Food additives are found in all processed foods these days and a good percentage of our foods are now processed. (The food additive industry is a multi billion dollar industry).
The Federal Drugs Administration (FDA) explains food additives in great detail. The descriptions are useful and show how much food additives have become part of 21st Century living.
See Food Additives and Ingredients:
https://www.fda.gov/food/food-ingredients-packaging/food-additives-petitions
The FDA website claims that in general they are safe and do not make children hyperactive.
However there are some contrary opinions.
Some food additives do seem to be able to make some, if not all children hyperactive.
Take calcium propionate (282) an anti fungal is used in bread to prevent spoiling from moulds.
A study in the Journal of Paediatric Health in 2002 reported that this food preservative might induce irritability, restlessness, inattention and food disturbances in some children, particularly when ingested on a regular basis. These changes appeared to be reversible when the 282 food additive was removed from the diet of these children.
Food additives are usually given a unique number which is usually the same throughout the world.
In Europe an ‘E‘ is added - E282.