Endotoxin is one of the contaminants of cotton dust that may be responsible for respiratory illness within textile workers. Epidemiological studies have shown that both dust and endotoxin in the air of cotton mills are closely correlated to the presence of respiratory symptoms. Currently occupational exposure standards in both the UK and USA are set on dust levels rather than endotoxin, primarily as it is considered that endotoxin sampling is unreliable and not reproducible and could give significantly varying results when performed by different technicians.