Do You Know Your Plastics?

Have you ever wondered what those symbols found at the bottom of plastic containers mean? They look like these:


An ex-colleague once informed me, with great conviction, that the numbers represent the number of times you can use the plastic container before it starts to leak toxic substances. It sounds believable at first, but if you think again, how do you define the number of times you use a container? You can use it to store an item and leave it undisturbed for weeks – is that single use? Or is it defined by the number of times you replace the whatever substance you have in the container??

I actually believed my ex-colleague for some time (shame).

Anyway, back to the true meaning of those numbers 1 to 7. They are known as the ASTM Resin Identification Code (RIC). ASTM stands for the American Society for Testing and Materials. The code was first developed in the 1980s when communities in the USA started to implement recycling programmes. Classifying plastics in this manner enables recycling facilities to more effectively sort plastics before they are recycled.

There are 7 codes in all, with Code 7 comprising a mix bag of plastic types which do not fit in the other 6 categories.

Table showing plastic resin identification codes, what they represent and where the plastics are found (Source:

Two websites that I find to be an informative read are this one by the a NZ recycling company and this one by BBC.

Key points to note:

  • All plastics marked with these numbers are known as thermoplastics and are chemically recyclable (yes even styrofoam or polystyrene).
  • The infographic below explains why thermoplastics are recyclable, as compared with another type of plastics called thermosetting plastics (found in electrical fittings like plug sockets and also tableware). Basically, thermoplastics melt under heat, and can be reused after that. Thermosetting plastics burn and release toxic gases upon application of heat.
Thermoplastics vs thermosetting plastics. (Source:
  • Although all plastics marked with the codes 1 to 7 are recyclable, not all are popular with recycling companies due to cost and logistical issues. It is important to check which types of plastics are accepted by your local recycling company.
  • The most commonly recycled plastics are those under Code 1, 2 and 4.
  • I gleaned the following information from the Veolia website. Veolia is a large recycling company in Singapore. Notice that they do not take products made of stytofoam. This is likely due to the fact that styrofoam tends to break into very small parts, making them hard to separate from the rest of the recyclables. Also, styrofoam can leak potentially toxic chemicals when heated.


What can and cannot be recycled by Veolia. (Source: Veolia company site)
  • On a final note, something that is of concern for everyone who uses plastics – how safe are they? Generally, 1, 2, 4 and 5 are ok, as in they are no known to leach harmful chemicals. Plastics to be avoided for food and drinks or anything related to human and animal consumption are 3, 6 and 7. You might want to reconsider the use of styrofoam as food and drink containers.



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