Technical report on airborne endotoxin measurement validation studies.
NIOSH 1998 Jul; :1-16
The optimal and standardized methods for measuring endotoxin have not been established. Several publications have suggested that one or another combination of collection and extraction methods are superior. However, the results of these studies give mostly contradictory signals. The discrepancy between studies and the need for better understanding and standardization of the methods is nowhere clearer than in the area of indoor air quality where different laboratories have reported more than 100 fold differences in the "normal" levels of airborne endotoxin. In this project, we developed an aerosol chamber capable of achieving mass balance for both gravimetric measurements, and to a lesser extent, endotoxin and LPS measurements. By using gravimetric measurements and LPS measurements, we established two internal standards for comparison of the levels of endotoxin activity recovered from the aerosol chamber. We found that changes in the extraction media used for the endotoxin samples caused large shifts in the apparent potency of the starting materials. These shifts would have suggested that a nonionic detergent (Tween-20) was a superior means of extracting endotoxin from filters. However, by comparison with the internal standards, and by computing yields based on a mass balance, we were able to show that this appearance was merely an artifact of Tween-20's interference with the Limulus assay. The highest valid yields of both endotoxin activity and LPS were achieved by collection of aerosol on capillary-pore polycarbonate filters and extraction in a phosphate triethylamine buffer.
Endotoxins; Dust-analysis; Sample-preparation; Analytical-methods; Bioassays; Solvent-extraction; Microorganisms
Environmental Health Harvard School of Public Hlth 665 Huntington Ave Boston, MA 02115
Pulmonary System Disorders
National Institute for Occupational Safety and Health
Harvard University, Boston, Massachusetts