Plastics are labeled in a classification system called the Resin Identification Code. It is the number printed on the bottom of most (not all) plastic bottles and containers. Resin is synonymous with polymer or plastic. The system was developed in 1988 by the US-based Society of Plastics Industry to facilitate the recycling of post-consumer plastics, which does not mean that the product is actually recyclable.
Below I will explain the different types and their safety and toxicity.
1. Polyethylene terephthalate or PET or PETE
PET is typically used to make bottles for soft drinks, water, juice, mouthwash, sports drinks and containers for ketchup, salad dressing, jelly and jam but also packages for cosmetics and household cleaners. PET is considered safe, but it can actually leach the toxic metal antimony, which is used during its manufacture. Leaching will increase with time and with higher temperatures. PET plastic should not be reused because cleaning detergents and high temperatures can cause chemicals to leach out of the plastic.
2. High-Density Polyethylene or HDPE
Polyethylenes are the most widely used family of plastics in the world. HDPE is hard, opaque and can withstand somewhat high temperatures and is made from petroleum. It is often used for milk, water and juice bottles, as well as bottles for cleaning supplies and shampoo. It's also used to make toys, grocery bags and cereal box liners. HDPE (like most plastics) has been found to release estrogenic chemicals (meaning they can potentially disrupt your hormones and even alter the structure of human cells, posing risks to infants and children) but is considered a low-hazard plastic.
3. Polyvinyl chloride or V of Vinyl or PVC
Polyvinyl chloride (PVC) is a thermoplastic polymer and contains toxic chemicals, including DEHP, a type of phthalate used as a plastics softener. Phthalates is a type of chemical causing many species to become more female by disrupting the endocrine system. They have shown to cause testicular cancer, genital deformations, low sperm counts and infertility in a number of species, including polar bears, deer, whales and otters, just to name a few. Scientists believe the same adverse effects can occur in humans. PVC has already been linked to chronic diseases such as allergies, asthma and autism.Because of these health issues, the use of PVC has decreased but it is still popular and in common use since it is cheap and versatile. The base monomer in PVC is vinyl chloride that can be combined with various other chemicals to create resins that can be rigid or flexible. PVC can be found in plastic toys, shower curtains, inflatable structures tablecloths, clear food (e.g., take-out) and non-food packaging, shampoo bottles, mouthwash bottles.
PEVA (polyethylene vinyl acetate) and EVA (ethylene vinyl acetate) are the popular alternatives to PVC, but they are not perfect. They are made from petrochemicals (petroleum and natural gas), a fossil fuel pollutant, and although they are chlorine-free (and fewer volatile organic compounds (VOCs)), they still contain other chemicals. Also, as a study by the North Carolina School of Science and Mathematics has shown, both PEVA and PVC had negative effects on living organisms.
4. Low density polyethylene (LDPE)
LDPE is considered a low hazard plastic and is used in bags used for bread, fresh produce, newspapers, garbage, paper milk cartons and hot and cold beverage cups. While LDPE does not contain BPA, some studies have shown that it can leach the endocrine disruptor nonylphenol (added to LDPE as a stabilizer), especially when exposed to ultraviolet light (sunlight).
5. Polypropylene (PP)
Polypropylene (PP) is a thermoplastic polymer. It is strong, tough, has a high resistance to heat and acts as a barrier to moisture, so it is often used in containers for hot food. Other uses are yogurt containers, Britta filters, baby bottles, containers for medications, thermal vests, car parts, microwavable containers. Most PP are microwave and dishwasher safe, meaning the plastic will not warp when heated. It doesn´t mean it is healthy to do so.
6. Polystyrene (PS)
The production of polystyrene, more commonly known as Styrofoam, requires benzene, a known carcinogen. Polystyrene is known to leach styrene into your food. Styrene is a compound that and is considered a brain and nervous system toxicant and is a possible human carcinogen, according to the United States Environmental Protection Agency (EPA) and the International Agency for Research on Cancer (IARC). Leaching increases with higher temperatures, so using Styrofoam containers and cups for hot food and drinks is not a good idea. Polystyrene can be found in disposable cutlery, CD and DVD cases, foam cups and take-out containers.
7. Other (all other plastics)
The last category is a general category for all other plastics that are not included in number 1-6 and also includes bioplastics. Polycarbonate (PC) is a common plastic in this category that is derived from BPA (see my blog post on water bottles to learn more about BPA). PC can be found in baby bottles, sippy cups, water containers, metal food can liners, snowboards, car parts, computers etc.
Alternatives to BPA are Bisphenol S (BPS) and Bisphenol F (BPF), but studies have shown that the adverse effects of these two substitutes to be in the same order of magnitude and of similar action as BPA and thus are also endocrine disrupting. Endocrine disrupting means that they mimic or interfere with your body's hormones and disrupt your endocrine system. The glands of your endocrine system and the hormones they release are involved in regulating mood, growth and development, tissue function, metabolism, as well as sexual function and reproductive processes. Some manufacturers advertise with the fact that their products are BPA-free, but be cautious and check that it doesn´t contain BPS or BPF. More on the dangers of BPA-free products, check this article.
In the next blog I will talk about why plastics are a big problem when it comes to disposing of them.