The association between vitamin D status and parameters for bone density and quality is modified by Body Mass Index
Sohl, E. ; Jongh, R.T. de; Swart, K.M.A. ; Enneman, A.W. ; Wijngaarden, J.P. van; Dijk, S.C. van; Ham, A.C. ; Zwaluw, N.L. van der; Brouwer-Brolsma, E.M. ; Velde, N. van der; Groot, C.P.G.M. de; Velde, S.J. te; Lips, P. ; Schoor, N.M. van - \ 2015
Calcified Tissue International 96 (2015)2. - ISSN 0171-967X - p. 113 - 122.
quantitative ultrasound parameters - mineral density - postmenopausal women - d deficiency - physical performance - 25-hydroxyvitamin d - risk-assessment - older persons - population - metaanalysis
The association of vitamin D status with bone mineral density (BMD) and Quantitative Ultrasound measurements (QUS) has been inconsistent in previous studies, probably caused by moderating effects. This study explored (1) the association of vitamin D status with QUS and BMD, and (2) whether these associations were modified by body mass index (BMI), age, gender, or physical activity. Two-independent cohorts of the Longitudinal Aging Study Amsterdam (LASA-I, 1995/1996, aged =65; LASA-II, 2008/2009, aged 61–71) and baseline measurement of the B-vitamins for the prevention of osteoporotic fractures (B-PROOF) study (2008–2011, aged 65+) were used. QUS measurements [broadband ultrasound attenuation (BUA) and speed of sound (SOS)] were performed at the calcaneus in all three cohorts (N = 1,235, N = 365, N = 1319); BMD was measured by Dual X-ray absorptiometry (DXA) in B-PROOF (N = 1,162 and 1,192 for specific sites) and LASA-I (N = 492 and 503). The associations of vitamin D status with BUA and BMD were modified by BMI. Only in persons with low-to-normal BMI (
Structural bisphenol analoques differentially target steroidogenesis in murine MA-10 Leydig cells as well as the glucocorticoid receptor
Roelofs, M.J.E. ; Berg, M. van den; Bovee, T.F.H. ; Piersma, A.H. ; Duursen, M.B.M. van - \ 2015
Toxicology 329 (2015). - ISSN 0300-483X - p. 10 - 20.
endocrine-disrupting chemicals - tetrabromobisphenol-a tbbpa - brominated flame retardants - one-generation reproduction - in-vitro - fetal testis - exogenous progesterone - gene-expression - risk-assessment - united-states
Although much information on the endocrine activity of bisphenol A (BPA) is available, a proper human hazard assessment of analogues that are believed to have a less harmful toxicity profile is lacking. Here the possible effects of BPA, bisphenol F (BPF), bisphenol S (BPS), as well as the brominated structural analogue and widely used flame retardant tetrabromobisphenol A (TBBPA) on human glucocorticoid and androgen receptor (GR and AR) activation were assessed. BPA, BPF, and TBBPA showed clear GR and AR antagonism with IC50 values of 67 µM, 60 µM, and 22 nM for GR, and 39 µM, 20 µM, and 982 nM for AR, respectively, whereas BPS did not affect receptor activity. In addition, murine MA-10 Leydig cells exposed to the bisphenol analogues were assessed for changes in secreted steroid hormone levels. Testicular steroidogenesis was altered by all bisphenol analogues tested. TBBPA effects were more directed towards the male end products and induced testosterone synthesis, while BPF and BPS predominantly increased the levels of progestagens that are formed in the beginning of the steroidogenic pathway. The MA-10 Leydig cell assay shows added value over the widely used H295R steroidogenesis assay because of its fetal-like characteristics and specificity for the physiologically more relevant testicular ¿4 steroidogenic pathway. Therefore, adding an in vitro assay covering fetal testicular steroidogenesis, such as the MA-10 cell line, to the panel of tests used to screen potential endocrine disruptors, is highly recommendable.
