Last updated on March 6, 2022.
Plastics are made from chemicals and petroleum, which you read about in Part 1 of this series. Today, I want to tell you about the chemical contents of plastics by resin code, the number on the bottom surrounded by a triangle. More importantly, I want to inform you of the ways they may be toxic to our health.
Resin Identification Codes (RICs)
The plastics industry created RICs in 1988 as part of their campaign to boost plastic’s image. They even lobbied to have state legislatures adopt them. But this little symbol on almost all plastic packaging is misleading. Many assume that the recycling symbol or RIC means that a package is automatically recyclable. However, that is not true, it actually only refers to the type of plastic resin used.
To reduce confusion, ASTM, the organization that regulates the RIC system, updated the symbol from the chasing arrows to a solid triangle in 2013. “However, manufacturers aren’t required to change their equipment to incorporate the new symbol, which is why you still see the arrows on many plastic products,” according to an article on Oceano.org.1 So it’s still easy for people who don’t know to mistake the RIC as a recycling symbol versus an industry tag for the plastic.
“Thanks to the intelligent strategy that the plastic industry came up with in the early 1980s of imprinting a recycling code on the most commonly consumed plastic items, a large majority of consumers think that the bulk of the plastics they consume are recyclable and actually do get recycled through their local curbside recycling program. In reality, only a small percentage of the contents of a recycling box is recycled.”2
The RICs / Types of Plastics
Next, let’s look at the 7 RICs and types of plastics, what they are used for, their characteristics, their chemical contents, and their potential toxicity. Note that this is not an exhaustive list; nor is each category exhaustive in the standard products or characteristics.
“Despite how useful these additives are in the functionality of polymer products, their potential to contaminate soil, air, water and food is widely documented…These additives can potentially migrate and undesirably lead to human exposure via e.g. food contact materials, such as packaging.”3
#1 PET/PETE: Polyethylene terephthalate
Standard products: Water bottles, soda bottles, salad dressing bottles, food containers such as cooking oil and peanut butter, wrinkle-proof clothing, fleece blankets, padding in pillows and comforters, carpeting, other polyester fabrics.
About: PET is the most valuable type of plastic and the most recycled. There are typically two types: one is made with a blow molding machine; the other is thermoform which is made by heating a plastic sheet until pliable and then molded into a specific shape. The main difference is in molecular weight. Higher molecular weight items, such as bottles and jugs made from blow molding, are more valuable than their thermoform counterparts. Thermoform, though more difficult to sell, is often recycled into carpeting.4
Chemical content: “A chemical called antimony trioxide is used as a catalyst and flame retardant in making PET, and this antimony additive is considered a possible carcinogen.” The amount in one single water bottle is minimal, but leaching increases with heat. Think of those water bottles stored in the car during the summer. “There is research showing that PET may leach phthalates too, even though the plastics industry says that phthalates are not required to make PET.”5 Regardless, think about switching to metal or glass containers whenever possible.
#2 HDPE: High-density Polyethylene
Standard products: Milk jugs, water bottles, juice, bottles, bleach, dish and laundry detergent bottles, shampoo and conditioner bottles, cleaner containers, over-the-counter medicine bottles, cereal box liners, Tyvek home insulation, plastic-wood composites, snowboards, 3D printing filament, and wire covering. It is even used in some plastic surgery procedures.
About: This is one of the most widely used plastics because of its versatility. It is strong, flexible, cost-effective, moisture-resistant, and resistant to most chemical solvents. It has high tensile strength and has both a high-impact resistance and melting point. “The polyethylene polymer has the simplest basic chemical structure of any polymer, making it easy to process and thus extremely popular for low value, high volume applications.”6
Chemical content: While this is considered a ‘safer’ plastic for food and drink use, there is evidence that these release endocrine-disrupting chemicals, especially when exposed to UV. “The main leaching culprits are estrogen-mimicking nonylphenols and octylphenols, which are added to polyethylene as stabilizers and plasticizers.”7 Those chemicals disrupt the body’s hormones and can cause cancer, reproductive problems, birth defects, and other developmental disorders.
