Almost 60 percent of the Valley's air pollution is caused by vehicular emission, despite authorities carrying out mandatory emission tests and on-the-spot checks on all four wheeled vehicles.

Private vehicles are required to go for tests annually while those for hire have to do it every six months. But with rising import of vehicles and an ill-enforced ban on vehicles over 20 years old, there is little they can do. Three wheelers on two-stroke engines have been banned from the Valley, but two wheelers with the same engines have not.

Constable Hari Sharan Poudel sits in the garage of the Valley Traffic Police office in Baggikhana every day and conducts vehicle emission checks for petrol-based four wheelers imported before 1998. He uses a Bosch monitor to see if the vehicles are emitting more than 1000PPM (particulate matter smaller than 10 micrometer) of hydrocarbons and three percent carbon monoxide. Some of the vehicles are older than 30 years but miraculously pass the test. "They fix their carburettors so that it gets more oil and less oxygen, which gives a low emission result on the monitor," he explains.

In the Transport Office in Kusunti, it's the same story, except that the check is on vehicles imported after 1998. The traffic office in Satdobato checks vehicles that run on diesel engines. If a vehicle passes the test it gets a green sticker. But once on the streets, the vehicle owner goes back to the mechanic and readjusts the carburettor to economise on oil, thus increasing emissions to above the legal standard. In an attempt to control this manipulation, the Ministry of Environment Science and Technology (MEST) regularly conducts spot checks with the help of the Valley Traffic Police.

Air quality monitoring results in six places within the Valley by MEST show pollution levels in Putali Sadak, Patan Hospital, and Thamel area as the highest. Anything above 120 micrograms per cubic metre is unhealthy, and these areas usually show above 120. "We only have a system to check emissions and monitor air quality.

Decreasing pollution will require effective implementation of the law," says Khum Raj Panjali, joint secretary of the Environment Department of MEST. The department has recently completed a study on how to improve the Valley's air quality and control air pollution, which they will soon be recommending to the government, says Panjali.

(Alok Tumbahangphey)