The SOLUTIONS project: Challenges and responses for present and future emerging pollutants in land and water resources management
Brack, W. ; Altenburger, R. ; Schuurmann, G. ; Krauss, M. ; Brink, P.J. van den - \ 2015
Science of the Total Environment 503-504 (2015). - ISSN 0048-9697 - p. 22 - 31.
effect-directed analysis - community tolerance pict - waste-water - risk-assessment - environmental contamination - organic micropollutants - chemical footprint - complex-mixtures - treatment plants - stress-response
SOLUTIONS (2013 to 2018) is a European Union Seventh Framework Programme Project (EU-FP7). The project aims to deliver a conceptual framework to support the evidence-based development of environmental policies with regard to water quality. SOLUTIONS will develop the tools for the identification, prioritisation and assessment of those water contaminants that may pose a risk to ecosystems and human health. To this end, a new generation of chemical and effect-based monitoring tools is developed and integrated with a full set of exposure, effect and risk assessment models. SOLUTIONS attempts to address legacy, present and future contamination by integrating monitoring and modelling based approaches with scenarios on future developments in society, economy and technology and thus in contamination. The project follows a solutions-oriented approach by addressing major problems of water and chemicals management and by assessing abatement options. SOLUTIONS takes advantage of the access to the infrastructure necessary to investigate the large basins of the Danube and Rhine as well as relevant Mediterranean basins as case studies, and puts major efforts on stakeholder dialogue and support. Particularly, the EU Water Framework Directive (WFD) Common Implementation Strategy (CIS) working groups, International River Commissions, and water works associations are directly supported with consistent guidance for the early detection, identification, prioritisation, and abatement of chemicals in the water cycle. SOLUTIONS will give a specific emphasis on concepts and tools for the impact and risk assessment of complex mixtures of emerging pollutants, their metabolites and transformation products. Analytical and effect-based screening tools will be applied together with ecological assessment tools for the identification of toxicants and their impacts. The SOLUTIONS approach is expected to provide transparent and evidence-based candidates or River Basin Specific Pollutants in the case study basins and to assist future review of priority pollutants under the WFD as well as potential abatement options.
Acute tier-1 and tier-2 effect assessment approaches in the EFSA Aquatic Guidance Diocument: are they sufficiently protective for insecticides? : Are they sufficiently protective for insecticides?
Wijngaarden, R.P.A. van; Maltby, L. ; Brock, T.C.M. - \ 2015
Pest Management Science 71 (2015)8. - ISSN 1526-498X - p. 1059 - 1067.
species sensitivity distributions - pyrethroid insecticide - lambda-cyhalothrin - chronic toxicity - daphnia-magna - chironomus-riparius - gamma-cyhalothrin - risk-assessment - joint toxicity - chlorpyrifos
BACKGROUND The objective of this paper is to evaluate whether the acute tier-1 and tier-2 methods as proposed by the Aquatic Guidance Document recently published by the European Food Safety Authority (EFSA) are appropriate for deriving regulatory acceptable concentrations (RACs) for insecticides. The tier-1 and tier-2 RACs were compared with RACs based on threshold concentrations from micro/mesocosm studies (ETO-RAC). A lower-tier RAC was considered as sufficiently protective, if less than the corresponding ETO-RAC. RESULTS ETO-RACs were calculated for repeated (n =¿13) and/or single pulsed applications (n =¿17) of 26 insecticides to micro/mesocosms, giving a maximum of 30 insecticide¿×¿application combinations (i.e. cases) for comparison. Acute tier-1 RACs (for 24 insecticides) were lower than the corresponding ETO-RACs in 27 out of 29 cases, while tier-2 Geom-RACs (for 23 insecticides) were lower in 24 out of 26 cases. The tier-2 SSD-RAC (for 21 insecticides) using HC5/3 was lower than the ETO-RAC in 23 out of 27 cases, whereas the tier-2 SSD-RAC using HC5/6 was protective in 25 out of 27 cases. CONCLUSION The tier-1 and tier-2 approaches proposed by EFSA for acute effect assessment are sufficiently protective for the majority of insecticides evaluated. Further evaluation may be needed for insecticides with more novel chemistries (neonicotinoids, biopesticides) and compounds that show delayed effects (insect growth regulators).
Mechanistic modelling of toxicokinetic processess within Mytiophyllum
Heine, S. ; Schmitt, W. ; Schaffer, A. ; Gorlitz, G. ; Buresova, H. ; Arts, G. ; Preuss, T.G. - \ 2015
Chemosphere 120 (2015). - ISSN 0045-6535 - p. 292 - 298.
