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1.
Nutr Neurosci ; 26(5): 429-444, 2023 May.
Article in English | MEDLINE | ID: mdl-35343884

ABSTRACT

OBJECTIVES: Strong reward responsiveness to food and insufficient inhibitory control are thought to be implicated in the development and maintenance of obesity. This narrative review addresses the role of inhibitory control in obesity and weight loss, and in how far inhibitory control is a promising target for weight loss interventions. METHODS: PubMed, Web of Science, and Google Scholar were searched for papers up to May 2021. 41 papers were included. RESULTS: Individuals with obesity have poorer food-specific inhibitory control, particularly when hungry, and less concurrent activation of inhibitory brain areas. Moreover, this was strongly predictive of future weight gain. More activation of inhibitory brain areas, on the other hand, was predictive of weight loss: individuals with successful weight loss initially show inhibitory brain activity comparable to that of normal weight individuals. When successful weight maintenance is achieved for at least 1 year, this inhibitory activity is further increased. Interventions targeting inhibitory control in obese individuals have divergent effects. Firstly, food-specific inhibitory control training is particularly effective for people with low inhibitory control and high BMI. Secondly, neuromodulation paradigms are rather heterogeneous: although rTMS to the left dorsolateral prefrontal cortex induced some weight-loss, multiple sessions of tDCS reduced food consumption (desire) and induced weight loss in two thirds of the papers. Thirdly, neurofeedback results in successful upregulation of brain activity and connectivity, but occasionally leads to increased food intake. In conclusion, inhibitory control is implicated in obesity. It can be targeted to promote weight loss although major weight losses have not been achieved.


Subject(s)
Obesity , Transcranial Direct Current Stimulation , Humans , Obesity/therapy , Brain , Weight Loss
2.
Appetite ; 170: 105901, 2022 03 01.
Article in English | MEDLINE | ID: mdl-34968564

ABSTRACT

OBJECTIVE: Health goal priming has been shown to stimulate healthy food choices by activating an individual's weight-control goal. The present study combined fMRI with a novel virtual reality food choice task to elucidate the underlying neural mechanisms of health goal priming. Previous research has suggested that the ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC) play a role in the incorporation of health considerations into the food choice process. Responses may be more representative for those found in real life when assessed in an environment similar to the actual choice environment. Therefore, the first aim of the study was to explore if a novel virtual reality food choice task is sufficiently sensitive to detect basic valuation processes in food choice. The second aim was to examine whether increased activation in the dlPFC drives the effects of health goal priming. METHODS: Fifty-six female participants performed an fMRI food choice task embedded in a virtual supermarket environment. They chose between perceived healthy and unhealthy products in a health prime, hedonic prime, and non-food control condition, while activation in brain areas involved in self-control and valuation (vmPFC, dlPFC) was assessed. RESULTS: There were no differences in relative preference for perceived healthy products over unhealthy products between the conditions. There were also no main effects of prime condition on brain activation in the vmPFC and dPFC during food choice. Across conditions, activation in the vmPFC correlated with the tastiness of the chosen product during food choice. CONCLUSIONS: Although the study does not provide support for health goal priming triggering neural self-control mechanisms, results did show that virtual reality has potential for a more realistic fMRI food choice paradigm.


Subject(s)
Magnetic Resonance Imaging , Virtual Reality , Choice Behavior/physiology , Female , Food Preferences/physiology , Goals , Humans , Magnetic Resonance Imaging/methods , Prefrontal Cortex/diagnostic imaging , Prefrontal Cortex/physiology
3.
J Eur Acad Dermatol Venereol ; 34(11): 2574-2583, 2020 Nov.
Article in English | MEDLINE | ID: mdl-32163645

