J Douwes

Massey University, Palmerston North City, Manawatu-Wanganui, New Zealand

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Publications (158)498.47 Total impact

  • J Douwes, C Brooks, N Pearce
    European Respiratory Journal 05/2011; 37(5):986-90. · 7.13 Impact Factor
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    ABSTRACT: Phase III of the International Study of Asthma and Allergies in Childhood (ISAAC) was conducted in eight Pacific countries, five of which (Samoa, Fiji, Tokelau, French Polynesia and New Caledonia) collected environmental questionnaire (EQ) data. We report the findings of the EQ analyses below. The major factors associated with current wheeze were regular margarine consumption (prevalence odds ratio [POR] 1.19, 95%CI 1.01-1.40), paracetamol use (POR 1.35, 95%CI 1.11-1.64), electric cooking (POR 1.42, 95%CI 1.11-1.80), regular exercise (POR 1.44, 95%CI 1.18-1.75) and maternal smoking (POR 1.16, 95%CI 1.01-1.33). Protective factors included having older siblings (two or more POR 0.69, 95%CI 0.58-0.82; one POR 0.86, 95%CI 0.71-1.05), and being born in the country of the survey (POR 0.74, 95%CI 0.63-0.87). Risk factors for rhinoconjunctivitis included regular consumption of meat, butter, margarine and nuts, regular exercise, regular television viewing, paracetamol use and passive smoking. Eczema was associated with regular meat, pasta and butter consumption, regular television viewing, paracetamol use and passive smoking. Regular meat and margarine consumption, paracetamol use, electric cooking and passive smoking are risk factors for symptoms of asthma, rhinoconjunctivitis and eczema in the Pacific. However, most of these associations were weak, and account for only a small proportion of cases.
    The International Journal of Tuberculosis and Lung Disease 08/2008; 12(7):799-806. · 2.76 Impact Factor
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    ABSTRACT: The aim of the present study was to assess which factors contribute to the lower prevalence of allergic diseases in farmers' children, and the importance of timing of exposure. In a cross-sectional questionnaire survey, asthma symptoms, hay fever and eczema were assessed, as well as current, early and prenatal farm-related exposures in 1,333 farmers' children and 566 reference children aged 5-17 yrs. Farmers' children had a lower incidence of asthma symptoms and eczema. Current and maternal exposure during pregnancy to animals and/or grain and hay reduced the risk of asthma symptoms, hay fever and eczema. The exposure-response association for maternal exposure was nonlinear for most outcomes. After mutual adjustment, the effects of prenatal exposure remained unchanged whereas current exposure remained protective only for asthma medication, asthma ever and hay fever. Exposure during the first 2 yrs was not associated with symptoms, after controlling for prenatal exposure. A combination of prenatal and current exposure was most strongly associated with wheeze (odds ratio (OR) 0.48, 95% confidence interval (CI) 0.28-0.80), asthma medication (OR 0.50, 95% CI 0.30-0.82), asthma ever (OR 0.50, 95% CI 0.33-0.76), hay fever (OR 0.47, 95% CI 0.30-0.73) and eczema (OR 0.46, 95% CI 0.30-0.70). Prenatal exposure may contribute to the low prevalence of asthma, hay fever and eczema in farmers' children, but continued exposure may be required to maintain optimal protection.
