Dick Heederik - Academia.edu (original) (raw)

Papers by Dick Heederik

A cross-sectional study was conducted among 393 workers from 21 bakeries to study the relationshi... more A cross-sectional study was conducted among 393 workers from 21 bakeries to study the relationship between wheat allergen exposure and wheat sensitization and work-related allergic symptoms. Ex- posure to wheat allergens was characterized by a recently developed and validated immunoassay. Specific IgE antibodies against wheat flour and common allergens were measured by immunoassays, and work-related allergic symptoms were registered by

International Journal of Adaptive Control and Signal Processing, 1997

Animal Reproduction Science, 1997

ABSTRACT Endotoxins are part of the outer membrane of Gram-negative bacteria and are present ubiq... more ABSTRACT Endotoxins are part of the outer membrane of Gram-negative bacteria and are present ubiquitously in the environment. The lipopolysaccharide (LPS) part of the molecule is responsible for its toxic properties. Environmental monitoring is usually performed by sampling airborne dust and subsequent analysis of aqueous extracts by using a LAL assay. The kinetic version of this assay can measure concentrations as low as in the pg/m3 range. A generally accepted protocol is not yet available. Endotoxin levels are related to the occurrence of Gram-negative bacteria. Animal faeces and bacteria contaminated plant materials contribute most to organic dust related endotoxin exposure. Endotoxin exposure is therefore most prevalent in agricultural and related industries. Acute health effects are dry cough and shortness of breath accompanied by a decrease in lung function, fever reaction and malaise, and sometimes dyspnea and headaches occurring a few hours after the start of the endotoxin exposure. Epidemiological and experimental studies suggest that chronic endotoxin exposure may lead to chronic bronchitis and reduced lung function. Depending of the relevant health effect, no effect levels range from 9 to 170 ng/m3. The Dutch Expert Committee on Occupational Standards (DECOS) of the National Health Council proposed a health based recommended limit value of 50 Endotoxin Units/m3 (4.5 ng/m3) over an 8 hour exposure period.

Occupational and environmental medicine, Jan 28, 2015

Indoor Air, 2015

Aiming to identify factors causing the adverse health effects associated with moisture damaged in... more Aiming to identify factors causing the adverse health effects associated with moisture damaged indoor environments, we analyzed immunotoxicological potential of settled dust from moisture damaged and reference schools in relation to their microbiological composition. Mouse RAW264.7 macrophages were exposed to settled dust samples (n= 25) collected from moisture damaged and reference schools in Spain, The Netherlands and Finland. After exposure, we analyzed production of inflammatory markers [nitric oxide (NO), tumor necrosis factor (TNF)α, interleukin (IL)-6 and macrophage inflammatory protein (MIP)2] as well as mitochondrial activity, viability, apoptosis and cell cycle arrest. Furthermore, particle counts, concentration of selected microbial groups as well as chemical markers ergosterol, 3-hydroxy fatty acids, muramic acid, endotoxins and glucans were measured as markers of exposure. Dust from moisture damaged schools in Spain and The Netherlands induced stronger immunotoxicological responses compared to samples from reference schools; the responses to Finnish samples were generally lower with no difference between the schools. In multivariate analysis, IL-6 and apoptosis responses were most strongly associated with moisture status of the school. The measured responses correlated with several microbial markers and numbers of particles, but the most important predictor of the immunotoxicological potential of settled dust was muramic acid concentration, a marker of Gram positive bacteria. This article is protected by copyright. All rights reserved.

PLOS ONE, 2015

This prospective cohort study describes carriage of livestock-associated methicillin-resistant St... more This prospective cohort study describes carriage of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in household members from 49 farrowing pig farms in the Netherlands (2010-2011). Of 171 household members, 4% were persistent MRSA nasal carriers, and the MRSA prevalence on any given sampling moment was 10% (range 7-11%). Working in the stables (of which 98% was MRSA-positive, prevalence ratio (PR) = 2.11 per 10 hours), working with sows (PR=1.97), and living with an MRSA-positive pig farmer (PR=4.63) were significant determinants for MRSA carriage. Significant protective factors were carriage of methicillin-susceptible Staphylococcus aureus (MSSA) (PR=0.50), and wearing a facemask when working in the stables (37% decreased prevalence). All MRSA strains during the study period were known livestock-associated types. The bacteriophage φ3 was not found in household members. Transmission from pigs and the environment appeared to be important determinants; human-to-human transmission could not sufficiently be differentiated. Wearing a facemask when working in the stables and carriage of MSSA are potential interventional targets.