partition-coefficients - cuticular membranes - risk-assessment - aquatic macrophytes - water permeability - plant cuticles - sensitivity - diffusion - chemicals - linuron
Effects of chemicals are, in most cases, caused by internal concentrations within organisms which rely on uptake and elimination kinetics. These processes might be key components for assessing the effects of time-variable exposure of chemicals which regularly occur in aquatic systems. However, the knowledge of toxicokinetic patterns caused by time-variable exposure is limited, and gaining such information is complex. In this work, a previously developed mechanistic growth model of Myriophyllum spicatum is coupled with a newly developed toxicokinetic part, providing a model that is able to predict uptake and elimination of chemicals, as well as distribution processes between plant compartments (leaves, stems, roots) of M. spicatum. It is shown, that toxicokinetic patterns, at least for most of the investigated chemicals, can be calculated in agreement with experimental observations, by only calibrating two chemical- specific parameters, the cuticular permeability and a plant/water partition coefficient. Through the model-based determination of the cuticular permeabilities of Isoproturon, Iofensulfuron, Fluridone, Imazamox and Penoxsulam, their toxicokinetic pattern can be described with the model approach. For the use of the model for predicting toxicokinetics of other chemicals, where experimental data is not available, equations are presented that are based on the log (Poct/wat) of a chemical and estimate parameters that are necessary to run the model. In general, a method is presented to analyze time-variable exposure of chemicals more in detail without conducting time and labour intensive experiments.
Theoretically exploring direct and indirect chemical effects across ecological and exposure scenarios using mechanistic fate and effects modelling
Laender, F. de; Morselli, M. ; Baveco, H. ; Brink, P.J. van den; Guardo, A. Di - \ 2015
Environment International 74 (2015). - ISSN 0160-4120 - p. 181 - 190.
active ingredient chlorpyrifos - outdoor experimental ditches - insecticide dursban(r) 4e - planktonic food-web - community responses - effect assessments - risk-assessment - aquatic ecosystems - lake maggiore - dyna model
Predicting ecosystem response to chemicals is a complex problem in ecotoxicology and a challenge for risk assessors. The variables potentially influencing chemical fate and exposure define the exposure scenario while the variables determining effects at the ecosystem level define the ecological scenario. In absence of any empirical data, the objective of this paper is to present simulations by a fugacity-based fate model and a differential equation-based ecosystem model to theoretically explore how direct and indirect effects on invertebrate shallow pond communities vary with changing ecological and exposure scenarios. These simulations suggest that direct and indirect effects are larger in mesotrophic systems than in oligotrophic systems. In both trophic states, interaction strength (quantified using grazing rates) was suggested a more important driver for the size and recovery from direct and indirect effects than immigration rate. In general, weak interactions led to smaller direct and indirect effects. For chemicals targeting mesozooplankton only, indirect effects were common in (simple) food-chains but rare in (complex) food-webs. For chemicals directly affecting microzooplankton, the dominant zooplankton group in the modelled community, indirect effects occurred both in food-chains and food-webs. We conclude that the choice of the ecological and exposure scenarios in ecotoxicological modelling efforts needs to be justified because of its influence on the prevalence and magnitude of the predicted effects. Overall, more work needs to be done to empirically test the theoretical expectations formulated here.
Impact of predicted changes in rainfall and atmospheric carbon dioxide on maize and wheat yeilds in the Central Rift Valley of Ethiopia
Muluneh, A. ; Biazin, B. ; Stroosnijder, L. ; Bewket, W. ; Keesstra, S.D. - \ 2015
Regional Environmental Change 15 (2015)6. - ISSN 1436-3798 - p. 1105 - 1119.
fao crop model - climate-change - risk-assessment - aquacrop model - rainy-season - east-africa - dry spell - variability - drought - trends
This study assesses potential impacts of climate change on maize and wheat yields in the Central Rift Valley (CRV) of Ethiopia. We considered effects of elevated atmospheric carbon dioxide (CO2) and changes in rainfall during the main (Kiremt) and the short (Belg) rainfall cropping seasons during the two future periods (2020–2049 and 2066–2095). The MarkSimGCM daily weather generator was used to generate projected rainfall and temperature data using the outputs from ECHAM5 general circulation model and ensemble mean of six models under A2 (high) and B1 (low) emission scenarios. Crop yield simulations were made with the FAO’s AquaCrop model. The projected rainfall during Kiremt increases by 12–69 % while rainfall during Belg decreases by 20–68 %. The combined effect of elevated CO2 and projected climate factors increases maize yield by up to 59 % in sub-humid/humid areas of the CRV, but could result in a decrease of up to 46 % in the semiarid areas under ECHAM5 model. However, the maize yield increases in all parts of the CRV under the ensemble mean of models. Wheat yield shows no significant response to the projected rainfall changes, but increases by up to 40 % due to elevated CO2. Our results generally suggest that climate change will increase crop yields in the sub-humid/humid regions of the CRV. However, in the semi-arid parts the overall projected climate change will affect crop yields negatively.
