Occupational asthma due to various agents. Absence of clinical and functional improvement at an interval of four or more years after cessation of exposure

Chest. 1989 Nov;96(5):1046-9. doi: 10.1378/chest.96.5.1046.


We have previously shown that in some subjects with occupational asthma caused by various agents, there is no improvement approximately two years after exposure ended. These results could be explained by the short interval between diagnosis and follow-up. In the current study, we saw 28 subjects with occupational asthma at two intervals, 2.3 years (range, three months to 5.7 years) and 5.8 years (range, 4.3 to 10.9 years) after the cessation of exposure. Various causes of occupational asthma were included. The diagnosis was confirmed in 26 of the cases by specific inhalation challenges in the laboratory, and in the remaining two cases by combined monitoring of peak expiratory flow rates and bronchial responsiveness. All subjects had symptoms of asthma at both follow-up assessments. There were no changes in the need for medication, spirometry, or bronchial hyperresponsiveness. Depending on the interval of the follow-up, four to six subjects required inhaled steroid agents in addition to the usual bronchodilators, 11 had FEV1 less than 80 percent of predicted, and 26 or 27 had an abnormal PC 20 histamine. Only two subjects demonstrated sustained improvement in PC 20 at the first and second follow-ups, and one other showed changes during the second follow-up assessment which were not present at the first. We conclude that except for three subjects, the need for medication did not diminish, nor did airway obstruction and hyperresponsiveness improve in this group of subjects with occupational asthma long after exposure ended. These results differ from other studies, which demonstrated that some recovery takes place in a greater proportion of individuals.

MeSH terms

  • Asthma / diagnosis
  • Asthma / etiology*
  • Bronchial Provocation Tests
  • Cyanates / adverse effects
  • Dust / adverse effects
  • Flour / adverse effects
  • Follow-Up Studies
  • Forced Expiratory Volume
  • Humans
  • Middle Aged
  • Occupational Diseases / diagnosis
  • Occupational Diseases / etiology*
  • Pollen
  • Time Factors


  • Cyanates
  • Dust
  • isocyanic acid