Interlaboratory evaluation of endotoxin analyses in agricultural dusts--comparison of LAL assay and mass spectrometry.
Endotoxin exposure is associated with wheeze and asthma morbidity, while early life exposure may reduce risk of allergy and asthma. Unfortunately, it is difficult to compare endotoxin results from different laboratories and environments. We undertook this study to determine if lipopolysaccharide (LPS) extraction efficiency could account for differences among laboratories. We generated and collected aerosols from chicken and swine barns, and corn processing. We randomly allocated side-by-side filter samples to five laboratories for Limulus assay of endotoxin. Lyophilized aliquots of filter extracts were analyzed for 3-hydroxy fatty acids (3-OHFAs) as a marker of LPS using gas chromatography-mass spectrometry. There were significant differences in endotoxin assay and GC-MS (LPS) results between laboratories for all dust types (p < 0.01). Patterns of differences between labs varied by dust type. Relationships between assay and GC/MS results also depended on dust type. The percentages of individual 3-OHFA chain lengths varied across labs (p < 0.0001) suggesting that each lab recovered a different fraction of the LPS available. The presence of large amounts of particle associated LPS and absence of a freezing thawing cycle were associated with lower correlations between LPS and bioactivity, consistent with an absence of Limulus response to cell-bound endotoxin. These data suggest that extraction methods affect endotoxin measurements. The LAL methods may be most suitable when comparing exposures within similar environments; GC-MS offers additional information helpful in optimizing sample treatment and extraction. GC-MS may be of use when comparing across heterogeneous environments and should be considered for inclusion in future studies of human health outcomes.
Reynolds
Stephen J
SJ
Department of Environmental and Radiological Health Sciences, Colorado State University, Ft. Collins, CO 80523-1681, USA. Stephen.Reynolds@Colostate.edu
Milton
Donald K
DK
Heederik
Dick
D
Thorne
Peter S
PS
Donham
Kelley J
KJ
Croteau
Elizabeth A
EA
Kelly
Kevin M
KM
Douwes
Jeroen
J
Lewis
Daniel
D
Whitmer
Mike
M
Connaughton
Ian
I
Koch
Sharon
S
Malmberg
Per
P
Larsson
Britt-Marie
BM
Deddens
Jim
J
Saraf
Anita
A
Larsson
Lennart
L
D000336:Aerosols; D016902:Air Pollution, Indoor / Q000032:analysis*; D000822:Animal Husbandry; D000818:Animals; D002645:Chickens; D004391:Dust / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D007753:Laboratories; D008033:Limulus Test; D008070:Lipopolysaccharides / Q000032:analysis*; D015203:Reproducibility of Results; D013552:Swine; D003313:Zea mays
D000336:Aerosols; D004391:Dust; D008070:Lipopolysaccharides