    European Respiratory Journal 05/2008; 32(3):603-11. · 7.13 Impact Factor
  • Asthma: Critical Debates, 03/2008: pages 35 - 45; , ISBN: 9780470693889
  • N. Pearce, J. Douwes
    International Journal of Epidemiology 01/2008; 38(2):610-611. · 9.20 Impact Factor
  • Occupational and Environmental Medicine 11/2007; 64(12):e29-e29. · 3.23 Impact Factor
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    ABSTRACT: Farm exposures may protect against childhood asthma, hay fever and eczema. Whether farm exposures also confer protection in adult farmers remains unclear. Moreover, little is known about the role of timing of exposure. We assessed the effects of current and childhood farm exposures on asthma, hay fever and eczema in farmers and a rural nonfarming control population. We conducted a cross-sectional questionnaire survey in 2509 farming families (response rate 78%) and 1001 nonfarming families (response rate 67%), which included 4288 farmers and 1328 nonfarmers. Farmers were less likely to have asthma symptoms, hay fever and eczema; no significant differences were observed among dairy, sheep and beef, and horticulture farmers. A combination of current and childhood exposure was more strongly associated with shortness of breath (OR 0.50, CL 0.39-0.66), wheeze (OR 0.60, CL 0.49-0.73), asthma medication (OR 0.48, CL 0.37-0.63); and asthma ever (OR 0.56, CL 0.46-0.68) than current exposure alone (OR 0.63, CL 0.47-0.84; OR 0.80, CL 0.65-0.99; OR 0.68, CL 0.51-0.9; OR 0.69, CL 0.56-0.85 respectively) or childhood exposure alone (OR 0.97, CL0.65-1.44; OR 1.01, CL 0.75-1.34; OR 0.78, CL 0.51-1.19; OR 0.87, CL 0.63-1.19 respectively). Moreover, the combined number of years of farm exposure in childhood and adulthood showed a dose-dependent inverse association with symptom prevalence. Although both current and childhood farm exposures may play a role in the observed low prevalence of asthma symptoms in adult farmers, continued long-term exposure may be required to maintain optimal protection.
    Allergy 11/2007; 62(10):1158-65. · 6.00 Impact Factor
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    ABSTRACT: Asthma control, defined by asthma symptoms and lung function, and asthma medication use, was assessed in 123 adolescent asthmatics. Sputum eosinophilia (>or= 2.5% eosinophils) and bronchial hyperresponsiveness (BHR) to hypertonic saline were also measured to assess whether these additional objective parameters might aid in determining asthma control; 54.5% of subjects had adequately controlled asthma; 50.4% of all subjects reported inhaled corticosteroid use in the preceding 12 months; however, only 22.3% reported regular use. Although BHR and median eosinophil numbers were significantly higher in the inadequately controlled asthmatics, BHR and sputum eosinophilia had poor sensitivity for detecting inadequate asthma control.
    Journal of Asthma 05/2007; 44(4):261-6. · 1.83 Impact Factor
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    ABSTRACT: Dust collection by study participants instead of fieldworkers would be a practical and cost-effective alternative in large-scale population studies estimating exposure to indoor allergens and microbial agents. We aimed to compare dust weights and biological agent levels in house dust samples taken by study participants with nylon socks, with those in samples taken by fieldworkers using the sampling nozzle of the Allergology Laboratory Copenhagen (ALK). In homes of 216 children, parents and fieldworkers collected house dust within the same year. Dust samples were analyzed for levels of allergens, endotoxin, (1-->3)-beta-D-glucans and fungal extracellular polysaccharides (EPS). Socks appeared to yield less dust from mattresses at relatively low dust amounts and more dust at high dust amounts than ALK samples. Correlations between the methods ranged from 0.47-0.64 for microbial agents and 0.64-0.87 for mite and pet allergens. Cat allergen levels were two-fold lower and endotoxin levels three-fold higher in socks than in ALK samples. Levels of allergens and microbial agents in sock samples taken by study participants are moderately to highly correlated to levels in ALK samples taken by fieldworkers. Absolute levels may differ, probably because of differences in the method rather than in the person who performed the sampling. Practical Implications Dust collection by participants is a reliable and practical option for allergen and microbial agent exposure assessment. Absolute levels of biological agents are not (always) comparable between studies using different dust collection methods, even when expressed per gram dust, because of potential differences in particle-size constitution of the collected dust.
    Indoor Air 01/2007; 16(6):414-25. · 4.20 Impact Factor
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    ABSTRACT: An increased risk of asthma symptoms has previously been shown in 772 pine sawmill workers. The aim of the current study was to assess the association between dust exposure, lung function and atopy. Subjects with (n = 59) and without (n = 167) asthma symptoms were randomly selected from the previous survey. Lung function and atopy were determined using spirometry and skin-prick tests, respectively. Inhalable dust levels were measured on the same day. The geometric mean dust concentration was 0.52 mg x m(-3). Exposure to dry but not to green dust was associated with asthma symptoms. Green dust was associated with atopic sensitisation, particularly against outdoor allergens; no association was found for dry dust. Forced vital capacity, forced expiratory volume in one second and peak expiratory flow were significantly lower in workers exposed to high levels of green dust (-350 mL, -260 mL and -860 mL x s(-1), respectively) and dry dust (-230 mL, -190 mL and -850 mL x s(-1), respectively). These associations were observed both in subjects with and without asthma symptoms. No associations with cross-shift changes in lung function were found. Exposure to green pine sawdust may be a risk factor for atopy. Both green and dry dust were associated with obstructive as well as restrictive pulmonary effects.
