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Biomedical subjects

Jeroen Douwes

Publications and source records attributed to Jeroen Douwes.

At least 19 recordsLinked to original sources
PubMed2006

Hay fever and asthma symptoms in conventional and organic farmers in The Netherlands.

BACKGROUND: Farming has been associated with respiratory symptoms and with protection against atopy. To date, effects of organic farming on respiratory health have not been studied. AIMS: To (1) compare hay fever and asthma-like symptoms in organic and conventional farmers and (2) assess associations between current and childhood farm exposures and respiratory health effects by conducting a survey. METHODS: Questionnaire data from 1205 conventional and 593 organic farmers were evaluated. Associations between health effects and farm exposures were assessed by logistic regression analyses. RESULTS: Organic farmers reported less wheezing with shortness of breath and slightly more hay fever than conventional farmers. However, organic farming was not an independent determinant of hay fever when adjusted for farming practices and potential confounders. Livestock farmers who grew up on a farm had a threefold lower prevalence of hay fever than crop farmers without a farm childhood (odds ratio (OR) 0.3, 95% confidence interval (CI) 0.1 to 0.5). Both crop farmers who grew up on a farm and livestock farmers who did not grow up on a farm had a reduced prevalence, although less pronounced and not statistically significant. Use of disinfectants containing quaternary ammonium compounds was positively related to hay fever (OR 2.1, 95% CI 1 to 4.4). No effects of farming practices were found for asthma. CONCLUSIONS: Our study adds to the evidence that a farm childhood in combination with current livestock farming protects against allergic disorders. This effect was found for both organic and conventional farmers.

Adult↗
PubMed2006

Innate immune activation in neutrophilic asthma and bronchiectasis.

BACKGROUND: The role of the innate immune system in the pathogenesis of asthma is unclear. Activation of innate immune receptors in response to bacterial lipopolysaccharide, viral infection and particulate matter triggers a pre-programmed inflammatory response, which involves interleukin (IL)8 and neutrophil influx. The inflammatory response in asthma is heterogeneous. AIM: To test the hypothesis that innate immune activation may be a relevant inflammatory mechanism in neutrophilic asthma where IL8 levels are increased. METHODS: Induced sputum was obtained from non-smoking adults with asthma (n = 49), healthy controls (n = 13) and a positive reference group with bronchiectasis (n = 9). Subjects with asthma were classified into inflammatory subtypes using induced sputum cell counts. Sputum was examined for mRNA expression of the innate immune receptors toll-like receptor (TLR)2, TLR4 and CD14, and inflammatory cytokines. A separate sputum portion was dispersed and the supernatant assayed for surfactant protein A, IL8, soluble CD14 and endotoxin. RESULTS: Expression of innate immune receptors was increased in subjects with bronchiectasis and neutrophilic asthma compared with other asthma subtypes and controls. Increased expression of the receptors TLR2, TLR4 and CD14, as well as the pro-inflammatory cytokines IL8 and IL1beta, was observed. Subjects with neutrophilic asthma had higher airway levels of endotoxin than the other groups studied. CONCLUSION: There is evidence of activation of the innate immune system in asthma which results in the production of pro-inflammatory cytokines and may contribute to the pathogenesis of neutrophilic asthma.

Adult↗
PubMed2006

Does early indoor microbial exposure reduce the risk of asthma? The Prevention and Incidence of Asthma and Mite Allergy birth cohort study.