The minimum detectable difference (MDD) and the interpretation of treatmentr related effects of pesticides in experimental ecosystems
Brock, T.C.M. ; Hammers-Wirtz, M. ; Hommen, U. ; Preuss, T.G. ; Ratte, H.T. ; Roessink, I. ; Strauss, T. ; Brink, P.J. van den - \ 2015
Environmental Science and Pollution Research 22 (2015)2. - ISSN 0944-1344 - p. 1160 - 1174.
zero dose control - risk-assessment - insecticide - mesocosms - models - replicability - microcosms - responses - recovery - systems
In the European registration procedure for pesticides, microcosm and mesocosm studies are the highest aquatic experimental tier to assess their environmental effects. Evaluations of microcosm/mesocosm studies rely heavily on no observed effect concentrations (NOECs) calculated for different population-level endpoints. Ideally, a power analysis should be reported for the concentration–response relationships underlying these NOECs, as well as for measurement endpoints for which significant effects cannot be demonstrated. An indication of this statistical power can be provided a posteriori by calculated minimum detectable differences (MDDs). The MDD defines the difference between the means of a treatment and the control that must exist to detect a statistically significant effect. The aim of this paper is to expand on the Aquatic Guidance Document recently published by the European Food Safety Authority (EFSA) and to propose a procedure to report and evaluate NOECs and related MDDs in a harmonised way. In addition, decision schemes are provided on how MDDs can be used to assess the reliability of microcosm/mesocosm studies and for the derivation of effect classes used to derive regulatory acceptable concentrations. Furthermore, examples are presented to show how MDDs can be reduced by optimising experimental design and sampling techniques.
Framework to determine the effectiveness of dietary exposure mitigation to chemical contaminants
Fels, H.J. van der; Edwards, S. ; Kennedy, M. ; O'Hagan, A. ; O'Mahony, C. ; Scholz, G. ; Steinberg, P. ; Tennant, D. ; Chiodini, A. - \ 2014
Food and Chemical Toxicology 74 (2014). - ISSN 0278-6915 - p. 360 - 371.
chromatography-mass spectrometry - solid-phase microextraction - extraction-gas chromatography - single-laboratory validation - fusarium mycotoxin content - methyl mercury exposure - spme-gc-ms - risk-assessment - baby-food - fish consumption
In order to ensure the food safety, risk managers may implement measures to reduce human exposure to contaminants via food consumption. The evaluation of the effect of a measure is often an overlooked step in risk analysis process. The aim of this study was to develop a systematic approach for determining the effectiveness of mitigation measures to reduce dietary exposure to chemical contaminants. Based on expert opinion, a general framework for evaluation of the effectiveness of measures to reduce human exposure to food contaminants was developed. The general outline was refined by application to three different cases: 1) methyl mercury in fish and fish products, 2) deoxynivalenol in cereal grains, and 3) furan in heated products. It was found that many uncertainties and natural variations exist, which make it difficult to assess the impact of the mitigation measure. Whenever possible, quantitative methods should be used to describe the current variation and uncertainty. Additional data should be collected to cover natural variability and reduce uncertainty. For the time being, it is always better for the risk manager to have access to all available information, including an assessment of uncertainty; however, the proposed methodology provides a conceptual framework for addressing these systematically.
A technical investigation on tools and concepts for sustainable management of the subsurface in The Netherlands.
Griffioen, J. ; Wensem, J. van; Oomes, J.L. ; Barends, F. ; Breunese, J. ; Bruining, H. ; Olsthoorn, T. ; Stams, A.J.M. ; Stoel, A.E. van der - \ 2014
Science of the Total Environment 485-486 (2014). - ISSN 0048-9697 - p. 810 - 819.
risk-assessment - groundwater sustainability - resources management - decision-making - mining-industry - european-union - water - storage - policy - framework
In response to increasing use of the subsurface, there is a need to modernise policies on sustainable use of the subsurface. This holds in particular for the densely populated Netherlands. We aimed to analyse current practice of subsurface management and the associated pressure points and to establish a conceptual overview of the technical issues related to sustainable management of the subsurface. Case studies on the exploitation of subsurface resources (including spatial use of the subsurface) were analysed, examining social relevance, environmental impact, pressure points and management solutions. The case studies ranged from constructing underground garages to geothermal exploitation. The following issues were identified for the technological/scientific aspects: site investigation, suitability, risk assessment, monitoring and measures in the event of failure. Additionally, the following general issues were identified for the administrative aspects: spatial planning, option assessment, precaution, transparency, responsibility and liability. These issues were explored on their technological implications within the framework of sustainable management of the subsurface. This resulted into the following key aspects: (1) sustainability assessment, (2) dealing with uncertainty and (3) policy instruments and governance. For all three aspects, different options were identified which might have a legal, economic or ethical background. The technological implications of these backgrounds have been identified. A set of recommendations for sustainable management of the subsurface resources (incl. space) was established: (1) management should be driven by scarcity, (2) always implement closed loop monitoring when the subsurface activities are high-risk, (3) when dealing with unknown features and heterogeneity, apply the precautionary principle, (4) responsibility and liability for damage must be set out in legislation and (5) sustainability should be incorporated in all relevant legislation and not only in environmental legislation. Other aspects to be considered are the reversibility of the impacts from subsurface activities and the abandonment of installations.