ABSTRACT

BACKGROUND: In shared decision making (SDM), patients and physicians work together to choose the best treatment option for an individual patient. Atopic dermatitis (AD) and psoriasis are particularly suitable for SDM, considering that the best treatment option depends on a patient's preferences and values (preference-sensitive decisions). Currently, it is unknown to what extent SDM is applied in treatment decisions for these diseases in the Netherlands. OBJECTIVES: Primary, to assess the current extent of SDM in AD and psoriasis in the Netherlands amongst patients and dermatologists. Secondary, to assess the degree to which patients and physicians endorse SDM, to explore which characteristics are related to their preference to be involved in SDM and to identify which barriers and facilitators for SDM they perceive. METHODS: Two similar online surveys, one for patients with AD or psoriasis and one for (resident) dermatologists, were carried out. The surveys comprised validated questionnaires (shared decision making questionnaire (SDM-Q; range 0-100), Control Preference Scale) and study-specific statements mainly regarding barriers and facilitators for SDM. RESULTS: The responses of 219 patients and 147 physicians were analysed. Dermatologists experienced significantly more SDM than patients (SDM-Q 82 vs 55; P < 0.01). Most patients and dermatologists prefer to share treatment decisions. Mainly facilitators for SDM were perceived, including the positive perception of patients and dermatologists regarding SDM. The perceived barriers included lack of continuity of care by the same physician and lack of time. CONCLUSION: Despite the dermatologists' optimistic perspective, patients experience a limited extent of SDM and physicians should be aware of this gap. Improvement of SDM in AD and psoriasis is needed. The positive attitude of patients and dermatologists towards the process and outcome of SDM is important facilitators, while barriers were mainly perceived on an organizational level.


Subject(s)
Dermatitis, Atopic , Physicians , Psoriasis , Decision Making , Decision Making, Shared , Dermatitis, Atopic/therapy , Humans , Netherlands , Patient Participation , Physician-Patient Relations , Psoriasis/therapy , Surveys and Questionnaires
4.
Neuroimage ; 171: 246-255, 2018 05 01.
Article in English | MEDLINE | ID: mdl-29337278

ABSTRACT

The abundant exposure to food cues in our environment is one of the main drivers of overconsumption. Food evaluation is important for the regulation of food intake by the brain and it's interaction with hunger state. Children are especially susceptible to food cues. Understanding the mechanisms behind this regulation in healthy individuals across the life span can help to elucidate the mechanisms underlying overconsumption and aid the development of future obesity prevention strategies. Few functional neuroimaging studies have been done in children and elderly. Furthermore, it is unknown how hunger state affects neural food cue reactivity in these groups, since this has not been examined consistently. We examined the effects of hunger state and age on the brain responses to low- and high calorie foods. On two mornings, 122 participants (17 children; 38 teens; 36 adults; 31 elderly) performed a food image viewing task while being scanned using fMRI, either fasted or sated. Hunger induced greater activation during high versus low calorie food image viewing than satiety in the bilateral dorsomedial (dmPFC) and in the right dorsolateral prefrontal cortex (dlPFC) across all age groups. There was no significant main effect of age group on high versus low calorie food image viewing and no interaction between age group and hunger state. The greater activation of the dlPFC across all age groups during high calorie food image viewing in a fasted state might reflect increased inhibitory control in response to these foods. This may underlie the ability to resist overconsumption of high calorie foods. Furthermore, increased medial prefrontal cortex activation during hunger might reflect increased reward value of high calorie foods, which declines with satiation. Further studies are needed to better understand these results. Notably, overweight and obese individuals should be included to examine whether these responses are altered by weight status across the life span.


Subject(s)
Brain/physiology , Cues , Hunger/physiology , Adolescent , Adult , Age Factors , Aged , Child , Female , Functional Neuroimaging , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Photic Stimulation , Satiation/physiology
7.
Eur Radiol ; 25(3): 800-11, 2015 Mar.
Article in English | MEDLINE | ID: mdl-25354556

