Take time to locate this symbol on plastic containers. The SPI resin identification code assigns each of these resins a number from 1 to 6.What does the number mean? The plastics industry has determined the number should be in an inconspicuous location, so buying decisions are not influenced. For those concerned about their health and the planets health it is a number worth seeking out when making purchases.

The overwhelming majority of plastic packaging is made with one of six resins:

1. polyethylene terephthalate (PETE): This plastic is the easiest to recycle. Used for soda bottles, water and medicines. It can be recycled into fibers used in polyester products.
2. high density polyethylene (HDPE): Prevalent in water bottles, those ubiquitous plastic storage containers, plastic shopping bags and many other rigid plastic containers. Over 60 million tons are used world-wide. It can be recycled, but is not bio-degradable.
3. polyvinyl chloride (PVC or vinyl): A lucrative plastic, pvc is widely used in the construction trade. PVC finds many routes to enter our lives, with the addition of plasticizers to soften the material it is used in shower curtains and baby bottles. The material has been determined to be hazardous as it leeches out toxic by products which affect the air quality. The chemical by products are potentially hazardous.
4. low density polyethylene (LDPE): This is tough product, virtually unbreakable. One of its applications is the plastic that surrounds and holds six packs in place…and has wrapped itself around wildlife and fish, killing them. Used for toys and for durable rigid plastic containers. Can be recycled.
5. polypropylene (PP): This plastic has a wide range of applications, from money to ink pens, fiber, rope, carpet. PP is also used to make clear films and roofing materials. It can be recycled.
6. polystyrene (PS): Used to plastics and resin products, foam and packaging materials. Avoid this substance. It is often found in restaurant take out containers. It does not break down.
7. Other, mainly polycarbonate or mixtures of the other plastics: Used in sunglasses, plastic drinking bottles, this resin has been studied extensively and leeches toxins, notably bisphenol A. Not favored by recycling companies.

For information of safe baby bottles, this green guide can help. And this green guide rates common household plastics.