Plastic #1: is polyethylene terephtalate, also known as PETE or PET. Disposable drink and water bottles are made of #1 plastic it’s usually clear. This plastic is considered generally safe. However, it is known to have a porous surface so they are recommended for single use. This plastic is easily recycled.
Plastic #2: This is high density polyethylene, or HDPE. Usually opaque detergent bottles, milk jugs, juice bottles, are made of this. This plastic is considered safe and has low risk of leaching. It is also picked up by most recycling programs.
Plastic #3: is polyvinyl chloride, or PVC. It is used to make saran wrap, bottles, and pipes. PVC is a very strong plastic but it is not considered safe to cook or store food in. There are phthalates in #3 plastics (softening chemicals that interfere with hormonal development). #3 plastic is not usually accepted by recycling programs.
Plastic #4: is low density polyethylene (LDPE). It is generally used to make plastic grocery bags and food wraps. This plastic is considered safe, but sadly very difficult to recycle and most often not accepted by recycling programs.
Plastic #5: is polypropylene. Yogurt and similar wide-necked containers are made from it. You’ll also find it in medicine bottles, ketchup and syrup bottles, and straws. This plastic is generally considered safe, and is finally being accepted by many recycling programs.
Plastic #6: this is polystyrene, or Styrofoam. Many disposables are made from number #6 plastics. Evidence suggests that this type of plastic leaches potentially toxic chemicals, especially when heated. It is difficult to recycle.
Plastic #7: In a nutshell number seven is a smorgasbord of plastics that were invented after 1987. Polycarbonate is in this category, and the much dreaded BPA. Plastics used in anything from cell phones, baby bottles to toys. Use of #7 plastic is considered potentially harmful since we don’t really know what’s in it. #7 plastic is difficult to recycle.
To summarize, when possible it's better for you and the environment to avoid plastics all together and use glass.