ABSTRACT

OBJECTIVES: Investigation of DNA damage induced by CT x-rays in paediatric patients versus patient dose in a multicentre setting. METHODS: From 51 paediatric patients (median age, 3.8 years) who underwent an abdomen or chest CT examination in one of the five participating radiology departments, blood samples were taken before and shortly after the examination. DNA damage was estimated by scoring γ-H2AX foci in peripheral blood T lymphocytes. Patient-specific organ and tissue doses were calculated with a validated Monte Carlo program. Individual lifetime attributable risks (LAR) for cancer incidence and mortality were estimated according to the BEIR VII risk models. RESULTS: Despite the low CT doses, a median increase of 0.13 γ-H2AX foci/cell was observed. Plotting the induced γ-H2AX foci versus blood dose indicated a low-dose hypersensitivity, supported also by an in vitro dose-response study. Differences in dose levels between radiology centres were reflected in differences in DNA damage. LAR of cancer mortality for the paediatric chest CT and abdomen CT cohort was 0.08 and 0.13 ‰ respectively. CONCLUSION: CT x-rays induce DNA damage in paediatric patients even at low doses and the level of DNA damage is reduced by application of more effective CT dose reduction techniques and paediatric protocols. .


Subject(s)
DNA Damage/radiation effects , Histones/metabolism , Neoplasms, Radiation-Induced/prevention & control , Tomography, X-Ray Computed/adverse effects , Biomarkers/metabolism , Child , Child, Preschool , Dose-Response Relationship, Radiation , Female , Humans , Infant , Male , Monte Carlo Method , Prospective Studies , Radiation Dosage , Radiometry/methods
8.
J Water Health ; 13(2): 587-99, 2015 Jun.
Article in English | MEDLINE | ID: mdl-26042989

ABSTRACT

The need to improve the access to safe water is generally recognized for the benefit of public health in developing countries. This study's objective was to identify critical parameters which are essential for improving the performance of ceramic pot filters (CPFs) as a point-of-use water treatment system. Defining critical production parameters was also relevant to confirm that CPFs with high-flow rates may have the same disinfection capacity as pots with normal flow rates. A pilot unit was built in Cambodia to produce CPFs under controlled and constant conditions. Pots were manufactured from a mixture of clay, laterite and rice husk in a small-scale, gas-fired, temperature-controlled kiln and tested for flow rate, removal efficiency of bacteria and material strength. Flow rate can be increased by increasing pore sizes and by increasing porosity. Pore sizes were increased by using larger rice husk particles and porosity was increased with larger proportions of rice husk in the clay mixture. The main conclusions: larger pore size decreases the removal efficiency of bacteria; higher porosity does not affect the removal efficiency of bacteria, but does influence the strength of pots; flow rates of CPFs can be raised to 10-20 L/hour without a significant decrease in bacterial removal efficiency.


Subject(s)
Ceramics , Developing Countries , Family Characteristics , Filtration/instrumentation , Water Purification/instrumentation , Aluminum Silicates , Clay , Escherichia coli , Filtration/methods , Humans , Silver , Temperature , Water Microbiology , Water Pollutants , Water Purification/methods
9.
J Water Health ; 12(4): 727-35, 2014 Dec.
Article in English | MEDLINE | ID: mdl-25473982

ABSTRACT

Quantitative microbial risk assessments (QMRAs) of contaminated drinking water usually assume the daily intake volume is consumed once a day. However, individuals could consume water at multiple time points over 1 day, so the objective was to determine if the number of consumption events per day impacted the risk of infection from Campylobacter jejuni during short-term contamination events. A probabilistic hydraulic and risk model was used to evaluate the impact of multiple consumption events as compared to one consumption event on the health risk from the intake of contaminated tap water. The fraction of the population that experiences greater than 10(-4) risk of infection per event at the median dose was 6.8% (5th-95th percentile: 6.5-7.2%) for one consumption event per day, 18.2% (5th-95th: 17.6-18.7%) for three consumption events per day, and 19.8% (5th-95th: 14.0-24.4%) when the number of consumption events varied around 3.49 events/day. While the daily intake volume remained consistent across scenarios, the results suggest that multiple consumption events per day increases the probability of infection during short-term, high level contamination events due to the increased coincidence of a consumption event during the contamination peak. Therefore, it will be important to accurately characterize this parameter in drinking water QMRAs.


