Indoor dust and air concentrations of endotoxin in urban and rural environments.
Résumé
AIMS: Studies in European children from a farming background have shown that these children have a reduced risk of asthma and atopic sensitization compared to their urban counterparts. It has been suggested that this might be due to exposure to high levels of endotoxin in the farming environment. The aim of this study was to compare indoor endotoxin concentrations in air and dust samples from randomly selected urban and rural dwellings. METHODS: In the rural area, endotoxins were analysed in farmhouses and non-farmhouses as well as housing characteristics, lifestyle factors and agricultural practices likely to influence air and dust endotoxin levels. RESULTS: Endotoxin levels were significantly higher in floor (6,600 ng ± 6,000 vs 3,600 ng ± 5,000 and 3,800 ng ± 17,000; p<0.001) and mattress dust (2,900 ng ± 4,000 vs 1,100 ng ± 2,000 and 800 ng ± 2,600; p<0.001) from farmhouses compared to other rural and urban homes. However, no difference was observed between endotoxin concentrations in the air of urban and rural houses and airborne endotoxin levels did not correlate to dust levels. Lack of ventilation and direct entry into the house were correlated with an increase in dust endotoxin levels. CONCLUSIONS: These results confirm that dairy farming is associated with high exposure to endotoxins in indoor dust samples. No difference was observed between indoor airborne concentrations between urban and rural houses. These results suggest that measuring endotoxin in dust is the most relevant method to assess endotoxin exposure. © 2012 The Authors Letters in Applied Microbiology © 2012 The Society for Applied Microbiology.