What are the 6 pollutants that harm human health and the environment?

According to the World Health Organization (WHO), particle pollution, ground-level O3, CO, sulfur oxides, nitrogen oxides, and lead (Pb) are the six major air pollutants which harm human health and also the ecosystem.

Further Readings – 

1. World Health Organisation (WHO)
2. Air Pollutants
3. National Clean Air Programme – NCAP