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Utility of an alternative bicycle commute route of lower proximity to motorised traffic in decreasing exposure to ultra-fine particles, respiratory symptoms and airway inflammation – a structured exposure experiment

Tom Cole-Hunter12, Rohan Jayaratne2, Ian Stewart1, Matthew Hadaway1, Lidia Morawska2 and Colin Solomon34*

Author Affiliations

1 Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Brisbane, QLD 4059, Australia

2 International Laboratory for Air Quality and Health, Queensland University of Technology, 2 George Street, Brisbane, QLD 4001, Australia

3 School of Life Sciences, Queensland University of Technology, 2 George Street, Brisbane, QLD 4001, Australia

4 School of Health and Sport Sciences, University of the Sunshine Coast, Sippy Downs Drive, Sippy Downs, QLD 4556, Australia

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Environmental Health 2013, 12:29  doi:10.1186/1476-069X-12-29

Published: 8 April 2013

Abstract

Background

Bicycle commuting in an urban environment of high air pollution is known to be a potential health risk, especially for susceptible individuals. While risk management strategies aimed to reduce exposure to motorised traffic emissions have been suggested, only limited studies have assessed the utility of such strategies in real-world circumstances.

Objectives

The potential to lower exposure to ultrafine particles (UFP; < 0.1 μm) during bicycle commuting by reducing proximity to motorised traffic was investigated with real-time air pollution and intermittent acute inflammatory measurements in healthy individuals using their typical higher proximity, and an alternative lower proximity, bicycle commute route.

Methods

Thirty-five healthy adults (mean ± SD: age = 39 ± 11 yr; 29% female) completed two return trips, one each in the condition of their typical route (HIGH) and a pre-determined alternative route of lower proximity to motorised traffic (LOW); proximity being determined by the proportion of on-road cycle paths. Particle number concentration (PNC) and diameter (PD) were monitored in-commute in real-time. Acute inflammatory indices of respiratory symptoms (as a scalar of frequency from very low to very high / 1 to 5), lung function and spontaneous sputum (for inflammatory cell analyses) were collected immediately pre-commute, and immediately and three hours post-commute.

Results

In the condition of LOW, compared to in the condition of HIGH, there was a significant decrease in mean PNC (1.91 x e4 ± 0.93 × e4 ppcc vs. 2.95 × e4 ± 1.50 × e4 ppcc; p ≤ 0.001), and the mean frequency of in-commute offensive odour detection (2.1 vs. 2.8; p = 0.019), dust and soot observation (1.7 vs. 2.3; p = 0.038) and nasopharyngeal irritation (1.5 vs. 1.9; p = 0.007). There were no significant differences between LOW and HIGH in the commute distance and duration (12.8 ± 7.1 vs. 12.0 ± 6.9 km and 44 ± 17 vs. 42 ± 17 min, respectively), or other indices of acute airway inflammation.

Conclusions

Exposure to PNC and offensive odour, and nasopharyngeal irritation, can be significantly lowered when utilising a route of lower proximity to motorised traffic whilst bicycle commuting, without significantly affecting commute distance or duration. This may bring health benefits for both healthy and susceptible individuals.

Keywords:
Air pollution; Bicycle commuting; Ultrafine particle; Respiratory symptom; Lung function; Inflammatory cell; Risk management