Different compositions of pharmaceuticals in Dutch and Belgian rivers explained by consumption patterns and treatment efficiency
Laak, T.L. ter; Kooij, P.J.F. ; Tolkamp, H. ; Hofman, J. - \ 2014
Environmental Science and Pollution Research 21 (2014)22. - ISSN 0944-1344 - p. 12843 - 12855.
waste-water treatment - personal care products - treatment plants - environmental concentrations - transformation products - aquatic environment - risk-assessment - drinking-water - removal - fate
In the current study, 43 pharmaceuticals and 18 transformation products were studied in the river Meuse at the Belgian-Dutch border and four tributaries of the river Meuse in the southern part of the Netherlands. The tributaries originate from Belgian, Dutch and mixed Dutch and Belgian catchments. In total, 23 pharmaceuticals and 13 transformation products were observed in samples of river water collected from these rivers. Observed summed concentrations of pharmaceuticals and transformation products in river water ranged from 3.5 to 37.8 µg/L. Metformin and its transformation product guanylurea contributed with 53 to 80 % to this concentration, illustrating its importance on a mass basis. Data on the flow rate of different rivers and demographics of the catchments enabled us to calculate daily per capita loads of pharmaceuticals and transformation products. These loads were linked to sales data of pharmaceuticals in the catchment. Simple mass balance modelling accounting for human excretion and removal by sewage treatment plants revealed that sales could predict actual loads within a factor of 3 for most pharmaceuticals. Rivers that originated from Belgian and mixed Dutch and Belgian catchments revealed significantly higher per capita loads of pharmaceuticals (16.0¿±¿2.3 and 15.7¿±¿2.1 mg/inhabitant/day, respectively) than the Dutch catchment (8.7¿±¿1.8 mg/inhabitant/day). Furthermore, the guanylurea/metformin ratio was significantly lower in waters originating from Belgium (and France) than in those from the Netherlands, illustrating that sewage treatment in the Belgian catchment is less efficient in transforming metformin into guanylurea. In summary, the current study shows that consumption-based modelling is suitable to predict environmental loads and concentrations. Furthermore, different consumption patterns and wastewater treatment efficiency are clearly reflected in the occurrence and loads of pharmaceuticals in regional rivers.
Safety aspects of genetically modified crops with abiotic stress tolerance
Liang, C. ; Prins, T.W. ; Wiel, C.C.M. van de; Kok, E.J. - \ 2014
Trends in Food Science and Technology 40 (2014)1. - ISSN 0924-2244 - p. 115 - 122.
risk-assessment - salt tolerance - transcription factors - salinity tolerance - transgenic plants - drought tolerance - gene flow - vegetable crops - gm crops - ipt gene
Abiotic stress, such as drought, salinity, and temperature extremes, significantly reduce crop yields. Hence, development of abiotic stress-tolerant crops by modern biotechnology may contribute to global food security. Prior to introducing genetically modified crops with abiotic stress tolerance to the market, a food and environmental safety assessment is generally required. Although worldwide harmonised comparative approach is currently provided, risk assessors still face challenges to assess genetically modified crops with abiotic stress-tolerance. Here, we discuss current developments of abiotic stress tolerance as well as issues concerning food and environmental safety assessment of these crops, including current approaches, challenges and future directions.
