Two days before Diwali, the national capital's air quality dropped to season's worst on Friday, with the decreased wind speed leading to accumulation of pollutants and affecting dispersion.The Supreme Court-mandated Environment Pollution (Prevention and Control) Authority is expected to take a call on Friday on several recommendations made by a 10-member anti-pollution task force.

The recommendations include banning construction work at night in Delhi-NCR from October 26 to 30 and closure of industries that have not switched to piped natural gas.The city's overall air quality index (AQI)stood at 315 at 8:30 am on Friday, while it was 311 on Thursday evening.Most ofthe places in the national capital recorded the AQI in the "verypoor" category, while the situation inched towards "severe" insome areas.The AQI in Nehru Nagar, Ashok Vihar, Jahangirpuri, Rohini, Wazirpur,Bawana, Mundka and Anand Vihar was 340, 335, 339, 349, 344, 363, 381 and 350,respectively, according to Central Pollution Control Board's data.

The AQI in the neighbouring towns of Baghpat, Ghaziabad,Greater Noida, Gurgaon, and Noida was 312, 336, 311, 312 and 320, respectively.AnAQI between 0 and 50 is considered 'good', 51 and 100 'satisfactory', 101 and200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500'severe'.

The Ministry of Earth Sciences' air quality forecast andresearch service, SAFAR, said, "The decrease in wind speed has started tonegatively influence Delhi's air quality by drastically decreasing ventilationcoefficients and thereby affecting dispersion."Calm surface winds willcontinue for the next two days. Consequently, the AQI is predicted to oscillatebetween high and middle range of the "very poor" category, it said.

The System of Air Quality and Weather Forecasting andResearch (SAFAR) said another western disturbance is likely to affect thewestern Himalayan region by October 28. In view of this, the situation onDiwali may not be as bad as last year.

A 10-member task force on the Graded Response Action Plan(GRAP) recommended on Thursday that construction activities in Delhi andsatellite towns of Gurgaon, Faridabad, Noida, Greater Noida, Ghaziabad, Sonepatand Bahadurgarh be banned between 6 pm and 6 am from October 26 to October 30.

The task force, headed by Central Pollution Control BoardMember Secretary Prashant Gargava, also recommended closure of coal-basedindustries, barring power plants, in these satellite towns during the period."InDelhi, industries which have not yet shifted to piped natural gas will remainclosed from October 26 to 30," it said and asked all implementing agenciesto take strict action for checking stubble burning in Punjab and Haryana andensure enforcement of the Supreme Court's directions regarding firecrackers andimpound "visibly" polluting vehicles.

All these measures are part of the CPCB-formulated GradedResponse Action Plan, which lists stricter anti-pollution measures to befollowed according to the severity of the situation.Green firecrackers,developed by a gamut of laboratories led by CSIR-NEERI, have finally hit themarkets, albeit in less quantity, mainly due to delay in finalising chemicalcompositions and granting manufacturing licences.

With Delhi's air quality plummeting to dangerous levelsaround Diwali every year, the Supreme Court last year banned pollutingfirecrackers and ordered that only green firecrackers, which cause 30 per centless pollution, can be manufactured and sold.The Delhi government has alsoprepared a dust action plan, under which officials have been regularly visitingconstruction sites, ensuring sprinkling of water to prevent dust emission andcarrying out an immediate repair of roads, according to Delhi EnvironmentMinister Kailash Gahlot.

The Delhi government is also going to distribute fivemillion N95 anti-pollution masks to students in government and private schools.

The CPCB also has a 15-day plan for the critical periodbetween November 1 and November 15, when pollution levels are maximum inDelhi-NCR, in the works.