Abstract

This purpose of this study was to examine the relationship between exposure to wheat flour, soya flour and fungal amylase and the development of work-related symptoms and sensitization in bread and cake bakery employees who have regular exposure to these substances. The study populations consisted of 394 bread bakery workers and 77 cake bakery workers whose normal jobs involved the sieving, weighing and mixing of ingredients. The groups were interviewed with the aim of identifying the prevalence, nature and pattern of any work-related respiratory symptoms. They were also skin-prick tested against the common bakery sensitizing agents, i.e., wheat flour, soya flour, rice flour and fungal amylase. The results of personal sampling for sieving, weighing and mixing operations at the bakeries from which the study groups were taken were collated in order to determine typical exposures to total inhalable dust from the ingredients, expressed as 8 hour time-weighted average exposures. Data from the health surveillance and collated dust measurements were compared with the aim of establishing an exposure-response relationship for sensitization. The prevalence of work-related symptoms in bread bakery and cake bakery ingredient handlers was 20.4% and 10.4% respectively. However, in a large proportion of those reporting symptoms in connection with work, the symptoms were intermittent and of short duration. It is considered that the aetiology of such symptoms is likely to be due to a non-specific irritant effect of high total dust levels, rather than allergy. None of the cake bakers and only 3.1% of the bread bakers had symptoms which were thought to be due to allergy to baking ingredients. Using skin-prick testing as a marker of sensitization, the prevalence of positive tests to wheat flour was 6% for the bread bakers and 3% for the cake bakers. Comparable prevalences for soya flour were 7% and 1% respectively. However, the prevalence of positive skin-prick tests to fungal amylase was 16% amongst the bread baking group with only a single employee (1%) in the cake baking group having a positive test. Furthermore, this employee had previously worked in a bread bakery. The difference in rates of sensitization to wheat flour between the bread and cake bakers is not statistically significant, whereas the difference for soya flour is at the borderline of statistical significance (p = 0.045). In contrast, the difference in fungal amylase sensitization is significant at the 0.1% level. For both bread and cake bakers, the 8 hour time-weighted average exposures for each of the activities showed a wide variation with mixing having the lowest average exposure and sieving the highest. Out of the allergens studied in this investigation, fungal amylase is the principal sensitizer in large scale bread bakeries, with the main source of exposure being the handling of bread improvers. In contrast, the risk of sensitization to wheat flour is low in both bread and cake bakeries. The absence of positive skin-prick tests in the subgroup of cake bakery employees who regularly handle fungal-amylase-containing flour suggests that their levels of exposure are below the threshold for sensitization to amylase.

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