Make up largest fraction of PM2.5; fertilizers, agriculture and untreated sewage causing the rise
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/nitrogen-emissions-going-study
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/hindu-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/undefined