#3 PVC: Polyvinyl Chloride
Standard products: Think all vinyl products. Shower curtains, medical bags, medical tubing, shrink wrap, children’s toys, binders, school supplies, plastic furniture, garden hoses, vinyl clothing and outerwear, wire and cable insulation, vinyl records, carpet backing, flooring, credit cards, clamshell packaging, plumbing pipes, vinyl siding, window frames, fences, decking, other construction materials.
About: “PVC can take on a staggering variety of personalities – rigid, filmy, flexible, leathery – thanks to the ease with which it can be blended with other chemicals.”8 PVC is versatile as it can be adapted to many applications depending on the plasticizing additives. It is strong and resistant to moisture and abrasion. It can be produced clear or colored. About three-quarters of all vinyl produced goes into construction applications.
Chemical content: PVC is known as the poison plastic because it leaches toxins for its entire life cycle and should be avoided whenever possible. Vinyl is manufactured by polymerizing a chemical called vinyl chloride. It can contain up to 55% additives, mainly phthalates. The chemicals it may release during its lifetime include cancer-causing dioxins, endocrine-disrupting phthalates, bisphenol A (BPA), lead, mercury, cadmium, and other heavy metals. “The problem with PVC is that its base monomer building block is vinyl chloride, which is highly toxic and unstable, thus requiring lots of additives to calm it down and make it usable. But even in its final ‘stabilized’ form, PVC is not very stable.”9 The additives leach out and you can inhale and ingest them.
#4 LDPE: Low-density Polyethylene
Standard products: Film applications like bags, such as those used for bread, shopping, dry-cleaning, newspapers, frozen foods, produce, and garbage. Also used for shrink wraps, linings for cartons and cups, container lids, some squeeze bottles, orthotics, and prosthetics.
About: LDPE is a soft, flexible, lightweight plastic material, known for its low-temperature flexibility, toughness, and corrosion resistance. But it is not recyclable in any practical sense. Citing data from the Environmental Protection Agency (EPA), one large recycling corporation noted that “the overwhelming majority of products made from LDPE end up in landfills…Dumping tons of LDPE in landfills can have devastating consequences…plastic buried in landfills can leach into the soil and introduce chemicals into the groundwater.” They can threaten marine life in coastal areas, and “lightweight plastic bags can be blown great distances by the wind, ending up in bodies of water where animals eat them or become tangled in them.”10 Plastic bags causes huge environmental problems.
Chemical content: These can leach some of the same chemicals as #2 HDPE plastic. It is a thermoplastic made from the polymerization of ethylene. While ethylene is considered a building block of plastic, it is highly flammable and reactive. It is created by Ethane Cracker Plants, which use an environmentally questionable process to extract the ethane to make ethylene. While difficult to avoid, steer clear of this plastic whenever possible.
#5 PP: Polypropylene
Standard products: Polypropylene is used in packaging, yogurt cups, sour cream and soft cheese containers, prescription bottles, butter/margarine containers, plastic to-go containers, leftover containers, freezer meal containers, the filter cases of some disposable home water filters, electrical wiring, and plastic bottle caps because polypropylene can withstand pressure. It is also used in vehicles for bumpers, carpets, and other parts. Polypropylene allows moisture to escape and stays dry, making it ideal for use in disposable diapers.
About: Polypropylene is sometimes referred to as the “safe” plastic, but there really is no safe plastic when it comes to food. All plastic has the capacity to poison us in certain circumstances. Polypropylene is a stronger plastic than other types, but it is generally not recyclable because there isn’t sufficient reprocessing capacity. Polypropylene is more stable and resists heat better than other plastics. So it is generally considered safer for foods and hot liquids because it leaches fewer chemicals (though it still does leach, which is why you should use glass or metal containers for your food).11 However, this is what many leftover and freezer meal containers are made from. Have you ever noticed rough patches or surface defects in your leftover containers? Any disruptions on the surface mean the polypropylene has been compromised, which increases the chances that it will leach chemicals into your food, especially when heating it.