Safety assessment of plant varieties using transcriptomics profiling and a one-class classifier
Dijk, J.P. van; Mello, C.S. de; Voorthuijzen, M.M. ; Hutten, R.C.B. ; Maisonnave Arisi, A.C. ; Jansen, J.J. ; Buydens, L.M.C. ; Voet, H. van der; Kok, E.J. - \ 2014
Regulatory Toxicology and Pharmacology 70 (2014)1. - ISSN 0273-2300 - p. 297 - 303.
potato-tubers - microarray data - risk-assessment - food - identification - components - gene
An important part of the current hazard identification of novel plant varieties is comparative targeted analysis of the novel and reference varieties. Comparative analysis will become much more informative with unbiased analytical approaches, e.g. omics profiling. Data analysis estimating the similarity of new varieties to a reference baseline class of known safe varieties would subsequently greatly facilitate hazard identification. Further biological and eventually toxicological analysis would then only be necessary for varieties that fall outside this reference class. For this purpose, a one-class classifier tool was explored to assess and classify transcriptome profiles of potato (Solanum tuberosum) varieties in a model study. Profiles of six different varieties, two locations of growth, two year of harvest and including biological and technical replication were used to build the model. Two scenarios were applied representing evaluation of a ’different’ variety and a ‘similar’ variety. Within the model higher class distances resulted for the ‘different’ test set compared with the ‘similar’ test set. The present study may contribute to a more global hazard identification of novel plant varieties
A simulation study on effects of exposure to a combination of pesticides used in an orchard and tuber crop on the recovery time of a vulnerable aquatic invertebrate
Focks, A. ; Luttik, R. ; Zorn, M. ; Brock, T.C.M. ; Roex, E. ; Linden, T. van der; Brink, P.J. van den - \ 2014
Environmental Toxicology and Chemistry 33 (2014)7. - ISSN 0730-7268 - p. 1489 - 1498.
asellus-aquaticus - risk-assessment - gammarus-pulex - life-history - sensitivity - ecosystems - contamination - chlorpyrifos - chemicals - toxicity
The aim of the present study was to assess whether population effects and recovery times increase when a population of a vulnerable aquatic invertebrate is exposed to concentrations of 1 or multiple pesticides. The 2 sets of pesticide combinations tested are typical for orchard and tuber crops in The Netherlands. Exposure concentrations were predicted using the FOCUS step 3 modeling framework and the Dutch drainage ditch scenario. Recovery times were assessed using the MASTEP population model. We simulated the population dynamics and pesticide effects in a Monte Carlo style by using median effective concentration values drawn from an arthropod species sensitivity distribution. In the tuber scenario, exposure to ¿-cyhalothrin resulted in long-term effects, whereas exposure to the co-occurring compound fluazinam hardly resulted in (additional) effects. In the orchard scenario, 3 pesticides resulted in large effects just after exposure, but pulse exposures to these compounds did not coincide. The probabilities of effects for the single compounds added up for the combination; in contrast, the recovery times were not higher for the combination compared to those associated with exposure to the individual compounds. The conclusion from the present study's simulations is that exposure to the evaluated pesticide packages may lead to increased mortality probabilities and effect sizes of the combination, but does not lead to longer recovery times for populations with synchronized reproduction than when exposed to the individual compounds.
Merging validation and evaluation of ecological models to evaluation': a review of terminology and a practical approach
Augusiak, J.A. ; Brink, P.J. van den; Grimm, V. - \ 2014
Ecological Modelling 280 (2014). - ISSN 0304-3800 - p. 117 - 128.
individual-based models - risk-assessment - environmental-models - quality-assurance - simulation-model - complex-systems - beech forests - assessments - verification - uncertainty
Confusion about model validation is one of the main challenges in using ecological models for decision support, such as the regulation of pesticides. Decision makers need to know whether a model is a sufficiently good representation of its real counterpart and what criteria can be used to answer this question. Unclear terminology is one of the main obstacles to a good understanding of what model validation is, how it works, and what it can deliver. Therefore, we performed a literature review and derived a standard set of terms. ‘Validation’ was identified as a catch-all term, which is thus useless for any practical purpose. We introduce the term ‘evaludation’, a fusion of ‘evaluation’ and ‘validation’, to describe the entire process of assessing a model's quality and reliability. Considering the iterative nature of model development, the modelling cycle, we identified six essential elements of evaludation: (i) ‘data evaluation’ for scrutinising the quality of numerical and qualitative data used for model development and testing; (ii) ‘conceptual model evaluation’ for examining the simplifying assumptions underlying a model's design; (iii) ‘implementation verification’ for testing the model's implementation in equations and as a computer programme; (iv) ‘model output verification’ for comparing model output to data and patterns that guided model design and were possibly used for calibration; (v) ‘model analysis’ for exploring the model's sensitivity to changes in parameters and process formulations to make sure that the mechanistic basis of main behaviours of the model has been well understood; and (vi) ‘model output corroboration’ for comparing model output to new data and patterns that were not used for model development and parameterisation. Currently, most decision makers require ‘validating’ a model by testing its predictions with new experiments or data. Despite being desirable, this is neither sufficient nor necessary for a model to be useful for decision support. We believe that the proposed set of terms and its relation to the modelling cycle can help to make quality assessments and reality checks of ecological models more comprehensive and transparent. Keywords Model validation; Terminology; Decision support; Documentation; Ecological models; Risk assessment
Effects of the antibiotic enrofloxacin on the ecology of tropical eutrophic freshwater microcosms
Rico, A. ; Rocha Dimitrov, M. ; Wijngaarden, R.P.A. van; Satapornvanit, K. ; Smidt, H. ; Brink, P.J. van den - \ 2014
Aquatic Toxicology 147 (2014). - ISSN 0166-445X - p. 92 - 104.
