NEW DELHI: Delhi's air quality took a turn for the worse this week. A difficult season for the vulnerable — children, elderly and those with a compromised immune system — is in the offing, with pollution levels jumping four times in just 38 days between September 1 and October 8.
Delhi's air quality was "good" for a couple of months during the monsoons, became "moderate" mid-September onward and slid to "poor" towards September-end. In comparison, Mumbai, Hyderabad, Chennai, Pune and Kolkata continue to remain in the "good" category.
On Saturday, the AQI value was 259 in the "poor" range. While minimum temperature was around 23 degrees Celsius, the wind speed at many locations remained less than a metre per second. The vertical wind speed at RK Puram on Saturday evening was in the negative, while the horizontal wind speed was 1.6 metres per second.
Scientists said the transition is the result of the change in meteorological conditions. "The temperature has started falling and wind speed is very low. And because Delhi is a land-locked city, particulate matter cannot escape the region easily," explained a scientist from System of Air Quality and Weather Forecasting Research (SAFAR) under the ministry of earth sciences.
SAFAR's AQI values are based on PM2.5 (fine, respirable polluting particles) concentrations recorded at 10 locations. The Central Pollution Control Board's AQI showed the values in Gurgaon and Agra to be in "poor" and "very poor" categories on Friday and Saturday, indicating how air quality in the entire region has started deteriorating.
Meanwhile there has been little movement on taking emergency measures to fight pollution. In similar circumstances on October 2, when AQI was between 200 and 300, Beijing issued a "yellow alert" which immediately imposed restrictions on construction work, outdoor barbecues and straw burning by farmers.
In Delhi, air pollution control policies announced last year, such as penalties for visibly polluting vehicles, parking restrictions, crackdown on waste burning and deployment of 4,000 buses to improve public have are not fully in place, with some measures being implemented lethargically. On a brighter side, however, the Centre for Science and Environment has examined annual averages since 2011 and found a marginal decline in 2015. The annual average concentration of PM 2.5 in 2011 was 130.4 micrograms per cubic metre, 167 in 2012, 143 in 2013, 151 in 2014 and about 118 in 2015.
"It clear that we are approaching the big winter problem and pollution is going to rapidly pick up now. The slight reduction in annual average last year could be because of the SC's intervention against heavy commercial vehicles," said Anumita Roy Chowdhury, head of CSE's clean air campaign.
The apex court had ordered trucks passing through to capital to pay an environment compensation charge. After the imposition of the fee in November last year, there was a decline of 35% in the number of trucks entering the city by March, according to the court-mandated note submitted by Environment Pollution Control Authority.
"The reduction in pollution shows that if you act on sources, the levels can reduce," added Chowdhury. "But it also indicates that action locally has to be even more aggressive. There should be emergency restriction measures for vehicles, immediate closure of Badarpur power plant and crackdown on construction projects that violate norms."
