World’s most polluted cities
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India is home to 14 of 20 of the planet’s most polluted cities, according to PM2.5 concentrations – particulate matter smaller than 2.5 microns – the pollutant seen as the most harmful to human health
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Human hair 60μm wide

1 micron (μm) = 0.001mm
PM10   PM2.5
10μm   2.5μm

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PM2.5: Particles enter blood stream via respiratory system and travel throughout body. Health effects include asthma, lung cancer, heart disease, acute respiratory infections and stroke
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Average PM2.5 concentration 2019 (μg/m3)

India    Ghaziabad 110.2
China    Hotan 110.1
Pakistan Gujranwala 105.3 
Pakistan Faisalabad 104.6
India    Delhi 98.6
India    Noida 97.7
India    Gurugram 93.1
Pakistan Raiwind 92.2 
India    Greater Noida 91.3
India    Bandhwari 90.5
India    Lucknow 90.3
Pakistan Lahore 89.5
India    Bulundshahr 89.4
India    Muzaffarnagar 89.1
India    Bagpat 88.6
China    Kashgar 87.1
India    Jind 85.4
India    Faridabad 85.0
India    Coraut 85.0
India    Bhiwadi 83.4
    
       
World Health Organisation PM2.5 target: 10 μg/m3
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Source: 2019 World Air Quality Report, IQAir AirVisual
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