BACKGROUND: Exposure to microbial agents might inhibit the development of atopy and asthma. OBJECTIVE: We measured the association between microbial exposure assessed at 3 months and the development of atopic sensitization and doctor-diagnosed (DD) asthma and wheeze in the first 4 years in a birth cohort study of children with atopic mothers. METHODS: Endotoxin, fungal (1-->3)-beta-D-glucans, extracellular polysaccharides from the genera Penicillium and Aspergillus (EPS-Pen/Asp), and dust on living room floors were measured at 3 months of age. Serum IgE levels against common allergens were determined at 1 and 4 years, and questionnaire information about respiratory morbidity was collected yearly. RESULTS: Microbial levels in mattresses were low and not associated with serum IgE levels, DD asthma, and wheeze. Floor levels of biocontaminants and dust, on the other hand, were inversely associated with DD asthma, being most pronounced for endotoxin (odds ratio [OR], 0.40; 95% CI, 0.21-0.77) and EPS-Pen/Asp (OR, 0.42; 95% CI, 0.18-0.99). Mutual adjustment for other exposures did not significantly alter the results for endotoxin and only moderately affected the results for EPS-Pen/Asp. Persistent wheeze was also consistently less common in the high-exposure group, being significant only for EPS-Pen/Asp (OR, 0.37; 95% CI, 0.15-0.96). Transient wheeze and wheeze in the past 12 months were also reduced, but effects were smaller and not significant. Relationships with serum-specific IgE levels, which could only be assessed in 41% at age 4 years, were less pronounced and statistically significant only for EPS-Pen/Asp. CONCLUSIONS: Early exposure to common microbial contaminants, including fungal agents, might protect against asthma. CLINICAL IMPLICATIONS: Microbial exposure in early life might protect against asthma and might constitute a novel target for prevention.

Allergens↗
PubMed2006

Childhood asthma and indoor aeroallergens and endotoxin in Palestine: a case-control study.

This study was carried out to evaluate the relationship between wheezing or sensitization and concentrations of mites, cat and dog allergens, and bacterial endotoxin in Palestine. A nested case-control involved analysis of mattress and floor dust from a 110 children's houses with reported wheezing and without wheezing. We found no consistent associations between allergen levels and either wheeze or specific atopic sensitization. Furthermore, no clear associations between mattress endotoxin levels and wheeze or atopy were found. Endotoxin in floor dust was inversely associated with atopic sensitization and wheeze, statistically significant only for atopic wheeze. Finally, a nonsignificant inverse association was observed between living room endotoxin and atopy within the non-wheezing control group. In conclusion, although our study found mostly negative results, it does suggest that endotoxin on living room floors might protect against atopic wheeze. However, this finding should be interpreted with caution due the relatively small sample size of the study and requires further confirmation.

Air Pollutants↗
PubMed2006

Endotoxin, (1 --> 3)-beta-D-glucans and fungal extra-cellular polysaccharides in New Zealand homes: a pilot study.

Bacterial endotoxin, fungal (1 --> 3)-beta-D-glucans, and extracellular polysaccharides from Aspergillus and Penicillium (EPS-Asp/Pen) have been suggested to be stable markers of microbial exposure. This paper describes a pilot study in which we measured endotoxin, (1 --> 3)-beta-D-glucans, EPS-Asp/Pen and mite allergen in house dust collected in 32 homes in Wellington, New Zealand. Endotoxin (GM 60,295 EU/g; GSD 2.4) and glucan (GM 2,687 microg/g; GSD 1.5) levels were higher in comparison to previous international studies, whereas EPS-Asp/Pen levels (37,347 Units/g; GSD 1.9) appeared comparable. Concentrations expressed per square meter were highly correlated among the measured components (p < 0.05). When expressed per gram of dust only (1 --> 3)- beta -D-glucans and EPS-Asp/Pen were correlated (r=0.55, p < 0.01; n=32). Endotoxin and glucan levels were higher (borderline statistically significant; p < 0.10) in homes with self-reported water damage. A positive association (p < 0.10) was also found for dust mite and a combination of self-reported mould, dampness and water damage. EPS levels were higher in homes where residents indicated the presence of mould spots on the wall, but this did not reach statistical significance. In conclusion, levels of microbial contaminants in a small random sample of New Zealand homes were high and weakly associated with water damage.

Air Pollution, Indoor↗
PubMed2005

Interlaboratory evaluation of endotoxin analyses in agricultural dusts--comparison of LAL assay and mass spectrometry.

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.

Aerosols↗
PubMed2005

Overview of personal occupational exposure levels to inhalable dust, endotoxin, beta(1-->3)-glucan and fungal extracellular polysaccharides in the waste management chain.

