Occupational asthma caused by exposure to ash wood dust (Fraxinus americana)

A 63 year old man reported rhinitis and asthma, which occurred only at work where he was exposed to ash wood dust. Monitoring of peak expiratory flow rates (PEFR) and bronchial responsiveness to histamine when off work and at work showed increased variation of PEFR at work but no significant changes in nonspecific bronchial responsiveness assessed by the provocation concentration producing a 20% fall in FEV1 (PC20). Specific inhalation challenges were carried out in a special challenge room with ash wood dust. During the exposure for only 3 minutes, the mean concentration of particles was 3 mg-m3 and about 50% of particles had a diameter less than 10 mu. An immediate bronchospastic reaction was documented. Antibodies to a human serum albumin (HSA) ash wood conjugate were not significantly increased.