Drinking Container Safety: Common Materials

Erin mentioned some potential hazards from drinking out of plastic containers (BPA) and aluminum, and asked me to add to the list of do's and don'ts for choosing what to drink from. During my research I gathered more information than most people can absorb in one article, so I'm going to split the metals off into a separate post and cover the other common materials today. There may be a third article for uncommon materials if I dig up even more data.

Plastics
There are more kinds of plastic on the market than I care to list. Most plastics are petroleum-based, and the few that aren't are chemically similar to the petroleum-based plastics. Some plastics are made with or treated with BPA (Bisphenol A) or phthalates, both of which are endocrine disruptors (they mimic hormones produced by your body's endocrine or ductless glands). BPA is bad news and has received a lot of press over the last few years, so avoid it as best you can.

Plastics are formed by purifying and twisting basic hydrocarbons to create selected monomers. These monomers are then chemically or physically bonded together to form polymers (hence the use of the "poly-" in most names) with interesting properties.

Plastics are usually separated by the industry-standard recycling number stamped or cast into the plastic.

#1: PET (Polyethylene Terephthalate)

• Clear and smooth, this is the plastic commonly used for single-use (disposable) soft drink bottles and peanut butter jars.  
• Avoid prolonged heat, as that may cause harmful chemicals to leach out of the PET. 
• Bacterial growth is more of a problem when reusing bottles that contained sugary drinks than any chemical hazards.

#2: HDPE (High-density Polyethylene)

• Considered "Food grade" by the FDA, this is the safest choice. 
• Milk and water jugs are normally made from HDPE, so it has a track record as a safe plastic to use with food and drink. 
• Most 5-gallon buckets are made of HDPE. 
• David's Nalgene bottle which he finally managed to break was made of HDPE.
• PEX (cross-linked Polyethylene) water pipe is made of HDPE and is rated for hot and cold water.

#3: PVC (Polyvinyl Chloride)

• The common water and sewer pipe plastic. When heated, PVC can release phthalates and other chemicals, which is why hot water piping requires the use of CPVC (Chlorinated PVC) pipe. CPVC is less likely to leach chemicals into the water inside it, so it is a safer choice.
• PVC is also used in plastic films or sheets for things like shower curtains and cheap rain gear, but making it flexible requires the use of softening agents that can be harmful. Collecting water in a PVC poncho is less of a risk than trying to store water in a can lined with the poncho.

#4: LDPE (Low-density Polyethylene)

• Typically used for films like bread wrappers, LDPE is normally a single-use plastic that is food safe. 
• Thin films may be useful as a liner for a container, but will lack the strength to be of much use for storing or transporting water by themselves.

#5: PP (Polypropylene)

• Available in a wide variety of types, PP is opaque or translucent and has a high melting point which makes it safe for microwaves and dishwashers.
• One of the safer plastics available, you'll see it used in yogurt  and food containers. (In my opinion, yogurt isn't quite food, but it wants to be.)

#6: PS (Polystyrene)

• Hard or foamed, PS is the common material found in plastic dinnerware and styrofoam cups. 
• PS can release unpolymerized styrene, which is a slow poison that accumulates in a body's fat over time.
• Handy as an insulator, but not a good choice for storing food or water.

#7: Mixed or Other

• Literally mixed plastics of unknown origin. This one is a gamble, since you have no idea of what is in the mix.
• If you see a "7" and the letters "PC" on a container, it means that it is made of Polycarbonate which is made using BPA. 
• This is the "last resort" of plastics for food or water.

Naturals
Coconut shells, dried gourds, and folded leaves are all examples of natural cups.

• If the material you've chosen comes from an edible part of a plant, it's safe to use as a cup as long as it hasn't started to rot.
• Broad, smooth leaves will be safer than narrow, fuzzy ones because the "hairs" on leaves is where many plants keep their poisons. The fuzzy leaves also collect more dust and dirt that you'll have to clean out of your water before drinking it.
• Leather can be used for short-term storage of liquids. The use of wine skins for several thousand years has proven that it's a safe choice.
• Wood is usually a safe choice as there are few poisonous types of wood in the world, but avoid cedars, birches, and gum trees if you're making cups and bowls since they're all toxic. Some of the more exotic woods of the world are also toxic, but you're less likely to find them laying around.

Glass and Ceramics

• While different materials, these are similar in structure and composition. Both are primarily made of silicon, a stable and abundant element.
• Glass and glazed ceramics are smooth on the molecular level, leaving very little space for bacteria to grow. This also makes them easy to clean. 
• Heavier than plastics and much more fragile, glass is a good option for stationary prepping (hunkering down or shelter in place) and long-term food storage like canned vegetables.
• Unglazed and partially-fired ceramics are porous and will provide ample opportunity for nasty things to grow in your food and water. They are useful for transporting, but not for storing foods and water. 
• Unglazed ceramics are a lot easier to make. Old-school crocks for making pickles and sauerkraut were often only glazed on the inside to save money in production while still being safe for food use.

Obviously,  if you have no other choices you'll use whatever you can find to hold water. This information is for when you have choices.