Pravin Shukla (37), an Andheri resident, took two hours longer to reach his Worli office last Thursday because poor visibility had reduced traffic to a crawl on the western express highway.

Shukla, a marketing executive, and many others were held up by smog – an unhealthy mix of smoke and fog. But weathermen dismissed the smog cover as a common winter feature in Mumbai. “Air pollutants floating high in the atmosphere move closer to the surface with a dip in temperature,” said RV Sharma, deputy director (western region) of the Indian Meteorological Department.

Mumbai’s air pollution data shows that levels of respiratory suspended particulate matter (RSPM), the main ingredient of smog, are currently double the permissible limit. According to data collected by the Maharashtra Pollution Control Board (MPCB), the average RSPM in November this year was 200 pg/mg3. The permissible standard set by MPCB is 100 pg/m3. Last year, RSPM levels stood at 203 pm/m3 during November.

From 1999, when the RSPM levels were at 101 pm/m3, the pollution level has increased marginally every year. “This year, we have not seen any significant increase in air pollution compared to last year,” said Indrani Gupta, who monitors air quality at the Worli-based National Environmental Engineering Research Institute.

Anumita Roychowdhury, associate director with the Delhi-based Centre for Science and Environment, said: “We haven’t seen any increase in pollution levels. But the smog presence could be felt for a longer duration if the wind speed is less and allows pollutants to settle down.”

Rapid construction growth could be a contributor to rising air pollution. According to environmental body, Toxic Link, 3000 metric tonnes of concrete waste is dumped in the city daily. “Dust particles and smoke from biogas are main causes of smog,” said Pradhan Parthasarthy, a climate scientist with The Energy and Resource Institute. But there has been no study to prove that concrete waste directly causes smog.

Scientists said a sharper drop in temperature or rise in air pollution could worsen the situation. The average minimum temperature from November to December has been around the 22-degree Celsius mark, far above last year when the temperature dipped to 16 degree Celsius.