The Tamil Nadu government on Sunday told the National Green Tribunal that the ambient air quality around the Sterlite Copper plant in Thoothukudi has improved since its closure in May, reported The Hindu.

Senior counsel CS Vaidyanathan, appearing for the state government, submitted data collected by the Tamil Nadu Pollution Control Board showing reduced levels of sulphur dioxide and other chemicals in the ambient air near the plant. The National Green Tribunal is hearing a petition filed by Vedanta Limited, which owns the plant, to reopen it.

The Tamil Nadu Pollution Control Board submitted a comparative study to a three-member committee of the tribunal showing the change in levels of sulphur dioxide, reported The Hindu Business Line. Vedanta had claimed that there was no considerable change in the ambient air quality after the copper smelter plant’s closure.

According to the data, sulphur dioxide levels on September 22, 2017, were around 20 micrograms per cubic metre. This was down to 5 micrograms per cubic metre on October 12 and October 13. Similarly, there was a reduction in the level of nitrogen dioxide within the same period.

Fathima Babu and Thermal S Raja, who are intervenors in the matter, said the pollution control board’s data showed an improvement in the ambient air quality in the neighbourhood, according to PTI.

Sterlite’s counsel, however, said it contested the pollution control board’s submissions as the company was neither intimated nor called upon to participate in the sampling exercise as per norms.

On April 9, the pollution control board had rejected the plant’s application to renew its licence to operate beyond March 31, 2018.

Thirteen people agitating against the expansion of the smelter were killed in police firing on May 22 and May 23, prompting the state government to permanently shut down the plant on May 28.

Residents of Thoothukudi had been up in arms against the plant for the past two decades, claiming that it had contaminated the region’s air and water. Large-scale protests began in February, and May 22 was the 100th day of the agitation.