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Who put this polymer in the trash?! A blog about plastics
KC Nattinger
November 13, 2011 - 8:13pm

Garbology, the study of waste, tells us interesting things about changes in our waste over time. In the 1950s, there was relatively little plastic in our landfills. Today, landfills hold around 16% plastic.

Why the big change? Companies used to package the things they sold in paper, and people also used to buy fewer things. My grandma would always can her own apple sauce in glass jars and reuse the jars each year. Now, people mostly just buy apple sauce, and it often comes in a plastic container.

Plastic has many uses, some of which make our lives much easier, and most uses of plastic make things cheaper. Try looking at the price difference between plastic food storage containers and glass ones. But there’s another cost to consider. Unlike glass, plastic breaks down over time, leaching chemicals into whatever it’s in contact with.

As scientists begin studying these chemicals, they are finding that many of them are harmful to humans. You may wonder why companies were allowed to sell plastic products without first researching whether or not these products would poison us and the world we live in, but that’s for another blog.

Plastics not only leach toxic chemicals into us when we use them, but when they are disposed of improperly—dumped on the ground or in the ocean—these plastics are famous for harming wildlife. But plastic doesn’t just hurt dolphins and sea turtles; it poisons the entire ecosystem, including us humans. Even if it’s properly disposed of in landfill, plastic can harm wildlife.

Making a bad problem even worse, plastic is notoriously difficult to recycle. Unlike glass or metal, plastic bottles can’t be turned into plastic bottles again. They must be turned into a lower quality of plastic—like the material used in park benches—that often times can’t be recycled again.

Plus, there are hundreds of different types of plastics out there, and some can be recycled, while others can’t. What happens if two types accidentally get mixed? The plastic is no longer as useful for making new things, and may not even be recycled.

The different types of plastic are labeled by a number on the bottom of the container—and different numbers can be recycled in different places.

Let’s take a tour of the most common types of plastic. Peruse all the plastics or click on a plastic number below.


#1 Polyethylene terephthalate (PET or PETE)

Found in: Soft drink, water, and beer bottles; mouthwash bottles; peanut butter containers; salad dressing and vegetable oil containers; ovenable food trays.

Recycling: Put into a mixed glass, metal, and plastic bin.

Recycled into: Polar fleece, fiber, tote bags, furniture, carpet, paneling, straps, (occasionally) new containers

PET plastic is the most common for single-use bottled beverages, because it is inexpensive, lightweight, and easy to recycle. It poses a low risk of leaching breakdown products. Recycling rates remain relatively low (around 20%), though the material is in high demand by remanufacturers.

#2 High-density polyethylene (HDPE)

Found in: Milk jugs, juice bottles; bleach, detergent, and household cleaner bottles; shampoo bottles; some trash and shopping bags; motor oil bottles; butter and yogurt tubs; cereal box liners

Recycling: Put into a mixed glass, metal, and plastic bin.

Recycled into: Laundry detergent bottles, oil bottles, pens, recycling containers, floor tile, drainage pipe, lumber, benches, doghouses, picnic tables, fencing

HDPE is a versatile plastic with many uses, especially for packaging. It carries low risk of leaching and is readily recyclable into many goods.

#3 Polyvinyl chloride (V or PVC "Vinyl")

Found in: Window cleaner and detergent bottles, shampoo bottles, cooking oil bottles, clear food packaging, wire jacketing, medical equipment, siding, windows, piping

Recycling: Put into a mixed glass, metal, and plastic bin.

Recycled into: Decks, paneling, mudflaps, roadway gutters, flooring, cables, speed bumps, mats

PVC is tough and weathers well, so it is commonly used for piping, siding, and similar applications. PVC contains chlorine, so its manufacture can release highly dangerous dioxins. If you must cook with PVC, don't let the plastic touch food. Also never burn PVC, because it releases toxins.

#4 Low density polyethylene (LDPE)

Found in: Squeezable bottles; bread, frozen food, dry cleaning, and shopping bags; tote bags; clothing; furniture; carpet

Recycling: LDPE is not often recycled through curbside programs. Plastic shopping bags can be returned to many stores for recycling.

Recycled into: Trash can liners and cans, compost bins, shipping envelopes, paneling, lumber, landscaping ties, floor tile

LDPE is a flexible plastic with many applications. Historically it has not been accepted through most American curbside recycling programs, but more and more communities are starting to accept it.

#5 Polypropylene (PP)

Found in: Some yogurt containers, syrup bottles, ketchup bottles, caps, straws, medicine bottles

Recycling: Not accepted in all places. Check with your local recycling agency.

Recycled into: Signal lights, battery cables, brooms, brushes, auto battery cases, ice scrapers, landscape borders, bicycle racks, rakes, bins, pallets, trays

Polypropylene has a high melting point and is often chosen for containers that must accept hot liquid. It is gradually becoming more accepted by recyclers.

#6 Polystyrene (PS)

Found in: Disposable plates and cups, meat trays, egg cartons, carry-out containers, aspirin bottles, compact disc cases

Recycling: Usually not recyclable in curbside or mixed recycling bins. Check with your local recycling agency to see if there is a drop-off program in your area.

Recycled into: Insulation, light switch plates, egg cartons, vents, rulers, foam packing, carry-out containers

Polystyrene can be made into rigid or foam products: in the latter case it is popularly known as the trademark Styrofoam. Evidence suggests polystyrene can leach potential toxins into foods. The material has long been of concern to environmentalists for dispersing widely across the landscape and for being notoriously difficult to recycle. Most places still don't accept it.

#7 Other: (multi-layered or mixed)

Found in: Three- and five-gallon water bottles, 'bullet-proof' materials, sunglasses, DVDs, iPod and computer cases, signs and displays, certain food containers, nylon

Recycling: Number 7 plastics have traditionally not been recycled.

Recycled into: Plastic lumber, custom-made products

A wide variety of plastic resins that don't fit into the previous categories are lumped into number 7. A few are even made from plants (polyactide) and are compostable. Polycarbonate is number 7 and is the hard plastic that has parents worried these days, after studies have shown it can leach potential hormone disruptors.