This is the most common plastic type you will come across, used in bottles and polyester fiber. It may leach antimony or phthalates. Usually able to be recycled.
As another common plastic, you can find it in toys, kitchenware, laundry detergent bottles, and plastic trash bags. Relatively safe, HDPE is commonly recycled.
Many window frames/doors are made from this, as well as cling wrap and clear food packaging. Food in PVC packaging releases endocrine disrupters; when burned toxins are released. It is rarely recycled.
Bags, such as bread bags and tote bags, are LDPE. Some furniture and athletic wear are also products of this. As a safer plastic, there is a low risk of chemicals leaching into other items from the plastic. Some recycling programs take #4 and most grocery stores will recycle the shopping bags.
Reusable containers, furniture, some bottles, and clothing are derived from this. Some recycling centers will take this plastic, as it is mostly harmless.
Rarely recycled, PS releases toxins (styrene) into food and other objects, which increases with heat. Takeout containers and almost all kinds of disposable plates & cups are made of PS.
The recycling #7 is just a category for other plastics that don't fall under any of the six above groups. Some examples are polycarbonates and resins. Reusable water bottles & coolers and some equipments (medical and dental) are from these. These plastics are toxic and will leach into other objects. Rarely recycled.
"Plastic Purge: How to Use Less Plastic, Eat Better, Keep Toxins Out of Your Body, and Help Save the Sea Turtles!" by Michael Sanclements