Visibility suffers due to pollutants, weather

Mumbai: Despite the overall average air quality index (AQI) of Mumbai being moderate at 133, visibility remained poor across the city due to heavy concentration of pollutants, dust, and weather conditions. Experts said the haze is likely to persist for another few days.

“Visibility suffers not only due to dust, but also due to the formation of secondary pollutants that are very fine and hang in the atmosphere. One example is ozone, which is formed when nitrogen oxide combines with hydrocarbons in the presence of sunlight,” said Rakesh Kumar, former director of the National Environmental Engineering Research Institute.

As per data from the Central Pollution Control Board (CPCB), only four stations in Mumbai had poor quality air, with AQI scores ranging 201 to 300. Chembur had an AQI of 286 due to concentration of PM2.5 particles while Siddharth Nagar in Worli had an AQI of 221, primarily due to pollution by ozone particles. The AQI in Govandi and Kandivali was 234 and 269 due to high concentration of PM2.5 and PM10 particles, respectively.

All remaining CPCB stations in the city had moderate AQI between 101 and 200, which triggers breathing issues in people with lung, asthma and heart diseases, according to pollution control board classifications. Despite the ‘moderate’ tag, the concentration of pollutants at most stations was far beyond the safe limit of 40μg/m3 for PM2.5 and 60μg/m3 for PM10 particles prescribed by the National Ambient Air Quality Standards.

Other experts also said the weather was partly to blame for the poor visibility. “Presently, winds at the surface are slightly cool with warmer moist winds above them. Moisture holds on to pollutants, and it is only the cool air that sinks. Humidity is also quite high. These conditions effectively stop the dispersal of pollutants, causing the hazy atmosphere,” said Sushma Nair, scientist at the Indian Meteorology Department, Mumbai.

Meanwhile, on Tuesday, Santacruz recorded a minimum temperature of 19.8 degrees Celsius and a maximum of 31.9 degrees Celsius, whereas Colaba recorded a low of 22 degrees Celsius and a high of 32 degrees Celsius. Minimum temperatures in the city are unlikely to dip to 16-17 degrees Celsius as expected earlier, said experts.

“The winds dominating are mostly easterly and south easterly, so it is unlikely that the temperature will drop even to 18 degrees Celsius. But the maximum temperature will be in the range of 30-32 degrees Celsius, which is lower than last week, so it won’t be uncomfortable,” said Nair.