Question

Food Grains such as wheat ,rice and vegetable food and even meat are found to contain pesticides residues how and why this happens

Answer 1

this is because most of the manufacturers and producers want to increase their profit by reducing the cost of production.
this result in using a lot of artificial Chemicals and pesticides in case of Agricultural Products to increase the shelf life this making it out in the market for a longer period of time.

hope it helps you

Answer 2

The farmers are using more pesticides to get rid of those pesticides. but those pesticides are absorbed by the surrounding crops. The crops absorbs the pesticides and stores them in their storage cell in the food grains