Commuting safety.

Map of Fort Collins and routes traveled in the study.

A study by a Colorado State University professor finds that people who commute via bicycle are exposed to more of air pollutants such as particulate matter and black carbon than those who commute by vehicles; drivers, however, are exposed to greater levels of carbon monoxide (CO). John Volcken a mechanical engineering professor, launched the study to see if changing commuting routes or methods could reduce exposure to dirty air, as Stephanie Paige Ogburn writes for KUNC.

To conduct the study, Volcken tested nonsmoking volunteers between the ages of 18 and 65 in the Fort Collins, Colorado, area  who commuted at least 1.5 miles to work, and who had no regular exposure to dust and fumes at their workplace. The study was conducted between September 2012 and February 2014, with each of 45 volunteers asked to commute eight days within a four- to 12-week period. The participants were asked to drive for four of those days, and to bike to work on the other four, using their own vehicles and bicycles. They were presented with choices of direct routes (on roads with more traffic) and alternative routes (on roads with less traffic).

While driving or riding, participants carried backpacks outfitted with equipment to measure air pollution. The study ran through all seasons, and commutes were not scheduled during holidays to avoid unusual traffic patterns. A movement sensor in the backpack assessed compliance.

The Roads Less Traveled

The study found that when participants bicycled on the alternative routes, their exposure to pollutants was lower than when they cycled on direct routes, and that proved true for both morning and evening commutes. Similar results were found when volunteers were driving vehicles, with the alternative routes exposing drivers to less air pollution than the direct routes, and the results weren’t appreciably changed by driving with windows opened or closed.

Although the study found that driving a vehicle exposed volunteers to slightly less particle pollution than riding a bicycle, the study could not address the question in greater detail, it says, because of factors such as cabin air settings, whether the windows were partly or completely open, seasonal differences, “and the within-person analysis.”

Exposure ‘Well Below’ Limits

Mean exposures to carbon monoxide were lower for those who were bicycling, on direct or alternative routes, both morning and evening, than for those driving vehicles on direct routes, the study found. However, the study found that switching to a route with less traffic did not help bicyclists in the long-run, because the beneficial effect of less pollution was cancelled out by the fact that the alternative route took longer to travel. But, all levels of pollution exposure found in the study were “well below” Environmental Protection Agency limits for black carbon, particulate matter, and carbon monoxide. On the other hand, exposure over many years can add up, she notes.

Ogburn quotes Volcken as saying in the United States, air pollution is the 9th highest cause of disease. He went on to say:

That’s because air pollution leads to respiratory disease like asthma, it leads to heart disease and cancer, and so when you add up all these bad ways that air pollution can harm the body, it becomes a big driver of poor health.

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