Subject(s)
Campylobacter Infections/epidemiology , Campylobacter jejuni/physiology , Drinking Behavior , Drinking Water/microbiology , Campylobacter Infections/microbiology , Computer Simulation , Humans , Models, Statistical , Models, Theoretical , Netherlands/epidemiology , Risk Assessment/standards , Time Factors
10.
Am J Transplant ; 13(9): 2472-8, 2013 Sep.
Article in English | MEDLINE | ID: mdl-23914734

ABSTRACT

Adult-to-adult living donor liver transplantation (A2ALDLT) is an accepted mode of treatment for end-stage liver disease. Right-lobe grafts have usually been preferred in view of the higher graft volume, which lowers the risk of a small-for-size syndrome. However, donor left hepatectomy is associated with less morbidity than when it is compared to right hepatectomy. Laparoscopic donor hepatectomy (LDH) has been considered almost exclusively in pediatric transplantation. The results of laparoscopic left-liver graft procurement for calculated small-for-size A2ALDLT in four donors are presented. The graft-to-recipient body weight ratio was <0.8 in all recipients. The mean portal vein flow and the pressure and hepatic artery flows were measured at 190 ± 56 mL/min/100 g, 13 ± 1.4 mm/Hg and 109 ± 19 mL/min, respectively. No early postoperative donor complications were recorded. One graft was lost due to intrahepatic abscesses. Asymptomatic stenosis of a right posterior duct was treated with a Roux-en-Y loop 4 months later in one donor. We show that LDH of the full-left lobe is feasible. LDH is a very demanding operation, potentially decreasing donor morbidity. Standardization of this procedure, making it accessible to the growing number of experienced laparoscopic liver surgeons, could help renewing the interest for A2ALDLT in the Western world.


Subject(s)
Hepatectomy/methods , Liver Transplantation/methods , Living Donors , Adult , Female , Humans , Laparoscopy , Liver/anatomy & histology , Liver/surgery , Male , Middle Aged , Tissue and Organ Harvesting
11.
Eur J Nucl Med Mol Imaging ; 40(8): 1214-22, 2013 Aug.
Article in English | MEDLINE | ID: mdl-23636802

ABSTRACT

PURPOSE: Standardized added metabolic activity (SAM) is a PET parameter for assessing the total metabolic load of malignant processes, avoiding partial volume effects and lesion segmentation. The potential role of this parameter in the assessment of response to chemotherapy and bevacizumab was tested in patients with metastatic colorectal cancer with potentially resectable liver metastases (mCRC). METHODS: (18)F-FDG PET/CT was performed in 18 mCRC patients with liver metastases before treatment and after five cycles of FOLFOX/FOLFIRI and bevacizumab. Of the 18 patients, 16 subsequently underwent resection of liver metastases. Baseline and follow-up SUVmax, and SAM as well as reduction in SUVmax (∆SUVmax) and SAM (∆SAM) of all liver metastases were correlated with morphological response, and progression-free and overall survival (PFS and OS). RESULTS: A significant reduction in metabolic activity of the liver metastases was seen after chemotherapy with a median ∆SUVmax of 25.3% and ∆SAM of 94.5% (p = 0.033 and 0.003). Median baseline SUVmax and SAM values were significantly different between morphological responders and nonresponders (3.8 vs. 7.2, p = 0.021; and 34 vs. 211, p = 0.002, respectively), but neither baseline PET parameters nor morphological response was correlated with PFS or OS. Follow-up SUVmax and SAM as well as ∆SAM were found to be prognostic factors. The median PFS and OS in the patient group with a high follow-up SUVmax were 10.4 months and 32 months, compared to a median PFS of 14.7 months and a median OS which had not been reached in the group with a low follow-up SUVmax (p = 0.01 and 0.003, respectively). The patient group with a high follow-up SAM and a low ∆SAM had a median PFS and OS of 9.4 months and 32 months, whereas the other group had a median PFS of 14.7 months and a median OS which had not been reached (p = 0.002 for both PFS and OS). CONCLUSION: (18)F-FDG PET imaging is a useful tool to assess treatment response and predict clinical outcome in patients with mCRC who undergo chemotherapy before liver metastasectomy. Follow-up SUVmax, follow-up SAM and ∆SAM were found to be significant prognostic factors for PFS and OS.


