Shape of the association between endotoxin in school dust and children's lung function

Within the framework of the SINPHONIE study, this study aimed to examine the dose-response relationship between increasing endotoxin concentrations and reduced lung function parameters, seeking potential threshold effects and accounting for regional differences.

Spirometry data from 3870 schoolchildren across 21 European countries were analysed to assess the impact of endotoxin exposure on lung function parameters. A general additive model was applied, adjusting for country, age, height, weight and sex. Additionally, a linear regression model with random effects was employed, treating country as a panel variable. In that latter model, "asthma ever" was also included as a possible moderator of endotoxin effects.

For most parameters, a linear decline in lung function was observed with increasing endotoxin levels, with no clear threshold effect. For example, forced expiratory volume in 1 s decreased by 4.8 mL per an increase in endotoxin concentration of 1000 EU·m^-2 and peak expiratory flow by 10 mL·s^-1 (both p<0.001). However, some parameters showed a plateau at higher endotoxin concentrations. The association remained mostly unchanged and statistically significant across most spirometry values except for forced vital capacity, when adjusting for country as a panel variable. "Asthma ever" was reported for 272 (7.3%) of 3737 children. While these children performed significantly worse in the lung-function test, "asthma ever" did not increase vulnerability to endotoxin.

The school environment in general and endotoxin levels in particular, have an impact on children's respiratory health, calling for additional efforts for improvements, including improved cleaning measures and ventilation.