    European Respiratory Journal 11/2006; 28(4):791-8. · 7.13 Impact Factor
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    ABSTRACT: Low sensitization rates to common allergens have been observed in farm children, which might be due to high exposure to microbial agents. It is not known how microbial agents modify the association between specific allergen exposure and sensitization. To examine the relations between house dust mite allergen exposure and mite sensitization in farm and nonfarm children and to assess the effects of microbial agents levels on this association. Major mite allergens of Dermatophagoides pteronyssinus (Der p 1) and Dermatophagoides farinae (Der f 1), endotoxin, beta(1,3)-glucans and fungal extracellular polysaccharides were measured in mattress dust of 402 children participating in a cross-sectional study in five European countries. Mite allergen (Der p 1 + Der f 1) levels were divided into tertiles with cut-offs 1.4 and 10.4 microg/g. Sensitization was assessed by measurement of allergen-specific immunoglobulin E against house dust mite. Prevalence ratios of mite sensitization for medium and high when compared with low mite allergen levels were 3.1 [1.7-5.7] and 1.4 [0.7-2.8] respectively. Highest mite sensitization rates at intermediate exposure levels were consistently observed across country (except for Sweden) and in both farm and nonfarm children. The shape of the dose-response curve was similar for above and below median mattress microbial agent levels, but the 'sensitization peak' appeared to be lower for above median levels. Our data suggest a bell-shaped dose-response relationship between mite allergen exposure and sensitization to mite allergens. In populations with high microbial agent levels and low sensitization rates, the curve is shifted down.
    Allergy 06/2006; 61(5):640-7. · 6.00 Impact Factor
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    ABSTRACT: Asthma is a common chronic respiratory disease, and many epidemiological studies have documented an increasing trend over the past few decades. Comparative studies have shown that asthma is more prevalent in Westernised societies than in rural or developing regions. Environmental factors are likely to be important in explaining such disparities and increasing trends. Although allergen exposure and atopic sensitisation have been thought to be important in the pathogenesis of asthma, recent cross-sectional and longitudinal studies suggest that allergic sensitisation is likely a marker rather than a causative factor for asthma. There is accumulating evidence confirming the role of early exposure to infections in altering the regulation of cytokine production and reduction of subsequent development of atopic disorders. The consistent finding of a lower prevalence of asthma in subjects brought up in a farming environment and the inverse relationship between microbial exposure and asthma symptoms further support the importance of early environmental exposure affecting the risk of subsequent development of asthma. Confirmation of the pathogenetic role of these environmental determinants may allow us to develop primary preventive strategies against the development of asthma and related atopic diseases.
    The International Journal of Tuberculosis and Lung Disease 04/2006; 10(3):242-51. · 2.76 Impact Factor
  • N Pearce, J Douwes
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    ABSTRACT: Until recently, most studies reported that asthma prevalence has increased in recent decades. The best indication of what is now happening globally will be provided by Phase III of the International Study of Asthma and Allergies in Childhood (ISAAC) study. Some individual ISAAC centres in Western countries, as well as several studies in adults, have already reported no increase or even a decrease in asthma prevalence over the last 10 years. 'Established' risk factors for asthma cannot account for the global prevalence increases, the international patterns or the recent declines in prevalence in some Western countries. It seems that the 'package' of changes in the intrauterine and infant environment occurring with 'Westernisation' is causing increased susceptibility to the development of asthma and/or allergy. The 'package' includes changes in maternal diet, increased foetal growth, smaller family size, reduced infant infections, increased use of antibiotics and paracetamol and immunisation, all of which have been (inconsistently) associated with an increased risk of childhood asthma, but none of which can alone explain the increases in prevalence. It is likely that the 'package' is more than the sum of its parts, and that these social and environmental changes are all pushing our immune systems in the same direction. To know what that direction is requires that better aetiological theories of asthma are developed to replace the allergen theory, or to incorporate it as a special case. Global comparisons of asthma prevalence and assessment of time trends will continue to play a major role in this process.
