New Delhi: Air quality in the capital has deteriorated ahead of Diwali and the odd-even scheme aimed at mitigating its effects by reducing traffic, official data showed.

The overall air quality in Delhi is once again in the “poor" category, after a weather disturbance last week improved wind flow and brought air quality to “moderate" levels, according to the System of Air Quality Weather Forecasting and Research (SAFAR), of the Union ministry of earth sciences. This is likely to worsen further to “very poor" levels on Tuesday.

Farmers in states such as Punjab and Haryana burn stubble after the crop is harvested with the wind carrying the smoke and dust to Delhi.

On Monday, levels of particulate matter (PM) 10 were reported to be “moderate" (191 mgm-3) and that of PM2.5 was found to be “poor" (96 mgm-3). Both are hazardous to human health, but PM2.5 is more damaging as it is smaller and can enter the blood through the lungs.

However, Monday’s air quality forecast shows the situation may not deteriorate to “severe" levels until the start of November because of a new western disturbance in the Himalayan region. The weather system may improve wind flow and prevent pollution levels from increasing further, offering some respite to residents of the capital city.

The anti-cyclonic circulation formed after the retreat of the monsoon would strengthen again at the beginning of November and lead to stagnant wind flow, causing pollution to rise during the first week of the month.

Weather conditions may prove favourable, but external sources of pollution, mainly the bursting of firecrackers and stubble burning, could play spoilsport and worsen the situation. “In a landlocked city like Delhi, it may lead to rapid accumulation and may trigger high-pollution events. If local emissions are controlled, it will be a good check to observe and avoid air quality crises," said the SAFAR forecast.

“The air quality may vary from day to day, depending on the weather. So, the situation on Diwali may not be as bad as last year, but we will have to wait for a few more days. According to the current forecast, a deterioration to ‘severe’ levels is expected only during the first week of November," said Gufran Beig, project director for SAFAR.

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