Interventions to reduce the impact of outdoor air pollution on asthma: A systematic review.

<bold>Introduction:</bold> Exposure to air pollution can cause adverse effects to people living with chronic lung disease. In people with asthma, it's not clear whether startegies to reduce outdoor air pollution can impact clinical symtopms and lung function. <bold>Methods:</bold> The systematic review was conducted of seven databases for English literature between April 2012 to March 2022. Any study that mentioned air pollution exposure reduction and asthma was reviewed. Two reviewers (SH & RMM) screened and extracted the data separately using a standardised form based on the Cochrane data extraction tool. The risk of bias was assessed using Risk of Bias 2 (ROB2) tool. Outcome measures included asthma control test(ACT), childhood-ACT (c-ACT), exacerbations, forced expiratory volume in the first second (FEV1) and FEV/forced vital capacity(FVC) ratio. The study was registered with PROSPERO, CRD42022341648. <bold>Results:</bold> Of the 11 116 identified studies, 8 met the inclusion criteria with 11 195 043 participants in total. Clean air policy implementationmedestly improved lung functionwith FVC b and FEV1 by 0.02L/year and 0.01L/year respectively. Reduction to exposure to outdoor smoke pollution with use of a mobile application alerts resulted in behavioural changeand improved asthma control test scores, mean[SD] =21.5[2.3] compared to 20[2.4] over 8 weeks; p<0.001. ACT improved during low levels of pollution ralated to Covid-19 lockdown, mean[SD] ACT= 17.3[4.7] vs 19.7[4.5]; p<0.001 and with associated decline in mean daily admissions, 4.5 [3.4] vs 2.8[2.5] days; p<0.001. <bold>Conclusion:</bold> Air quality alerts results in behavioural change that can modesty improve asthma control. Clean air policy implementation modesty improve lung function.