Study objective: To compare exposure to microorganisms associated with allergic alveolitis (AA) and with febrile reactions to inhaled mold dust (organic dust toxic syndrome [ODTS]) in farmers and in normal subjects.
Design: A prospective study in which exposure was evaluated within two weeks of medical consultation for AA or ODTS. Samples were collected during normal farming (background) and during the handling of materials associated with disease or causing maximal exposure in reference farms (worst case).
Setting: Swedish farms
Participants: Eleven farmers with a confirmed diagnosis of AA from ten farms, 16 subjects with symptoms of ODTS from 12 farms, and 17 reference farmers.
Measurements and results: Worst-case samples representative of the exposure preceding disease were obtained on four farms where five farmers had had AA; the samples contained on average 2.6 +/- 1.8 x 10(9) (SD) spores/m3 of air. On six farms where nine farmers had had ODTS, representative samples averaged 13 +/- 13 x 10(9) spores/m3, and on reference farms this figure was 0.12 +/- 0.20 x 10(9) spores/m3. The daily spore dose associated with allergic alveolitis was 2 x 10(9) spores/d, which was ten times higher than on reference farms. The average dose associated with ODTS was 2 x 10(10) spores. Worst-case samples, collected during 10 to 30 min, contributed to more than 90 percent of the day exposure on farms where AA or ODTS had occurred.
Conclusion: Allergic alveolitis was associated with high exposure levels on most weekdays for weeks, and ODTS was associated with extreme exposure occurring on a single day. There was no correlation with individual spore types and disease and the present results are compatible with a hypothesis that common cell wall components of microorganisms may cause "toxic" symptoms and stimulate immune reactions.