Towards an occupational exposure limit for endotoxins

Endotoxins are part of the outer membrane of Gram-negative bacteria and are present ubiquitously in the environment. The lipopolysaccharide (LPS) part of the molecule is responsible for its toxic properties. Environmental monitoring is usually performed by sampling airborne dust and subsequent analysis of aqueous extracts by using a LAL assay. The kinetic version of this assay can measure concentrations as low as in the pg/m 3 range. A generally accepted protocol is not yet available. Endotoxin levels are related to the occurrence of Gram-negative bacteria. Animal faeces and bacteria contaminated plant materials contribute most to organic dust related endotoxin exposure. Endotoxin exposure is therefore most prevalent in agricultural and related industries. Acute health effects are dry cough and shortness of breath accompanied by a decrease in lung function, fever reaction and malaise, and sometimes dyspnea and headaches occurring a few hours after the start of the endotoxin exposure. Epidemiological and experimental studies suggest that chronic endotoxin exposure may lead to chronic bronchitis and reduced lung function. Depending of the relevant health effect, no effect levels range from 9 to 170 ng/m 3 . The Dutch Expert Committee on