Supermarket baker's asthma: how accurate is routine health surveillance?

A scoping review to identify strategies that work to prevent four important occupational diseases

BACKGROUND

Despite being largely preventable, many occupational diseases continue to be highly prevalent and extremely costly. Effective strategies are required to reduce their human, economic, and social impacts.

METHODS

To better understand which approaches are most likely to lead to progress in preventing noise-related hearing loss, occupational contact dermatitis, occupational cancers, and occupational asthma, we undertook a scoping review and consulted with a number of key informants.

RESULTS

We examined a total of 404 articles and found that various types of interventions are reported to contribute to occupational disease prevention but each has its limitations and each is often insufficient on its own. Our principal findings included: legislation and regulations can be an effective means of primary prevention, but their impact depends on both the nature of the regulations and the degree of enforcement; measures across the hierarchy of controls can reduce the risk of some of these diseases and reduce exposures; monitoring, surveillance, and screening are effective prevention tools and for evaluating the impact of legislative/policy change; the effect of education and training is context-dependent and influenced by the manner of delivery; and, multifaceted interventions are often more effective than ones consisting of a single activity.

CONCLUSIONS

This scoping review identifies occupational disease prevention strategies worthy of further exploration by decisionmakers and stakeholders and of future systematic evaluation by researchers. It also identified important gaps, including a lack of studies of precarious workers and the need for more studies that rigorously evaluate the effectiveness of interventions.

Health surveillance for occupational asthma

PURPOSE OF REVIEW

The outcome for workers with occupational asthma is improved for those with an earlier diagnosis. Health surveillance at work is in principle designed to identify such cases, so that the risks to the individual worker, and coworkers, can be reduced. There is recent evidence to suggest that the uptake and quality of such surveillance could be improved. This review has assessed current approaches to health surveillance for occupational asthma.

RECENT FINDINGS

The article covers a review of the utility of questionnaires, lung function testing, immunological investigations, and other tests, including exhaled nitric oxide, sputum eosinophilia, and exhaled breath condensate specifically in the context of workplace-based health surveillance.

SUMMARY

Questionnaires remain a key component of respiratory health surveillance, although maybe limited by both sensitivity and specificity for early occupational asthma. The role of lung function testing is debated, although is recommended for higher level health surveillance. Various examples of immunological testing in health surveillance are discussed, but more evidence is needed in many specific areas before more general recommendations can be made. Evidence is discussed in relation to the utility of newer approaches such as exhaled nitric oxide, sputum eosinophilia, and exhaled breath condensate.

Prevalence of sensitization to 'improver' enzymes in UK supermarket bakers

BACKGROUND

Supermarket bakers are exposed not only to flour and alpha-amylase but also to other 'improver' enzymes, the nature of which is usually shrouded by commercial sensitivity. We aimed to determine the prevalence of sensitization to 'improver' enzymes in UK supermarket bakers.

METHODS

We examined the prevalence of sensitization to enzymes in 300 bakers, employed by one of two large supermarket bakeries, who had declared work-related respiratory symptoms during routine health surveillance. Sensitization was determined using radioallergosorbent assay to eight individual enzymes contained in the specific 'improver' mix used by each supermarket.

RESULTS

The prevalence of sensitization to 'improver' enzymes ranged from 5% to 15%. Sensitization was far more likely if the baker was sensitized also to either flour or alpha-amylase. The prevalence of sensitization to an 'improver' enzyme did not appear to be related to the concentration of that enzyme in the mix.

CONCLUSIONS

We report substantial rates of sensitization to enzymes other than alpha-amylase in UK supermarket bakers; in only a small proportion of bakers was there evidence of sensitization to 'improver mix' enzymes without sensitization to either alpha-amylase or flour. The clinical significance of these findings needs further investigation, but our findings indicate that specific sensitization in symptomatic bakers may not be identified without consideration of a wide range of workplace antigens.

