Performances of the BC-112 NIOSH cyclone for the measurement of endotoxins in bioaerosols: A study in laboratory conditions

Abstract

The BC-112 cyclone is a personal bioaerosol sampler with of a metallic main body (2mm inlet), a first collection stage (1.5mL collection tube) and a final collection stage (37mm three pieces cassette). A laboratory study has been carried out with E. coli experimental bioaerosols in order to investigate the efficiency of the cyclone for the measurement of airborne endotoxins in laboratory conditions. A first set of experiments allowed the validation of a protocol for the removal of endotoxins from contaminated BC-112 cyclones. The study also showed that endotoxins deposited on the inner cassette walls during sampling. Endotoxins deposits accounted for 18–42% of the total endotoxins measured in the bioaerosols and an adaptation of the analytical protocol was necessary in order to take such deposits into account. Furthermore, the type of filter mounted in the cassette significantly (p < 10−4) influenced the concentration of airborne endotoxins measured in the experimental bioaerosol. Teflon and PVC filters led to the highest concentrations while, surprisingly, fiberglass filters led to the lowest ones. An optimal configuration was set for the sampling devices including a PVC filter as collecting medium and extraction of collected endotoxins directly into the cassette. In such a configuration and with our experimental conditions the side by side comparison of the closed-face cassette (CFC) and the BC-112 cyclone showed a significant correlation (r = 0.99; n = 16; p < 10−4) between measurements done with the two sampling devices. The results also highlight that experimental biases may occur when comparing the collection or the overall efficiency of bioaerosol samplers using microbial surrogates and bioaerosol chambers. We concluded that the BC-112 cyclone was suitable for the assessment of airborne endotoxins providing protocol adaptations and that the overall efficiency of the device for the measurement of airborne endotoxins should be investigated in real exposure conditions as well as in other laboratory conditions.