What are plastics 3 4 6 7?

What Do the Numbers on Plastics Mean? (And Why #3, #4, #6, and #7 Matter)

Ever flipped over a plastic bottle or container and seen that tiny number inside the recycling symbol? That’s the resin identification code—a system designed to help sort plastics by their material type. While most people recognize #1 (PETE) and #2 (HDPE) as the most widely accepted in recycling programs, the others—especially #3, #4, #5, #6, and #7—are a different story.

Plastics labeled #3 through #7 are often more challenging to recycle. #3 plastics, made from PVC (polyvinyl chloride), can release harmful chemicals when burned or processed, making them undesirable for many recycling facilities. #4 plastics, or LDPE (low-density polyethylene), include things like grocery bags and wrap—flexible but often excluded from curbside pickup unless returned to specific drop-off points.

#6 refers to polystyrene, commonly known as Styrofoam. Despite its widespread use in takeout containers and packaging, it’s rarely recycled due to its low weight-to-volume ratio and contamination issues. Then there’s #7—a catch-all category for mixed or "other" plastics, including polycarbonate and bioplastics. These are often not recyclable through standard systems and require special processing.

So what does this mean for you? Just because a plastic has a recycling symbol doesn’t guarantee it’ll be recycled. Local programs vary, and many can’t handle #3, #4, #6, or #7 materials. The key is to check with your local waste authority—and when in doubt, it’s better to reduce or reuse than to assume something is recyclable.

Understanding these codes helps us make smarter choices, pushing us toward fewer single-use items and a more thoughtful approach to plastic consumption.