The biggest concern is that these products contain potentially carcinogenic chemicals and endocrine disrupters that may leach into food and drink. Consumer-advocacy groups have scrutinized three plastics, in particular: polystyrene (basically Styrofoam); polyvinyl chloride, used to make PVC-based cling wrap; and polycarbonate plastic (think hard-plastic water bottles, kids' sippy cups, and even baby bottles). The FDA reports that all of these plastics are safe. But consumer-advocacy organizations -- such as the Institute for Agriculture and Trade Policy and the Environmental Working Group -- suggest otherwise.
For recycling purposes, plastics are assigned a number, which is marked on the bottom of containers. Avoid polystyrene (#6), polyvinyl chloride (#3), and polycarbonate (#7) plastics for storing food, as these are most likely to leach chemicals. Store and microwave food in glass or ceramic dishes. Use old-fashioned parchment paper to pack sandwiches. Babies and young children are at greater risk for health problems associated with the chemicals in plastics. Avoid bottles and sippy cups made of polycarbonate. These contain bisphenol A (BPA), an endocrine disrupter.
Don't buy water in plastic bottles; not only is this habit wasteful, but there's no evidence that bottled water is any safer overall than tap water. Single-use water bottles can also be havens for bacteria if you refill and reuse them. Many reusable plastic water bottles are made of polycarbonate, so to reduce possible leaching, do not fill them with warm or hot liquids, and recycle old or scratched bottles. Your safest bet is probably a refillable metal water bottle.
Avoid any type of plastic in your kitchen whenever possible. Food packaged in plastic should be rewrapped in parchment or stored in glass or ceramic containers.