Alandur’s air has highest NO2 concentration, Chennai's avg twice WHO limit
The WHO recommends an annual NO2 concentration of no more than 10 μg/m³, while the NAAQS (National Ambient Air Quality Standards) standard is 40 μg/m³
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CHENNAI: With the concentration of nitrogen dioxide (NO2) in Chennai’s air exceeding the World Health Organisation (WHO)’s prescribed limits, Alandur is the worst affected, with a high concentration of the harmful gas lingering in the atmosphere 86 per cent of the year.
According to a 2023 report by Greenpeace India, the city's annual average NO2 was twice the WHO guideline, exceeding the limit at all the Continuous Ambient Air Quality Monitoring stations (CAAQM) except Perungudi. Alandur recorded an average NO2 concentration of 57 μg/m³ (microgram per cubic metre).
"The highest average was recorded at Alandur Bus Depot in southern Chennai, near busy roads and an airport. Two stations, Gandhi Nagar Ennore and Royapuram, located within 10 metres of major roads, also surpassed the WHO guideline. Road traffic is a major source of NO2 pollution," the report said.
The WHO recommends an annual NO2 concentration of no more than 10 μg/m³, while the NAAQS (National Ambient Air Quality Standards) standard is 40 μg/m³.
The report added that overwhelming scientific evidence links NO2 exposure to adverse health impacts such as the risks of asthma, airway inflammation, respiratory irritation, and the worsening of existing respiratory conditions. It can impair lung development, intensify allergies and increase susceptibility to respiratory mortality and death from circulatory diseases, ischemic heart disease and, even, lung cancer.
Around 10 per cent of the total population in Chennai consists of children under six, who are particularly vulnerable to NO2. "Recent research suggests that NO2 pollution in Chennai in 2015 may have contributed to up to 1,420 cases of pediatric asthma. The five-year trend in NO2 concentration recorded by CAAQM monitors is increasing with six out of eight stations showing a worsening trend.
Road transport is the third largest source of emissions in Chennai, accounting for 9 per cent in the EDGAR (Emissions Database for Global Atmospheric Research) emissions inventory," it said.
Greenpeace India recommended the government to revise NAAQS and focus on strengthening the ability of primary healthcare services in diagnosing air pollution.
