If you’ve ever turned over a plastic water bottle or empty container of laundry detergent, you’ve probably noticed the little triangular recycling symbol with three arrows chasing each other. The other day, I looked a little more closely and noticed a number inside the triangle. It’s entirely possible you’re sitting here thinking, "duh," but if you’re not, keep reading. I started flipping over empty plastic containers and noticing that sometimes the number is different. Fast forward to a bunch of research later (big thanks to the Environmental Protection Agency), and I now know that plastics can have a number on the bottom that ranges from 1 to 7. What exactly do those numbers mean?

According to the EPA, plastic makers actually created this number system to distinguish between different kinds of plastic. The thin type of plastic making up your disposable water bottle is different than the heavy-duty plastic of your fabric softener bottle. A triangle with a 1 inside of it, for example, stands for "Poly(ethylene terephthalate)," or the type of plastic that’s normally used in water bottles.

Here’s the thing, each town typically has different rules about which types of plastic they do and don’t recycle. Theoretically, the numbers inside the triangle can help you identify the type of plastic so you can determine if you should recycle it. If you’re like me, you might be panicking a tiny bit at the thought of memorizing/remembering/keeping track of all the different names and numbers of each type of plastic.

But rest assured, I’ve noticed that most town recycling websites simply describe which plastics you should and shouldn’t recycle, and don’t get into numbers. For example, the New York Department of Sanitation from my home sweet home says I can recycle ridged plastics and describes what those are in great detail ("plastic bottles, jugs and jars; rigid plastic caps and lids; rigid plastic food containers…").

So if anything, may you take this recycling symbol guide as a reminder to head over to your town’s website and check out which plastics you should and shouldn’t recycle. That plastic shopping bag for example? It’s usually not on the recycling list (though you can probably recycle those at your local grocery store). There are also probably strict guidelines about which types of paper and metal you can and can’t recycle.

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