Indoor dust and air concentrations of endotoxin in urban and rural environments

Abstract

Significance and Impact of the Study: Rural dairy farming is associated with high exposure to indoor endotoxins as compared to rural nonfarming houses and urban houses. The time spent on the mattress (7 h for an adult) and of the proximity of the contaminated source should be taken into account with the other causes of exposure. AbstractStudies 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. In the rural area, endotoxins were analysed in farmhouses and nonfarmhouses as well as housing characteristics, lifestyle factors and agricultural practices likely to influence air and dust endotoxin levels. Endotoxin levels were significantly higher in floor (6600 AE 6100 vs 3600 AE 5600 and 3800 AE 17 000 ng g À1 ; P < 0Á001) and mattress dust (2900 AE 4100 vs 1100 AE 2400 and 800 AE 2600 ng g À1 ; P < 0Á001) 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. 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.

Influence of early-life exposures on food sensitization and food allergy in an inner-city birth cohort

“…This finding is similar to those of previous longitudinal studies for eczema 28 and asthma, 29 but to our knowledge, this is the first study to prospectively examine this relationship for the development of food allergy. Previous studies have demonstrated that endotoxin levels are lower in urban environments than in rural farming areas, 30,31 and a recent study examining the indoor microbiome in the same URECA cohort found that exposure to specific allergens and bacteria was associated with reduced sensitization to inhalant allergens as well as recurrent wheeze (in press). Therefore, while it has been previously suggested that the high rates of allergy and asthma in the inner city contradict the hygiene hypothesis, 32 both of these studies suggest that this is not actually the case.…”

Children’s residential exposure to selected allergens and microbial indicators: endotoxins and (1→3)-β-D-glucans

“…We could only compare the concentrations found in our study with other studies conducted in children's homes. Significant differences between urban and rural environment were noticed [39]. It therefore seems that endotoxins concentrations demonstrated by us are too low to protect children in the way defined in the "hygienic hypothesis".…”

A mechanistic review of silica-induced inhalation toxicity

“…If this is the case, these findings strongly suggest that silica exposure deteriorates phagocytic ability of alveolar macrophages against foreign matter and consequently elevates bioactive LPS concentration in the lung, because LPS is ubiquitous in the environment: LPS is part of the outer membrane of the cell wall of Gram-negative bacteria (Heine et al, 2001), such as Escherichia coli (E. coli), Salmonella, Shigella, Pseudomonas and Neisseria, and thus LPS molecules are present in the air of laboratory animal rooms (Kaliste et al, 2002(Kaliste et al, , 2004Ooms et al, 2008) and in indoor air (Bouillard et al, 2005;Larsson et al, 2004;Sebastian et al, 2006;Simpson et al, 1999). In addition, multiple studies show that measurable amount of endotoxin exists in house dust (Barnig et al, 2013;Gehring et al, 2002;Gereda et al, 2001;Holst et al, 2015;Jacobs et al, 2013;Ownby et al, 2013;Park et al, 2001), which is presumed to exacerbate asthma (Kanchongkittiphon et al, 2015). Accordingly, it is highly likely that exposure to a-quartz deteriorates the phagocytic ability of M2 macrophages, which results in the elevation of bioactive LPS concentration in the lung.…”