In most of the civilized areas, the problem of contamination is known, because it affects the environment and the people living in it. So there are techniques to create a sustainable living, where the waste enters in a cycle of recycling without creating a wasteland that sooner or later will bring consequences of great importance.
If a plastic is made of different elements, that's the reason behind the plastic markings. With the symbol to identify the plastic is easy, and there are regulations that curiously aren't widely adopted because places like Asia sell a lot of products without markings. A big mistake!
Although it's also very problematic when the specifications are too generic that they open a door for uncertainty. It happens this way with the famous seven that means "other". Let's remind the plastics here: 1 for PETE, 2 for HDPE, 3 for PVC, 4 for LDPE, 5 for PP and 6 for PS.
Sadly the number of plastics in those 7 is very important, with different industries relying on them.
Uncategorized plastics seem a recipe for a disaster in the future, and allow manufacturers to be irresponsible. This is a good point to remember in the task of asking for more efforts and rationality in this regard.