The study of occupational risk factors and interventions for baker's allergy and asthma among supermarket bakery workers
Doctoral Thesis
2013
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University of Cape Town
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Background: Baker's asthma is the most serious manifestation of occupational allergy among bakery workers. It is caused by IgE-mediated sensitisation and subsequent allergic reaction in the airways to specific occupational airborne allergens in flour or baking ingredients. Major aims of this study were to: characterise asthma phenotypes and environmental exposure to flour allergens among bakers and modifying factors; study associations between phenotype and environmental exposure and identify potential modifying factors of this association; determine the effectiveness of specific interventions in reducing exposure and the risk of sensitisation or allergic respiratory disease. Methods: A cross-sectional study was conducted among 517 bakery workers employed in 31 supermarkets. Health outcomes were assessed using a standardized questionnaire, immunological tests (sIgE, sIgG), methacholine challenge test and fractional exhaled nitric oxide (FeNO). Exposure assessment conducted pre- and post-intervention entailed determination of inhalable concentration of particulate mass and specific allergen levels. The intervention employed a group-randomised design to evaluate dust control measures. Results: Prevalence of probable occupational asthma (POA, 13%) was higher than atopic (AA, 6%), non-atopic (NAA, 6%) and work-aggravated asthma (WAA, 3%). Sensitisation to flour allergens was a major determinant of elevated FeNO among bakers. Bread bakers had the highest dust particulate (mean = 1.33 mg/m3) and allergen exposures. Exposure response relationships followed a bell-shaped curve, with the prevalence of IgE- sensitisation, allergic symptoms and POA, increasing up to 10-15 μg/m3 of airborne wheat allergen concentrations before declining. The association for IgE sensitization was not modified by IgG4 to wheat. The overall effect of the intervention revealed a 50% decrease in mean flour dust, wheat allergen and rye exposures in bakeries. Conclusion: Occupational asthma is the most common phenotype among supermarket bakery workers, with sensitisation to cereal flour allergens being the main determinant of allergic airway inflammation. The bell-shaped exposure response relationship is not modified by the presence of blocking antibodies and is probably due to a healthy worker effect. The multi-pronged intervention strategy was effective in reducing airborne flour dust and allergen levels. It is recommended that further studies investigate the long term health impact of these interventions in reducing the disease burden.
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Reference:
Baatjies, R. 2013. The study of occupational risk factors and interventions for baker's allergy and asthma among supermarket bakery workers. University of Cape Town.