16s ribosomal-rna - risk-assessment - fluoroquinolone antibiotics - microbial-populations - veterinary medicines - aquatic microcosms - primary producers - ciprofloxacin - community - toxicity
The main objective of the present study was to assess the ecological impacts of the fluoroquinolone antibiotic enrofloxacin on the structure and functioning of tropical freshwater ecosystems. Enrofloxacin was applied at a concentration of 1, 10, 100 and 1000µg/L for 7 consecutive days in 600-L outdoor microcosms in Thailand. The ecosystem-level effects of enrofloxacin were monitored on five structural (macroinvertebrates, zooplankton, phytoplankton, periphyton and bacteria) and two functional (organic matter decomposition and nitrogen cycling) endpoint groups for 4 weeks after the last antibiotic application. Enrofloxacin was found to dissipate relatively fast from the water column (half-dissipation time: 11.7h), and about 11% of the applied dose was transformed into its main by-product ciprofloxacin after 24h. Consistent treatment-related effects on the invertebrate and primary producer communities and on organic matter decomposition could not be demonstrated. Enrofloxacin significantly affected the structure of leaf-associated bacterial communities at the highest treatment level, and reduced the abundance of ammonia-oxidizing bacteria and ammonia-oxidizing archaea in the sediments, with calculated NOECs of 10 and
Influence of climate variables on the concentration of Escherichia coli in the Rhine, Meuse, and Drentse Aa during 1985–2010
Vermeulen, L.C. ; Hofstra, N. - \ 2014
Regional Environmental Change 14 (2014)1. - ISSN 1436-3798 - p. 307 - 319.
fecal-indicator concentrations - land-use change - water-quality - air-temperature - risk-assessment - e. coil - disease - survival - river - cryptosporidium
This study evaluates the relationship between the climate variables temperature and precipitation and the concentration of Escherichia coli bacteria in the Rhine, Meuse, and Drentse Aa for the period 1985–2010. Data from 4,679 E. coli concentration measurements spread over a total of 13 locations in these three river systems were used in this study. The variables water temperature, precipitation, and river discharge were correlated with E. coli measurements. Water temperature was found to correlate negatively, and this is in line with expectations that higher temperature increases microorganism die-off. Precipitation and discharge were found to correlate positively, and this is in line with expectations that runoff from agricultural lands brings along pathogens from manure and increases the chance of sewer overflows. The data of the Meuse were fit to a linear model that explained E. coli concentrations from a time component, the climate variables and a locations dummy variable, in order to assess the relative contribution of the different variables. This model had an R2 of 0.49, meaning that climate variables and location can account for nearly half of the observed variation in E. coli concentrations in surface water, even when other factors, such as land-use variables, are not taken into account. The effect of the different climate variables was found to differ with scale, with temperature being relatively important at a local scale, and discharge being mainly of importance at larger scales. From our results, we expect that climate change, mainly the projected increased precipitation, may increase E. coli concentrations overall. Other waterborne pathogens that follow similar transmission pathways as E. coli may be similarly impacted by climate change
Preventing Campylobacter at the Source: Why Is It So Difficult?
Wagenaar, J.A. ; French, N.P. ; Havelaar, A.H. - \ 2013
Clinical infectious diseases 57 (2013)11. - ISSN 1058-4838 - p. 1600 - 1606.
united-states - new-zealand - disease burden - broiler meat - vertical transmission - foodborne pathogens - source attribution - risk-assessment - poultry - spp.