Occupational and Environmental Medicine, 2000

OBJECTIVESThis study was part of the East African pesticides project. The general objective was t... more OBJECTIVESThis study was part of the East African pesticides project. The general objective was to assess health hazards posed by handling, storage, and use of pesticides, on agricultural estates and small farms with a view to developing strategies for prevention and control of pesticide poisoning. The aim of this paper is to describe the prevalence of symptoms in this population,

Occupational and environmental medicine, 2014

Respiratory health effects of damp housing are well recognised, but less is known about the effec... more Respiratory health effects of damp housing are well recognised, but less is known about the effect of dampness and water damage in schools. The HITEA study previously reported a higher prevalence of respiratory symptoms in pupils from moisture damaged schools, but the role of specific microbial exposures remained unclear. To study associations between school dampness, levels of fungal and bacterial markers, respiratory symptoms and lung function in children. Primary schools in Spain, the Netherlands and Finland were selected on the basis of the observed presence (n=15) or absence (n=10) of moisture, dampness and/or mould. Settled dust was repeatedly sampled in 232 classrooms and levels of 14 different microbial markers and groups of microbes were determined. Parental reports of respiratory symptoms were available from 3843 children aged 6-12 years, of whom 2736 provided acceptable forced spirometry testing. Country-specific associations between exposure and respiratory health were e...

Occupational and environmental medicine, 2014

A multidisciplinary intervention study aimed at reducing quartz exposure in the Dutch constructio... more A multidisciplinary intervention study aimed at reducing quartz exposure in the Dutch construction industry was performed. We aimed to assess the effect of the intervention on exposure level and psycho-social and organisational factors. Eight participating construction companies were randomly allocated to an intervention (n = 4) or control group (n = 4). Following the Intervention Mapping approach, the intervention aimed at engineering, organisational and psycho-social factors. Pre and post-intervention respirable quartz measurements (n = 300) were taken from workers from all eight companies. Questionnaires and observation forms were used to assess pre and post psycho-social and organisational factors. Pre-intervention assessment demonstrated highest respirable quartz levels for concrete drillers, tuck pointers and demolishers (GM respectively 0.20, 0.18 and 0.12 mg/m(3)), exceeding the Dutch occupational exposure limit (OEL) in 62% of the measurements. Identified control measures r...

Occupational and environmental medicine, 2014

Soluble platinum salts are well known respiratory sensitising agents leading to work related sens... more Soluble platinum salts are well known respiratory sensitising agents leading to work related sensitisation in the work environment. No quantitative exposure response relation has been described for soluble platinum salts. The objective of this study was to explore exposure response relations for soluble platinum salt exposed workers. A retrospective cohort study was conducted using routinely collected health surveillance data and soluble platinum exposure data. Workers who newly entered between 1 January 2000 and 31 December 2010 were included and the relation between measured soluble platinum exposure and sensitisation (as determined by skin prick testing) was analysed in more than 1000 refinery workers from 5 refineries from whom a total of more than 1700 personal exposure measurements were available. Exposure response relations were analysed in survival analysis considering changes in exposure over time. Associations were explored for present exposure, cumulative exposure and ave...

The Annals of occupational hygiene, 2014

Quartz exposure can cause several respiratory health effects. Although quartz exposure has been d... more Quartz exposure can cause several respiratory health effects. Although quartz exposure has been described in several observational workplace studies, well-designed intervention studies that investigate the effect of control strategies are lacking. This article describes a baseline exposure study that is part of a multidimensional intervention program aiming to reduce quartz exposure among construction workers. In this study, personal respirable dust and quartz exposure was assessed among 116 construction workers (bricklayers, carpenters, concrete drillers, demolishers, and tuck pointers). Possible determinants of exposure, like job, tasks, and work practices, use of control measures, and organizational and psychosocial factors, were explored using exposure models for respirable dust and quartz separately. Stratified analyses by job title were performed to evaluate the effect of control measures on exposure and to explore the association between control measures and psychosocial fact...

