A cohort study of wastewater treatment plant workers: Association between levels of biomarkers of systemic inflammation and exposure to bacteria and fungi, and endotoxin as measured using two methods

Abstract

Work in wastewater treatment plants (WWTPs) can be associated with exposure to airborne microorganisms and endotoxin from the working environment. The aim of this study was to obtain knowledge about whether serum levels of the markers of systemic inflammation, C-reactive protein (CRP) and serum amyloid A (SAA), are associated with personal exposure to endotoxin, measured using the Limulus (endotoxin_Limulus) and the rFC (endotoxin_rFC) assays, as well as bacteria and fungi in a cohort of WWTP workers. Exposure and blood samples were collected for 11 workers over one year. Exposure to endotoxin_Limulus-day and endotoxin_rFC-day correlated significantly (r = 0.80, p<0.0001, n = 104), but endotoxin_Limulus-day was 4.4 (Geometric mean (GM) value) times higher than endotoxin_rFC-day (p<0.0001). The endotoxin_Limulus-day, endotoxin_rFC-day, bacteria, and fungal exposure as well as serum levels of CRP_-day (GM=1.4 mg/l) and SAA_-day (GM=12 mg/l) differed between workers. Serum levels of SAA_day correlated significantly with CRP_day (r = 0.30, p = 0.0068). The serum levels of CRP_day were associated significantly with exposure to endotoxin_Limulus-day. Exposure, SAA and CRP data were also analyzed as av. of each season, and SAA_season was associated positively and significantly with endotoxin_{Limulus-season} and endotoxin_rFC-season and negatively with fungal_season exposure. In conclusion, CRP_day was associated with the endotoxin_Limulus-day and SAA_season with endotoxin_{Limulus-season} and endotoxin_rFC-season exposure. Thus, we hereby document that WWTP workers are exposed to airborne endotoxin which seems to have a negative impact on their health.

Keywords: Inflammation; LPS; MALDI-TOF MS; Occupational exposure; Occupational exposure limit; Wastewater.