Every year, in the run-up to Deepavali, awareness drives are organised across the State and pamphlets are handed out as part of an effort to mitigate the impact of air and noise pollution on one particular day.

While focussing on Deepavali is indeed important, as the spike in pollution levels each year indicate, the underlying long-term trends in air quality and noise levels across the million-plus cities are equally worrisome, State-wide data for the past few years show.

In Chennai, for example, an average resident is regularly exposed to noise twice as loud as the level experienced in 1985. By 2010, a third of the city’s geographic area had been categorised as “areas of noise discomfort” by an IIT-Madras study.

The Tamil Nadu Pollution Control Board’s pre-Deepavali pollution baseline, one of the few instances in which comprehensive pollution measurements are taken across the State on the same day, is also slowly inching up. “The baseline itself has been going up. The cities are growing, and population density is increasing. It’s inevitable,” said a TNPCB official.

Increasing motorisation, the rise in population density and even flyovers on narrow roads, which increase noise levels through a ricochet effect, all have contributed to this trend. Studies done at the IIT-Madras have shown that 70 per cent of Chennai’s pollution load can be attributed to the vehicles on its roads. Now, the rest of the State is replicating this model.

“Urbanisation and increasing motorisation are serious challenges,” says Anumita Roychowdhury of the Centre for Science and Environment. “You can relocate industries and power plants, but you cannot relocate vehicles.”

Small cities, due to their density, are also becoming the air pollution hotspots, she says. “This is going to have very serious public health implications.” Since the prevailing pollution level itself is increasing, Deepavali becomes a “double whammy,” and air and noise pollution reaches “critical levels” in certain high-density neighbourhoods, Ms. Roychowdhury points out.

At Triplicane in Chennai, for example, during the 2013 Deepavali, particulate matter content was nine times more than the standard. And the maximum noise levels exceeded 120 dB — the range in which prolonged exposure leads to hearing loss.

Tamil Nadu could set an example, making it mandatory for all cities to meet basic air and noise quality standards, Ms. Roychowdhury says. With the Air Quality Index kicking in across the country from next year, she says, each city must come up with a clean air action plan. The focus on the impact of pollution during Deepavali must also translate into a holistic approach to better city design and the basic quality of living standards.