Delhi witnessed one of the most severe episodes of air pollution in the winter of 2016 but no criminal cases were registered that year under the air act, which empowers state pollution control boards to take action against polluting industries and individuals, the latest data by National Crime Records Bureau (NCRB) shows.The NCRB said only 25 cases were filed across the country under the Air (Prevention and Control of Pollution) Act, 1981, last year, half the number filed in 2015. Delhi was not among the three states that registered criminal cases under the act. Maharashtra filed 21 cases and Jharkhand and Uttar Pradesh filed only two last year, the bureau said.The national capital has been reeling under “very poor” category air quality for the past few weeks. This year, the pollution levels entered the “severe” zone on November 7 and the Air Quality Index (AQI) hit its peak of 486, highest so far, on November 9. December has not been any different. Delhi woke up to another hazy morning on Tuesday because of the toxic air with the AQI close to the outer limit in the “very poor” category. Monday’s average AQI hovered around 390, almost touching the hazardous mark. An AQI value above 400 on the scale of 500 is considered severe pollution.A Lancet Commission on Pollution and Health report in October said India registered 1.81 million deaths caused partly by air pollution in 2015, the highest among all the countries.Environmental law experts said it reflects the poor state of the enforcement of rules specifically made to tackle air pollution, especially with regard to industries.“Despite having some of the most polluted cities in the world, our implementation of air pollution laws is zero. The responsible authorities are not filing any cases for violations. They say they are taking action but they are not enforcing anything,” Ritwick Dutta, an environmental lawyer, said.In most cases, industries are the violators. They are legally obliged to have certification from the pollution control boards under the air act and the Water (Prevention and Control of Pollution) Act, 1974, but few companies actually have proper certification, according to Dutta.The minimum punishment under the air act is 18 months of imprisonment but nobody has gone to jail for violating it since it was promulgated in 1981, he added.India’s pollution control boards have the power to file criminal cases against industries and individuals for violating the provisions of the act but they rarely do so. Part of the problem is the lack of a dedicated legal team, giving boards the resources only to issue notices and, in some instances, extract fines, a senior official at the board, who was not authorised to speak to the media, said.However, a member secretary of the Central Pollution Control Board disagreed. “It is a question of availability of information. Cases are being filed and people do get fined and imprisoned,” A Sudhakar said.He acknowledged that the state pollution control boards that are supposed to file the cases were not sharing the information with the CPCB, which is the national pollution regulator. Only five state boards -- Maharashtra, Gujarat, Haryana, Meghalaya and Himachal Pradesh -- submitted the information to the CPCB.The cases listed by the state boards were filed for violations under the air and water acts.Debadityo Sinha, a resident fellow at Vidhi Centre for Legal Policy, said even when cases are filed, the conviction rate is low.