Here is a quick guide to the plastic numbers and their safety rulings. The number will appear inside a triangle usually at the bottom of a plastic product.
#1 PETE or PET used for most clear beverage bottles
#2 HDPE used for most cloudy bottles eg. milk bottles
#3 PVC or V used in some cling wraps, soft bottles and vinyl/ PVC. Avoid plastics with #3 as they contain toxic breakdown products #4 LDPE (low density polyethylene) used in food storage bags and some soft bottles
#5 PP (polypropylene) used in rigid containers, some baby bottles, some cups and bowls.
#6 Polystyrene Avoid as it is considered a xenoestrogen and a possible carcinogen by the World Health Organisation
#7 Usually polycarbonate Avoid as it releases BPA into the contents of the container
There is one study that has found #5 to have leached chemicals that disrupt hormone activity but it is widely accepted to be safe. I would try to avoid plastics as much as possible. Use them in moderation. Never heat food in plastic. Always transfer your food to a glass plate or bowl when heating. Never cover with cling wrap to heat. Use a paper towel. Avoid ice blocks and invest in some glass lidded bowls. Dont put plastic in the dishwasher and a good rule of thumb is that if it has an odour or smell, there is something leaching from it.