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What Do Those Recycling Symbols and Codes Mean?

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Earth Day is here again, serving as an annual reminder of the need to reduce, reuse, and recycle our way to a better planet.

When it comes to the last part of that familiar three-”R” mantra, most people know enough to separate certain items from the rest of their garbage, but much of our modern recycling routine remains a mystery. From the recycling symbol itself to what those numbers on plastic containers actually mean, there's a lot you can learn from your trash before it becomes someone else's treasure.

An International Symbol With An Earthy Origin

The universal recycling symbol—three folded arrows that form a triangle, with the head of one arrow pointing to the tail of the next—was created in 1970 by University of Southern California student Gary Anderson as part of a contest tied to the very first Earth Day. Each arrow of the design represents one of the steps in the recycling process: collecting the recyclable goods after use, breaking them down and reforming them, and then packaging new products in the containers.

Originally designed as an inverted triangle, the symbol was later rotated to the pyramid-like orientation commonly used now.

The Number Game

The American Society of Plastics Industry first began using numbers inside the recycling symbols on plastic containers in 1988 as a way to assist with sorting them. The “Resin Identification Code” uses seven numbers to identify the type of synthetic material used to manufacture the container, with the higher numbers representing less commonly used plastics.

Here's a primer on each of the codes:

1. Polyethylene Terephthalate (PETE/PET)
Usually accompanied by the letters “PETE” or “PET,” this resin is generally used for soda bottles and other containers for edible and non-edible goods. When it's not being used to manufacture containers, you might recognize it by another name: polyester. (Yes, it's the stuff that insulates your jackets.) It's also one of the most widely accepted forms of plastic in curbside recycling programs, though the amount of useable material available for new products after breaking down this plastic is relatively small.

2. High Density Polyethylene (HDPE)
The second most widely used resin for plastic bottles, HDPE is a stiff, strong material with a high resistance to chemicals, which has made it the go-to plastic for food items like milk and juice, as well as household cleaners and trash bags. It's also easy to break down in the recycling process and easy to reform, making it one of the most efficient consumer plastics. Most curbside recycling programs have no problem with accepting products made from this plastic.

3. Polyvinyl Chloride (PVC)
First discovered in the 19th century, PVC is commonly used in building materials today—especially pipes and plumbing material—due to its strength and chemical resistance (although it's occasionally used for some household products). It has a nasty habit of releasing highly carcinogenic toxins into the atmosphere when it's burned, so recycling is a significantly less appealing option for PVC disposal, and it's usually not accepted by curbside recycling programs.

4. Low Density Polyethylene (LDPE)
This plastic is becoming more common today, especially for manufacturing squeeze bottles and grocery bags. Plastics made from LDPE are usually very strong, and they're regularly used as sealants because of this quality. While they weren't included in curbside recycling programs at first, plastics made from LDPE are now becoming more commonly accepted.

5. Polypropylene (PP)
Regarded as one of the “safest” plastics produced today, PP is generally used for squeezable bottles, bottle caps, and straws. Along with LDPE, it's also used for Tupperware and other food-storage containers that can be reused over time. It has an extremely high melting point, so it's one of the best consumer plastics for items that will be exposed to heat. Like LDPE, it's becoming more common for curbside recycling programs to accept items made from this plastic.

6. Polystyrene (PS)
More commonly known as styrofoam, this type of plastic is not only notoriously difficult to recycle, but it's also been shown to leach dangerous toxins over time into anything packaged in it—and even greater amounts of toxins when it's burned. This is the resin usually found in disposable serving trays, egg cartons, and cups, and it's rarely accept by curbside recycling programs due to the danger it poses and the difficulty of recycling it. Basically, this is the worst of the bunch.

7. Everything Else
There are countless other plastics, but very few of them are easily recycled in curbside programs, making this category the catch-all for everything that could conceivably be broken down and reformed, but might be better off reused or reformed in some way that doesn't require a chemical process. This category encompasses everything from bulletproof material to those large water jugs on office coolers, and is rarely included in curbside recycling programs.

Safety In Numbers

For anyone wondering which plastics are safe to reuse in their current form, it's widely accepted that HDPE (2), LDPE (4), and PE (5) can be reused multiple times for edible items, as they're generally resistant to chemicals, haven't been shown to degrade, and don't leach dangerous substances into their contents.