    The International Journal of Tuberculosis and Lung Disease 03/2006; 10(2):125-32. · 2.76 Impact Factor
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    ABSTRACT: Asthma is a common chronic respiratory disease, and many epidemiological studies have documented an increasing trend over the past few decades. Comparative studies have shown that asthma is more prevalent in Westernised societies than in rural or developing regions. Environmental factors are likely to be important in explaining such disparities and increasing trends. Although allergen exposure and atopic sensitisation have been thought to be important in the pathogenesis of asthma, recent cross-sectional and longitudinal studies suggest that allergic sensitisation is likely a marker rather than a causative factor for asthma. There is accumulating evidence confirming the role of early exposure to infections in altering the regulation of cytokine production and reduction of subsequent development of atopic disorders. The consistent finding of a lower prevalence of asthma in subjects brought up in a farming environment and the inverse relationship between microbial exposure and asthma symptoms further support the importance of early environmental exposure affecting the risk of subsequent development of asthma. Confirmation of the pathogenetic role of these environmental determinants may allow us to develop primary preventive strategies against the development of asthma and related atopic diseases.
    The International Journal of Tuberculosis and Lung Disease 02/2006; 10(2 in the series]" class="no-underline contain" target="_blank">PDF 100.6kb):242-251. · 2.76 Impact Factor
  • N. Pearce, J. Douwes
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    ABSTRACT: Until recently, most studies reported that asthma prevalence has increased in recent decades. The best indication of what is now happening globally will be provided by Phase III of the International Study of Asthma and Allergies in Childhood (ISAAC) study. Some individual ISAAC centres in Western countries, as well as several studies in adults, have already reported no increase or even a decrease in asthma prevalence over the last 10 years. `Established' risk factors for asthma cannot account for the global prevalence increases, the international patterns or the recent declines in prevalence in some Western countries. It seems that the `package' of changes in the intrauterine and infant environment occurring with `Westernisation' is causing increased susceptibility to the development of asthma and/or allergy. The `package' includes changes in maternal diet, increased foetal growth, smaller family size, reduced infant infections, increased use of antibiotics and paracetamol and immunisation, all of which have been (inconsistently) associated with an increased risk of childhood asthma, but none of which can alone explain the increases in prevalence. It is likely that the `package' is more than the sum of its parts, and that these social and environmental changes are all pushing our immune systems in the same direction. To know what that direction is requires that better aetiological theories of asthma are developed to replace the allergen theory, or to incorporate it as a special case. Global comparisons of asthma prevalence and assessment of time trends will continue to play a major role in this process.
    The International Journal of Tuberculosis and Lung Disease 01/2006; 10(1 in the series]" class="no-underline contain" target="_blank">PDF 75.9kb):125-132. · 2.76 Impact Factor
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    ABSTRACT: Endotoxin exposure is associated with wheeze and asthma morbidity, while early life exposure may reduce risk of allergy and asthma. Unfortunately, it is difficult to compare endotoxin results from different laboratories and environments. We undertook this study to determine if lipopolysaccharide (LPS) extraction efficiency could account for differences among laboratories. We generated and collected aerosols from chicken and swine barns, and corn processing. We randomly allocated side-by-side filter samples to five laboratories for Limulus assay of endotoxin. Lyophilized aliquots of filter extracts were analyzed for 3-hydroxy fatty acids (3-OHFAs) as a marker of LPS using gas chromatography-mass spectrometry. There were significant differences in endotoxin assay and GC-MS (LPS) results between laboratories for all dust types (p < 0.01). Patterns of differences between labs varied by dust type. Relationships between assay and GC/MS results also depended on dust type. The percentages of individual 3-OHFA chain lengths varied across labs (p < 0.0001) suggesting that each lab recovered a different fraction of the LPS available. The presence of large amounts of particle associated LPS and absence of a freezing thawing cycle were associated with lower correlations between LPS and bioactivity, consistent with an absence of Limulus response to cell-bound endotoxin. These data suggest that extraction methods affect endotoxin measurements. The LAL methods may be most suitable when comparing exposures within similar environments; GC-MS offers additional information helpful in optimizing sample treatment and extraction. GC-MS may be of use when comparing across heterogeneous environments and should be considered for inclusion in future studies of human health outcomes.
