Objectives:
To study the associations between exposure to bioaerosols and work-related symptoms, lung function and biomarkers of airway inflammation in compost workers.

Material and Methods:
Personal full-shift exposure measurements were performed on 47 workers employed at five windrow plants (n=20) and five reactor plants (n=27). Samples were analyzed for endotoxins, bacteria, fungal and actinomycetes spores. Health examinations were performed on workers and 37 controls before and after work on the day exposure was measured. The examinations included symptoms recorded by questionnaire, lung function by spirometry and nasal dimensions by acoustic rhinometry (AR). The pneumoproteins CC16, SP-D and SP-A were measured in a blood sample drawn at the end of the day.

Results:
The levels of endotoxins (median 3 EU/m³ , range 0–730 EU/m³) and actinomycetes spores (median 0.2 × 10⁶ spores/m³, range 0–590 × 10⁶ spores/m³) were significantly higher in reactor plants compared to windrow plants. However, windrow composting workers reported more symptoms than reactor composting workers, probably due to use of respiratory protection. Exposure-response relationships between actinomycetes spores exposure and respiratory effects, found as cough and nose irritation during a shift, was significantly increased (OR 4.3, 95% CI 1.1–16, OR 6.1, 95% CI 1.5–25, respectively, p<0.05) among workers exposed to 0.02–0.3 × 10⁶ actinomycetes spores/m³, and FEV1/FVC% decreased cross shift (b=–3.2, SE=1.5%, p<0.01). Effects were weaker in the highest exposed group, but these workers used respiratory protection, frequently limiting their actual exposure. No relationships were found between exposure and pneumoprotein concentrations.

Conclusions:
The major agent in the aerosol generated at compost plants was actinomycetes spores which was associated with work related cough symptoms and work-shift lung function decrease.