State-owned System of Air Quality and Weather Forecasting And Research (SAFAR) which monitors pollution levels has predicted severe air quality in New Delhi in the next two days.
"Air Pollution is stunting our children's brains, affecting their health in more ways than we suspected".
Particulate matter (PM) is a term used to describe the mixture of solid particles and liquid droplets in the air.
Some examples include dust, ash and sea-spray.
Particulate matter varies in size, i.e. the diameter or width of the particle. In all these cities, the air quality was monitored to be "severe" or "very poor".
"Air pollution is an invisible killer and we need to step up our efforts to address the causes". UKHACC pointed towards road transport to be the major source of the most serious pollutants and asked the government to increase clean air zones in towns and cities along with offering financial incentives to businesses and households to shift to more sustainable forms of travel.
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A WHO assessment released earlier this year found that 14 out of the 20 most polluted cities in the world are in India.
The findings are based on 2015 data from more than 2,500 sites.
Levels of nitrogen oxide, or NOx, have declined since the start of the century, due in part to better filtering of the harmful gas.
The overall percentage of those affected somewhat decreases; however, the hard particles, nitrogen dioxide and ozone concentration still appear to be the most unsafe for people. Children are affected before they are even born, the report found. Residents celebrate by lighting lamps and bursting firecrackers, which have caused a sharp spike in pollution levels in previous years.
The Mediterranean region, meanwhile, recorded particularly high levels of toxic ozone, which is formed from chemical reactions of NOx and sunlight.
The report was published ahead of the WHO's first global conference on air pollution and health.
In the report, titled "Air Pollution and Child Health: Prescribing Clean Air", deaths of about 600,000 children under 15 years of age in 2016 were attributed to the joint effects of ambient and household air pollution. At 430, Ghaziabad had the poorest Air Quality Index (AQI), followed by Kanpur with an AQI of 422.
Expected outcomes include a strong commitment to decreasing air pollution by implementing policies and reforms, and making civic infrastructure such that children's exposure to polluted air is minimised. "It attains more importance in geographies like India where more than a million people lose their lives to the health emergency".