American Industrial Hygiene Association journal, 1998

Exposure to high airborne levels of noninfectious microorganisms is recognized as a cause of resp... more Exposure to high airborne levels of noninfectious microorganisms is recognized as a cause of respiratory symptoms and disease among workers handling biological materials, such as farmers, sawmill workers, and workers handling municipal waste and fuel chips. Risk assessment is difficult because occupational exposure limits for noninfectious microorganisms have not been established. Many different methods are used for the measurement of airborne microorganisms, which are based on impaction, impingement, or filtration. Samples can be analyzed by methods that are culture-based or nonculture-based and that may estimate different microbial entities: culturable microorganisms by culture-based methods, microbial cells by microscopic methods, and microbial constituents and products by chemical, biochemical and immunochemical methods. Sources of errors and validation studies of these methods are reviewed and methods are evaluated for exposure assessment in epidemiological studies and for futu...

Occupational and Environmental Medicine, 2014

The Annals of occupational hygiene, 2014

Construction workers are at risk of developing occupational contact dermatitis. Gloves, when used... more Construction workers are at risk of developing occupational contact dermatitis. Gloves, when used properly, may protect against chemicals and coarse materials. We investigated the prevalence and determinants of contact dermatitis in a population of Dutch construction workers and aimed at validating questionnaire items on hand hygiene. A cross-sectional study was conducted at 13 construction sites, yielding data of 177 subjects (95% response rate). A questionnaire covering questions on hand hygiene and contact dermatitis symptoms was used. Agreement between workplace observations and a number of questionnaire items was assessed by calculating Cohen's kappa. Log-binomial regression analysis was used to assess the association between contact dermatitis and various hand hygiene-related determinants. The 1-year prevalence of self-reported contact dermatitis in our study sample was 46.9%. Multiple regression analysis showed a positive association with difficulties with hand cleaning (...

Annals of Agricultural and Environmental Medicine, 2015

Occupational and environmental medicine, Jan 10, 2014

Numerous environmental contaminants have been linked to adverse reproductive health outcomes. How... more Numerous environmental contaminants have been linked to adverse reproductive health outcomes. However, the complex correlation structure of exposures and multiple testing issues limit the interpretation of existing evidence. Our objective was to identify, from a large set of contaminant exposures, exposure profiles associated with biomarkers of male reproductive function. In this cross-sectional study (n=602), male partners of pregnant women were enrolled between 2002 and 2004 during antenatal care visits in Greenland, Poland and Ukraine. Fifteen contaminants were detected in more than 70% of blood samples, including metabolites of di(2-ethylhexyl) and diisononyl phthalates (DEHP, DiNP), perfluoroalkyl acids, metals and organochlorines. Twenty-two reproductive biomarkers were assessed, including serum levels of reproductive hormones, markers of semen quality, sperm chromatin integrity, epididymal and accessory sex gland function, and Y:X chromosome ratio. We evaluated multipollutant...

American Industrial Hygiene Association Journal, 1996

The effect of different materials and methods for filter elution on potato antigen yield was stud... more The effect of different materials and methods for filter elution on potato antigen yield was studied using parallel airborne dust samples from a potato processing plant. Sonication plus vortexing showed on average a 13% higher yield than gentle shaking. Type of filter (glass fiber or Teflon®), elution buffer (phosphate or bicarbonate), and the addition of 0.05% Tween–20 to the elution buffer had no significant effect on antigen yield. Addition of 0.5% Tween–20 instead of 0.05% resulted in a mean increase of 11%. The authors conclude that potato antigens can be readily eluted from airborne dust sampled on filters, and that the type of filter, elution buffer, and elution conditions have little effect on elution efficiency. Similar studies should be performed for other antigens of interest.

The European respiratory journal, 2014

Recently, a locus centred on rs9273349 in the HLA-DQ region emerged from genome-wide association ... more Recently, a locus centred on rs9273349 in the HLA-DQ region emerged from genome-wide association studies of adult-onset asthma. We aimed to further investigate the role of human leukocyte antigen (HLA) class II in adult-onset asthma and a possible interaction with occupational exposures. We imputed classical HLA-II alleles from 7579 single-nucleotide polymorphisms in 6025 subjects (1202 with adult-onset asthma) from European cohorts: ECRHS, SAPALDIA, EGEA and B58C, and from surveys of bakers and agricultural workers. Based on an asthma-specific job-exposure matrix, 2629 subjects had ever been exposed to high molecular weight (HMW) allergens. We explored associations between 23 common HLA-II alleles and adult-onset asthma, and tested for gene-environment interaction with occupational exposure to HMW allergens. Interaction was also tested for rs9273349. Marginal associations of classical HLA-II alleles and adult-onset asthma were not statistically significant. Interaction was detected...