An official American Thoracic Society proceedings: work-related asthma and airway diseases. Presentations and discussion from the Fourth Jack Pepys Workshop on Asthma in the Workplace

Work-related asthma is a common occupational lung disease. The scope of the Fourth Jack Pepys Workshop that was held in May 2010 went beyond asthma to include discussion of other occupational airway diseases, in particular occupationally related chronic obstructive pulmonary disease (COPD) and bronchiolitis. Aspects explored included public health considerations, environmental aspects, outcome after diagnosis, prevention and surveillance, and other work-related obstructive airway diseases. Consistent methods are needed to accurately estimate the comparative burden of occupation-related airway diseases among different countries. Challenges to accomplishing this include variability in health care delivery, compensation systems, cultural contexts, and social structures. These factors can affect disease estimates, while heterogeneity in occupations and workplace exposures can affect the underlying true prevalence of morbidity. Consideration of the working environment included discussion of practical methods of limiting exposure to respiratory sensitizers, methods to predict new sensitizers before introduction into workplaces, the role of legislated exposure limits, and models to estimate relative validity of various ameliorative measures when complete avoidance of the sensitizer is not feasible. Other strategies discussed included medical surveillance measures and education, especially for young individuals with asthma and new workers about to enter the workforce. Medical outcomes after development of sensitizer-induced occupational asthma are best following earlier diagnosis and removal from further exposure, but a subset may be able to continue working safely provided that exposure is reduced under close follow-up monitoring. It was recognized that occupationally related COPD is common but underappreciated, deserving further study and prevention efforts.

Health surveillance for occupational respiratory disease

BACKGROUND

Occupational lung diseases remain common, and health surveillance is one approach used to assist identification of early cases.

AIMS

To identify areas of good practice within respiratory health surveillance and to formulate recommendations for practice.

METHODS

Published literature was searched since 1990 using a semi-systematic methodology.

RESULTS

A total of 561 documents were identified on Medline and Embase combined. Other search engines did not identify relevant documents that had not already been identified by these two main searches. Seventy-nine of these were assessed further and 36 documents were included for the full analysis.

CONCLUSIONS

Respiratory health surveillance remains a disparate process, even within disease type. A standard validated questionnaire and associated guidance should be developed. Lung function testing was common and generally supported by the evidence. Cross-sectional interpretation of lung function in younger workers needs careful assessment in order to best identify early cases of disease. More informed interpretation of the forced expiratory volume in 1 s/forced vital capacity ratio, for example by using a lower limit of normal for each worker, and of longitudinal lung function information is advised. Immunological tests appear useful in small groups of workers exposed to common occupational allergens. Education, training and improved occupational health policies are likely to improve uptake of health surveillance, to ensure that those who fail health surveillance at any point are handled appropriately.

Impact of worker education on respiratory symptoms and sensitization in bakeries

BACKGROUND

Flour exposure is known to cause significant respiratory problems.

AIMS

To investigate the development of work-related sensitization, the period between first exposure and the development of symptoms (latent period) and the impact of workplace training programmes on respiratory health in plant bakers.

METHODS

Two hundred and sixty-four bakers were investigated by assessing work-related respiratory symptoms and latent period before symptoms/sensitization, spirometry and testing for an array of workplace-specific IgE.

RESULTS

There was a significant relationship between the presence of work-related respiratory symptoms and flour dust allergen-specific IgE. Latent periods varied widely: median for work-related nasal symptoms 36 months, cough 42 months and chest tightness 120 months. Latent periods were shorter for workers with evidence of flour sensitization (work-related wheeze: mean 13 months with sensitization, 97 months without, P < 0.05, work-related nasal symptoms, respectively; mean 19 months, 71 months, P < 0.01). Those warned of the health implications of flour dust had less work-related wheeze (warned; 1%, not warned 11%, P < 0.05). There was an excess of work-related symptoms and work-related-specific IgE combined in those who had not been warned of these health implications (12 versus 1%, P <0.01).