INTRODUCTION: In the past decade, we studied occupational bioaerosol exposures in various sites of the waste management chain. In this paper we present an overview of exposure levels of inhalable dust, endotoxin, beta(1-->3)-glucan (known or probable inducers of airways inflammation), and extracellular polysaccharide antigens of Aspergillus and Penicillium species (EPS-Pen/Asp; a common and probably more specific marker of fungal exposure). METHODS: Over 450 personal bioaerosol samples were taken. Mixed regression analyses were performed to estimate exposure determinants, between- and within-worker variance of exposure, and determinants of these variances. Furthermore, we explored whether the type of waste affected the bioaerosol composition of the dust. RESULTS: Endotoxin and glucan exposure levels were relatively low and comparable for waste collection and transferral, green waste composting and use of biomass in power plants. Exposure levels were 5-20 times higher in domestic waste transferral with sorting, and composting of both domestic and domestic and green waste ( approximately 300-1000 EU m(-3) for endotoxin, and 5-10 mug m(-3) for glucan). Observed exposure exceeded Dutch occupational exposure limits at all sites. EPS-Pen/Asp exposure was detected in 20% of waste collectors and 49% of compost workers. Exposure variability within tasks was large (geometric standard deviation > 2), with smaller between-worker than within-worker variance. Type of company and waste largely explained between-worker variance (40-90%), although within companies no major task-related determinants could be established. Markers of exposure correlated moderately to strongly. Relative endotoxin and glucan content in the dust was only weakly associated with handled waste. CONCLUSIONS: Occupational bioaerosol exposure in the waste management chain is lowest for outdoor handling of waste and highest when waste is handled indoors. However, exposure variability is large, with greater within-worker than between-worker variance. Occupational exposure limits for organic dust and endotoxins are frequently exceeded, suggesting workers are at risk of developing adverse health effects.

Air Pollutants, Occupational↗
PubMed2004

Working Group report 4: exposure assessment for biological agents.

This Working Group was assembled to review and evaluate methods currently used to estimate work site exposures to biological agents and to present recommendations on suitable measurement strategies. The current state of exposure assessment was evaluated for environments with organic dust including agriculture, composting, sewage and waste treatment processing, peat moss harvesting and handling, cotton and textile processing, greenhouse work, and grass seed processing. Methods for measurement of microbial contaminants in indoor environments were also considered. Important methods are emerging that use quantitative PCR for assessment of microbial agents. Difficulties exist with optimization of extraction to yield contaminant-free DNA without significant DNA loss. Advances in assays for microbial agents (e.g., endotoxin and glucans) as well as allergens have increased the utility of exposure assessment for these agents. A crucial area for further development is international harmonization of methodologies to reduce interlaboratory variability and to facilitate establishment of exposure guidelines. Endotoxin exposure assessment using the Limulus amebocyte lysate method is a high priority for harmonization because of its importance as a pulmonary inflammatory agent in many occupational settings.

Air Pollution, Indoor↗
PubMed2004

Atopic and non-atopic asthma in a farming and a general population.

BACKGROUND: In a previous study inverse associations between asthma and exposure to fungal spores and endotoxins in atopic farmers and positive associations with the same factors in non-atopic farmers were documented. No external reference population had been included. We, therefore, compared this farming population with the general population from an adjacent region. METHODS: Random samples of a farming (n=2,106) and a rural (n=351) and urban (n=727) general population were selected. Atopy was assessed by serum IgE and asthma by questionnaires. RESULTS: The asthma prevalence was 4.0% among farmers, 5.7% in the rural, and 7.6% in the urban population. Atopy was similar (9-10%). Most asthmatics were not atopic, 67-75%. Farmers had asthma less often than the general population OR 0.52 (95% CI 0.36-0.75); both atopic (OR 0.33 (95% CI 0.15-0.69)) and non-atopic asthma (OR 0.60 (95% CI 0.39-0.93)). CONCLUSION: This may indicate a protective effect of the farm environment on asthma but a healthy worker effect may also play a role.

Adult↗
PubMed2004

Can bacterial endotoxin exposure reverse atopy and atopic disease?

