Polypropylene is a plastic that’s used in many products, including food storage containers. You can recognize it as the number 5 surrounded by a triangle on the bottom. It’s generally considered one of the safer plastics and isn’t known to have any cancer-causing effects.

We live in a very plastic world. Nearly everything we eat, drink, or own contains plastic or is contained in plastic. Some plastics, like those that contain BPA or other harmful chemicals, can negatively affect our bodies or the world we live in.

Polypropylene, a complex plastic, is generally considered safe for humans. But what do we know about this useful and ubiquitous product?

Polypropylene is a plastic. Of the commercial plastics on the market today, polypropylene is considered one of the safest.

It’s FDA-approved for food contact, so you’ll find polypropylene in food containers like those that hold yogurt, cream cheese, and butter products. Because it has a high heat tolerance, it’s also often used in packaging of food that can be heated in a microwave.

Some surgical devices and implants are also made of polypropylene, and polypropylene fibers are commonly used to weave area rugs for indoor and outdoor use.

Polypropylene, which is derived from petroleum, is considered by the Environmental Protection Agency (EPA) to be a safer choice than some other types of plastics. It’s not known to cause cancer in humans, and it’s less flammable in fabrics than wool.

It’s important to note, however, that some newer research does point to toxicity in certain polypropylene containers.

The researchers in a 2019 study looked at many kinds of plastic in a wide range of products. They found that the toxicity of a particular plastic varied dramatically from product to product because of each product’s manufacturing process.

In this study, researchers found that some polypropylene products affected androgen hormones and caused a toxic or stress response in cells.

More research is needed, especially since plastics are chemically complex, and each product could have different effects.

This research hasn’t changed the FDA’s or the EPA’s recommendations for the use of polypropylene.

Bisphenol A (BPA) is a chemical used in the manufacturing of polycarbonate plastics. It’s also used in epoxy resins that coat the insides of canned goods and water supply pipes.

BPA leaches into food and water supplies easily. More than 93 percent of the urine samples examined in a CDC study contained BPA concentrations.

Although the FDA has said that small amounts of BPA are safe for humans, some environmental and health experts are concerned that exposure to BPA could lead to problems with brain development, immune function, learning abilities, reproductive disorders, and other health issues.

The growing concern around BPA has led to the production of several types of BPA-free plastics. Polypropylene is one type of plastic that’s free of BPA.

To make it easier for consumers to recycle and for recycling facilities to process plastics, containers are labeled with a resin ID code.

This code is identified as a number between 1 and 7 stamped on the bottom of a package and framed by arrows forming a triangle.

Polypropylene’s number is 5. Here’s an at-a-glance guide to resin recycling codes:

NameResin IDFound inWhat to know
Polyethylene terephthalate (PET)1Plastic water and drink bottles, condiment containersGenerally safe, but at high temperatures may leak a metal called antimony.
High-density polyethylene (HDPE)2Jugs and bottles, plastic bagsReleases low levels of chemicals that raise estrogen levels.
Polyvinyl chloride (PVC)3Sandwich meat containers, sturdy bags for bedding, toysCan contain toxins such as DEHP, which the EPA says is likely to cause cancer in humans in high concentrations. May also contain dioxins, vinyl chloride, and other toxins that can cause birth defects, learning difficulties in children, hormonal dysregulation, and cancer.
Low-density polyethylene (LDPE)4Dry cleaner and bread bags, shrink wrapsGenerally considered safe.
Polypropylene (PP)5Potato chip bags, diapers, yogurt containersGenerally considered safe.
Polystyrene (PS)6Styrofoam cups, egg cartons, packing peanuts, cigarettesStyrene, a chemical believed to cause cancer, can leach out of polystyrene containers, though the amount of styrene in packaged foods is very low.
Other miscellaneous plastics7Oven baking bags, other plastic containersThis is a catch-all category for plastic that doesn’t fall into the other categories. It contains BPA and is generally not considered safe.

Because plastic is everywhere, eliminating it entirely is a tall order. Here are some tips for reducing plastic use, as well as using it more safely:

  • Doctors don’t recommend heating food in plastic containers because heat increases the chances that chemicals will seep out of the container and into your food. Choose to heat food in glass or metal containers instead.
  • Choose products marked “BPA-free” if you can. Try to avoid plastics that are marked with recycle codes 3 or 7, unless there’s a leaf beside the number (which indicates the plastic is BPA-free). There’s typically a higher risk that these plastics contain BPA and other potentially harmful chemicals.
  • Discard any plastic containers you’ve had since before 2012. That’s the year the FDA banned the use of BPA in sippy cups, baby bottles, and baby formula containers.
  • Avoid using plastic or coated roasting and steaming bags. Heat may cause chemicals to be released into your food from these products.
  • Don’t refill plastic water bottles labeled with a resin recycling code 1. They are intended as single-use containers.
  • Avoid handling cash register receipts coated with a shiny film. According to advocacy group Breastcancer.org, that shiny coating contains BPA.
  • You may want to consider replacing your plastic serve-ware and storage containers with glass or metal alternatives over time. Although polypropylene remains a safer alternative to some other types of plastic, the manufacturing process for plastic products may not be good for the environment.

Polypropylene is a plastic that’s used to make everything from rugs to sour cream containers. It’s generally considered to be one of the safer plastics. The FDA has approved its use as a food container material, and there are no known cancer-causing effects associated with polypropylene.

You can tell you’re using a polypropylene container if the number 5 surrounded by a triangle is on the bottom of the container.

If you’re concerned about the possibility of chemicals leaching out of a polypropylene package, you can take some steps to minimize your exposure. Transfer food into a glass or metal container before you heat it, and don’t reuse containers that are intended as single-use packaging.