© 2007 American Thoracic Society doi: 10.1164/rccm.200701-061ED
Asthma among Health Care ProfessionalsUppsala University, Uppsala, Sweden
Toronto Western Hospital, Toronto, Ontario, Canada Health care professionals have been recognized for centuries (as by Ramazzini and Linnaeus) to have occupational risks of respiratory infection, such as tuberculosis, leading to preventive measures including medical surveillance. Work-related asthma has been appreciated more recently (especially since the "epidemic" of sensitization to natural rubber latex in the early 1990s) (1–3). This includes occupational asthma (asthma caused by work) from respiratory sensitizers such as glutaraldehyde (4), used to sterilize endoscopes; natural rubber latex from protective gloves; diisocyanates, used for orthopedic casts or support moldings for radiotherapy; and medications that may become airborne (e.g., penicillins and psyllium). Irritant-induced occupational asthma has occurred from an accidental spill of glacial acetic acid in a hospital (5), and from mixing cleaning products, releasing chlorones. Work-related asthma symptoms have been associated with reported exposures to chemical spills of processing/developing chemicals among radiographers (2). Lesser exposures to asthma triggers, such as nebulized pentamidine (6) or cleaning products, can exacerbate asthma in health care settings. Finally, symptoms that mimic asthma occur, due to irritable larynx syndrome, from mucous membrane irritation on exposure to scented products, or with darkroom exposures in radiographers (darkroom disease) (7). The study by Delclos and colleagues (8) in this issue of the Journal (pp. 667–675) provides further information about exposures associated with asthma in subgroups of health care professionals. Questionnaire data was combined with a job-exposure matrix (9) developed from the National Institute for Occupational Safety and Health (NIOSH) National Occupational Exposure survey from 1988, cross-linked with a list of known asthmagens current to 1997(10), and updated by local hospital walk-through surveys in 2002. It has been suggested that a job-exposure matrix may be more reliable than self-reported exposures and less subject to recall bias for the presence of asthma (11). In this study, self-reported natural rubber latex glove use by patients with asthma and subjects without asthma showed little difference when compared with the job-exposure matrix. However, for other exposures, self-reports from patients with asthma were better associated with the job-exposure matrix than self-reports from nonasthmatic subjects. Because many exposure products likely had odors or could potentially exacerbate asthma, patients with asthma (or those with asthmalike symptoms, including irritable larynx syndrome) may be more aware of these, increasing reporting rates. An interesting association was found between cleaning products for building surfaces, determined from the job-exposure matrix, and the outcomes of reported asthma and airway hyperresponsiveness symptoms. Although such products have been associated with asthma among professional cleaners (12), this has been less recognized among health care professionals, emphasizing the importance of considering bystander exposures in the diagnosis of work-related asthma (as these products were likely used mainly by others in the work area). The study is an excellent illustration of the mixed exposures that may occur in many work settings, not only to potential respiratory sensitizers but also to potential exacerbating factors for asthma. As frequently occurs in clinical evaluation of symptomatic workers exposed to cleaning products, the authors could not identify the responsible agent(s), which can cause difficulty in advising exposure modification for affected workers with occupational asthma. The association of the outcomes of this study with instrument cleaning and with aerosolized medication exposures is not unexpected. Instrument cleaning products, with direct or indirect exposure for health care professionals, reported to cause sensitization and occupational asthma include glutaraldehyde (4) and enzyme-containing products. The specific responsible agents within these exposure categories and variation in asthma rates over time would be important to address in future studies. Changes in use/exposure to aerosolized ribavirin (13) or pentamidine, or a switch from glutaraldehyde to ortho-phthalaldehyde (a presumed less potent sensitizer) (14) may, for example, affect the incidence of work-related asthma. Increasing population rates of atopy and asthma, and new infections (causing increased infection-control measures in health care facilities), make these important workplaces to address. The study (8) also demonstrates that this type of survey can identify time trends in occupational asthma using a job-exposure matrix when applied to a defined exposure, latex gloves, despite the authors' inability to provide data on incidence rates for new-onset asthma, and despite the application of the job-exposure matrix to the longest job held as a health care worker, which was not necessarily the job at which the worker developed asthma. The authors recognized changes in hospital use of powdered natural rubber latex gloves over time and analyzed exposure data by division into the periods before, during, and after increased use of powdered natural rubber glove use (1992–2000 representing the period of high use in the health care facilities surveyed). Of interest, they found significant associations during the high-exposure period for natural rubber latex gloves and the two outcome variables: physician-diagnosed asthma since starting work as a health care professional and a symptom-based predictor of airway hyperresponsiveness in the previous 12 months. Associations were not present for latex glove use in the other two time periods, suggesting that effects were truly due to changes in powdered natural rubber latex glove usage. Results are consistent with reported changes in sensitization and occupational asthma from natural rubber latex gloves in association with preventive measures to reduce powder, protein, and unnecessary natural rubber latex glove use in other studies (3). The findings validate the effectiveness of preventive measures to reduce occupational asthma when a specific cause can be recognized and exposure significantly reduced or eliminated. Understanding the asthma-related effects from exposures in health care settings and other workplaces has importance for effective prevention by changing products or reducing exposures (15). Medical surveillance for health care workers, including physicians, may be appropriate for exposures such as enzymes and diisocyanates, and perhaps other agents after a better understanding of relevant exposures is achieved. Work-related asthma should be considered early in every adult with asthma and investigated appropriately. The best prognosis of sensitizer-induced occupational asthma occurs with early diagnosis, identification of the cause, and exposure intervention (16). Work-exacerbated asthma is managed by general reduction of exposure to potential aggravating factors, in and out of the work environment, and optimizing asthma medication. The study by Delclos and colleagues (8) provides information that may allow preventive measures targeted to groups of exposure agents. Areas for future research include further identification of current important sensitizers in health care facilities. Physicians should lead by example in the implementation and evaluation of preventive measures in their own working environments. FOOTNOTES Conflict of Interest Statement: A.R.-A. has no financial relationship with a commercial entity that has an interest in the subject of this manuscript. S.M.T. has performed medical assessments relating to compensation claims, insurance companies, and employers, amounting to receipt of approximately Can $24,000 per year. REFERENCES
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