Dampness and microbial secondary metabolites in schools and respiratory symptoms in children: the HITEA study

Abstract

Introduction: Dampness and mould exposure have been linked to respiratory symptoms, but studies on causative agents are limited. We aim to explore whether microbial secondary metabolites explain associations between moisture and mould in schools and the presence of respiratory symptoms in pupils. Methods: Primary schools in Spain, the Netherlands and Finland were selected based on presence (n=29) or absence (n=26) of reported and observed dampness and/or mould. Ten dust samples per school were collected and targeted for 188 secondary metabolites using liquid chromatography/mass spectrometry. In total 30 different metabolites were found. Information was obtained from 9068 children (response 62%) on respiratory symptoms and potential determinants using parent-administered questionnaires. Associations between metabolites and respiratory symptoms were analyzed by mixed logistic regression. Results: In Finland pupils attending damp schools reported more often respiratory symptoms in the past 12 months, like current wheeze (Odds Ratio(OR) 1.6; 95%CI (1.1-1.8)), phlegm (OR 1.3; 0.9-1.8), nocturnal dry cough (OR 1.3; 1.0-1.8) and nasal symptoms (OR 1.3; 1.0-1.7). Mutual adjustment for average number of metabolites per school did not affect associations, while associations between metabolite load and symptoms changed slightly when adjusting for school dampness. In Finland higher metabolite loads tended to be associated with an increased symptom prevalence. Associations were not different for metabolites of a predominantly indoor or outdoor context. While the overall average number of detectable metabolites did not affect respiratory symptoms, in the Netherlands symptoms were associated with average numbers of ‘indoor’ metabolites and in Finland with ‘outdoor’ metabolites. Conclusions: Secondary metabolites do not seem to explain the moisture damage effect in schools in our study. Also the evidence for their effect on respiratory symptoms in pupils was weak.