water sources

Reusable bottles: plastic, glass, or metal?

After the closure of fountains and other water sources due to the coronavirus, water bottles have become essential, but which one is the most recommended?

One of the “secondary effects” of the pandemic has been the closure of fountains and other water sources, for example, in some public spaces or in educational centers. There are many children who already last year went to school with their own bottles or the adults who also took them to work. However, today, due to the coronavirus, carrying reusable bottles is no longer optional, but is sometimes essential. If last week we talked about the return of the fanny pack, in this case, the one that returns is a renewed version of the canteen. The question is: which one do I choose?

The classic flexible plastic bottles that we buy in supermarkets or vending machines were not designed to be reused. But, despite the urban legends, this does not mean that because we reuse them a couple of times we are going to die intoxicated. They currently do not contain BPA, the famous bisphenol that could act as an endocrine disruptor if its intake exceeds certain doses. Bisphenol can migrate from packaging to food, especially if it is subjected to high temperatures. Instead, PET (polyethylene terephthalate) is used.

The problem is that this type of plastic is not very resistant and can easily deteriorate with use. In the cracks that form in the plastic, along with moisture and possible heat, bacteria and fungi find their home and can “breed.” Let’s not forget that our own oral bacteria enter and leave there like Pedro at home.

The type of plastic with which the container is made is usually identified through the recycling code (this symbol in the shape of a triangle with arrows). The “BPA Free” bottles have the recycling codes 1, 2, 4, and 5. The 1 is the aforementioned PET, polyethylene terephthalate.

In addition to the possible risk of bacteriological contamination when reusing these bottles, we must not lose sight of the sustainability problem posed by the massive use of this type of disposable plastics. Although we reuse the bottle several times, it takes relatively little time to “get ugly” and we end up replacing it with another with the environmental impact it entails.

Especially for children, due to their resistance to shocks and lightweight, plastic bottles are usually chosen (to be understood, similar to those carried by cyclists). This type of plastic is still not my favorite material, because, despite being stronger than flexible disposable bottles, when we wash them in the dishwasher or subject them to high temperatures it can also degrade. If the bottles contain a hot liquid (coffee, herbal teas, etc.), the plastic degrades even faster.

In the event that we are looking for a bottle to contain only cold water or at room temperature, the ideal would be to look for a BPA-free plastic. A good choice would be a degradation resistant polymer such as high-density polyethylene (HDPE, number 2). Notice to sailors! If we choose a bottle of this type, please buy it in establishments that offer us guarantees. It is not advisable to buy them in bazaars, or in markets, of dubious quality. Also, watch out for the “pitorritos”: if they are difficult to remove and the child is going to end up using his -dirty- hands, they may not be the best option either.

My favorite material, if you didn’t have a bad habit of breaking just looking at it, would be glass. Glass is an inert substance that does not produce transmission of compounds to liquids, neither when cooling nor heating the container. Another important advantage is that it does not retain flavor either (a common complaint from users of plastic or metal bottles). To solve the problem of breakage, glass bottles in silicone or neoprene sleeves are currently on the market.

Most metal bottles are made of stainless steel or aluminum and are also safe materials with respect to the migration of toxic substances. It is true that there could be a slight transfer from the metal to the liquid, but there is probably no greater risk than when we use stainless steel or aluminum cookware, which is considered safe. What is the main drawback of metal? That, as we mentioned, transfers a metallic flavor to the water.

According to Ana Romero, a specialist in Materials Science at the University of Castilla-La Mancha in Toledo, the “ideal” metal would be a biometal. But taking into account the prices of titanium, gold, silver, or platinum, it may be appropriate to look for a less ambitious solution. A good choice could be 316 L stainless steel, which is austenitic stainless steel (organic, resistant to oxidation, and corrosion). We can find bottles with this material easily by doing a search in the browser.

Aluminum has a clear disadvantage compared to stainless steel, which is that it is less resistant. It would deform when accumulating backpacks, when falling to the ground or even if we sat on it (which can happen).

There are many valid options, but to focus the shot on two, I would recommend a glass bottle with a silicone/neoprene sleeve to an adult. And for children, metal bottles, since they are light and more resistant than glass. The cabbages are not there to increase the risk of accidents.

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