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Oral Session 11 – Asthma

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O11.1 ENDOTOXIN EXPOSURE AND ATOPIC SENSITIZATION IN ADULT PIG FARMERS

D. Heederik1, L. Portengen1, L. Preller2, G. Doekes1.1Institute for Risk Assessment Sciences (IRAS), University of Utrecht, The Netherlands; 2Department of Chemical Exposure Assessment, TNO Chemistry, The Netherlands

Introduction: Recent studies have reported a considerable lower prevalence of atopic sensitization and symptoms of respiratory allergy in children growing up on farms compared with their peers living in the same rural areas. We therefore wanted to evaluate whether adult farmers also have a reduced risk for atopic sensitization and whether such a possible reduced risk is associated with endotoxin exposure.

Methods: Complete data on endotoxin exposure, total serum IgE, and presence of IgE to house dust mite, grass pollen, birch pollen, and cat dander were available for 162 pig farmers from a cross sectional case–control study. Exposure to endotoxin was measured on more than one occasion and modelled in detail. Exploratory analysis was performed using non-parametric modelling and was followed by classical multiple logistic regression.

Results: IgE to one or more common allergens was detected in sera from 28 pig farmers (17%) and average (geometric mean (geometric SD)) total serum IgE was 37 (4) IU/mL. A strong inverse relation was found between endotoxin exposure and sensitization to common allergens for exposures up to 75 ng/m3, with an OR (95% confidence interval (CI)) of 0.3 (0.1 to 0.9) for >75 versus ⩽75 ng/m3 endotoxin. No association was found between endotoxin and total serum IgE.

Conclusions: The prevalence of atopic sensitization to common allergens in adult pig farmers is low. Exposure to endotoxin or related exposures appear to protect from sensitization to common allergens in an adult working population exposed to high levels of endotoxin.

O11.2 PROGRESSION OF SYMPTOMS IN LABORATORY ANIMAL ALLERGY

L. Elliott1, D. Heederik2, D. Loomis1.1Department of Epidemiology, University of North Carolina School of Public Health, Chapel Hill, NC, USA; 2Institute of Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands

Introduction: Laboratory animal allergy (LAA), characterised by symptoms of rhinitis, conjunctivitis, and skin rash, is a common illness among workers exposed to laboratory animals. A possible corollary of LAA is LAA asthma. This study evaluates the continuum of disease from allergy symptoms to asthma in a dynamic cohort of workers exposed to animals in a pharmaceutical company.

Methods: Information about allergy and asthma symptoms from exposure to laboratory animals was collected from workers enrolled in a medical surveillance program during the period 1 January 1991 to 30 April 2003. The life table method was used to compare asthma free survival between workers with and without symptoms of allergy. A Cox proportional hazards model was used to examine the effects of covariates on the development of asthma.

Results: A total of 603 workers contributed 2527.4 person years to the study over the 12.3 year period. At baseline examination, 108 workers reported the presence of at least one LAA related symptom, and 47 workers developed LAA during follow up. Progression of symptoms manifested as an increase in number and severity (for example, from rhinitis to asthma) of symptoms. The probabilities for development of asthma by the 11th year of follow up were 0.367 and 0.052 for the initially symptomatic and initially asymptomatic workers, respectively. The crude hazard ratio for LAA asthma comparing initially symptomatic to asymptomatic employees was 9.39 (95% confidence interval 4.21 to 20.93), which was reduced to 7.39 (3.29 to 16.60) after adjusting for gender and family history of allergy. Females developed asthma at a rate of 3.4 (to 18.07) times that of males, which remained unchanged when controlling for exposure to specific tasks.

Conclusions: This study supports the hypothesis that LAA related allergy symptoms are a major risk factor for the development of asthma, and that a progression of symptoms occurs from rhinitis to asthma among workers exposed to laboratory animals. It also suggests heightened risk of asthma for women who work with laboratory animals, a finding that has not been previously reported.

O11.3 OCCUPATIONAL ASTHMA IN NEW ZEALAND PINE PROCESSING SAWMILL WORKERS: A CASE–CONTROL STUDY

J. Douwes1,2, D. McLean1,2, T. Slater1,2, N. Travier1, SooCheng1,2, N. Pearce1,2, .1Centre for Public Health Research, Massey University, Wellington, New Zealand; 2Wellington Asthma Research Group, Otago University, New Zealand

Introduction: We have previously shown an increased risk of asthma in 772 pine sawmill workers (Phase I). In the current study (Phase II) which was conducted a year later we investigated lung function, atopy, and wood dust exposure in 59 workers with, and 167 workers without asthma symptoms.

Methods: Asthma cases and controls were selected randomly from the phase I study. Pre-shift and post-shift lung function were assessed using spirometry. Atopic sensitisation against pine pollen, mould, cockroach, house dust mite, grass, tree, cat, and dog was determined by using skin prick tests (SPT). Personal inhalable dust samples were collected on the same day.

Results: The geometric mean dust concentration was 0.52 mg/m3 (geometric SD, 2.66; range 0.02 to 6.24; n = 183). Dust levels were significantly associated with job title defined exposure categories used in phase I. A large proportion of the asthmatics was atopic (80% versus 49% of the controls), and a strong association was found between atopy (⩾1 positive SPT) and asthma (adjusted odds ratio (OR) 3.7; 95% confidence interval 1.8 to 7.9; n = 212). The OR increased to 5.7 (2.3 to 13.9; n = 177) after excluding all subjects (n = 36) who changed asthma status after Phase I. The strongest associations were found with mite, grass, and pets, whereas no association was found with pine pollen. Forced expiratory volume in 1 second (FEV1), peak expiratory flow, and FEV1/forced vital capacity (FVC) values were significantly lower in asthmatics compared with controls (after adjusting for height, age, sex, ethnicity, and smoking). Both pre-shift and post-shift FVC and FEV1 were lower in workers highly exposed to ‘green’ dust (compared with non-exposed workers) but these associations disappeared after adjusting for ethnicity. Preliminary analyses showed no significant associations between measured exposure and both cross shift decline in, and baseline values of, lung function.

