nuking by numbers

My husband was startled recently as he caught me in the kitchen holding a plastic container of leftover Tom Khar Gung soup over my head while I squinted up at the bottom of it. He inquired as to what in the world I was doing. My usual state of being environmentally freaked out rendered my behavior perfectly reasonable however... I was trying to determine the level of nastiness of the plastic container-- based on which number was at the center of the little triple arrow recycle symbol-- and whether I would need to add the annoying step of transferring the soup to a safer container before nuking it. My willingness to eat soup nuked in a plastic container of an acceptibly low level of nastiness was probably influenced by a dislike for obstacles between me and hot, coconuty, spicy goodness of Tom Khar Gung soup.
The number was 5. Awesome. Nuking as is.
Had the number been 3, 6, or 7, however, I would've huffed through the precious fraction of a minute it would've taken to transfer the soup to a ceramic or glass bowl for safer nuking. Plastics labeled 3, 6, or 7 are more toxic than plastics labeled 1, 2, 4, or 5. At least I wouldn't have lost any time digging out the cling wrap though, which I know to be at especially high risk for leaching chemicals during microwave heating; instead I use a plastic vented dome that fits over almost any dish and never touches the food (and can be found where kitchen supplies are sold). Waxed paper, a paper towel or a plate can also be safely used for covering foods.
Anyway long story short... 1, 2, 4, or 5 = good; 3, 6, or 7 = bad.

The long story's long version is illustrated in this guide to the different recycling number labels, which may or may not appear with the letters beneath them (from The Daily Green, WebMD, and Health Observatory):

(Polyethylene terephthalate ethylene) Found in soft drink, water and beer bottles, salad dressing containers, and ovenable food trays. It poses low risk of leaching breakdown products and is safe for single use, but these bottles should not be reused, refilled, or heated.

(High density polyethylene) Found in milk jugs, juice bottles, some trash and shopping bags, butter and yogurt tubs, and cereal box liners. It carries low risk of leaching and is readily recyclable into many goods. Unlike plastics labeled "1", these are safe to refill and reuse.

(Polyvinyl chloride) Found in clear food packaging, cling wrap, and plastic squeeze bottles. PVC may release toxic breakdown products (including pthalates) into food and drinks. The risk is highest when containers start wearing out, are put through the dishwasher or when they are heated (including microwaved). PVC materials can off-gas toxic plasticizers into your home. Also never burn PVC because it releases toxins.


(Low density polyethylene) Found in grocery store bags, most plastic wraps, Ziplock bags, squeezable bottles, bread bags, frozen foodbags, shopping bags, furniture, and carpet. Generally considered safe.

(Polypropylene) Found in most Rubbermaid, deli soup, syrup and yogurt containers, other clouded plastic containers, ketchup bottles, caps, medicine bottles and straws. It has a high melting point so is often chosen for containers that must accept hot liquid. Generally considered safe.



(Polystyrene) Found in styrofoam items such as food trays, egg cartons, disposable cups, plates, and bowls, and carry-out containers, and rigid plastics like opaque plastic cutlery. Number 6 plastics can leach potentially toxic breakdown products (including styrene) into foods, particularly when heated.

A wide range of plastic resins that don't fit into the other six categories are lumped into number 7. Some are quite safe, but the ones to worry about are the hard polycarbonate varieties, as found in various drinking containers (like older Nalgene bottles), three- and five-gallon water bottles, and nylon. Studies have shown polycarbonate can leach bisphenol A, a potential hormone disruptor, into liquids, but other #7 plastics like copolyester, polyamide, acrylic and polylactic acid (PLA) are safer choices because they don’t contain BPA.


That's a lot of information to remember when squinting up at the bottom of a food container, so, again, long story short... 1, 2, 4, or 5 = good; 3, 6, or 7 = bad. Note that “microwave safe” doesn't mean that there's no leaching of chemicals, and there's greater leaching of chemicals into fatty foods. Discard worn or scratched bottles and avoid using harsh detergents that can break down the plastic and increase chemical leaching.
(The soup was delicious.)