Most of us are familiar with the little numbers inside the chasing arrows on plastics. But we may not realize that even though a plastic has a number assigned to it, it may not be recyclable. The numbers are known as resin identification codes, and they are used to distinguish types of plastic from each other. The codes were devised in the 1980s and since then, many new types of plastic have come onto the market. Unfortunately, these new plastics don't have codes and are difficult to recycle.

To help you distinguish recyclable plastics from those that can't be recycled, we've compiled a quick list of the resin codes, noting their recyclability and if they can leach any harmful chemicals into food. In all cases, check with your sanitation department to determine if a given type of plastic can be recycled. And remember, it is often better to use tempered glass and ceramic containers, which will outlast most plastic containers by many years. If you must use plastic, try to find products made from post-consumer recycled content plastic. For more information, see our Plastics FAQ.

1 recycle1. PET (or PETE)
Polyethylene terephthalate: Used in clear plastic bottles

Widely accepted for recycling

Note that single-use bottles are not designed for storing water and bacteria may build up in screw threads. Reusable bottles should not be used to store hot liquids since this may degrade the plastic overtime.

2 plastic recycle2. HDPE
High-density polyethylene: Used in milk and juice bottles, retail bags, yogurt containers

Widely accepted for recycling

3 plastic recycle3. V or PVC 
Polyvinyl chloride: Used in food containers and utensils, pipe, children's toys, clothing and accessories, binders/notebooks, upholstery

Limited recyclability, primarily PVC pipe

AVOID: The production and incineration of PVC releases carcinogenic dioxins into the atmosphere. Furthermore, some products, such as certain food wraps, can leach hormone-disrupting phthalates into foods.

4 plastic recycle4. LDPE
Low-density polyethylene: Used in thin plastic bags, grocery bags, bread bags, squeeze bottles

Widely accepted for recycling; check with your sanitation department to see if they are accepted.

5 plastic recycle5. PP
Polypropylene: Used in yogurt containers, margarine clubs, prescription bottles and straws

Recyclable; check with your sanitation department to see if accepted.

6 plastic recycle6. PS
Polystyrene: Used in foam plastic cups and containers

Recyclable; check with your sanitation department to see if accepted.

Avoid: Can leach carcinogenic styrene into liquids.

7 plastic recycle7. PC, PLA and miscellaneous plastics (Other)
Other: Used in food containers, water bottles, baby bottles, plastic bags

This category encompasses several types of plastic including polycarbonate (sometimes listed as PC), which can leach hormone-disrupting bisphenol-A into liquids. However, #7 plastics also include bio-based plastics such as those made from polylactic acid (PLA) derived from corn.

Not recyclable; however, some bio-based plastics such as PLA can be composted in municipal composters.

Avoid: Polycarbonate (PC)

OK for use: Bio-based plastic; however, single-use containers should not be used to store foods.

Note: Check with your sanitation department if you have any questions about which plastics are accepted for recycling in your area.

Images from Wikimedia Commons.

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Plastics by the numbers
Make sure you know what you're recycling, or if it can even be recycled.