What do the numbers mean on the bottom of the plastic
container?
As of 1.1.2016
If you must use plastics here is a breakdown


#1 PETE or PET (NOT SAFE due to antimony leaching)
Polyethylene terephthalate

#
2 HDPE (SAFE)
High density polyethylene

#3 PVC or V
(NOT SAFE due to phthalates)
Polyvinyl chloride

#
4 LDPE (SAFE)
Low density polyethylene

#5 PP (SAFE)
Polypropylene

#6 PS
(NOT SAFE for hot liquids, alcohol or fatty foods due to styrene)
Polystyrene

#7 plastics including polycarbonates that contain bisphenol A (BPA)
(NOT
SAFE due to BPA)
Polycarbonate
My personal thoughts are to stay away from plastics all together when it comes to
cooking and storing food items. Glass and stainless steel is still the best choice.

You should
NEVER heat in any kind of plastic even if the manufacturer says it is
microwave safe!

Below is a breakdown of what the government has to say about plastics.
Are plastics safe?