History and results of the two inter-laboratory round robin endotoxin assay studies on cotton dust.
BACKGROUND
In the US cotton industry, airborne cotton dust levels are regulated, and other countries are moving to specify safety limits for airborne endotoxins. There is concern about potential respiratory health hazards associated with agricultural and other organic dusts. In laboratories, ranking which samples have high and low levels of endotoxin is usually in good agreement between laboratories. When different laboratories assay identical samples, the levels differ. The objective of this research was to evaluate the intra- and inter-laboratory variability for 13 laboratories measuring endotoxin in cotton dust.


METHODS
Two inter-laboratory round robin endotoxin assay studies were conducted using cotton dust. In the first round robin, each laboratory used their normal in-house assay method and then used a common extraction protocol. In the second round robin, a common extraction protocol and endotoxin assay kit was used.


RESULTS
The intra-laboratory results had small variations but inter-laboratory results had very high variations. The inter-laboratory results using a common extraction protocol showed reduced differences. Using the same extraction protocol and endotoxin assay kit, the intra-laboratory variation was small and inter-laboratory variation was reduced but not enough for inter-laboratory agreement. Most of the laboratories were able to discern between the high and low endotoxin concentration dusts.


CONCLUSIONS
Standardization has reduced the differences in results between laboratories and possibly further standardization may bring closer inter-laboratory agreement.
Chun
David T W
DT
Cotton Quality Research Station, Agricultural Research Service, U.S. Department of Agriculture, Clemson, South Carolina 29633, USA. dtwchun@mindspring.com
Bartlett
Karen
K
Gordon
Terry
T
Jacobs
Robert R
RR
Larsson
Britt-Marie
BM
Larsson
Lennart
L
Lewis
Daniel M
DM
Liesivuori
Jyrki
J
Michel
Olivier
O
Milton
Donald K
DK
Rylander
Ragnar
R
Thorne
Peter S
PS
White
Eugene M
EM
Brown
Mary E
ME
Gunn
Varina S
VS
Würtz
Helle
H
D000391:Air Microbiology; D000395:Air Pollutants, Occupational / Q000032:analysis; D032561:Cotton Fiber; D004391:Dust / Q000032:analysis*; D004731:Endotoxins / Q000032:analysis*; D006801:Humans
D000395:Air Pollutants, Occupational; D004391:Dust; D004731:Endotoxins