Inter-laboratory analysis of endotoxin in cotton dust samples.
BACKGROUND
Currently there are no mandated exposure limits for endotoxin, but recommended limits have been proposed and interest expressed in developing quantitative standards for endotoxin. A limitation for developing a quantitative standard for endotoxin is the measurement variability between laboratories. Inter-laboratory variability of up to four orders of magnitude has been reported for replicate samples. To evaluate both the intra- and inter-laboratory variability, Round-Robin studies were conducted using replicate samples of cotton dust.


METHODS
Replicate samples of cotton dust were collected using vertical elutriators (VE) in a model cardroom. Each participating laboratory evaluated the samples for endotoxin using: their normal extraction procedure; a common extraction procedure; and a common extraction procedure and the same type and lot of a commercially available endotoxin kit.


RESULTS
These studies demonstrated that both intra- and inter-laboratory variability is reduced by using a common extraction protocol and a common assay kit; however, significant differences remained between the laboratories.


CONCLUSIONS
The data suggest that intra-laboratory assays can be used to assess the relative differences between endotoxin samples, however, the inter-laboratory variability suggests that limitations remain for developing a reliable exposure assessment assay that could be used for a quantitative exposure standard.
Jacobs
Robert R
RR
Graduate Program in Public Health, Eastern Virginia Medical School, Norfolk, Virginia 23501-1980, USA. jacobsrr@evmsmail.evms.edu
Chun
David
D
D000395:Air Pollutants, Occupational / Q000032:analysis*; D016902:Air Pollution, Indoor / Q000032:analysis*; D032561:Cotton Fiber; D004391:Dust / Q000032:analysis; D004731:Endotoxins / Q000032:analysis*; D019981:Health Care Sector; D007221:Industry
D000395:Air Pollutants, Occupational; D004391:Dust; D004731:Endotoxins