CONCLUSIONS

Reporting of 'being warned' of potential health implications from breathing flour dust protected strongly against the reporting of important health end points. Latent periods for the development of work-related symptoms varied widely. Simple health messages, which may be overlooked in worker training programmes, can have significant benefits for worker health in the bakery population.

Prevention of occupational asthma

Prevention of occupational asthma related to a work-sensitizing agent ideally would be achieved by avoidance of exposures that cause immunologic sensitization and subsequent asthma. There are a few examples in which a sensitizing agent has been removed from a work process and others in which exposure has been significantly changed or reduced with associated reduced rates of sensitization and disease. Additional measures include containment, use of robots, ventilation measures, exposure monitoring, and use of respiratory protective devices. Secondary prevention includes medical surveillance, which may involve periodic respiratory questionnaires, spirometry, and immunologic tests aiming to detect sensitization or disease early to allow intervention and improve outcomes. Education measures for workers to understand the meaning of work-related respiratory symptoms and appropriate workplace safety measures have not been formally evaluated but may also be expected to enhance protective measures and lead to earlier diagnosis. Tertiary prevention includes medical management and workers' compensation.

Assessment of respiratory health surveillance for laboratory animal workers

BACKGROUND

Occupational asthma is the most common work-related respiratory disease in the UK. Individuals whose work potentially puts them at risk include those exposed to laboratory animals. Workplace health surveillance programmes aim to minimize these health risks but are recognized to be challenging to implement effectively.

AIMS

To evaluate the efficacy of the respiratory health surveillance programme provided by a National Health Service occupational health service (OHS) to individuals potentially exposed to respiratory sensitizers at work with laboratory animals.

METHODS

Case notes from the OHS respiratory health surveillance programme over a 2 year period were examined. Symptom detection by the OHS surveillance questionnaire was compared to a cross-sectional survey using items from the validated International Union Against Tuberculosis and Lung Disease (IUATLD) questionnaire. The surveillance spirometry records were audited against good standards of practice.

RESULTS

The response rate for the anonymized survey using IUATLD questions was 60% and detected similar numbers of potential work-related symptoms to the OHS surveillance questionnaire. Over 80% of spirometry records met accepted standards for technique, effort and recording. In this study of 85 individuals over 2 years, three cases of occupational asthma were identified.

CONCLUSIONS

The current surveillance appears to be effective in identifying potential cases of occupational asthma. Modification of the questionnaire content and layout might improve response rates. This study suggests that spirometry does not detect new cases other than those already identified by questionnaire.

A diagnostic model for the detection of sensitization to wheat allergens was developed and validated in bakery workers

OBJECTIVES

To develop and validate a prediction model to detect sensitization to wheat allergens in bakery workers.

STUDY DESIGN AND SETTING

The prediction model was developed in 867 Dutch bakery workers (development set, prevalence of sensitization 13%) and included questionnaire items (candidate predictors). First, principal component analysis was used to reduce the number of candidate predictors. Then, multivariable logistic regression analysis was used to develop the model. Internal validation and extent of optimism was assessed with bootstrapping. External validation was studied in 390 independent Dutch bakery workers (validation set, prevalence of sensitization 20%).

RESULTS

The prediction model contained the predictors nasoconjunctival symptoms, asthma symptoms, shortness of breath and wheeze, work-related upper and lower respiratory symptoms, and traditional bakery. The model showed good discrimination with an area under the receiver operating characteristic (ROC) curve area of 0.76 (and 0.75 after internal validation). Application of the model in the validation set gave a reasonable discrimination (ROC area=0.69) and good calibration after a small adjustment of the model intercept.

CONCLUSION

A simple model with questionnaire items only can be used to stratify bakers according to their risk of sensitization to wheat allergens. Its use may increase the cost-effectiveness of (subsequent) medical surveillance.

Variability in the diagnosis of occupational asthma and implications for clinical practice

PURPOSE OF REVIEW

The purpose of this review is to provide a summary of recent evidence relating to occupational asthma diagnosis.