If you have polypropylene leftover containers from before 2013, replace them. These contained phthalates and bisphenol A (BPA). And if you do replace them, please buy stainless steel or glass containers and just avoid the chemicals in plastic altogether.
Chemical content: Polypropylene is a rigid and crystalline thermoplastic made from the polymerization of the propene monomer. There is ongoing research about the health effects of certain additives leaching from polypropylene, such as oleamide, a polymer lubricant and a bioactive compound. Oleamide does occur naturally in the human body, but the long-term effects of synthetic oleamide are not yet known. In a 2021 study entitled “Plastic additive oleamide elicits hyperactivity in hermit crabs,” scientists found that it may be perceived as a feeding cue by marine species, thus increasing the consumption of microplastics.12
#6 PS: Polystyrene
“Most recognizable when puffed up with air into that synthetic meringue known technically as expanded polystyrene and popularly by the trademark Styrofoam.” -Susan Freinkel, author of Plastic: A Toxic Love Story13
Standard products: The foam form, called Expanded Polystyrene (EPS), also known as Styrofoam, is used in egg cartons, meat trays, single-use food and take-out containers, coffee cups, vehicles, bike helmets, packing peanuts, and home insulation. The rigid form is used for single-use food containers, cutlery, CD and DVD cases, disposable razors, etc. “It is also combined with rubber to create an opaque high impact polystyrene used for model assembly kits, coat hangers, electronic housings, license plate frames, aspirin bottles and medical and lab equipment, including test tubes and petri dishes.”14
About: It may be difficult to avoid this stuff in home insulation, vehicles, and bike helmets, but it should be avoided at all costs when it comes to food and beverages. I wrote a lot about polystyrene in my series on Styrofoam and polystyrene food containers. These containers and cups leach styrene into food and beverages and thus enter your body. Styrene is known to likely be carcinogenic. It is considered a brain and nervous system toxicant and causes problems in the lungs, liver, and immune system.
Chemical content: Polystyrene is a synthetic polymer made from the polymerization of styrene. It is a chemically produced plastic that can be made into a hard or foam plastic. The foam is created by expanding the styrene by blowing various chemical gases into it. Polystyrene is made from ethylene and benzene, both hydrocarbons derived from by-products of petroleum and natural gas (also known as petrochemicals).
#7: OTHER Plastics
This is the catch-all category for all ‘other plastics.’ Any plastic items not made from the above six plastic RICs are grouped together as #7’s. These include acrylic, nylon, polycarbonate, epoxy resins, polylactic acid (PLA), and multilayer combinations of different plastics. These are never recyclable except through a few rare and expensive take-back programs, because of the vast array of resins and chemicals mixed together. Below are some of the individual plastic types that fall under #7.
Acrylic: This is a rigid thermoplastic that is strong, diverse, and resilient; and it can be clear or solid colored. Acrylics are used to make bulletproof windows, LEGOs, dental fillings and dentures, airplane windows, aquariums, shower doors, vehicle parts, helmets, and even textiles such as clothing, tents, and sails. This is a stable plastic and is considered a ‘safer’ plastic, except for certain ones used in dental applications. Those, specifically acrylic methacrylate resins, are suspected to be cytotoxic (toxic at the cellular level) because they leach chemicals such as formaldehyde and methyl methacrylate.15 That being said, keep those LEGOs out of your toddler’s mouths.
Nylon: This belongs to a group of plastic resins called polyamides that include Kevlar and Velcro. Invented by DuPont in the 1930s, nylon was originally invented to be a synthetic alternative for silk, for example, stockings. Nylon can be fiber, solid, or film. Items made from it include clothing, toothbrush and hairbrush bristles, rope*, instrument strings, tents, parachutes, carpets, tires, food packaging, boat propellers, skateboard wheels, and mechanical and automotive parts.
*NOTE: Most rope and nets used in commercial fishing are made from nylon and present a huge problem in the oceans. The rope and nets break away from the fishing vessels and become threats to fish, sea turtles, and marine mammals who get entangled in them. Since nylon is plastic, it will not decompose and will remain in the ocean for decades or longer.
