Mumbai’s air quality dropped to “very unhealthy” levels on the first day of the New Year. At 10 am, the air quality index, which measures the amount of pollutants in the air, was 281.

An Air Quality Index reading up to 50 is considered “good” and up to 100 is considered “satisfactory”. A reading between 401 and 500 is ranked “severe” on the index, which means the air is dangerously filled with pollutants.

The air quality was worst around Bandra Kurla Complex, which recorded PM2.5 levels of 306 at 3.30 pm. At Navi Mumbai, the air was sightly better, at an AQI reading of 107.

The city’s air quality has been steadily dipping since the last week of December, the Hindustan Times reported.

“The wind speed picked up pace after Christmas, which has dispersed pollutants at the surface,” The Asian Age quoted Gufran Beig, the project director of the System of Air Quality Forecasting and Research, or SAFAR, as saying. “As the speed decreases, pollutant particles get suspended on the surface.”