Formalin is being used by the traders as a preservative in fish, fruits, meat, milk, vegetables and a wide variety of food items.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/formalin-treated-food-items-cause-deadly-diseases
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/new-nation-bangladesh
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/bangladesh
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/south-asia
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/food-safety
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/food-contamination
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/cancer
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/asthma
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/skin-diseases
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/toxins