Subject(s)
Colorectal Neoplasms/pathology , Fluorodeoxyglucose F18/pharmacokinetics , Liver Neoplasms/diagnostic imaging , Liver Neoplasms/secondary , Positron-Emission Tomography , Radiopharmaceuticals/pharmacokinetics , Aged , Antibodies, Monoclonal, Humanized/therapeutic use , Antineoplastic Agents/therapeutic use , Antineoplastic Combined Chemotherapy Protocols , Bevacizumab , Camptothecin/analogs & derivatives , Colorectal Neoplasms/drug therapy , Female , Fluorouracil , Humans , Leucovorin , Liver Neoplasms/drug therapy , Male , Middle Aged , Multimodal Imaging , Organoplatinum Compounds , Tomography, X-Ray Computed , Treatment Outcome
12.
Br J Cancer ; 106(12): 1926-33, 2012 Jun 05.
Article in English | MEDLINE | ID: mdl-22596235

ABSTRACT

BACKGROUND: The purpose of this study was to assess the role of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and (18)F-fluorodeoxyglucose positron emission tomography computed tomography (FDG-PET/CT) for evaluation of response to chemotherapy and bevacizumab and for prediction of progression-free survival (PFS) in patients with metastatic colorectal cancer (mCRC) with potentially resectable liver lesions. METHODS: A total of 19 mCRC patients were treated with FOLFOX/FOLFIRI and bevacizumab followed by surgery. Dynamic contrast-enhanced magnetic resonance imaging and FDG-PET/CT were performed before treatment and after cycle 5. PET results were quantified by calculating maximum standardised uptake value (SUV(max)) whereas area under the enhancement curve (AUC), initial AUC (iAUC) and the endothelial transfer constant (K(trans)) were used to quantify DCE-MRI. Pathological analysis of the resection specimen was performed, including measurement of microvessel density (MVD) and proliferation index. RESULTS: Both AUC and iAUC were significantly decreased following bevacizumab therapy (median change of 22% (P=0.002) and 40% (P=0.001) for AUC and iAUC, respectively). Progression-free survival benefit was shown for patients with >40% reduction in K(trans) (P=0.019). In the group of radiological responders, the median baseline SUV(max) was 3.77 (IQR: 2.88-5.60) compared with 7.20 (IQR: 4.67-8.73) in nonresponders (P=0.021). A higher follow-up SUV(max) was correlated with worse PFS (P=0.012). Median MVD was 10.9. Progression-free survival was significantly shorter in patients with an MVD greater than 10, compared with patients with lower MVD (10 months compared with 16 months, P=0.016). CONCLUSION: High relative decrease in K(trans), low follow-up SUV(max) and low MVD are favourable prognostic factors for mCRC patients treated with bevacizumab before surgery.


Subject(s)
Antibodies, Monoclonal, Humanized/administration & dosage , Colorectal Neoplasms/pathology , Liver Neoplasms/diagnosis , Liver Neoplasms/secondary , Magnetic Resonance Imaging/methods , Multimodal Imaging/methods , Positron-Emission Tomography , Tomography, X-Ray Computed , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Bevacizumab , Camptothecin/analogs & derivatives , Camptothecin/therapeutic use , Colorectal Neoplasms/diagnosis , Colorectal Neoplasms/mortality , Disease-Free Survival , Female , Fluorodeoxyglucose F18 , Fluorouracil/therapeutic use , Humans , Leucovorin/therapeutic use , Liver Neoplasms/mortality , Male , Middle Aged , Neoadjuvant Therapy , Organoplatinum Compounds/therapeutic use
13.
Neuroimage ; 55(1): 296-303, 2011 Mar 01.
Article in English | MEDLINE | ID: mdl-21111829

