The city on Thursday suffered the longest and noisiest Diwali night in recent memory and even hospitals were not spared, said an environmental platform that criss-crossed the city through the night.

Data from the state pollution control board corroborates the claim.

Metro accompanied the Sabuj Mancha team that was on the roads from 8pm on Thursday till 2am on Friday.

The court-mandated window for bursting firecrackers — 8pm to 10pm — was routinely violated. Frequent bursting of firecrackers was reported from across the city from 7pm and the assault continued past 2am in many neighbourhoods.

“We have been monitoring noise violations in the city on Diwali for 14 years. We have never come across violations of such scale. The Diwali 2024 night was clearly the longest and noisiest one in recent times, reviving memories of the violations that were common in the late 1990s,” environment activist Naba Dutta said.

“The situation was almost the same everywhere in the city and places nearby, such as Chandernagore and Barasat,” said Biswajit Mukherjee, a retired chief law officer of the state pollution control board.

Once you allow the entry of illegal fireworks into the market, it is impossible to stop the violations,” said Mukherjee.

According to the pollution control board data, the noise graph started soaring early evening and returned to normal well past midnight.

Hospitals hit hard

The seven-member Sabuj Mancha team did not come across any bursting of fireworks in the hospital compounds. However, the use of fireworks in the immediate neighbourhood, especially in high-rises, was routine.

“We visited four hospitals. The noise level was high at all four but the scale of violation varied. Ramakrishna Mission Seva Pratishthan, on Sarat Bose Road, was worst hit,” said Dutta.

The data generated by the team vindicates the statement.

“At BC Roy Post Graduate Institute of Paediatric Sciences, the highest noise level was 98.6 decibel and the average was 78.1 around 8.30pm. The noise limit for hospitals is 50 decibel from 6am to 10pm. On Sarat Bose Road, where a cracker was going off every nine seconds, the highest noise level was 101.6 decibel,” said Sudipta Bhattacharya, a member of the green team.

According to sound experts, an increase of 10 decibel means doubling of the pressure on the ear of those exposed to the sound.

Lake Town

The green team, accompanied by senior state pollution control board officials, visited the Lake Town-Bangur area past midnight.

The PCB officials called up police and three youths who were bursting crackers at a park were arrested. According to the green team data, the highest noise level in the area was 107.3 decibel and the gap between two cracker explosions was less than a second.

“In most cases, it was almost impossible to locate the violations as a large number of offenders were residents of high-rises,” a police officer said.

PCB figures

A study of the data recorded by the PCB noise measuring stations across the city and greater Calcutta shows the noise levels, both the average and the peak value, started increasing after 6pm. They reached the peak after 10pm, often around midnight, and started to settle around 3pm.

For example, the measuring station at Ballygunge science college recorded an average noise level of 51.96 decibel around 6.30pm. It rose to 71.2 around 10.30pm and dropped to 40.8 at 3am.

The maximum permissible level in residential areas at night is 45 decibel.

The station recorded a peak noise level of 118.8 decibel at 10.30pm.