Abstract
Background
Given the importance of physical activity to well-being, there is a need to encourage people to be physically active year-round. At the same time, many people are vulnerable to adverse health effects from air pollution, especially on smog alert days. This study was undertaken to determine when air pollution levels tend to be lowest so that the public can modify strenuous outdoor activity accordingly.
Methods
Existing hourly air pollution data for Toronto were analyzed to determine how pollutant levels varied from hour to hour throughout each 24-hour day, to identify the times when pollution levels are at their lowest on average.
Results
Pollutant levels vary throughout the day, with concentrations of some pollutants (such as ozone, particles and sulphur dioxide) being highest during mid-day, and others (such as carbon monoxide and nitrogen dioxide) being highest with morning rush hour. Overall, pollutant concentrations tend to be lowest before seven a.m. and after eight p.m.
Interpretation
The public should be encouraged to maintain regular physical activity outdoors while monitoring any air pollution-related symptoms. The intensity of outdoor activity should be reduced, or activities replaced with indoor exercise, at those Air Quality Index (AQI) levels that trigger individual symptoms and when AQI values exceed 50. Where possible, strenuous activity should be taken when and where air pollution levels tend to be lowest, namely early in the morning and in low-traffic areas. More research is required to guide development of health protective advice on exercising when air quality is poor.
Fr: Exercise, air pollution, smog, health promotion, motor activity
Réumé
Contexte
étant donné l’importance de l’activité physique pour le bien-être, il faudrait encourager les gens à être actifs à longueur d’année. Cependant, de nombreuses personnes sont vulnérables à la pollution atmosphérique, qui peut avoir des effets indésirables sur la santé, surtout les jours où l’on émet des avis de smog. Notre étude visait à déterminer les moments où les niveaux de pollution atmosphérique ont tendance à être les plus faibles, pour que la population puisse concentrer son activité physique intense à l’extérieur durant ces périodes.
Méthode
Nous avons analysé les données horaires existantes sur la pollution atmosphérique à Toronto pour déterminer les variations horaires des niveaux de polluants pendant chaque période de 24 heures, ce qui nous a permis de cerner les moments où les niveaux de pollution sont les plus faibles en moyenne.
Résultats
Les niveaux de polluants varient au cours de la journée. On détecte les plus fortes concentrations de certains polluants (l’ozone, les particules et l’anhydride sulfureux) vers midi, tandis que d’autres polluants (le monoxyde de carbone et le dioxyde d’azote) sont plus concentrés à l’heure de pointe du matin. Dans l’ensemble, les concentrations de polluants ont tendance à être les plus faibles avant 7 h et après 20 h.
Interprétation
Il faudrait encourager la population à pratiquer régulièrement une activité physique à l’extérieur tout en surveillant les symptômes pouvant être associés à la pollution atmosphérique. Il faudrait réduire l’intensité de l’activité à l’extérieur (ou pratiquer une activité physique à l’intérieur) lorsque l’indice de la qualité de l’air (IQA) atteint un niveau qui déclenche des symptômes chez la personne ou lorsque l’indice est supérieur à 50. Il est préférable de limiter l’activité physique intense aux moments et aux endroits où les niveaux de pollution atmosphérique ont tendance à être faibles, à savoir tôt le matin et dans les zones à faible densité de circulation. Il faudrait pousser la recherche pour orienter l’élaboration de conseils de protection de la santé portant sur l’activité physique lorsque l’air est de mauvaise qualité.
Footnotes
Acknowledgements: This research was supported in part by the Health Policy Research Program, Health Canada (Project Number: 6795-15-2001/4400011). The views expressed herein are solely those of the authors and do not necessarily represent the views or policy of Health Canada.
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