Air quality levels in the city deteriorated after Deepavali last week.

On Sunday, the particulate matter sized 2.5 microns (PM 2.5) shot up to 318 microgram/cubic metre in Manali.

The Air Quality Index (AQI) registered by the Central Pollution Control Board’s (CPCB) Sameer App was 202, capable of causing breathing discomfort to most people on prolonged exposure.

Likewise, sulphur dioxide touched 65 micrograms/cubic metre.

On Saturday, the AQI was 194, which was the average of PM 2.5 levels registered at Manali.

Former Member Secretary of the Tamil Nadu Pollution Control Board K. Karthikeyan said that the sudden change in the weather had caused the pollution levels to increase.

“The wind speed has dropped. On Deepavali, the wind speed was quite good, which is why pollution levels remained low. Now, the particulate matter and other pollutants are not dispersing,” he said. A drop in temperature has also compounded the effect, he added.

The levels of nitrous oxides and sulphur dioxide have increased due to vehicular emissions, Mr. Karthikeyan said.

In the red

On November 9, the monitoring station at Alandur recorded a maximum of 295 of PM 2.5 and ground ozone level of 35.

On November 8, the station at Manali recorded a maximum PM 2.5 of 338 micrograms/cubic metre and on the previous day, the level was recorded as 402 microgram/cubic metre.

Environmental activist Sweta Narayan, stressed the need for the pollution control board to put out health advisories to protect the public and their health.

“The board must take action on industries violating pollution norms and take the community into confidence and make sure that the local sources of pollution are kept in check,” she added.