A cross-sectional study was conducted among 393 workers from 21 bakeries to study the relationshi... more A cross-sectional study was conducted among 393 workers from 21 bakeries to study the relationship between wheat allergen exposure and wheat sensitization and work-related allergic symptoms. Ex- posure to wheat allergens was characterized by a recently developed and validated immunoassay. Specific IgE antibodies against wheat flour and common allergens were measured by immunoassays, and work-related allergic symptoms were registered by

International Journal of Adaptive Control and Signal Processing, 1997

Animal Reproduction Science, 1997

ABSTRACT Endotoxins are part of the outer membrane of Gram-negative bacteria and are present ubiq... more ABSTRACT Endotoxins are part of the outer membrane of Gram-negative bacteria and are present ubiquitously in the environment. The lipopolysaccharide (LPS) part of the molecule is responsible for its toxic properties. Environmental monitoring is usually performed by sampling airborne dust and subsequent analysis of aqueous extracts by using a LAL assay. The kinetic version of this assay can measure concentrations as low as in the pg/m3 range. A generally accepted protocol is not yet available. Endotoxin levels are related to the occurrence of Gram-negative bacteria. Animal faeces and bacteria contaminated plant materials contribute most to organic dust related endotoxin exposure. Endotoxin exposure is therefore most prevalent in agricultural and related industries. Acute health effects are dry cough and shortness of breath accompanied by a decrease in lung function, fever reaction and malaise, and sometimes dyspnea and headaches occurring a few hours after the start of the endotoxin exposure. Epidemiological and experimental studies suggest that chronic endotoxin exposure may lead to chronic bronchitis and reduced lung function. Depending of the relevant health effect, no effect levels range from 9 to 170 ng/m3. The Dutch Expert Committee on Occupational Standards (DECOS) of the National Health Council proposed a health based recommended limit value of 50 Endotoxin Units/m3 (4.5 ng/m3) over an 8 hour exposure period.

Occupational and environmental medicine, Jan 28, 2015

Indoor Air, 2015

Aiming to identify factors causing the adverse health effects associated with moisture damaged in... more Aiming to identify factors causing the adverse health effects associated with moisture damaged indoor environments, we analyzed immunotoxicological potential of settled dust from moisture damaged and reference schools in relation to their microbiological composition. Mouse RAW264.7 macrophages were exposed to settled dust samples (n= 25) collected from moisture damaged and reference schools in Spain, The Netherlands and Finland. After exposure, we analyzed production of inflammatory markers [nitric oxide (NO), tumor necrosis factor (TNF)α, interleukin (IL)-6 and macrophage inflammatory protein (MIP)2] as well as mitochondrial activity, viability, apoptosis and cell cycle arrest. Furthermore, particle counts, concentration of selected microbial groups as well as chemical markers ergosterol, 3-hydroxy fatty acids, muramic acid, endotoxins and glucans were measured as markers of exposure. Dust from moisture damaged schools in Spain and The Netherlands induced stronger immunotoxicological responses compared to samples from reference schools; the responses to Finnish samples were generally lower with no difference between the schools. In multivariate analysis, IL-6 and apoptosis responses were most strongly associated with moisture status of the school. The measured responses correlated with several microbial markers and numbers of particles, but the most important predictor of the immunotoxicological potential of settled dust was muramic acid concentration, a marker of Gram positive bacteria. This article is protected by copyright. All rights reserved.

PLOS ONE, 2015

This prospective cohort study describes carriage of livestock-associated methicillin-resistant St... more This prospective cohort study describes carriage of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in household members from 49 farrowing pig farms in the Netherlands (2010-2011). Of 171 household members, 4% were persistent MRSA nasal carriers, and the MRSA prevalence on any given sampling moment was 10% (range 7-11%). Working in the stables (of which 98% was MRSA-positive, prevalence ratio (PR) = 2.11 per 10 hours), working with sows (PR=1.97), and living with an MRSA-positive pig farmer (PR=4.63) were significant determinants for MRSA carriage. Significant protective factors were carriage of methicillin-susceptible Staphylococcus aureus (MSSA) (PR=0.50), and wearing a facemask when working in the stables (37% decreased prevalence). All MRSA strains during the study period were known livestock-associated types. The bacteriophage φ3 was not found in household members. Transmission from pigs and the environment appeared to be important determinants; human-to-human transmission could not sufficiently be differentiated. Wearing a facemask when working in the stables and carriage of MSSA are potential interventional targets.

