Pesticide overuse, irrigation by untreated sewage water, poor sanitation at food markets, and faulty cold storages.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/safe-food-farm-fork
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/indian-express-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/food-contamination
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/food-safety-and-standards-authority-india-fssai
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/food-safety
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/india
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/food-adulteration
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/pesticides