There are millions of tons of pesticides and fertilisers used to grow crops across the world. Pesticides aim to kill pests, particularly insects (insecticides) and weeds (herbicides). But most of these chemicals end up in air, water, land - and food.

The other main source of contamination is those chemicals added to foods during processing. These are called additives. They are used for a wide variety of effects, such as colouring and stabilising, most having little to do with improving nutrition.

Check out chemical contamination in food gnerally: