Associations between airborne algae, ambient air pollution and lung function in a cross-sectional canadian population-based study

Airborne algae have been associated with respiratory illness in the setting of coastal harmful algae blooms but little is known about their effects in urban populations distributed across a country, and whether ambient air pollution is an effect modifier. Using cross-sectional data from 11,256 participants of the Canadian Health Measures Survey (CHMS), we tested the association between lung function expressed as a forced expiratory volume (FEV₁) and airborne concentrations of algae measured by a rotation impact sampler in the participant's city of residence on the day of spirometric testing. The daily upper 95th percentiles of algae ranged from 12.7 to 104.3 grains/m³. An interquartile range increase in algae was associated with a 2.55% (95%CI: 1.88, 3.23) decrease in percent predicted 1-s forced expiratory volume pp FEV₁, and a 2.54% (95%CI: -2.93, -2.14) decrease in pp FEV₁/forced vital capacity (FVC) after adjustment for participants' age, sex, education, annual income, active cigarette smoking, environmental tobacco smoke exposure, fine particulate air pollution (PM_2.5), total fungal spores and total pollen grains. An interquartile increase in PM_2.5 was associated with a 0.86% (95%CI: 0.78, 0.94) decrease in FEV₁, but we found no significant interaction between air pollutants and algae. Our findings suggest that independent of air pollution, airborne algae may influence lung function in urban populations widely distributed across Canada, and the observed effect was of larger magnitude than that of air pollution.