AGENTS, OLD AND NEW, CAUSING OCCUPATIONAL ASTHMA
- Cristina E Mapp MD, Dipartimento di Medicina Clinica e Sperimentale, Sezione di Igiene e Medicina del Lavoro, Via Fossato di Mortara 64/b, 44100 Ferrara, Italy
Asthma is common among adults of working age and affects 5–10% of the population worldwide. Occupational asthma has become a common work related respiratory disorder in the industrialised world.1 Blanc and Toren have shown that 9% of cases of adult asthma—including principally new onset asthma and, much more rarely, reactivation of pre-existing asthma—are attributable to occupational factors.2 Studies that have used information collected during military service suggest that occupational factors explain 25% of apparently new cases.3 From a practical point of view, addressing past and present occupational factors should be a priority in the assessment of adult onset asthma. In most cases, occupational exposures induce new onset asthma in a healthy subject, or workplace exposures may reactivate asthma in individuals who have been asymptomatic for years, or may aggravate pre-existing asthma. In each case, identifying which of these possibilities is true (that is, work related exposures as asthma inducers or asthma triggers) is relevant for the management of the disease, including prevention of additional cases, treatment, disability evaluation, and compensation.
To date, more than 250 agents capable of causing occupational asthma have been reported.4 5Substances that induce occupational asthma are classified as either high molecular weight allergens (> 5 kDa)—usually protein derived allergens—or as low molecular weight compounds. It has been hypothesised that low molecular weight chemicals could act as haptens and combine with a body protein to form a complete antigen.
Since 1989, the SWORD (surveillance of work related and occupational respiratory disease) project has provided a consistent and reliable estimate of the incidence and pattern of occupational respiratory diseases in the UK.1 Occupational asthma continues to be the most reported respiratory disease, although its incidence is lower than in previous years, with an estimated 822 cases (27% of total cases).1 Reporting from previous …