    Journal of Environmental Monitoring 12/2005; 7(12):1371-7. · 2.09 Impact Factor
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    ABSTRACT: Growing up on a farm and an anthroposophic lifestyle are associated with a lower prevalence of allergic diseases in childhood. This might be related to increased inhalatory exposure to microbial agents. To assess the association between microbial agents in house dust and atopic wheeze in farm children, Steiner school children and reference children. Levels of bacterial endotoxin, fungal beta(1,3)-glucans and fungal extracellular polysaccharides (EPS) in mattress and living room floor dust were measured in a population of 270 atopic (=Phadiatop-positive) children with self-reported wheezing, including 168 current atopic wheezers, and 441 non-atopic, non-symptomatic controls. These children were selected from a cross-sectional study in five European countries. In the study population as a whole, average levels of mattress dust endotoxin, EPS and glucans were slightly (1.1-1.2-fold; P<0.10) higher in control children than in atopic wheezers. Atopic wheeze was related to mattress levels of endotoxin, EPS and glucans in farm and farm-reference children. However, when adjusting for group (farm vs. farm-reference children), the associations became non-significant whereas the group effect remained. No associations between atopic wheeze and microbial agents were observed in Steiner and Steiner-reference children. For current atopic wheeze, the farm effect became non-significant after adjustment for microbial agent levels. Not only bacterial endotoxin but also mould components might offer some protection against atopic wheeze in children. However, the protective effect of being raised on a farm was largely unexplained by the mattress microbial agent levels measured in this study.
    Clinical & Experimental Allergy 10/2005; 35(10):1272-8. · 4.32 Impact Factor
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    J Douwes
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    ABSTRACT: (1-->3)-Beta-D-glucan are non-allergenic structural cell wall components of most fungi that have been suggested to play a causal role in the development of respiratory symptoms associated with indoor fungal exposure. This review describes the currently available epidemiological literature on health effects of (1-->3)-beta-D-glucan, focusing on atopy, airway inflammation and symptoms, asthma, and lung function. In addition to population studies, studies in human volunteers experimentally exposed to (1-->3)-beta-D-glucan are described as well as relevant animal studies. Furthermore, the review discusses exposure assessment methods, the potential for exposure control and it concludes with identifying research needs. The observational and experimental studies reviewed suggested some association between (1-->3)-beta-D-glucan exposure, airway inflammation and symptoms, however, results were mixed and specific symptoms and potential underlying inflammatory mechanisms associated with exposure could not be identified. Large observational studies using well validated exposure assessment methods are needed to further our knowledge regarding the potential health effects of indoor (1-->3)-beta-D-glucan exposure. PRACTICAL IMPLICATIONS: The currently available epidemiological data do not permit conclusions to be drawn regarding the presence (or absence) of an association between environmental (1-->3)-beta-D-glucan exposure and specific adverse health effects, nor is it clear from the currently available evidence which specific immunological mechanisms underlie the presumed health effects. More and larger observational studies are needed to asses whether (1-->3)-beta-D-glucan exposure plays a significant role in respiratory morbidity. In addition, existing methods to assess environmental (1-->3)-beta-D-glucan exposure require validation and further development before they can be used routinely in large scale epidemiological studies.
