Traffic-Related Air Pollution and Heart Rate Variability and Respiratory Function in Urban Cyclists
A summer day, a leafy street, a bicycle. Under the right circumstances cycling can be a delight, and it’s universally recommended as a healthy physical activity. But because of the shared nature of most streets, vehicular traffic is often an inescapable part of the cycling experience. While bike-specific infrastructure can reduce the risk of collisions, automotive pollution doesn’t stop where bike lanes begin.
A 2011 study published in Environmental Health Perspectives, “Traffic-Related Air Pollution and Acute Changes in Heart Rate Variability and Respiratory Function in Urban Cyclists,” sought to examine the health effects experienced while cycling in traffic. The researchers, based at Health Canada, Environment Canada, and the University of Ottawa, looked at the relationship between automotive pollution and changes in measures of cyclists’ heart rate variability, a measure of cardiovascular health.
In the study, 42 healthy, nonsmoking adults cycled for an hour on both busy and quiet streets as well as indoors. Factors such as carbon black and volatile organic compounds were measured along each route and participants’ health was examined before and after cycling.
The study’s findings include:
- Exposure to heavy traffic significantly decreased heart-rate variability (HRV) in the cyclists for up to three hours after they finished cycling. Decreased HRV is associated with a higher risk of heart attacks.
- Increased levels of ultra-fine particles were associated with a significant decrease in the high frequency measure of HRV four hours after the start of cycling.
- Nitrous oxide levels were inversely associated with variation in heartbeat-to-heartbeat intervals two hours after the start of cycling.
- Ambient ozone levels were inversely associated with heartbeat-to-heartbeat intervals three hours after the start of cycling.
- Levels of atmospheric volatile organic compounds were not associated with changes in HRV.
The researchers note that the study has some weaknesses, in particular the small sample size, but overall conclude that short-term exposure to automotive air pollution can contribute to changes in autonomic regulation of the heart. Because the health benefits of physical activity outweigh the risks, the researchers suggest, “When possible, it may be prudent to select cycling routes that reduce exposure to traffic.”
Drivers are not immune to the risks of breathing polluted air, of course. Another study in Environmental Health Perspectives, “Air Pollutants from Automotive Traffic Act on Glutamatergic Neurons,” showed that ultrafine particles, which easily pass through car air filtration systems, can cause brain neurons to show of signs of inflammation associated with premature aging and Alzheimer’s. And for drivers, unlike cyclists, not being in traffic isn’t an option.
Tags: bicycling, bicycle, bikes, safety, pollution, cars
Note to instructor: The suggested assignments are designed for flexibility. They can be used in whole or part and can be adapted to a particular task -- for example, the newswriting assignments could be applied to the writing of the headline, the lead, the nut graph or the full story. Material from the assignments could also be combined with other material, for example, in the writing of a background, feature or local-angle story.
- Summarize the study in fewer than 40 words.
- Express the study's key term(s) in language a lay audience can understand.
- Evaluate the study's limitations. (For example: Do the results conflict with those of other reliable studies? Are there weaknesses in the study's data or research design?)
Read the study-related San Francisco Chronicle article titled "Biking on Busy Streets Linked to Heart Risks."
- Reporter's use of the study: Evaluate what the reporter chose to include and exclude from the study. Would the audience have acquired a clear understanding of the study's findings and limits from this article?
- Reporter's use of other material: Assess the material in the article that is not derived from the study. (for example: Does the reporter place the study in the context of other research and to what effect? Does the reporter include reactions to the study from other researchers or interested parties [e.g., political groups business leaders, or community members] and are their credentials or possible biases made clear?)
- Write a lead (or headline or nut graph) based on the study.
- Spend 60 minutes exploring the issue by accessing sources of information other than the study. Write a lead (or headline or nut graph) based on the study but informed by the new information. Does the new information significantly change what one would write based on the study alone?
- Interview two sources with a stake in or knowledge of the issue. Be prepared to provide them with a short summary of the study in order to get their response to it. Write a 400-word article about the study incorporating material from the interviews.
- Spend additional time exploring the issue and then write a 1,200-word background article, focusing on major aspects of the issue.