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Big Questions
Why Is a Pineapple Called a Pineapple?
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by James Hunt

Ask an English-speaking person whether they've heard of a pineapple, and you'll probably receive little more than a puzzled look. Surely, every schoolchild has heard of this distinctive tropical fruit—if not in its capacity as produce, then as a dessert ring, or smoothie ingredient, or essential component of a Hawaiian pizza.

But ask an English-speaking person if they've ever heard of the ananas fruit and you'll probably get similarly puzzled looks, but for the opposite reason. The average English speaker has no clue what an ananas is—even though it's the name given to the pineapple in almost every other major global language.

In Arabic, German, French, Dutch, Greek, Hebrew, Hindi, Swedish, Turkish—even in Latin and Esperanto—the pineapple is known as an ananas, give or take local variations in the alphabet and accents. In the languages where it isn't, it's often because the word has been imported from English, such as in the case of the Japanese パイナップル (painappuru) and the Welsh pinafel.

So how is it that English managed to pick the wrong side in this fight so spectacularly? Would not a pineapple, by any other name, taste as weird and tingly?

To figure out where things went wrong for English as a language, we have to go back and look at how Europeans first encountered the fruit in question, which is native to South America. It was first catalogued by Columbus's expedition to Guadeloupe in 1493, and they called it piña de Indes, meaning "pine of the Indians"—not because the plant resembled a pine tree (it doesn't) but because they thought the fruit looked like a pine cone (umm, ... it still doesn't. But you can sort of see it.)

Columbus was on a Spanish mission and, dutifully, the Spanish still use the shortened form piñas to describe the fruit. But almost every other European language (including Portuguese, Columbus's native tongue) decided to stick with the name given to the fruit by the indigenous Tupí people of South America: ananas, which means "excellent fruit."

According to etymological sources, the English word pineapple was first applied to the fruit in 1664, but that didn't end the great pineapple versus ananas debate. Even as late as the 19th century, there are examples of both forms in concurrent use within the English language; for example, in the title of Thomas Baldwin's Short Practical Directions For The Culture Of The Ananas; Or Pine Apple Plant, which was published in 1813.

So given that we knew what both words meant, why didn't English speakers just let go of this illogical and unhelpful linguistic distinction? The ultimate reason may be: We just think our own language is better than everyone else's.

You see, pineapple was already an English word before it was applied to the fruit. First used in 1398, it was originally used to describe what we now call pine cones. Hilariously, the term pine cones wasn't recorded until 1694, suggesting that the application of pineapple to the ananas fruit probably meant that people had to find an alternative to avoid confusion. And while ananas hung around on the periphery of the language for a time, when given a choice between using a local word and a foreign, imported one, the English went with the former so often that the latter essentially died out.

Of course, it's not too late to change our minds. If you want to ask for ananas the next time you order a pizza, give it a try (though we can't say what you'd up with as a result).

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
Why Do They Build Oil Rigs in the Middle of the Ocean?
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Ryan Carlyle:

We put the rigs where the oil is!

There aren’t any rigs in the “middle” of the ocean, but it is fairly common to find major oilfields over 150 km off the coast. This happens because:

  • Shallow seas often had the correct conditions for oil formation millions of years ago. Specifically, something like an algae bloom has to die and sink into oxygen-free conditions on the sea floor, then that organic material gets buried and converted to rock over geologic time.
  • The continental shelf downstream of a major river delta is a great place for deposition of loose, sandy sediments that make good oil reservoir rocks.

These two types of rock—organic-rich source rock and permeable reservoir rock—must be deposited in the correct order in the same place for there to be economically viable oil reservoirs. Sometimes, we find ancient shallow seas (or lakes) on dry land. Sometimes, we find them underneath modern seas. In that latter case, you get underwater oil and offshore oil rigs.

In the “middle” of the ocean, the seafloor is primarily basaltic crust generated by volcanic activity at the mid-ocean ridge. There’s no source of sufficient organic material for oil source rock or high-permeability sandstone for reservoir rock. So there is no oil. Which is fine, because the water is too deep to be very practical to drill on the sea floor anyway. (Possible, but not practical.)

This post originally appeared on Quora. Click here to view.

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