RECENT FINDINGS

Recent evidence suggests that whilst prolonged asthmagen exposure worsens the prognosis, many steps in the diagnostic process are problematic for workers with possible occupational asthma. Certain workers suffer delay prior to specialist assessment, and assessment itself may be of variable quality. Emerging evidence suggests that whilst experts agree about certain aspects of case assessment, there is still likely to be variation in clinical practice. Implications of this variation for the workers assessed are relatively under researched.

SUMMARY

Future research needs to focus not only on improving diagnostic testing, but also on improving consistency and agreement over diagnosis.

Sensitization to wheat flour and enzymes and associated respiratory symptoms in British bakers

RATIONALE

Current literature suggests that flour exposed workers continue to be at risk of allergic sensitization to flour dust and respiratory ill health.

OBJECTIVES

A cross-sectional study of 225 workers currently potentially exposed to flour dust in British bakeries was performed to identify predictors of sensitization to wheat flour and enzymes.

RESULTS

Work-related nasal irritation was the most commonly reported symptom (28.9%) followed by eye irritation (13.3%) and work-related cough or chest tightness (both 10.2%). Work-related chest tightness was significantly associated (OR 7.9, 1.3-46.0) with co-sensitization to wheat flour and any added enzyme. Working at a bakery with inadequate control measures was not a risk factor for reporting work-related respiratory symptoms (OR 1.3, 0.4-3.7). Fifty-one workers were atopic and 23 (14%) were sensitized to workplace allergens. Atopy was the strongest predictive factor (OR 18.4, 5.3-64.3) determining sensitization. Current versus never smoking (OR 4.7, 1.1-20.8) was a significant risk factor for sensitization to wheat flour or enzymes in atopic workers only, corrected for current level and duration of exposure. This effect was not seen in non-atopic workers (OR 1.9, 0.2-17.9). Evidence of sensitization to less commonly encountered allergens was also seen to Aspergillus niger derived cellulase, hemicellulase and xylanase mix, in addition to glucose oxidase and amyloglucosidase mix.

CONCLUSIONS

The combination of health surveillance and exposure control in this population has been insufficient to prevent clinically significant workplace sensitization. Smoking may pose an additional risk factor for sensitization in atopic workers. Am. J. Ind. Med. 52:133-140, 2009.

Audit of quality of diagnostic procedures for occupational asthma

BACKGROUND

Previous studies have reported deficiencies in the quality of the diagnosis of occupational asthma. A low quality of diagnostic procedures means that the occupational cause of asthma is less likely to be revealed.

AIMS

To assess the current quality of the diagnosis of occupational asthma before referral to a specialist occupational medicine centre.

METHODS

The quality of diagnostic procedures was assessed by reviewing the files of 150 patients who were referred to the Finnish Institute of Occupational Health in 2003 with a suspicion of an occupational cause of their asthma. The quality indicators used were assessment of workplace exposures, spirometric studies, bronchodilator response, serial workplace measurements of peak expiratory flow (PEF) and the time since first symptoms to the final diagnosis. For each indicator, criteria to differentiate between sufficient and insufficient care were developed.

RESULTS

Exposure assessments, spirometric studies and bronchodilator responses were performed in 92, 87 and 79% of cases in the total study group, respectively. Workplace measurements of PEF had been performed in 51% of the cases, and the quality of measurements was sufficient in 52%. Workplace exposures had been assessed significantly more often in occupational health care than in other health care units. The median time from the beginning of symptoms to the final diagnosis was 3.2 years.

CONCLUSIONS

Although the diagnostic procedures were mostly of sufficient quality, the performance of serial measurements of PEF at the workplace and the time to diagnosis should be substantially improved.

Occupational exposures and adult asthma

Occupational exposures can cause a new onset of asthma in a subset of susceptible workers on the basis of sensitization to a specific work agent or a high-level irritant exposure. Epidemiologic studies give insight into the natural history of occupational asthma, including host factors and environmental factors leading to the development of occupational asthma, the progression, and the potential role of preventive measures. Work-exacerbated asthma has been a focus of studies only recently but is recognized as common among asthmatic workers and is a potential cause of significant morbidity and socioeconomic impact.

