The comparison of endotoxin levels between study populations and countries is limited as a result of differences in sampling, extraction, and storage procedures. The objective of this study is to assess the levels and determinants of endotoxin in mattress and living room floor dust samples from three European countries, namely, Germany, the Netherlands, and Sweden, using a standardized sampling, storage, and analysis protocol. The mattress and living room floor dust was collected from the homes of 1065 German, Dutch, and Swedish (pre-)school children. All the samples were collected in the cool season and analyzed for endotoxin in a central laboratory. The determinants were assessed by a standardized questionnaire. The endotoxin concentrations in mattress and living room floor dust were found to be the highest in German homes and lowest in the Swedish ones. Differences between the geometric means were small (factor 1.1-1.7). Most of the associations between endotoxin concentrations and potential determinants were not statistically significant and heterogeneous across countries. However, keeping pets and having more than four persons living in the home were consistently associated with up to 1.7-fold higher endotoxin concentrations in mattress and floor dust. Furthermore, having carpets or rugs, and opening the windows frequently was associated with up to 3.4-fold and 1.3-fold higher endotoxin concentrations in living room floor dust, respectively. The proportion of variance explained by the questionnaire variables was generally low. In conclusion, the data on housing characteristics did not accurately predict the endotoxin concentrations in house dust, and could only partly explain the differences between countries.
Practical implications: The differences between the endotoxin concentrations in German, Dutch, and Swedish homes are small. House dust endotoxin concentrations are associated with a number of housing factors, such as pet-ownership, floor cover, number of persons living in the home, and ventilation. The variability of the endotoxin levels between homes and countries can only be partly explained by these factors.