Polycarbonate: Originally designed as an engineering plastic to compete with die-cast metal and substitute glass because it is lightweight, strong, transparent, and shatter-proof. In the past, it was used in reusable water bottles and baby bottles until bisphenol A (BPA) was ruled toxic. “It is still a favorite for rigid products including CDs and DVDs, eyeglass lenses, dental sealants, lab equipment, snowboards, car parts and housing for cell phones, computers and power tools.” It is also still used in the large, blue water containers common in offices.16 This type of plastic is good for items not related to food or beverage. However, we should use it less overall in other applications when possible to reduce waste, because when polycarbonate breaks it cannot be recycled.
Epoxy resins: Known for high strength, low weight, temperature and chemical resistance. Used in many applications: high-performance adhesives, coatings, paint, sealant, insulators, wind turbine blades, fiber optics, electrical circuit boards, and parts for carts, boats, and planes. They are also used on the interior lining of most canned goods. Avoid these when possible, especially with food and beverage containers because they contain chemicals such as bisphenol A (BPA) and epichlorohydrin. The latter likely causes blood, respiratory, and liver damage and is a probable carcinogen.17
Polylactic Acid (PLA): This is a bio-based plastic made from lactic acid, which is a fermentation product of corn or cane sugar. This is the most common bioplastic, used in a variety of products including clothing, bottles, weed cloth, gift and credit cards, food packaging, diapers, wipes, and disposable dishes. PLA is advertised as compostable but it is only biodegradable under industrial composting conditions, which is still largely unavailable.18
This large family of plastics was introduced in 1954. Polyurethanes do not have an assigned RIC, but they are worth mentioning because they are so common. They come in foamed versions that are soft and flexible for uses in mattresses, cushioning in furniture, cars, and running shoes, spray foam insulation, and carpet underlay. They can take on a flexible form for hoses, tubing, gaskets, seals; and they can be tough and rigid for items such as insulating lining for buildings and refrigerators. Polyurethane can also be made into thin films or coatings, such as adhesives for food packaging and waterproof coatings for wood. When it is spun into fibers, it makes Spandex, Lycra, and even latex-free condoms.19
Polyurethane is made from isocyanates, a chemical that is potentially toxic, as it is the leading cause of occupational asthma. “As for our day-to-day use, polyurethanes have also been linked to a skin irritation known as contact dermatitis through direct contact with such polyurethane items as a toilet seat, jewelry and Spandex tapes sewn into underwear.” It is highly flammable and may contain flame retardant additives that go in mattresses and spray foam insulation. Flame retardants are full of chemical combinations that are considered trade secrets, so the public does not know what potential toxins are present in their items. Spray foam insulation, even once cured, can off-gas isocyanate methylene diphenyl diisocyanate (MDI), which has been linked to asthma and lung damage.20
What You Can Do
The best thing you can do is to keep learning, which you’re already doing if you’re reading this article. Stay informed and be aware of what chemicals you’re exposed to through plastics, packaging, and additives. Avoid those which are documented as toxic or even potentially toxic. Additionally, remember that few plastics are actually recycled, so reducing the plastics you purchase is essential to the environment and your health. Thank you for reading, please share and subscribe!
“We all need to separate the hopeful and increasingly fantastical act of recycling from the reality of plastic pollution. Recent data indicates that our recycling wishes, hopes, and dreams – perhaps driven in part by myths surrounding RICs – will not stop plastic from entering our oceans. Instead, if we truly want to protect the environment and marine life, we need to campaign for more plastic-free choices and zones, and for the reduction of plastic production and pollution.”21
To learn more about Bioplastics: The Packaging Industry and How We Can Consume Differently, Part 3
The different types of plastics used in packaging: Guide to my Packaging Industry Series
More about polystyrene #5: Guide to my Styrofoam and Polystyrene Containers are Poisoning Your Food Series
Article, “An overview of chemical additives present in plastics: Migration, release, fate and environmental impact during their use, disposal and recycling,” by John N.Hahladakis et al., Journal of Hazardous Materials, Volume 344, February 15, 2018.