ABSTRACT

Food selection is primarily guided by the visual system. Multiple functional neuro-imaging studies have examined the brain responses to visual food stimuli. However, the results of these studies are heterogeneous and there still is uncertainty about the core brain regions involved in the neural processing of viewing food pictures. The aims of the present study were to determine the concurrence in the brain regions activated in response to viewing pictures of food and to assess the modulating effects of hunger state and the food's energy content. We performed three Activation Likelihood Estimation (ALE) meta-analyses on data from healthy normal weight subjects in which we examined: 1) the contrast between viewing food and nonfood pictures (17 studies, 189 foci), 2) the modulation by hunger state (five studies, 48 foci) and 3) the modulation by energy content (seven studies, 86 foci). The most concurrent brain regions activated in response to viewing food pictures, both in terms of ALE values and the number of contributing experiments, were the bilateral posterior fusiform gyrus, the left lateral orbitofrontal cortex (OFC) and the left middle insula. Hunger modulated the response to food pictures in the right amygdala and left lateral OFC, and energy content modulated the response in the hypothalamus/ventral striatum. Overall, the concurrence between studies was moderate: at best 41% of the experiments contributed to the clusters for the contrast between food and nonfood. Therefore, future research should further elucidate the separate effects of methodological and physiological factors on between-study variations.


Subject(s)
Attention/physiology , Brain/physiology , Cues , Food , Hunger/physiology , Photic Stimulation/methods , Visual Perception/physiology , Appetite/physiology , Brain Mapping , Female , Humans , Male
14.
Radiol Case Rep ; 16(7): 1700-1707, 2021 Jul.
Article in English | MEDLINE | ID: mdl-34007387

ABSTRACT

Familial Mediterranean Fever (FMF) is an autosomal recessive disorder that is characterised by recurrent attacks of fever and painful polyserositis mainly affecting the peritoneum, synovium and pleura that usually begins in childhood. Even though diagnostic criteria have been proposed, conclusive imaging findings or haematological markers for the diagnosis or follow-up of FMF are still lacking. In this case report we present the 18F-FDG PET-CT findings in a 55 year old female during an attack of FMF. We briefly discuss the added value of 18F-FDG PET-CT in the diagnosis and the work-up of FMF, which may open up new applications for 18F-FDG PET-CT in non-infectious inflammatory diseases.

15.
Sci Rep ; 11(1): 12704, 2021 06 16.
Article in English | MEDLINE | ID: mdl-34135435

ABSTRACT

Olfactory loss (OL) affects up to 20% of the general population and is related to changes in olfaction-related brain regions. This study investigated the effect of etiology and duration of OL on gray matter volume (GMV) of these regions in 257 patients. Voxel-based morphometry was applied to measure GMV in brain regions of interest to test the effects of etiology and duration on regional GMV and the relation between olfactory function and regional GMV. Etiology of OL had a significant effect on GMV in clusters representing the gyrus rectus and orbitofrontal cortex (OFC), bilaterally. Patients with congenital anosmia had reduced GMV in the gyrus rectus and an increased OFC volume compared to patients with acquired OL. There was a significant association between volume of the left OFC and olfactory function. This implies that changes in GMV in patients with acquired OL are mainly reflected in the OFC and depend on olfactory function. Morphology of olfactory areas in the brain therefore seems to relate to olfactory function and the subsequent degree of exposure to olfactory input in patients with acquired OL. Differences in GMV in congenital anosmia are most likely due to the fact that patients were never able to smell.


