Walk to work on quieter roads to avoid exposure to peaks in harmful air pollution

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Researchers have advised through a new study that the best way to avoid exposure to harmful particulate matter in air pollution during peak hours is to walk to work on quieter side streets rather than main roads.

The recommendations have come after a research found statistically significant difference in the peaks of exposure to one of the components of air pollution – black carbon – when testing out two different a busy and a quite route.

Black carbon is one of the components of air pollution, and comes from incomplete combustion by diesel vehicles. It is known to be associated with a range of respiratory diseases, such as asthma, as well as with cardiovascular diseases.

Mrs Lee Koh, a researcher at the Blizard Institute at Queen Mary University of London, UK measured levels of black carbon particulate matter in air while walking between Whitechapel in the east of London to Moorgate between 16.00-19.00hr using main roads. She also measured the levels of this particular matter on a quieter route.

The motivation behind the study is to find ways using which people might be able to limit or reduce their exposure to harmful particulate matter in air pollution in most polluted cities across the globe.

“We found in this small study that people could avoid peaks in black carbon if they choose to walk a quieter route”, Mrs Koh said.

Walking the busy route six times between February and May produced measurements of black carbon that averaged 3339-6995 ng·m-3 for every five minutes (nanograms of black carbon per cubic metre per five minutes). When walking the quieter routes six times at the same time of day, the measurements ranged from 2555 to 5854 ng·m-3 for every five minutes, which, although slightly lower than the busy route, was not a statistically significant difference.

But, researchers found that there was a statistically significant difference in the peaks of exposure to black carbon between the two routes.

“The peaks are when a much higher levels of pollution are present. For example, when you stop to cross a busy road and so you are subject to a higher level of pollution compared to when walking away from the traffic,” she explained.

There were no peaks in black carbon exposure on the side-street route, while on the busy route there were three occasions when the levels of black carbon exceeded 10,000 ng·m-3 for every five minutes, ranging between 10,209 to 10,454 ng·m-3 for every five minutes.

To put these figures in context, the UK’s Daily Air Quality Index [1] has suggested that exposure to fine particles of air pollution known as PM2.5 (particulate matter that measures approximately 2.5 micrometers or less in diameter, of which black carbon is a constituent) should not exceed 35,000 ng·m-3 over a 24-hour period.

Mrs Koh concluded: “Our study suggests that, in London, it is possible to reduce exposure to peaks of black carbon particles (mainly from diesel soot) by choosing to walk a less polluted route. Government action will be required to further improve the general air quality around us.”