Workplace irritant exposures: do they produce true occupational asthma?

OBJECTIVE: To describe the features of irritant-induced asthma and discuss the diagnosis in relation to differing workplace irritant exposures and symptomatic responses. DATA SOURCES: A review of MEDLINE articles on this topic from January 1, 1985, through December 31, 2001 was performed. STUDY SELECTION: The author selected relevant articles for inclusion in the review.
RESULTS: Many reports indicate that unintentional high-level respiratory irritant exposures can induce the new onset of asthma. Cases that meet strict criteria for a syndrome of irritant-induced asthma, termed reactive airways dysfunction syndrome, can be diagnosed with relative certainty. Several reports of irritant-induced asthma, especially prevalence studies, have relied on historical data or have otherwise modified the reactive airways dysfunction syndrome criteria for diagnosis (eg, expanding the definition to include the symptom onset several days after exposure). Such modifications, or inclusion of cases with incomplete documentation, likely increase diagnostic sensitivity but may reduce the certainty of diagnosis for individual cases. Expanding exposure criteria to moderate or long-term low-level irritant exposures causes difficulty in excluding transient irritant exacerbation of underlying asthma or coincidental onset of asthma during working life. Although recent population studies suggest a greater relative risk of asthma in occupations with expected low-to-moderate respiratory irritant exposures, currently no objective laboratory tests exist to exclude coincidental asthma in such patients.
CONCLUSIONS: Irritant-induced asthma can be produced by high-level unintentional respiratory irritant exposures at work or outside the workplace. Lower levels of exposure to respiratory irritants at work are more common, and additional studies are needed to determine the airway effects of such exposures.