Agents, old and new, causing occupational asthma.

Asthma is common among adults of working age and aVects 5–10% of the population worldwide. Occupational asthma has become a common work related respiratory disorder in the industrialised world. 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. Studies that have used information collected during military service suggest that occupational factors explain 25% of apparently new cases. 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.