Campylobacteriosis in humans, caused by Campylobacter jejuni and Campylobacter coli, is the most common recognized bacterial zoonosis in the European Union and the United States. The acute phase is characterized by gastrointestinal symptoms. The long-term sequelae (Guillain-Barre syndrome, reactive arthritis, and postinfectious irritable bowel syndrome) contribute considerably to the disease burden. Attribution studies identified poultry as the reservoir responsible for up to 80% of the human Campylobacter infections. In the European Union, an estimated 30% of the human infections are associated with consumption and preparation of poultry meat. Until now, interventions in the poultry meat production chain have not been effectively introduced except for targeted interventions in Iceland and New Zealand. Intervention measures (eg, biosecurity) have limited effect or are hampered by economic aspects or consumer acceptance. In the future, a multilevel approach should be followed, aiming at reducing the level of contamination of consumer products rather than complete absence of Campylobacter.
Combining in vitro embryotoxicity data with physiologically based kinetic (PBK) modelling to define in vivo dose-response curves for developmental toxicity of phenol in rat and human
Strikwold, M. ; Spenkelink, A. ; Woutersen, R.A. ; Rietjens, I. ; Punt, A. - \ 2013
Archives of Toxicology 87 (2013)9. - ISSN 0340-5761 - p. 1709 - 1723.
stem-cell test - substituted phenols - 2-generation reproduction - pharmacokinetic models - protein-binding - risk-assessment - drug clearance - steady-state - human liver - metabolism
In vitro assays are often used for the hazard characterisation of compounds, but their application for quantitative risk assessment purposes is limited. This is because in vitro assays cannot provide a complete in vivo dose-response curve from which a point of departure (PoD) for risk assessment can be derived, like the no observed adverse effect level (NOAEL) or the 95 % lower confidence limit of the benchmark dose (BMDL). To overcome this constraint, the present study combined in vitro data with a physiologically based kinetic (PBK) model applying reverse dosimetry. To this end, embryotoxicity of phenol was evaluated in vitro using the embryonic stem cell test (EST), revealing a concentration-dependent inhibition of differentiation into beating cardiomyocytes. In addition, a PBK model was developed on the basis of in vitro and in silico data and data available from the literature only. After evaluating the PBK model performance, effective concentrations (ECx) obtained with the EST served as an input for in vivo plasma concentrations in the PBK model. Applying PBK-based reverse dosimetry provided in vivo external effective dose levels (EDx) from which an in vivo dose-response curve and a PoD for risk assessment were derived. The predicted PoD lies within the variation of the NOAELs obtained from in vivo developmental toxicity data from the literature. In conclusion, the present study showed that it was possible to accurately predict a PoD for the risk assessment of phenol using in vitro toxicity data combined with reverse PBK modelling.
Prediction of Bacillus weihenstephanensis acid resistance: The use of gene expression patterns to select potential biomarkers
Desriac, N. ; Postollec, F. ; Coroller, L. ; Sohier, D. ; Abee, T. ; Besten, H.M.W. den - \ 2013
International Journal of Food Microbiology 167 (2013)1. - ISSN 0168-1605 - p. 80 - 86.
gram-positive bacteria - oxidative stress - staphylococcus-aureus - virulence factors - risk-assessment - cereus group - subtilis - quantification - pcr - temperature
Exposure to mild stress conditions can activate stress adaptation mechanisms and provide cross-resistance towards otherwise lethal stresses. In this study, an approach was followed to select molecular biomarkers (quantitative gene expressions) to predict induced acid resistance after exposure to various mild stresses, i.e. exposure to sublethal concentrations of salt, acid and hydrogen peroxide during 5 min to 60 min. Gene expression patterns of unstressed and mildly stressed cells of Bacillus weihenstephanensis were correlated to their acid resistance (3D value) which was estimated after exposure to lethal acid conditions. Among the twenty-nine candidate biomarkers, 12 genes showed expression patterns that were correlated either linearly or non-linearly to acid resistance, while for the 17 other genes the correlation remains to be determined. The selected genes represented two types of biomarkers, (i) four direct biomarker genes (lexA, spxA, narL, bkdR) for which expression patterns upon mild stress treatment were linearly correlated to induced acid resistance; and (ii) nine long-acting biomarker genes (spxA, BcerKBAB4_0325, katA, trxB, codY, lacI, BcerKBAB4_1716, BcerKBAB4_2108, relA) which were transiently up-regulated during mild stress exposure and correlated to increased acid resistance over time. Our results highlight that mild stress induced transcripts can be linearly or non-linearly correlated to induced acid resistance and both approaches can be used to find relevant biomarkers. This quantitative and systematic approach opens avenues to select cellular biomarkers that could be incremented in mathematical models to predict microbial behaviour. Keywords: Bacillus; Acid resistance; Gene expression; Modelling; Biomarker; Food safety