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. METHOD: 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.

Endotoxins isolated from the air of a Danish paper mill and the relation to change in lung function: an 11-year follow-up.

BACKGROUND: A decline in lung function has been associated with farming, cotton spinning, and work in the animal feed industry. The aim of the study was to reveal if loss of lung function was associated to work at a paper mill. METHODS: Ninety-seven male paper workers (PW), and 55 control workers were examined. Hygiene samples included total dust, endotoxins, and microorganisms. Interview, pulmonary function testing, and skin prick test (SPT) were performed and yearly decline in lung function was calculated. RESULTS: The exposure for endotoxin (LPS) ranged from Median (Max-Min) 69 (370-6) EU/m3, in the wet-end of the paper machines to 6 (19-16) in the pulping area. The lung function decline among the controls was comparable to the decrements among the maintenance and repair workers at the paper factory, around 51-54 and 37-38 ml/year among smokers' and non-smokers, respectively. After adjustment for baseline FEV1, the variables associated to an increased loss of FEV1 were age smoking and cough. For FVC we found an inverse relation between exposure and yearly decline. CONCLUSION: No increase in loss of lung function is seen among workers exposed to up to 200 EU/m3 of LPS.

Second inter-laboratory study comparing endotoxin assay results from cotton dust.

Previously, a large two-part inter-laboratory round robin endotoxin assay study was completed. This first study showed that when cotton dust samples, which are practically identical, are assayed for endotoxin that the intra- laboratory results had a very small variation while intra-laboratory results of the sample had a very high variation. In the first part of the study, each laboratory followed its own in-house assay protocol; but in the second part of the study, when the extraction protocol was standardized, the inter-laboratory results showed a lower variation, which suggested that with further standardization, further reduction of differences between laboratories might be achieved in order that results between laboratories would become more comparable. The results stimulated interest in extending the study to include cotton dust with two levels of endotoxin, standardization of the extraction protocol, and using the same assay kit from the same production lot. The results of this second round robin endotoxin assay study indicate that differences between laboratories are still high, but most of the laboratories could discern the cotton dusts with the different levels of endotoxin.