Occupational and Environmental Medicine, 2000

OBJECTIVESThis study was part of the East African pesticides project. The general objective was t... more OBJECTIVESThis study was part of the East African pesticides project. The general objective was to assess health hazards posed by handling, storage, and use of pesticides, on agricultural estates and small farms with a view to developing strategies for prevention and control of pesticide poisoning. The aim of this paper is to describe the prevalence of symptoms in this population,

Occupational and environmental medicine, 2014

Respiratory health effects of damp housing are well recognised, but less is known about the effec... more Respiratory health effects of damp housing are well recognised, but less is known about the effect of dampness and water damage in schools. The HITEA study previously reported a higher prevalence of respiratory symptoms in pupils from moisture damaged schools, but the role of specific microbial exposures remained unclear. To study associations between school dampness, levels of fungal and bacterial markers, respiratory symptoms and lung function in children. Primary schools in Spain, the Netherlands and Finland were selected on the basis of the observed presence (n=15) or absence (n=10) of moisture, dampness and/or mould. Settled dust was repeatedly sampled in 232 classrooms and levels of 14 different microbial markers and groups of microbes were determined. Parental reports of respiratory symptoms were available from 3843 children aged 6-12 years, of whom 2736 provided acceptable forced spirometry testing. Country-specific associations between exposure and respiratory health were e...

Occupational and environmental medicine, 2014

A multidisciplinary intervention study aimed at reducing quartz exposure in the Dutch constructio... more A multidisciplinary intervention study aimed at reducing quartz exposure in the Dutch construction industry was performed. We aimed to assess the effect of the intervention on exposure level and psycho-social and organisational factors. Eight participating construction companies were randomly allocated to an intervention (n = 4) or control group (n = 4). Following the Intervention Mapping approach, the intervention aimed at engineering, organisational and psycho-social factors. Pre and post-intervention respirable quartz measurements (n = 300) were taken from workers from all eight companies. Questionnaires and observation forms were used to assess pre and post psycho-social and organisational factors. Pre-intervention assessment demonstrated highest respirable quartz levels for concrete drillers, tuck pointers and demolishers (GM respectively 0.20, 0.18 and 0.12 mg/m(3)), exceeding the Dutch occupational exposure limit (OEL) in 62% of the measurements. Identified control measures r...

Occupational and environmental medicine, 2014

Soluble platinum salts are well known respiratory sensitising agents leading to work related sens... more Soluble platinum salts are well known respiratory sensitising agents leading to work related sensitisation in the work environment. No quantitative exposure response relation has been described for soluble platinum salts. The objective of this study was to explore exposure response relations for soluble platinum salt exposed workers. A retrospective cohort study was conducted using routinely collected health surveillance data and soluble platinum exposure data. Workers who newly entered between 1 January 2000 and 31 December 2010 were included and the relation between measured soluble platinum exposure and sensitisation (as determined by skin prick testing) was analysed in more than 1000 refinery workers from 5 refineries from whom a total of more than 1700 personal exposure measurements were available. Exposure response relations were analysed in survival analysis considering changes in exposure over time. Associations were explored for present exposure, cumulative exposure and ave...

The Annals of occupational hygiene, 2014

Quartz exposure can cause several respiratory health effects. Although quartz exposure has been d... more Quartz exposure can cause several respiratory health effects. Although quartz exposure has been described in several observational workplace studies, well-designed intervention studies that investigate the effect of control strategies are lacking. This article describes a baseline exposure study that is part of a multidimensional intervention program aiming to reduce quartz exposure among construction workers. In this study, personal respirable dust and quartz exposure was assessed among 116 construction workers (bricklayers, carpenters, concrete drillers, demolishers, and tuck pointers). Possible determinants of exposure, like job, tasks, and work practices, use of control measures, and organizational and psychosocial factors, were explored using exposure models for respirable dust and quartz separately. Stratified analyses by job title were performed to evaluate the effect of control measures on exposure and to explore the association between control measures and psychosocial fact...