    Indoor Air 06/2005; 15(3):160-9. · 4.20 Impact Factor
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    ABSTRACT: Growing up on a farm and an anthroposophic lifestyle are associated with a lower prevalence of allergic diseases in childhood. It has been suggested that the enhanced exposure to endotoxin is an important protective factor of farm environments. Little is known about exposure to other microbial components on farms and exposure in anthroposophic families. To assess the levels and determinants of bacterial endotoxin, mould beta(1,3)-glucans and fungal extracellular polysaccharides (EPS) in house dust of farm children, Steiner school children and reference children. Mattress and living room dust was collected in the homes of 229 farm children, 122 Steiner children and 60 and 67 of their respective reference children in five European countries. Stable dust was collected as well. All samples were analysed in one central laboratory. Determinants were assessed by questionnaire. Levels of endotoxin, EPS and glucans per gram of house dust in farm homes were 1.2- to 3.2-fold higher than levels in reference homes. For Steiner children, 1.1- to 1.6-fold higher levels were observed compared with their reference children. These differences were consistently found across countries, although mean levels varied considerably. Differences between groups and between countries were also significant after adjustment for home and family characteristics. Farm children are not only consistently exposed to higher levels of endotoxin, but also to higher levels of mould components. Steiner school children may also be exposed to higher levels of microbial agents, but differences with reference children are much less pronounced than for farm children. Further analyses are, however, required to assess the association between exposure to these various microbial agents and allergic and airway diseases in the PARSIFAL population.
    Allergy 06/2005; 60(5):611-8. · 6.00 Impact Factor
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    ABSTRACT: A few studies have compared indoor allergens and endotoxin levels between urban and rural settings as important determinants for asthma and atopy in children. However, no study was done in the Middle East or investigated refugee camps. As part of a nested case-control study in Ramallah in 2001, we measured house dust mite and pet allergens, as well as endotoxin in dust collected from 110 children's mattresses and living room floors. Geometric mean (GM) concentrations of Dermatophagoides pteronyssinus (Der p1) antigen were 4.48 microg/g in mattress dust and 1.23 microg/g floor dust. The highest Der p1 levels were seen in refugee camps. Concentrations of Dermatophagoides farinae antigen (Der f1) were much lower (<0.08 microg/g dust). Concentrations of cat allergen (Fel d1) were highest in villages, and those of dog allergen (Can f1) were highest in mattresses from cities and in floor dust from refugee camps. GM of endotoxin levels were 25.7 EU/mg in mattress dust and 49 EU/mg dust in floor dust. Concentrations of Der p1 were high compared to Western European countries, but were lower compared to UK and Australia. Levels of pet allergens were lower than in Western Europe. Endotoxin levels were higher compared to developed countries. Indoor environmental factors such as dampness seemed to be important determinants for allergen and endotoxin, but living habits such as lack of mattress cover appeared unimportant.
    Allergy 07/2004; 59(6):623-31. · 6.00 Impact Factor

Publication Stats

4k Citations
498.47 Total Impact Points

Institutions

  • 2003–2014
    • Massey University
      • Centre for Public Health Research
      Palmerston North City, Manawatu-Wanganui, New Zealand
    • University of Otago
      • Welllington Cardiovascular Research Group
      Taieri, Otago Region, New Zealand
    • Friedrich-Schiller-University Jena
      • Institute of Immunology
      Jena, Thuringia, Germany
  • 2011
    • California Department of Public Health
      • Environmental Health Laboratory Branch (EHLB)
      California City, CA, United States
  • 2009
    • University of Birmingham
      • School of Geography, Earth and Environmental Sciences
      Birmingham, ENG, United Kingdom
  • 2004–2009
    • National Institute of Occupational Health (STAMI)
      • Department of Chemical and Biological Work Environment
      Oslo, Oslo, Norway
  • 2001–2009
    • Universiteit Utrecht
      • Institute for Risk Assessment Sciences (IRAS)
      Utrecht, Provincie Utrecht, Netherlands
    • Columbia University
      • Department of Environmental Health Sciences
      New York City, NY, United States
  • 2006
    • The Chinese University of Hong Kong
      • Department of Paediatrics
      Hong Kong, Hong Kong
  • 2000
    • University of Iowa
      • Department of Occupational and Environmental Health
      Iowa City, Iowa, United States
    • Kuopio University Hospital
      Kuopio, Eastern Finland Province, Finland
  • 1993–2000
    • Wageningen University
      Wageningen, Gelderland, Netherlands
  • 1996
    • University of Amsterdam
      • Department of Molecular Cell Biology
      Amsterdamo, North Holland, Netherlands