Individuals living in an urban environment are exposed simultaneously to fluctuating levels of traffic-related air pollution (TRAP) and noise. This is particularly the case for active transport mode users who are physically active in close proximity to traffic-related emissions. Current evidence highlights measurable associations between short-term exposure to TRAP, noise and acute cardiovascular effects. While traffic-related noise is itself known to affect cardiovascular outcomes, uncertainty remains with respect to the combined impact of TRAP and noise on cardiovascular health. In particular, some evidence suggests that air pollution effects on cardiovascular health may be modified by noise in traffic-influenced environments. Previously, few studies have investigated this interaction and inconsistent associations have been made. Therefore, further investigation of this interaction is warranted.
The TAPAS project, lead by CREAL, used an experimental component to investigate such outcomes in low and high motorised traffic environments with healthy adults. An intermittent cycling exercise scenario was used to emulate bicycle commuting, while a resting scenario was used to emulate passive travel such as using public transport. Fluctuating levels of TRAP (including UFP, BC, PM2.5, NOx) and noise (as specifically LAeq) of the environment were continuously monitored through-out the scenarios. Simultaneously, heart rate variability (HRV) of the participants was continuously monitored - heightened exposure to TRAP, especially UFP (< 0.1 µm particle diameter), has been shown to elicit changes in cardiac autonomic regulation as reflected by decreased HRV. The study findings, soon to be submitted for publication, highlighted that a complex interplay exists between TRAP, noise, sex and physical activity with respect to the impact on cardiovascular autonomic function in the urban environment. It is suggested that higher environmental noise enhances the negative effect of TRAP on cardiovascular autonomic function, and that sensitivity to this effect may exist in women and with the performance of physical activity such as active commuting. The apparent effect modification of sex and the interaction of TRAP and noise signify that these relationships need to be considered in future research.
Chronic exposure to elevated noise levels and the elicitation of the associated stress response in an individual may develop cardiovascular health detriments (such as hypertension) and a reduced quality of life. For future research, and as a preventative measure, such measures of noise, air pollution and HRV with ambulatory sensors could be communicated to a personal online server shared with a patient’s health care professional. This theme is being explored further with the CITI-SENSE project for which CREAL is a work package leader and case study location for outdoor urban quality.