Ambient air quality in the city has significantly deteriorated over the past decade and officials across the enforcement spectrum from the Transport Department to the Tamil Nadu Pollution Control Board (TNPCB) admit that the existing mechanisms to control vehicular pollution, which is the largest contributor, have largely been unsuccessful.

According to a recent TNPCB study, the level of carbon monoxide in the city ranges from 12 to 70 parts per million (ppm) as against the permitted 35 ppm. The study also points out that emission from nearly 50 per cent of the vehicles in the city exceeded permitted levels and the pollution load in the atmosphere increased by 3.5 per cent annually.

“About 70 per cent of privately run pollution testing units do not have the expertise or capability to test diesel vehicles,” said a senior TNPCB official. “A proposal to set up a joint emission check-up unit involving the Board, the traffic police and the Transport Department has been in cold storage for sometime. It would have empowered us to conduct surprise checks of testing centres and also fine motorists on the spot.”

P. Jeyapal runs one such testing centre, which is a rundown room with two chairs and a flickering computer screen. “The volume of vehicles that comes for testing is too low to make this a viable business venture. Unless enforcement forces people to take the test every six months as stipulated, no one is going to invest to run a proper facility,” he says.

While the city had about 130 emission test centres in 1997 when pollution control levels were introduced, it has come down to around 30 by 2010.

M.K. Subramanian, secretary of Automobile Association of Southern India, said: “Motorists can be given more options if the Transport Department provides licences for mobile testing units. This has worked very well in Mumbai as it allows testing units to go in search of motorists. Many do not take the test because they think it is unnecessary work.”

Speaking to The Hindu, Transport Commissioner S. Machendranathan said a national scheme for providing modern testing centres was being worked out.