Quantification of ergosterol and 3-hydroxy fatty acids in settled house dust by gas chromatography mass spectrometry: Comparison with fungal culture and determination of endotoxin by a Limulus amebocyte lysate assay

Ergosterol and 3-hydroxy fatty acids, chemical markers for fungal biomass and the endotoxin of gramnegative bacteria, respectively, may be useful in studies of health effects of organic dusts, including domestic house dust. This paper reports a method for the combined determination of ergosterol and 3-hydroxy fatty acids in a single dust, sample and a comparison of these chemical biomarkers determined by gas chromatography-mass spectrometry with results from fungal culture and Limulus assay, Analyses of replicate house dust samples resulted in correlations of 0.91 (ergosterol in six replicates; P < 0.01) and 0.91 (3-hydroxy fatty acids in nine replicates; P < 0.001). The amounts of ergosterol (range, 2 to 16.5 ng/mg of dust) correlated with those of total culturable fungi (range, 6 to 1,400 CFU/mg of dust) in 17 samples, (r = 0.65; P < 0.005). The amounts of endotoxin (range, 11 to 243 endotoxin units/mg of dust) measured with a modified chromogenic Limulus assay correlated with those of lipopolysaccharide (LPS) determined from 3-hydroxy fatty acid analysis of 15 samples, The correlation coefficient depended on the chain lengths of 3-hydroxy acids used to compute the LPS content, The correlation was high (r = 0.88 +/- 0.01; P < 0.001) when fatty acid chains of 10 to 14 carbon atoms were included; the correlation was much lower when hydroxy acids of 16- or 18-carbon chains were included. In conclusion, the results of the described extraction and analysis procedure for ergosterol and 3-hydroxy fatty acids are reproducible, and the results can be correlated with fungal culture and endotoxin activity of organic dust samples.