Studies have shown that endotoxin exposure in childhood is associated with a reduced risk of atopy and atopic asthma. It is commonly assumed that these effects only occur in early life. However, recent epidemiologic studies suggest that immune deviation might take place throughout life. Assuming that the immune system is not fixed after the first years of life, we hypothesize that endotoxin exposure might not only inhibit the development of atopic sensitization and disease at any time throughout life but might also reverse this process. This novel extension of the hygiene hypothesis is primarily based on the indirect evidence of several epidemiologic observations showing a reduction in atopy in adults highly exposed to endotoxin that is unlikely to be explained by protective effects alone. In addition, some animal studies demonstrated the potential of endotoxin to downregulate pre-existing airway eosinophilia and hyperreactivity. However, there is currently little direct evidence that endotoxin might reverse atopy and allergic diseases. Observational studies and randomized trials to test this hypothesis could ultimately lead to the development of novel treatments for atopic diseases, such as allergic asthma, hay fever, and eczema.

Bronchial Hyperreactivity↗
PubMed2004

Infections, medication use, and the prevalence of symptoms of asthma, rhinitis, and eczema in childhood.

BACKGROUND: The "hygiene hypothesis" postulates that infections during infancy may protect against asthma and atopy. There is also some evidence that antibiotic and/or paracetamol use may increase the risk of asthma. METHODS: The study measured the association between infections, and medication use early in life and the risk of asthma at age 6-7 years. It involved 1584 children who had been notified to public health services with serious infections at age 0-4 years, and 2539 children sampled from the general population. For both groups, postal questionnaires were completed by parents. RESULTS: There was little difference in the prevalence of current wheezing between the childhood infections group (prevalence = 23.5%) and the general population group (prevalence = 24.3%). There was also little difference whether the major site of infection was gastrointestinal (prevalence = 24.1%), invasive (prevalence = 24.6%) or respiratory (prevalence = 21.1%). However, in both groups, there were associations with antibiotic (OR = 1.78, 95% CI 1.49 to 2.14) or paracetamol (OR = 1.38, 95% CI 1.04 to 1.83) use in the first year of life or recent paracetamol use (OR = 2.10, 95% CI 1.78 to 2.49) and current wheezing. There was a weak protective effect of childhood infections in children who had not used antibiotics in the first year of life (OR = 0.78, 95% CI 0.55 to 1.10). CONCLUSIONS: These findings are consistent with other evidence that antibiotic use early in life may increase the risk of asthma. They are also consistent with some preliminary evidence associating paracetamol use with an increased risk of asthma. Any protective effect of notifiable childhood infections was weak.

Acetaminophen↗
PubMed2003

What proportion of rhinitis symptoms is attributable to atopy?

The aim of this study was to assess what proportion of patients with rhinitis symptoms (unrelated to infection) in population-based studies is attributable to atopy. We assessed the relevance of atopy in rhinitis in different countries and populations and between different age groups by performing a Medline search from 1980 onward on population-based studies. In the 22 identified population-based studies found, the overall proportion of rhinitis cases that were atopic was 61%, the proportion of noncases that were atopic was 20%, and the proportion of rhinitis cases that were attributable to atopy was 53%. There is variation between studies but little evidence of systematic geographic variation. For future research on the prevalence and possible increase of atopic rhinitis, it seems to be of major importance to differentiate between atopic and other forms of rhinitis.

Adolescent↗
PubMed2003

Reproducibility of allergen, endotoxin and fungi measurements in the indoor environment.

Measurements of biocontaminants in settled house dust once a year are commonly used to assess long-term exposure. To examine stability over time and seasonal variation, we measured concentrations of mite and cat allergens, endotoxin and mold spores in living room floor dust in 745 German homes collected twice a year in two different seasons. The study population consisted of adults and children living in five different areas in Germany. All dust samples were collected in a standardized manner from the living room floor and taken during the years 1995 to 1998. The median interval between the two dust samplings was approximately 7 months. Mite and cat allergens were measured in settled house dust by monoclonal antibodies, endotoxin by the limulus amebocyte lysate method, and total spore counts by cultural methods. Crude Pearson's correlation coefficients between log-transformed concentrations in the first and second dust samples ranged between 0.65 and 0.75 for allergens, 0.59 for endotoxin and only 0.06 for total spore counts. The strongest and most consistent seasonal effects were observed for fungi with highest levels in July-September. Cat allergen concentrations were found consistently to be increased in January-March. Mite allergens did not show a strong and consistent seasonal pattern. We conclude that repeated measurements of mite and cat allergens and endotoxin in settled house dust improve the estimate for annual mean concentrations. However, even a single observation of these biocontaminants may be a good proxy for a 1-year exposure since repeated measures were highly correlated. However, repeated measurements of fungi levels were only weakly correlated and thus repeated observations for assessment of annual means of total spore counts are needed.

