Scooters dominate traffic pollution in some Asian cities
14 May 2014, by Tamera Jones
Two-stroke scooters, ridden by billions across Asia, Africa and the Middle East, are the leading source of some of the most dangerous traffic pollution, say scientists.
They found that toxic pollutants from such scooters are up to 1000 times higher than from other vehicles.
The researchers add that banning or restricting two-stroke scooters could drastically improve air quality in many cities around the world.
'People think that cars and trucks, especially those that use diesel, are the main source of vehicular pollution. That might be true in some places, but we've found that two-stroke scooters dominate when it comes to vehicle pollution in a lot of cities,' says Dr. André Prévôt of the Paul Scherrer Institute in Switzerland.
'Two-stroke scooters contribute to around 60 per cent of so-called roadside primary organic aerosol in Bangkok, even though they only make up 10 per cent of fuel consumption.'
These popular scooters, made by the likes of Vespa, Suzuki and Honda, belch out a cocktail of harmful pollutants known as particulate matter. These include microscopic particles made of carbon and other organic materials, and so-called secondary organic aerosols. They also emit carcinogenic gases like benzene in super high amounts.
Particulate matter, much of it invisible to the naked eye, is particularly dangerous because it can penetrate deep into the lungs and bloodstream, causing heart attacks, cancer and lung problems.
'If you're in traffic and you've got an idling two-stroke scooter in front of you, it's not going to be good for you.' Dr André Prévôt, The Paul Scherrer Institute, Switzerland
Levels of benzene in exhaust fumes from an idling scooter can be a massive 300,000 micrograms per cubic metre. The EU annual limit is just 5 micrograms per cubic metre.
'This is the concentration in the exhaust of a scooter. So standing on a bike behind a scooter you might breath 10 per cent or 1 per cent of this concentration after some dilution. This is during a short time, but still amazingly high,' says Prévôt. 'If you're in traffic and you've got an idling two-stroke scooter in front of you, it's not going to be good for you.'
Most organic particulate matter is made up secondary organic aerosols, which are produced by sunlight or other atmospheric components chemically altering exhaust gases. This reaction creates more dangerous chemicals, in the form of reactive oxygen species, which are damaging to our lungs.
'Reactive oxygen species induce reactions in our lungs. The fluid in our lungs can only handle a certain amount of these species, otherwise they get damaged,' says Prévôt.
Despite this, at the moment regulations for scooters tend to be much more lax than for other vehicles, even in Europe. Worryingly, scientists predict that scooters will emit more volatile organic compounds than all other vehicles combined in Europe by 2020.
'A considerable number of two-stroke scooters are being used in some regions that don't have any emissions controls,' says Prévôt.
'The technology hasn't changed a lot. But it has for cars. The main thing is that the technology is outdated. We need to move towards four-stroke or electric scooters.'
Two-stroke scooters differ from four-stroke scooters in that they have an engine, which completes a power cycle in one crankshaft revolution, with just two strokes, or up and down movements. The four-stroke engine, in contrast, uses four strokes.
Since the late 1990s, China has already banned or restricted two-stroke scooter use in many of the country's large cities. This had led to a massive cut in traffic pollution.
In contrast, in cities like Dongguan where scooters haven't been banned, traffic pollution is still dangerously high.
'Vehicle pollution is much higher in Dongguan than it is in Guangzhou, even though the traffic volume is much higher in Guangzhou,' says Prévôt. 'Ironically, two-strokes weren't banned in Guangzhou because of air quality; it was more to do with safety.'
'We knew that these scooters were going to be big polluters, but we had no idea how bad they were until now. The good news is that four-stroke scooters are slowly getting more popular.'
The study is published in Nature Communications.
....and the below article in relation to pollution in Europe.... text not copied in as there are some charts etc at the below link
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