Diagnosis and management of work-related asthma: American College Of Chest Physicians Consensus Statement

BACKGROUND

A previous American College of Chest Physicians Consensus Statement on asthma in the workplace was published in 1995. The current Consensus Statement updates the previous one based on additional research that has been published since then, including findings relevant to preventive measures and work-exacerbated asthma (WEA).

METHODS

A panel of experts, including allergists, pulmonologists, and occupational medicine physicians, was convened to develop this Consensus Document on the diagnosis and management of work-related asthma (WRA), based in part on a systematic review, that was performed by the University of Alberta/Capital Health Evidence-Based Practice and was supplemented by additional published studies to 2007.

RESULTS

The Consensus Document defined WRA to include occupational asthma (ie, asthma induced by sensitizer or irritant work exposures) and WEA (ie, preexisting or concurrent asthma worsened by work factors). The Consensus Document focuses on the diagnosis and management of WRA (including diagnostic tests, and work and compensation issues), as well as preventive measures. WRA should be considered in all individuals with new-onset or worsening asthma, and a careful occupational history should be obtained. Diagnostic tests such as serial peak flow recordings, methacholine challenge tests, immunologic tests, and specific inhalation challenge tests (if available), can increase diagnostic certainty. Since the prognosis is better with early diagnosis and appropriate intervention, effective preventive measures for other workers with exposure should be addressed.

CONCLUSIONS

The substantial prevalence of WRA supports consideration of the diagnosis in all who present with new-onset or worsening asthma, followed by appropriate investigations and intervention including consideration of other exposed workers.

Effective health surveillance for occupational asthma in motor vehicle repair

BACKGROUND

Diisocyanates are the commonest reported cause of occupational asthma (OA) in the UK. Health surveillance should play an important part in the early detection of disease and the prevention of long-term morbidity.

AIM

To assess the efficacy of a UK-wide health surveillance programme provided to the motor vehicle repair industry.

METHODS

Analysis of respiratory questionnaire and spirometry results during the period 1995-2000 and more detailed assessment of the outcome of cases suggestive of OA between 1998 and 2000.

RESULTS

Approximately 3700 employees underwent health surveillance each year. As a result, a number (27%) required further assessment; information on 92 employees who were referred to their general practitioner (GP) for further assessment was examined. Half of these employees subsequently failed to see their GP and of those referred to a specialist only 63% attended that appointment. Of the 20 employees who did see a specialist, nine (45%) were subsequently diagnosed as having OA due to isocyanates, indicating a mean annual incidence rate of 0.79 per 1000 workers identified by surveillance. A year after identification, five of the diagnosed employees were still working in the same job.

CONCLUSIONS

Health surveillance is only one part of a process for identifying OA. In this programme, the high drop out rate of employees in the medical investigation process initiated by surveillance was a significant problem. Recommendations are suggested for the future operation of respiratory health surveillance programmes.

Prevalence of work-related symptoms and serum-specific antibodies to wheat flour in exposed workers in the bakery industry

BACKGROUND

Although baker's asthma (BA) is a common occupational asthma, there have been few reports on this disease in Korean subjects.

OBJECTIVES

We evaluated the prevalence of serum-specific IgE, IgG1, and IgG4 antibodies in relation to work-related respiratory symptoms in a single industrial bakery.

METHODS

Three hundred and ninety-two bakery workers were administered and taken a questionnaire regarding respiratory symptoms. For symptomatic workers, the methacholine bronchial challenge test and specific bronchoprovocation tests with wheat extracts were carried out. Skin prick tests were performed and serum-specific IgE, IgG1, and IgG4 antibodies to wheat flour were detected. The IgE- and IgG4-binding components were identified by immunoblotting.