Air Pollution, Indoor↗
PubMed2003

Respiratory symptoms and occupational exposures in New Zealand plywood mill workers.

OBJECTIVES: To study work exposure and respiratory symptoms in New Zealand plywood mill workers. METHODS: Personal inhalable dust (n = 57), bacterial endotoxin (n = 20), abietic acid (n = 20), terpene (n = 20) and formaldehyde (n = 22) measurements were taken and a respiratory health questionnaire was administered to 112 plywood mill workers. RESULTS: Twenty-six percent of the dust exposures exceeded 1 mg/m(3), however, none of the samples exceeded the legal limit of 5 mg/m(3) [geometric mean (GM) = 0.7 mg/m(3), geometric standard deviation (GSD) = 1.9]. Workers in the composer area (where broken sheets are joined together) were significantly (P < 0.01) more highly exposed. Endotoxin levels were low to moderate (GM = 23.0 EU/m(3), GSD = 2.8). Abietic acid levels ranged from 0.3 to 2.4 micro g/m(3) (GM = 0.7 micro g/m(3), GSD = 1.8) and were significantly (P < 0.05) higher for workers in the composer area of the process. Geometric mean levels of alpha-pinene, beta-pinene and Delta(3)-carene were 1.0 (GSD = 2.7), 1.5 (GSD = 2.8) and 0.1 (GSD = 1.4), respectively, and alpha-pinene and beta-pinene levels were significantly (P < 0.001) higher for workers in the 'green end' of the process, up to and including the veneer dryers. Formaldehyde levels ranged from 0.01 to 0.74 mg/m(3) [GM = 0.08 mg/m(3) (= 0.06 p.p.m.), GSD = 3.0]. Asthma symptoms were more common in plywood mill workers (20.5%, n = 112) than in the general population [12.8%, n = 415, adjusted OR (95% CI) = 1.5 (0.9-2.8)]. Asthma symptoms were associated with duration of employment and were reported to lessen or disappear during holidays. No clear association with any of the measured exposures was found, with the exception of formaldehyde, where workers with high exposure reported more asthma symptoms (36.4%) than low exposed workers [7.9%, adjusted OR (95% CI) = 4.3 (0.7-27.7)]. CONCLUSIONS: Plywood mill workers are exposed to inhalable dust, bacterial endotoxin, abietic acid, terpenes and formaldehyde, and they appear to have an increased risk of developing work-related respiratory symptoms. These symptoms may be due to formaldehyde exposure, although a potential causal role for other exposures cannot be excluded.

Abietanes↗
PubMed2002

Respiratory symptoms and dust exposure among male workers in small-scale wood industries in Tanzania.

Few studies have assessed respiratory symptoms and dust exposure levels in small-scale wood industry workers in Africa. We interviewed 546 workers exposed to wood dust and 565 control subjects using a respiratory health questionnaire. Inhalable dust measurements were collected for 106 workers. The dust exposure was high, and job title-based geometric mean exposure levels ranged from 2.9 to 22.8 mg/m3. Prevalence of respiratory symptoms in the previous 12 months was significantly higher in the exposed group compared with the nonexposed office workers. Allergy and sensitivity symptoms were reported regularly in the exposed group with Odds ratios and 95% confidence intervals (CIs) varying from 2.4 (95% CI = 1.8-3.1) for low- and 2.7 (1.8-4.0) for high-exposure groups compared with controls. We conclude that working in the small-scale wood industry in Tanzania is associated with an increased prevalence of respiratory symptoms.

Adult↗