Biomarkers of inflammation in workers exposed to compost and sewage dust

The association between exposure during handling of sewage and compost and the serum concentration of inflammatory biomarkers was studied.

A total of 44 workers exposed to sewage dust, 47 workers exposed to compost dust and 38 referents from the administrative staff participated. Microbial aerosols were collected by personal inhalable samplers. The concentrations of bacterial cells, spores from fungi and bacteria (actinomycetes) and endotoxins were determined by fluorescence and scanning electron microscopy and the Limulus assay. Fibrinogen, D-dimer, ICAM-1, VCAM-1 and IL-6 were determined by ELISA and C-reactive protein (CRP) by HS-MicroCRP assay in blood samples collected post-shift.

The exposure to dust ranged from 0.02 to 11 mg/m(3), endotoxins from 1 to 3160 EU/m(3) and bacteria from 0 to 209 × 10(6) cells/m(3). Fungal (0-41 × 10(6) spores/m(3)) and actinomycetes spores (0-590 × 10(6) actinomycetes spores/m(3)) were observed only at compost plants. The exposed workers had significantly higher fibrinogen (arithmetic mean 3.3 mg/ml) and CRP (geometric mean 1.5 mg/L) compared to the referents (2.8 and 1.0 mg/L, respectively). The serum concentration of CRP was negatively associated with forced expiratory volume in one second (FEV1) in  % of predicted. Exposure to inhalable dust and bacteria was positively associated with the serum concentration of ICAM-1.

This study suggests that exposure to bacteria and dust when handling sewage and compost may initiate an inflammation shown by an increase in serum concentration of ICAM-1. The higher concentrations of fibrinogen and CRP in exposed workers compared to the referents may reflect a low-grade systemic inflammation.