We measured endotoxin concentrations in the air and dust of randomly selected apartments and houses in the Strasbourg metropolitan area, and we determined whether characteristics of the home, including the presence of furry pets, may influence them.
Air and dust samples were taken from 100 dwellings randomly selected after stratification according to the Institut National de la Statistique et des Etudes Economiques. Individual air samples (three samples of 8 h each) were taken (n = 300) with a personal sampler, as previously described (1). Dust samples were taken from the floor and mattress of one occupied bedroom randomly selected following the methods recommended by international consensus. Endotoxin concentration in air and dust samples was assessed with the Limulus Amebocyte Assay (Chromogenix AB, Möndal, Sweden) as previously described (1) and expressed in ng/m3 and μg/g of house dust (HD), respectively. Residents were questioned to complete a modified version of the Medical Indoor Environment Counselor questionnaire (2), addressing some environmental and lifestyle features, including the type of building, type of floor, presence of mechanical ventilation, house plants, indoor furry pets and smokers, type of base and age of the mattress. anova was performed to assess the influence of characteristics of the home, after log-transformation of the data. Nonparametric tests were also used. Pearson correlation coefficients between the endotoxin levels in the three different type of samples (airborne, dust floor and mattress dust) were determined.
The mean concentration of endotoxins in the air, and in bedroom floor and mattress dust were 0.180 ng/m3 (95% CI: 0.125–0.235), 3.24 μg/g (95% CI: 1.697–4.783) and 1.70 μg/g (95% CI: 0.603–1.110), respectively. Endotoxin levels in floor dust were correlated with levels in mattress dust (r = 0.53, P = 0.002), but not with airborne levels (r = 0.053, P = 0.56). There was no significant association between endotoxin levels in dust or in the air and type of building, type of bedroom floor, use of mechanical ventilation, presence of furry pets, type of pet (cat, dog, cat and dog or other furry pets) or their presence in the bedroom (regardless of the type bedroom floor), presence of houseplants or smokers. Furthermore, endotoxin levels in mattress dust were not significantly associated with age of mattress and type of base (Table 1).
|n||Endotoxin levels||95% CI||P-value*|
|Geometric mean (ng/m3)||Arithmetic mean (ng/m3)|
|Type of building|
|Environmental tobacco smoke|
|Furry pets in the home|
|Cat + dog||2||0.360||0.630||−0.382 to 1.642|
Our data demonstrated that airborne endotoxin levels in urban domestic dwellings were 100–1000 times lower than those measured in air of occupational settings (3). It has been suggested that the presence of animals may have a protective effect on the onset of atopy (4). We found no correlation between the presence of furry pets and either airborne or dust endotoxin levels. This suggests that animals were not responsible for endotoxin levels in either air or dust. This is consistent with the showing by Lieutier-Colas et al. (1) that airborne endotoxin levels were not correlated with the presence of the rats in rat quarters. Michel et al. also reported that the presence of furry pets in homes did not influence the HD endotoxin levels (5). We also found no correlation between dust and airborne endotoxin levels. This suggests that it seems necessary to measure endotoxin in both dust and air to obtain a relevant assessment of exposure.