Sometimes we see these codes on water bottles or coffee lids, but what do they mean like for recycle or reuse or something? It turns out they are trying to tell you what kind of plastic it is. Here is a list to look up.
Polyethylene terephthalate (PET or PETE)
GOOD: Not known to leach any chemicals that are suspected of causing cancer or disrupting hormones.
High density polyethylene (HDPE)
GOOD: Not known to leach any chemicals that are suspected of causing cancer or disrupting hormones.
Polyvinyl chloride (V or PVC)
BAD: To soften into its flexible form, manufacturers add “plasticizers” during production. Traces of these chemicals can leach out of PVC when in contact with foods. According to the National Institutes of Health, di-2-ethylhexyl phthalate (DEHP), commonly found in PVC, is a suspected human carcinogen.
Low-density polyethylene (LDPE)
OK: Not known to leach any chemicals that are suspected of causing cancer or disrupting hormones, but not as widely recycled as #1 or #2.
Polypropylene (PP)
OK: Hazardous during production, but not known to leach any chemicals that are suspected of causing cancer or disrupting hormones. Not as widely recycled as #1 and #2.
Polystyrene (PS)
BAD: Benzene (material used in production) is a known human carcinogen. Butadiene and styrene (the basic building block of the plastic) are suspected carcinogens. Energy intensive and poor recycling.
Other (usually polycarbonate)
BAD: Made with biphenyl-A, a chemical invented in the 1930s in search for synthetic estrogens. A hormone disruptor. Simulates the action of estrogen when tested in human breast cancer studies. Can leach into food as product ages.
Ref: http://en.wikipedia.org/wiki/Plastic_recycling, http://www.care2.com/greenliving/which-plastics-are-safe.html