Optimization of the measurement method for airborne endotoxins in workplace atmospheres: experiments using...

Endotoxins are components of the outer membrane of bacteria that can become airborne during aerosol-generating work activities and cause adverse effects on workers' health. Filtration is the sampling method recommended by the EN 14031 standard for endotoxin measurements in workplace atmospheres. However, there are still differences in terms of practice regarding certain parameters of the measurement method. Thus, the storage of samples, the method of endotoxin extraction from the filter, and the type of filter are some parameters that still need to be studied to improve endotoxin recovery. For this purpose, laboratory experiments were performed based on 19 independent generations of an endotoxin aerosol coming from a suspension of 3 cultivable Gram-negative bacteria. Using a fix sampling time of 1 h, this experimental bioaerosol allow covering endotoxin concentrations from ~ 10 to ~ 104 EU/m3. Using the kinetic chromogenic LAL (Limulus Amebocyte Lysate) assay, our results show that a better recovery of endotoxins is achieved using 5 mL of pyrogen-free water compared to 10 mL, especially for glass fiber filters, with no change when the agitation time is reduced from 60 to 20 min. Except for polyvinylchloride, the type of filter (polycarbonate, Teflon, or glass fiber) does not have a great influence on the concentrations measured. However, PVC filters systematically gave a lower endotoxin concentration than the others. Finally, compared to the immediate processing of the cassette, storage of the samples at room temperature is possible for up to 8 d after sampling without altering the amount of endotoxin measured. These improvements make the results of the endotoxin concentration more robust and will help to make this measurement method more readily usable, especially with the simplification of the protocol steps and storage, providing a greater flexibility for analysts.