These fine dust particles can easily enter the lungs causing health and breathing issues.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/mumbai-surpasses-new-delhi-air-pollution
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/asian-age-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/mumbai
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/rspm-pm-10
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/centre-science-and-environment-cse
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-quality-standards