endotoxin contamination in airborne vertically elutriated (ve) and total cotton dust was investigated in yarn preparation areas two cotton textile mills in shanghai, china. the two cotton textile mills had been studied 5 years earlier. dusts from all areas of the textile mills contained endotoxins. endotoxin burdens in ve dusts from the carding area were similar in both mills while the endotoxin contamination of total dust from carding in mill 1 was over three fold greater than that of total dust from carding in mill 2. mean endotoxin levels were in all areas of both mills above the reported threshold for acute pulmonary function effects in humans. airborne endotoxic burden was generally higher than levels found 5 years previously in the same mills. extracts of the bulk cotton samples were evaluated for their relative interleukin 1 (il-1) inducing activity with peripheral blood mononuclear cells. measurement of culture supernatant fluids with a commercial elisa assay showed that extracts from four of seven samples induced significantly more il-1 than would have been predicted by the level of endotoxin in the samples. results indicated that factors other than endotoxin may be involved also in the overall response to cotton dust