RESULTS

Sixty-seven workers (17.1%) complained of work-related upper and lower respiratory symptoms. The prevalence of BA based on positive bronchoprovocation test results was 1.5%. The sensitization rate to wheat flour was 5.9% by skin prick test and 6.5% by ELISA, and was closely associated with the presence of atopy and work-related lower respiratory symptoms (P<0.001 for both). IgE immunoblotting revealed six major IgE-binding components (27, 31, 36, 43, 54, and 72 kDa). The presence of wheat-specific IgG1 and IgG4 antibodies was found to be significantly associated with exposure intensity (P<0.05 for both).

CONCLUSIONS

The overall prevalence of wheat sensitization in a Korean bakery was 5.9%. We confirmed that an IgE-mediated response is the major pathogenic mechanism for the induction of work-related symptoms in wheat-exposed workers. Wheat-specific IgG antibodies may represent current or previous exposure to wheat dust.

Identification of wheat gliadins as an allergen family related to baker's asthma

BACKGROUND

Flour is still one of the most common causes of occupational asthma worldwide. Thus far, little is known about the relevant allergens causing baker's asthma. Therefore the reliability of current diagnostic procedures is insufficient. Only few of the suspected causative wheat allergens have been hitherto characterized on the molecular level.

OBJECTIVE

The aim was to identify and characterize unknown wheat allergens related to baker's asthma to improve the reliability of diagnostic procedures.

METHODS

A wheat pJuFo cDNA phage display library was created and screened for IgE binding to wheat proteins with pooled sera from patients with baker's asthma. After identifying an alphabeta-gliadin, the frequency of sensitization was investigated by means of ELISA screening of 153 bakers' sera with the recombinant alphabeta-gliadin. Furthermore, the allergenicity of native total gliadin (alphabeta, gamma, omega) was analyzed by means of ImmunoCAP.

RESULTS

One cDNA clone was identified as an alphabeta-gliadin. Serum IgE antibodies to the recombinant allergen were found in 12% of bakers with occupational asthma. Of the asthmatic bakers, 33% showed sensitization to native total gliadin; 4% of them had negative results on routine IgE testing with wheat extract.

CONCLUSIONS

Gliadins represent a newly discovered family of inhalable allergens in baker's asthma. This finding demonstrates that water-insoluble proteins might also represent causative allergens.

Prevention of occupational asthma in Ontario

Occupational asthma continues to be one of the most common occupational lung diseases in industrialized areas. Primary and secondary preventive measures have been well described, but there are relatively few studies to support the effectiveness of such measures, although the benefits of tertiary measures such as early recognition and removal from further exposure to a causative sensitizing agent are well recognized. In Ontario, a combined approach of preventive measures has shown effectiveness in allergy and asthma from occupational exposure to natural rubber latex. In addition, a program to reduce exposure to diisocyanates and introduce medical surveillance was associated with earlier diagnosis and fewer cases in a compensation population. However there remain barriers to the early diagnosis of occupational asthma in Ontario, especially in workers of lower education and lower income. In addition, there is recognized need for further physician education to allow early suspicion and diagnosis of occupational asthma.

Baker's asthma

PURPOSE OF REVIEW

Baker's asthma is one of the leading causes of occupational asthma and this review describes recent developments in the field.

RECENT FINDINGS

The location of bakery production has undergone change and, subsequently, so has the location of baker's asthma. Innovations in the baking industry have also led to new, potentially allergenic, ingredients. A new family of cereal allergens has been identified, including wheat thioredoxin hb (Tri a25). New enzymes are being added to bread that may have allergic potential. The relationship of specific sensitization and baker's asthma has been confirmed in further studies. Measuring specific sensitization to bakery allergens is an essential part of making the diagnosis but there is a lack of standardization of allergen tests. Advancements are being made in the measurement of airborne allergens through the Measurement of Occupational Allergen Exposure project and the development of novel measurement techniques. This will enable better exposure-response relationships and more accurate risk assessment.

SUMMARY

Progress is being made to better identify bakery allergens and measure exposures accurately. Changes in the location of bread production and new allergens mean that the distribution and determinants of baker's asthma are changing.