Traffic-related air pollution and noise are associated with cardiovascular diseases, and alternation of heart rate variability (HRV), which reflects cardiac autonomic function, is one of the mechanisms. However, few studies considered the impacts of noise when exploring associations between air pollution and HRV. We explored whether noise modifies associations between short-term exposure to traffic-related air pollution and HRV in young healthy adults. In this randomized, crossover study, 40 young healthy adults stayed for 2 h in a traffic center and, on a separate occasion, in a park. Personal exposure to traffic-related air pollutants and noise were measured and ambulatory electrocardiogram was performed. Effects were estimated using mixed-effects regression models. Traffic-related air pollution and noise were both associated with HRV, and effects of air pollutants were amplified at high noise level (>65.6 A-weighted decibels (dB[A])) compared with low noise level (≤ 65.6 dB[A]). High frequency (HF) decreased by -4.61% (95% confidence interval, -6.75% to-2.42%) per 10 μg/m(3) increment in fine particle (PM2.5) at 5-min moving average, but effects became insignificant at low noise level (P>0.05). Similar effects modification was observed for black carbon (BC) and carbon monoxide (CO). We conclude that noise is an important factor influencing the effects of air pollution on HRV.

Canada is warming at double the rate of the global average caused in part to a fast-growing population and large land transformations, where urban surfaces contribute significantly to the urban heat island (UHI) phenomenon. The federal government released the strengthened climate plan in 2020, which emphasizes using nature-based solutions (NBSs) to combat the effects of UHI phenomenon. Here, the effects of two NBSs techniques are reviewed and analysed: increasing surface greenery/vegetation (ISG) and increasing surface reflectivity (ISR). Policymakers have the challenge of selecting appropriate NBSs to meet a wide range of objectives within the urban environment and Canadian-specific knowledge of how NBSs can perform at various scales is lacking. As such, this state-of-the-art review intends to provide a snapshot of the current understanding of the benefits and risks associated with the implantation of NBSs in urban spaces as well as a review of the current techniques used to model, and evaluate the potential effectiveness of UHI under evolving climate conditions. Thus, if NBSs are to be adopted to mitigate UHI effects and extreme summertime temperatures in Canadian municipalities, an integrated, comprehensive analysis of their contributions is needed. As such, developing methods to quantify and evaluate NBSs’ performance and tools for the effective implementation of NBSs are required.

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