Assessing the impact of non-exhaust emissions from traffic on the asthmatic airway

In this study, participants with mild to moderate asthma will ride stationary bicycles on sidewalks in three London, UK environments (busy road characterized by stop-and-go traffic, high speed continuous traffic, and urban background) to measure how exposure to traffic with different mixtures of non-tailpipe and tailpipe emissions affects lung function of asthmatic adults.

Poster abstract for HEI Annual Conference 2023

IONA: Impact of non-tailpipe pollution on the asthmatic airway

C Griffiths^1,2, J Scales^1,2, H Hajmohammadi^1,2, K Katsouyanni^3,4, I Mudway³, D Green³

¹Queen Mary, University of London (London, UK), ²Asthma UK Centre for Applied Research (UK), ³Imperial College London (London, UK),⁴University of Athens (Athens, GR)

Background. Particles arising from tire and brake wear, as well as resuspension of road dust, now represent a greater proportion of roadside particulate matter (PM) by mass than direct tailpipe emissions. These non-tailpipe emissions remain unregulated, and their health impacts under explored, particularly in vulnerable groups.

Epidemiological work has associated road dust resuspension to between 4% and 10% increases in all-cause mortality, greater than vehicle exhaust emissions. In vitro toxicological studies have observed oxidative stress and inflammatory responses when lung cells are incubated with brake dust in both human and animal models. There are no in vivo experimental studies evaluating the impact of non-exhaust pollution on human health.

Research Question. Does short-term exposure to non-tailpipe particulates impair lung function, as measured by FEV1, in asthmatic adults?

Methods. A randomised cross-over study of short-term respiratory impacts on 48 non-smoking adults with moderate asthma during and after exposure to two contrasting, and one comparison, exposure environments in central London, UK:

1. Busy road with stop-go traffic to enhance brake wear emissions
2. High speed continuous traffic, to enhance tire and road wear emissions
3. An urban background site away from clear traffic sources.

Adults with mild to moderate asthma will be exposed at each site for two hours using a static bicycle exercise protocol, with enhanced air pollution monitoring employing high-volume PM sampling to collect PM samples for compositional analysis to assist in source appointment into tailpipe and non-tailpipe fractions. Acute response endpoints (lung function: FEV₁ primary outcome, FeNO) will be examined pre-, during & post-exposures and then related to source appointed PM. Airway inflammatory markers associated with worsening of asthma symptoms will be examined using nasal lavage, which will be used to establish the biological dose of source specific PM. Plasma samples and PM filter samples will be banked for secondary analysis.

Progress to date. The study is progressing in line with initial timelines. Notable milestones include

• Established study sites and study documentation
• Established study
• Received institutional ethics approval
• Seeking NHS ethics approval
• Set up Independent Scientific Committee
• Setting up a pilot study evaluating protocol in healthy participants (Results presented in May)
• Received small grants (£5k) for sub-study

Future challenges and opportunities

• Uncertainties regarding recruiting participants for time intensive study 
• Seeking opportunities for analysis of bio-banked plasma samples, and banked filter samples.