Conclusions: Asthma was strongly associated with atopic sensitisation against common allergens but not pine pollens. Despite the higher risk for asthma and other respiratory symptoms, no direct association between occupational exposure and adverse effects on lung function could be demonstrated.

O11.4 EXPOSURE OF TEXTILE WORKERS AND BLADDER CANCER IN SPAIN

C. Serra1,2, D. Turuguet3, M. Kogevinas3, T. Stewart4, N. Malats3, D. Silverman4, F. Real3, N. Rothman4, A. Tardon5, R. Garcia-Closas6, A. Carrato7, G. Castaño-Vinyals3, M. Dosemeci4.1Pompeu Fabra University, Barcelona, Spain; 2Corporació Parc Tauli, Sabadell, Spain; Municipal Institute of Medical Research, Barcelona, Spain; 4National Cancer Institute, Bethesda, USA; 5Universidad de Oviedo, Spain; 6Hospital Unversitario de Canarias, Tenerife, Spain, 7Hospital General de Elche, Spain

Introduction: The textile industry has been traditionally associated with an increased bladder cancer risk attributed to exposure to aromatic amine based dyes. Weavers were found to be at high risk in some studies and the causative exposures are not well understood. We report a detailed analysis of bladder cancer risk in textile workers.

Methods: We conducted a hospital based case–control study in Spain between 1998 and 2001, including 1226 cases of bladder cancer and 1271 controls (87% males). Lifetime occupational history was recorded through a computer assisted personal interview and exposures in the textile industry were assessed by a detailed modular questionnaire. Occupations, specific locations, tasks, and materials used within the industry were recorded. Odds ratios (OR) and 95% confidence intervals (CI) were adjusted for age, sex, region, other high risk occupations, and smoking.

Results: In the study, 248 participants (126 cases, 122 controls) had ever been textile workers, including a higher proportion of women than the total study population. No overall excess risk was found for textile workers (odds ratio 1.1; 95% confidence interval 0.8 to 1.4) compared with non-textile workers. Excess risks were found for weavers (OR 1.9; 1.0 to 3.6), for those who had ever worked in winding (2.9, CI 1.0 to 8.5), warping, sizing, and/or dressing (7.23; 1.53 to 34.24), and for those with exposure to synthetic materials (1.88; 1.00 to 3.53) and cotton (1.5; 0.9 to 2.4). No excess risk was found for dyers and finishers. Risk estimates tended to be higher in women than in men.

Conclusions: Results from this detailed analysis on exposures in the textile industry suggest that the excess risk in weavers could be associated with chemicals used for sizing and/or dressing. Risks associated with production of synthetic materials have rarely been examined in the past, and could be associated with chemical substances used to synthesise textile fibres.

O11.5 OCCUPATION AND ASTHMA AMONG CHINESE WOMEN IN A POPULATION BASED COHORT

S. Krstev1, 2, B. T. Ji1, X. O. Shu3, A. Blair1, W. Zheng3, J. Lubin1, R. Vermeulen1, W. H. Chow1, M. Hauptmann1, N. Rothman1, Y. T. Gao4, M. Dosemeci1.1National Cancer Institute, NIH, DHHS, Bethesda, MD, USA; 2Clinical Centre of Serbia, Institute of Occupational Health, Belgrade, Serbia and Montenegro; 3Vanderbilt University, Nashville, TN, USA; 4Shanghai Cancer Institute, Shanghai, China

Introduction: Asthma is one of the most common respiratory diseases worldwide. We examined the associations between occupation and asthma using baseline survey data of a population based cohort study in Shanghai, China.

Methods: During 1997 to 1999, 75 044 women aged 40–70 years were recruited. Cases were 704 women who reported a physician diagnosed asthma. Controls were 27 295 women frequency matched to cases by year of birth and age at diagnosis. Lifetime occupational history and other information were obtained. Logistic regression was applied to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of asthma associated with occupations adjusting for potential confounders.

Results: Significantly increased prevalence for asthma were found for electronic and electric (OR 1.5; 95% CI 1.0 to 2.1), rubber and plastic (1.7; 1.2 to 2.6), and textile workers (1.3; 1.0 to 4.5), and in workers in the chemical (1.6; 1.2 to 2.2), watch production (2.0; 1.0 to 3.7), and construction (1.7; 1.1 to 2.7) industries. Asthma occurred mostly after a short term exposure (⩽10 years). Interestingly, an increased risk was found in elementary school teachers after short term employment (1.8; 1.0 to 3.1). A few occupations showed inverse associations with employment duration: electronic and electric workers (p = 0.03), plastic process machine operators (p = 0.05), and fibre pre-treatment workers exposed to cotton dust (p = 0.02). The associations between occupations and asthma were not materially changed after further adjusting for passive smoking and exposure to cooking fumes.

Conclusions: Our study identified some high risk occupations and industries for asthma in women. Further studies are needed to identify specific occupational exposures that are responsible for the increased risk of asthma.

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