Pneumoproteins in sewage workers exposed to sewage dust

Kari Kulvik Heldal,Dag G Ellingsen,Per Larsson,Lars Barregard

doi:10.1007/s00420-012-0747-7

Abstract

PurposeThe association between exposure to bacteria and endotoxins in sewage dust and the serum concentrations of pneumoproteins in sewage treatment plant workers were studied.MethodsForty-four workers from eight sewage treatment plants and 38 reference workers participated in the study. Microbial aerosol was collected by personal inhalable samplers. The concentrations of bacteria and endotoxins were determined by fluorescence microscopy and the Limulus assay, respectively. Pneumoproteins (Clara cell protein: CC16, and Surfactant proteins A and D: SP-A, SP-D) were determined by ELISA in blood samples collected post-shift.ResultsThe exposure to dust ranged from 0.02 to 9.3 (geometric mean (GM) 0.3 mg/m3, of bacteria from 0.3 to 4,900 × 103 (GM 27 × 103) cells/m3 and endotoxins from 1 to 3,160 (GM 28) EU/m3. The exposed workers had lower CC16 [arithmetic mean (AM) 4.9 ng/ml] compared to the referents (AM 6.4 ng/ml, p < 0.01). No significant difference was observed for SP-D and SP-A. Exposure to bacteria was positively associated with CC16 (p < 0.05) and SP-D (p < 0.05), adjusting for possible confounders.ConclusionsThis study showed that exposed workers had lower serum concentration of CC16 as compared to the referents, which may reflect a long-term effect on secretion of these pneumoproteins. The positive association between exposure to bacteria and the serum concentrations of CC16 and SP-D may be explained by a transient increased permeability of the lung–blood barrier.

Highlights

Workers at sewage treatment plants are exposed to a complex mixture of microorganisms, microbiological components, chemicals, and gases (Melbostad et al 1994; Douwes et al 2001; Spaan et al 2008)
The positive association between exposure to bacteria and the serum concentrations of CC16 and SP-D may be explained by a transient increased permeability of the lung–blood barrier
We have recently reported associations between exposure to endotoxin-containing dust and respiratory symptoms, such as airway irritation and cough among sewage workers (Heldal et al 2010)

Summary

Introduction

Workers at sewage treatment plants are exposed to a complex mixture of microorganisms, microbiological components, chemicals, and gases (Melbostad et al 1994; Douwes et al 2001; Spaan et al 2008). They are at risk of developing a range of adverse health eVects including airway irritation and pulmonary diseases such as toxic pneumonitis (Rylander 1999; Thorn and Kerekes 2001; Thorn et al 2002; Thorn and Beijer 2004). Air samples from sewage treatment plants consist mostly of bacteria, predominantly Gram-negative (Lundholm and Rylander 1983; Spaan et al 2008).

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