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Applied and Environmental Microbiology, October 2007, p. 6134-6143, Vol. 73, No. 19
0099-2240/07/$08.00+0     doi:10.1128/AEM.00851-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Optimization of Airborne Endotoxin Exposure Assessment: Effects of Filter Type, Transport Conditions, Extraction Solutions, and Storage of Samples and Extracts{triangledown}

Suzanne Spaan,1,2 Dick J. J. Heederik,1 Peter S. Thorne,3 and Inge M. Wouters1*

Division Environmental Epidemiology (EEPI), Institute for Risk Assessment Sciences (IRAS), Utrecht University, Utrecht, The Netherlands,1 Food and Chemical Risk Analysis, TNO Quality of Life, Zeist, The Netherlands,2 Environmental Health Sciences Research Center, University of Iowa, Iowa City, Iowa3

Received 16 April 2007/ Accepted 28 July 2007

Endotoxin exposure occurs in homes and occupational environments and is known to cause adverse health effects. In order to compare results from different studies and establish standards, airborne endotoxin exposures should be assessed using standardized methods. Although the European Committee for Standardization (CEN) developed guidelines for endotoxin exposure assessment, these leave room for individual interpretation. The influence of methods of sampling, extraction, and analysis has never been investigated in a full experimental design. Thus, we sought to fully elucidate the importance of all facets of endotoxin assessment. Inhalable dust samples collected simultaneously were used to investigate the effects on and interactions with airborne endotoxin concentration in two working environments of filter type (glass fiber or Teflon), transport conditions (with/without desiccant), sample storage (–20 or 4°C), extraction solution (pyrogen-free water [PFW] or PFW plus 0.05% Tween 20), extract storage (–20 or 4°C), and assay solution (PFW or PFW plus 0.05% Tween 20). Four hundred samples were collected and randomly distributed over the 20 combinations of treatments. There were no differences found for transport conditions and storage temperature of extracts. Also, no interactions between study variables existed. Sampling on glass-fiber filters, storage of samples in the freezer, and extraction in PFW plus 0.05% Tween 20 resulted in 1.3-, 1.1-, and 2.1-fold-higher estimated endotoxin concentrations, respectively. Use of PFW plus 0.05% Tween 20 in the assay solution had an additive effect. Thus, this study investigated gaps in the CEN protocol and provides data with which to fully specify a protocol for standardization of endotoxin exposure assessment.

* Corresponding author. Mailing address: Institute for Risk Assessment Sciences, Division Environmental Epidemiology, Utrecht University, P.O. Box 80178, 3508 TD Utrecht, The Netherlands. Phone: 31 30 253 9449. Fax: 31 30 253 9499. E-mail: i.m.wouters{at}iras.uu.nl

{triangledown} Published ahead of print on 3 August 2007.

Applied and Environmental Microbiology, October 2007, p. 6134-6143, Vol. 73, No. 19
0099-2240/07/$08.00+0     doi:10.1128/AEM.00851-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Spaan, S., Doekes, G., Heederik, D., Thorne, P. S., Wouters, I. M. (2008). Effect of Extraction and Assay Media on Analysis of Airborne Endotoxin. Appl. Environ. Microbiol. 74: 3804-3811 [Abstract] [Full Text]  


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