American Industrial Hygiene Association journal, 1998

Exposure to high airborne levels of noninfectious microorganisms is recognized as a cause of resp... more Exposure to high airborne levels of noninfectious microorganisms is recognized as a cause of respiratory symptoms and disease among workers handling biological materials, such as farmers, sawmill workers, and workers handling municipal waste and fuel chips. Risk assessment is difficult because occupational exposure limits for noninfectious microorganisms have not been established. Many different methods are used for the measurement of airborne microorganisms, which are based on impaction, impingement, or filtration. Samples can be analyzed by methods that are culture-based or nonculture-based and that may estimate different microbial entities: culturable microorganisms by culture-based methods, microbial cells by microscopic methods, and microbial constituents and products by chemical, biochemical and immunochemical methods. Sources of errors and validation studies of these methods are reviewed and methods are evaluated for exposure assessment in epidemiological studies and for futu...

Occupational and Environmental Medicine, 2014

The Annals of occupational hygiene, 2014

Construction workers are at risk of developing occupational contact dermatitis. Gloves, when used... more Construction workers are at risk of developing occupational contact dermatitis. Gloves, when used properly, may protect against chemicals and coarse materials. We investigated the prevalence and determinants of contact dermatitis in a population of Dutch construction workers and aimed at validating questionnaire items on hand hygiene. A cross-sectional study was conducted at 13 construction sites, yielding data of 177 subjects (95% response rate). A questionnaire covering questions on hand hygiene and contact dermatitis symptoms was used. Agreement between workplace observations and a number of questionnaire items was assessed by calculating Cohen's kappa. Log-binomial regression analysis was used to assess the association between contact dermatitis and various hand hygiene-related determinants. The 1-year prevalence of self-reported contact dermatitis in our study sample was 46.9%. Multiple regression analysis showed a positive association with difficulties with hand cleaning (...

Annals of Agricultural and Environmental Medicine, 2015

Occupational and environmental medicine, Jan 10, 2014

Numerous environmental contaminants have been linked to adverse reproductive health outcomes. How... more Numerous environmental contaminants have been linked to adverse reproductive health outcomes. However, the complex correlation structure of exposures and multiple testing issues limit the interpretation of existing evidence. Our objective was to identify, from a large set of contaminant exposures, exposure profiles associated with biomarkers of male reproductive function. In this cross-sectional study (n=602), male partners of pregnant women were enrolled between 2002 and 2004 during antenatal care visits in Greenland, Poland and Ukraine. Fifteen contaminants were detected in more than 70% of blood samples, including metabolites of di(2-ethylhexyl) and diisononyl phthalates (DEHP, DiNP), perfluoroalkyl acids, metals and organochlorines. Twenty-two reproductive biomarkers were assessed, including serum levels of reproductive hormones, markers of semen quality, sperm chromatin integrity, epididymal and accessory sex gland function, and Y:X chromosome ratio. We evaluated multipollutant...

American Industrial Hygiene Association Journal, 1996

The effect of different materials and methods for filter elution on potato antigen yield was stud... more The effect of different materials and methods for filter elution on potato antigen yield was studied using parallel airborne dust samples from a potato processing plant. Sonication plus vortexing showed on average a 13% higher yield than gentle shaking. Type of filter (glass fiber or Teflon®), elution buffer (phosphate or bicarbonate), and the addition of 0.05% Tween–20 to the elution buffer had no significant effect on antigen yield. Addition of 0.5% Tween–20 instead of 0.05% resulted in a mean increase of 11%. The authors conclude that potato antigens can be readily eluted from airborne dust sampled on filters, and that the type of filter, elution buffer, and elution conditions have little effect on elution efficiency. Similar studies should be performed for other antigens of interest.

The European respiratory journal, 2014

Recently, a locus centred on rs9273349 in the HLA-DQ region emerged from genome-wide association ... more Recently, a locus centred on rs9273349 in the HLA-DQ region emerged from genome-wide association studies of adult-onset asthma. We aimed to further investigate the role of human leukocyte antigen (HLA) class II in adult-onset asthma and a possible interaction with occupational exposures. We imputed classical HLA-II alleles from 7579 single-nucleotide polymorphisms in 6025 subjects (1202 with adult-onset asthma) from European cohorts: ECRHS, SAPALDIA, EGEA and B58C, and from surveys of bakers and agricultural workers. Based on an asthma-specific job-exposure matrix, 2629 subjects had ever been exposed to high molecular weight (HMW) allergens. We explored associations between 23 common HLA-II alleles and adult-onset asthma, and tested for gene-environment interaction with occupational exposure to HMW allergens. Interaction was also tested for rs9273349. Marginal associations of classical HLA-II alleles and adult-onset asthma were not statistically significant. Interaction was detected...