivalency factors

Risk assessment of parsley and dill based teas that contain alkenylbenzenes was performed. To this end the estimated daily intake (EDI) of alkenylbenzenes resulting from use of the teas was quantified. Since most teas appeared to contain more than one alkenylbenzene, a combined risk assessment was performed based on equal potency of all alkenylbenzenes or using a so-called toxic equivalency (TEQ) approach through defining toxic equivalency factors (TEFs) for the different alkenylbenzenes. The EDI values resulting from consuming one cup of tea a day were 0.2-10.1 μg/kg bw for the individual alkenylbenzenes, 0.6-13.1 μg/kg bw for the sum of the alkenylbenzenes, and 0.3-10.7 μg safrole equiv/kg bw for the sum of alkenylbenzenes when expressed in safrole equivalents. The margin of exposure (MOE) values obtained were generally

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
Wageningen University. Promotor(en): Cajo ter Braak, co-promotor(en): Hilko van der Voet. - Wageningen : Wageningen University - ISBN 9789462578197 - 205
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
Wageningen University. Promotor(en): Paul van den Brink. - Wageningen : Wageningen University - ISBN 9789462578104 - 152
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
Wageningen University. Promotor(en): Ruud Woutersen; Ivonne Rietjens, co-promotor(en): J.J.M. van de Sandt. - Wageningen : Wageningen University - ISBN 9789462577275 - 200
skin - absorption - permeability - in vitro - experiments - exposure assessment - risk assessment - toxicology - biocides - rodenticides - preservatives - disinfection - huid - absorptie - permeabiliteit - in vitro - 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.

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