Plastics are made of chemicals and when food is stored in them they tend to release these chemicals especially heavy metals like mercury etc. This is due to the heat and / or the chemicals of the food that come into contact with the plastic and react. That is why there are plastic containers which are specifically made for storing food and are categorised as 'food contact standard containers'. Most plastic carry bags don't come in this category (they are made by recycling old carry bags plastic chappals and any other plastic that is collected by the rag pickers.
Therefore, before storing food in a plastic container, see that the container is of food standards plastic.

It may be that no plastics are safe. We just don't have enough information about what's in them to know for sure. And manufacturers dont readily give out this proprietary information. We do know this: Most plastics can leach chemicals if subjected to heat, light, or rough treatment.

Unfortunately, there is no definitive answer to this question.

It may be possible that no plastics are safe. The problem is that we just don't have enough information about what's in them to know for sure. The recycling number tells us the type of plastic but not what other chemicals might have been added to affect its strength, color, texture, or even resistance to bacteria. And manufacturers dont readily give out this proprietary information.

We do know this: Most plastics can leach chemicals if subjected to heat, light, or rough treatment, so its unwise to put plastic in the microwave or dishwasher or to store hot foods in it. In my home, I try to stick to stainless steel and glass containers an ...more

To find out, reporter Michael Slater pays a visit to the Sydney labs of the CSIRO to meet packaging expert Dr Bob Steele.
Plastic is made from oil, coal and gas things we certainly wouldn't want to eat. Some plastics contain dangerous chemicals, so this, plus rumours of cancer, have made us a tad nervous about putting it near our food, especially when cooking.
Michael: So is there any threat to the public using plastic, particularly if you're heating food in the microwave?
Dr Steele: Not really. All the plastics we see and are used commonly with food contact have been thoroughly tested over many years for their food contact suitability and their safety.
Sounds good, but there's a catch. You see, you just can't put any old plastic pot in the microwave. Use the wrong plastic and your food could get contaminated.

Depends on nature of plastic.

If food grade

Leaving the safety apart, packaged foodstuff is not healthy...!