NEW DELHI: According to the State of Global Air report, Delhi has been ranked as the most polluted city in the world, followed by Kolkata, in terms of PM 2.5 concentrations. The report that was released on Wednesday is based on an analysis of pollution sources for a period ranging from 2010 to 2019 in 7,239 cities across the globe. It shows the pollution exposure in these cities and the associated health impacts on people.
It mainly analyses two key air pollutants — PM 2.5 and NO2. PM 2.5 is the most dominant pollutant in Delhi’s air that can enter the lungs and the bloodstream and can cause adverse impact on health. The report has divided the cities into 21 regions such as South Asia, East Asia and Africa, among others.
As per the report, among the most-populous cities in each region, Delhi tops the list of the 20 cities with the highest population-weighted annual average PM 2.5 exposures in 2019. Delhi with an annual average of 110 ug/m3 tops the list followed by Kolkata at 84 ug/3. The other cities in the list include Kano, Nigeria (83.6ug/M3), Lima, Peru (73.2ug/m3), Dhaka, Bangladesh (71.4 ug/M3) and Jakarta, Indonesia (67.3ug/M3), among others.
According to World Health Organisation air quality guidelines, the annual average permissible limit for PM 2.5 is 5 ug/m3 while for NO2, it is 10 ug/m3. However, as per Indian standards, the annual average permissible limit for PM 2.5 is 40 ug/m3.
The report highlights that while exposures to fine particulate or PM2.5 pollution tend to be higher in cities located in low-and middle-income countries, exposure to nitrogen dioxide is higher among high-income cities as well as low-and middle-income countries.
The most heavily polluted cities are located in South Asia, East Asia, Southeast Asia, West Sub-Saharan Africa, and Andean and Central Latin America. In the 20 cities with the highest PM2.5, exposures among these 103 cities (with high population density), residents in cities from India, Nigeria, Peru, and Bangladesh are exposed to PM2.5 levels that are several-fold higher than the global averages, the report said.
Long-term exposure to PM2.5 pollution is associated with illness and early death from a variety of diseases including ischemic heart disease, lung cancer, COPD, lower respiratory infections (such as pneumonia), stroke, type 2 diabetes, and adverse birth outcomes. According to researchers, this is the first such report that assesses NO2 exposures globally.
In cities, vehicles are often a major source of NO2 and people living close to roads and highways experience higher NO2 exposures. Exposure to NO2 can aggravate asthma symptoms and has also been linked to the development of asthma in children and adults, the analysis observed.