Styrofoam is made from polystyrene and was invented in 1965. Polystyrene is considered to be a safe packing material for collections. I personally have issues with packing “peanuts” due to the static charge they create. As a packing material, I recommend making pillows out of them by placing them in resealable plastic bags.
Styrofoam peanuts that do not have an anti-static coating are considered safe. Peanuts with an anti-static coating tend to be either pink or green in color. They are not considered safe for collections and should be avoided.
A number of packing peanuts are advertised as “environmentally friendly.” These are made from a starch material. I have several concerns. If you are shipping something in a box packed with these peanuts and the box gets wet, the peanuts will dissolve into a gooey mess and stop providing the cushion they were designed to give. I personally do not think these peanuts belong near collections.
To test, take a peanut and put it under running water. If it sheds water it is Styrofoam, and if it melts away it is starch based.