The India Meteorological Department said pollution levels have spiked due to calm conditions, marked by low wind speed and moisture.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/north-india-hit-biting-cold-delhi-air-quality-worse
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/asian-age-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/indian-meteorological-department-imd
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/punjab
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/haryana
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-quality-standards