Assessing the Impact of Non-exhaust Emissions on the Asthmatic Airway (IONA) Protocol for a randomised three exposure crossover study

Background People living with asthma are disproportionately affected by air pollution, with increased symptoms, medication usage, hospital admissions and the risk of death. To date there has been a focus on exhaust emissions, but traffic-related air pollution (TRAP) can also arise from the mechanical abrasion of tyres, brakes, and road surfaces. Non-exhaust emissions (NEE) currently make up a greater proportion of TRAP by mass than exhaust emissions. With the increasing weight of vehicle fleets due to electrification, and increasing uptake of larger vehicles, it is likely that NEE will continue to be an increasing health challenge. These NEE remain unregulated and underexplored in terms of their health impacts, particularly in vulnerable groups such as people living with asthma. To date, few real-world studies have attempted to explore the impacts of non-exhaust emissions on human health. We therefore created a study with the aim of investigating the acute impacts of NEE on the lung function and airway immune status of asthmatic adults. Methods The IONA study will expose adults with asthma in random order at three locations in London selected to provide the greatest contrast in the NEE components within TRAP. Health responses will be assessed before and after each exposure, with lung function measured by spirometry as the primary outcome variable. Discussion Collectively this study will provide us with valuable information on the health effects of NEE components within ambient PM2.5 and PM10, whilst establishing a biological mechanism to help contextualise current epidemiological observations.