Subject(s)
Gray Matter/pathology , Olfaction Disorders/etiology , Prefrontal Cortex/diagnostic imaging , Prefrontal Cortex/pathology , Adult , Female , Gray Matter/diagnostic imaging , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Olfaction Disorders/congenital , Olfaction Disorders/diagnostic imaging , Olfaction Disorders/pathology , Smell
16.
Chem Senses ; 35(9): 831-40, 2010 Nov.
Article in English | MEDLINE | ID: mdl-20876393

ABSTRACT

The intensity of the taste of a food is affected mostly by the amount of sugars (mono- and disaccharides) or salt it contains. To season savory-tasting foods mainly table salt (NaCl) is used and to sweeten foods, sugars like sucrose are used. Foods with highly intense tastes are consumed in smaller amounts. The optimal taste intensity of a food is the intensity at which it is perceived as most pleasant. When taste intensity decreases or increases from optimal, the pleasantness of a food decreases. Here, we investigated the brain representation of sweet and salty taste intensity using functional magnetic resonance imaging. Fifteen subjects visited twice and tasted a range of 4 watery solutions (0-1 M) of either sucrose or NaCl in water. Middle insula activation increased with increasing concentration for both NaCl and sucrose. Despite similar subjective intensity ratings, anterior insula activation by NaCl increased more with concentration than that by sucrose. Amygdala activation increased with increasing NaCl concentration but not sucrose concentration. In conclusion, sweet and salty taste intensity are represented in the middle insula. Amygdala activation is only modulated by saltiness. Further research will need to extrapolate these results from simple solutions to real foods.


Subject(s)
Brain/drug effects , Carbohydrates/adverse effects , Sodium Chloride/pharmacology , Sucrose/pharmacology , Taste/physiology , Amygdala/drug effects , Amygdala/physiology , Brain/physiology , Candy , Food Preferences/drug effects , Food Preferences/physiology , Humans , Magnetic Resonance Imaging/methods , Taste/drug effects
17.
Water Sci Technol ; 61(6): 1561-8, 2010.
Article in English | MEDLINE | ID: mdl-20351436

ABSTRACT

The absence of indicator organisms in drinking water does not provide sufficient guarantee for microbial safety. Therefore the water utilities are implementing water safety plans (WSP) to safeguard drinking water quality. Quantitative microbial risk assessment (QMRA) can be used to provide objective quantitative input for the WSP. This study presents several applications of treatment modelling in QMRA to answer the risk managers questions raised in the WSP. QMRA can estimate how safe the water is, how much the safety varies and how certain the estimate of safety is. This can be used in the WSP system assessment to determine whether treatment is meeting health-based targets with the required level of certainty. Quantitative data analysis showed that short events of only 8 hours per year can dominate the yearly average health risk for the consumer. QMRA also helps the design of physical and microbial monitoring. The study showed that the required monitoring frequency increases with increasing treatment efficacy. Daily monitoring can be sufficient to verify a treatment process achieving 2 log reduction of pathogens, but a process achieving 4 log reduction needs to be monitored every 15 minutes. Similarly, QMRA helps to prepare adequate corrective actions by determining the acceptable 'down time' of a process. For example, for a process achieving 2.5 log reduction a down time of maximum 6 hours per year is acceptable. These applications illustrate how QMRA can contribute to efficient and effective management of microbial drinking water safety.


Subject(s)
Environmental Monitoring/methods , Water Microbiology/standards , Water Supply/standards , Alveolata/isolation & purification , Bacteria/isolation & purification , Limit of Detection , Models, Theoretical , Risk Assessment , Water Purification
18.
Int J Hyg Environ Health ; 222(7): 1030-1037, 2019 08.
Article in English | MEDLINE | ID: mdl-31311691

