More pollution in taxis than on sidewalks

 作者:芮缔豚     |      日期:2019-03-02 02:07:01
By Kurt Kleiner The back seat of a taxi is one of the worst places to be for exposure to ultrafine particulate pollution, a new study has revealed. People on buses and those riding bikes are also exposed to a lot of the pollutant, while pedestrians and, ironically, those in private cars, are exposed to the least. Researchers from Imperial College London, UK, tracked exposure to fine particulate pollution second by second as volunteers travelled around a test area along a stretch of Marylebone Road, a busy street in the city. The researchers were interested in exposure to particles under 100 nanometres in diameter. Some studies suggest that ultrafine particles might pose an especially serious health hazard, and that brief exposures to high levels of particles might be more important than lower exposure over a longer period. To collect the data, the researchers equipped volunteers with portable particle detectors that recorded ultrafine particulate exposure once per second. Another volunteer followed with a video camera. Back at the lab, the video was synchronised with the particle record, allowing the researchers to see how exposure changed, for instance, while the volunteer was crossing an intersection on foot, or idling in traffic in a car. Overall, the heaviest exposure came from taking a cab, which exposed passengers to an average of 108,000 particles per cubic centimeter of air. The inside of a bus exposed them to 95,000 particles/cm3, but the inside of a private car exposed them to only 36,000 particles/cm3. Surbjit Kaur, the exposure analyst who led the research, says cabs might have such high exposures compared to cars because they are in use for so much of the day, or because they were recently used by a smoker. Cyclists, despite generating no pollution, inhale more than their fair share of it – 84,000 particles/cm3 – more than twice as much as the driver of a private car. At an average exposure of 46,000 particles/cm3, walkers seem relatively well off. However, simply crossing the street could cause particulate levels to spike at about 100,000 particles/cm3. Passing a cigarette smoker on the sidewalk was worse, though, driving levels up as high as 300,000 particles/cm3. The researchers did not calculate the cumulative exposure experienced by the volunteers during their journeys – the tests were designed to determine the differences between the different transport “microenvironments.” Journal reference: Atmospheric Environment (vol 40, p 386) More on these topics: