Effects of the inhaled dose of air pollution on health: a systematic review

The inhaled dose of air pollution (IDoAP) is an air pollution exposure quantification method that accounts for individuals' amount of inspired air (i.e. minute ventilation), and thus for the physical activity practised by individuals. We aimed to summarise the existing literature and identify research gaps on the health effects of IDoAP.We included original peer-reviewed research in PubMed, Scopus, SPORTDiscus, Embase and Cochrane prior to November 2024 and appraised bias following Cochrane and ROBINS-E tools. Title, abstract and full-text screening, data extraction and bias appraisal were completed in duplicate.Of 1888 screened studies, 25 studies were included, mostly focusing on healthy adults (21 out of 25 studies), overlooking susceptible populations such as pregnant individuals or those with pre-existing disease. Studies focused primarily on IDoAP of O3 (IDoAP-O3) (14 out of 25 studies) and particulate matter <2.5 µm in aerodynamic diameter (IDoAP-PM2.5) (13 out of 25 studies), with an exposure duration of up to 24 h. Lung function was the most studied outcome (19 out of 25 studies). Acute exposure to IDoAP-O3 was associated with reduced lung function: increasing IDoAP-O3 by 150 μg·m-3 led to a decrease in forced expiratory volume in 1 s (FEV1) of 0.27 L. This was driven by O3 concentration, while increases in minute ventilation did not affect FEV1 A number of research gaps were identified. These comprised research on susceptible and vulnerable populations, including residents of low-to-middle-income regions, and people with extreme occupational exposures; air pollutants other than O3 and PM2.5; and outcomes besides respiratory markers. Alternative statistical approaches are also required, such as multi-exposure models.Our findings support initiatives to generate low-pollution public corridors to keep IDoAP levels as low as possible to maximise health benefits from physical activity.