ABSTRACT

In the Netherlands, safe and sufficient drinking water is provided to the general population by ten drinking water companies. To guarantee safe drinking water the World Health Organization (WHO) developed a Water Safety Plan (WSP), a Risk Assessment and a Risk Management (RA/RM) framework. The objective of the study was to identify legally required RA approaches, to document application of RA/RM activities at Dutch drinking water companies and to determine to what extent these RA/RM activities as a whole cover all the elements of the WHO WSP approach. This study could be of interest to both managers of large water utilities and decision makers. The assessment was performed by means of a policy review and interviews with two to four staff members involved in RA/RM from all ten Dutch drinking water companies combined with a joint workshop. The drinking water companies are well aware of the potential hazards and risks that can influence the drinking water quality. To guarantee the supply of safe and sufficient drinking water, the Dutch drinking water sector uses six different legally required RA/RM approaches. This study shows that by using the six legally required RA/RM approaches, all WSP steps are covered. WSP entails a generic risk assessment for identifying all hazards and hazardous events from source to tap, whereas the six legally required RA/RM each focus on specific risks at an advanced level. Each risk assessment provides information on specific hazards and hazardous events covering a part of the water supply chain. These legal requirements are complemented with additional RA/RM activities at sector and water company level such as codes of practices and standard operating procedures. The outcomes of all RA/RM approaches combined provide information from source to tap. When using multiple RA/RM approaches, it is crucial to share and combine information derived from the different activities.


Subject(s)
Drinking Water , Risk Assessment , Humans , Netherlands , Water Quality , World Health Organization
19.
J Water Health ; 6(3): 301-14, 2008 Sep.
Article in English | MEDLINE | ID: mdl-19108550

ABSTRACT

Quantitative microbial risk assessment (QMRA) is increasingly applied to estimate drinking water safety. In QMRA the risk of infection is calculated from pathogen concentrations in drinking water, water consumption and dose response relations. Pathogen concentrations in drinking water are generally low and monitoring provides little information for QMRA. Therefore pathogen concentrations are monitored in the raw water and reduction of pathogens by treatment is modelled stochastically with Monte Carlo simulations. The method was tested in a case study with Campylobacter monitoring data of rapid sand filtration and ozonation processes. This study showed that the currently applied method did not predict the monitoring data used for validation. Consequently the risk of infection was over estimated by one order of magnitude. An improved method for model validation was developed. It combines non-parametric bootstrapping with statistical extrapolation to rare events. Evaluation of the treatment model was improved by presenting monitoring data and modelling results in CCDF graphs, which focus on the occurrence of rare events. Apart from calculating the yearly average risk of infection, the model results were presented in FN curves. This allowed for evaluation of both the distribution of risk and the uncertainty associated with the assessment.


Subject(s)
Campylobacter/isolation & purification , Filtration/methods , Fresh Water/analysis , Ozone , Water Microbiology/standards , Drinking , Fresh Water/microbiology , Models, Statistical , Monte Carlo Method , Organizational Case Studies , Risk Assessment/methods , Risk Assessment/statistics & numerical data
20.
Rev Sci Instrum ; 79(1): 013505, 2008 Jan.
Article in English | MEDLINE | ID: mdl-18248032

ABSTRACT

A highly sensitive imaging Thomson scattering system was developed for low temperature (0.1-10 eV) plasma applications at the Pilot-PSI linear plasma generator. The essential parts of the diagnostic are a neodymium doped yttrium aluminum garnet laser operating at the second harmonic (532 nm), a laser beam line with a unique stray light suppression system and a detection branch consisting of a Littrow spectrometer equipped with an efficient detector based on a "Generation III" image intensifier combined with an intensified charged coupled device camera. The system is capable of measuring electron density and temperature profiles of a plasma column of 30 mm in diameter with a spatial resolution of 0.6 mm and an observational error of 3% in the electron density (n(e)) and 6% in the electron temperature (T(e)) at n(e) = 4 x 10(19) m(-3). This is achievable at an accumulated laser input energy of 11 J (from 30 laser pulses at 10 Hz repetition frequency). The stray light contribution is below 9 x 10(17) m(-3) in electron density equivalents by the application of a unique stray light suppression system. The amount of laser energy that is required for a n(e) and T(e) measurement is 7 x 10(20)n(e) J, which means that single shot measurements are possible for n(e)>2 x 10(21) m(-3).

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