Airborne environmental endotoxin: a cross-validation of sampling and analysis techniques

Area of Science:

• Environmental Science
• Microbiology
• Analytical Chemistry

Background:

• Airborne endotoxin poses health risks in occupational settings.
• Accurate measurement of environmental endotoxin is crucial for exposure assessment.
• Existing methods may lack standardization or require complex analysis.

Purpose of the Study:

• To develop and validate a standard method for measuring airborne environmental endotoxin.
• To field test the method in an industrial setting (fiberglass insulation manufacturing).
• To identify the source and characteristics of airborne endotoxin in the facility.

Main Methods:

• Developed a method using capillary-pore membrane filters for sampling.
• Employed sonication bath extraction followed by kinetic-Limulus assay with resistant-parallel-line estimation (KLARE).
• Cross-validated with methanolysis and gas chromatography-mass spectrometry (GC-MS) for 3-hydroxy fatty acids (3-OHFA).

Main Results:

• The KLARE method showed high reproducibility (95% CI +/- 0.28 log10).
• KLARE results closely correlated with GC-MS 3-OHFA analysis (P = 0.23, avg diff 0.88%).
• Airborne endotoxin originated from gram-negative bacteria (Deleya aesta, Acinetobacter johnsonii) in washwater, becoming airborne during cleaning.

Conclusions:

• The developed standard procedure is accurate, precise, and sensitive for airborne environmental endotoxin measurement.
• The KLARE method provides a reliable tool for occupational exposure monitoring.
• Identified spray cleaning operations and contaminated washwater as sources of airborne endotoxin.