Study analyzes pollution’s effect on daily commute

The way in which one commutes can make a real difference in terms of what one’s exposure to in-transit or during-the-commute pollution is.

Tower Bridge, Sacramento

A related study conducted in Sacramento, California recently has been undertaken in order to learn more.

On this, the California Environmental Protection Agency Air Resources Board (ARB) in its “Study: Commuters’ exposures to air pollution greatly depends on mode of travel: Sacramento area study shows light rail commuters experience lowest pollution levelsnews release explains:

“The study, ‘Commuter exposure to PM2.5, BC, and UFP in six common transport microenvironments in Sacramento, California,’ conducted by researchers at the California Air Resources Board (CARB), was published recently in Atmospheric Environment, a prestigious scientific journal in the field of air pollution.

“The researchers concluded that electricity-powered light rail trains offer the least polluted travel environment, while commute trips by older technology diesel-powered trains experienced the highest average air pollution levels in Sacramento. Average concentrations of particulate matter and black carbon were statistically similar for cars, buses, and bicycle trips, and in between the levels found in the two types of train commutes. Since the average car and public transport trips are much faster than bicycle trips, they may offer shorter exposure durations; however, cycling has significant health benefits.

Those findings are not at all surprising; those outcomes very much expected.

According to information in the ARB release, in the study, exposures to air pollution were measured using a very innovative measurement tool – a backpack equipped with cutting-edge sensors for measuring pollution. Tasked with gathering data were recruited volunteers who were able to do so during their commutes using the so-called “state-of-the-science,” backpacks. Three distinct pollutants were measured and these were: fine particulate matter 2.5 micrometers or less in diameter (PM 2.5) and small enough to penetrate lungs when inhaled and which are then able to enter the bloodstream; much more minute specs known as ultrafine particles (UFP); and black carbon (BC), sooty matter emitted into the air from not only diesel engines but from additional sources of combustion as well. Automobile, bicycle, bus, light rail and train were the commute modes evaluated.

ARB further pointed out and calculations-based, estimates are that in California every year, early deaths from exposure to fine particulate matter pollution from all sources number 7,200, coupled with 5,200 visits to the emergency room while 1,900 require hospitalization.

“The study also compared air pollution exposure per mile for each mode, a useful metric for people to use when selecting a travel mode that offers the lowest air pollution exposure for their individual commute. Light rail commutes had the lowest average exposure per mile for all measured pollutants, and car trips experienced marginally higher per mile exposure, whereas train commutes with older diesel technologies experienced the largest exposure per mile of all of the motorized transportation commute modes. The study also offers advice for reducing exposure to air pollution during commute trips:

“• Car travelers can reduce their personal exposure to PM2.5, ultrafine particles, and black carbon by up to 75 percent by operating the air conditioner on recirculate mode.

“• Bicycle commuters can reduce exposures by between 15 and 75 percent by choosing dedicated bicycle pathways away from traffic sources.

“• Older technology diesel-powered train commute trips where the locomotive engine was pushing the rail cars experienced up to 90 percent lower ultrafine particle concentrations than ones where the locomotive engine was pulling the cars,” the ARB observed.

In cases where the passenger cars trail a locomotive, concentrations of pollutants entering the different passenger cars being locomotive-pulled may differ, passenger car to passenger car. A strong blowing wind can have an impact as well.

Finally, “‘[t]he study has useful implications for our efforts to link transportation and land use planning to develop more sustainable communities. One important finding is the need for more light rail and dedicated bike paths, as well as cleaner locomotives,’ CARB Research Division Chief Bart Croes said. ‘In addition, the portable technologies we employed to monitor air pollution levels in this project provide us with an important new tool for studying personal exposures and locating air pollution hotspots in disadvantaged communities and elsewhere,’” the above quote as published in the ARB news release in question.

There are more specifics on this study here.

Image credits: Michael Grindstaff (upper); Clean Air Revival (lower)

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