Two years or so ago most of us had given relatively little thought to single-use plastics. We bought things, we used things, we put the packaging in the bin. Possibly the recycling bin. Hopefully the right recycling bin. And we thought no more about it.

Then Blue Planet II aired on BBC One, specifically episode 7, and suddenly everyone was obsessed with where all this plastic was ending up. Rightly so, since it was clearly ending up in the wrong places, and causing all sorts of havoc in the process.

People started buying reusable cups, eschewing plastic straws and demanding the option of loose fruit and vegetables in supermarkets. Wooden disposable cutlery, oven-cook food containers, and bamboo straws became increasingly common.

And people started to ask more questions about refilling containers. Why do I need a new bottle each time I buy more shampoo or washing up liquid or ketchup, they asked. Why can’t we just refill the bottle? For that matter, couldn’t I take a container to the shop and just… fill it up?

Shops started to offer exactly that. One such place was Infinity Foods, based in Brighton in the UK. Actually, they’d always taken a strong line when it came to recycling and reducing waste, and had been offering refills of some products for years.

Where this gets interesting from a chemistry point of view is a Facebook post they made at the beginning of this month. It said, from the 1st of November, “your empty bottle can only be refilled with the same contents as was originally intended. This includes different brands and fragrances.”

Naturally this spawned lots of comments, many suggesting the change was “daft” and saying things like “I bet it is major corporations not wanting us to reuse the bottle.”

Infinity Foods argued that they were tightening up their policy in order to comply with legislation, specifically the Classification, Labelling and packaging of substances and mixtures (CLP) Regulation (EC) No 1272/2008 and others.

This post, and the comments, got me thinking. I’m old enough, just, to remember the days when random glass bottles were routinely filled with random substances. You wandered into the garage (it was always the garage) and there’d be something pink, or blue, or green, or yellow in a bottle. And it might have a hand-written label, and it might not, and even if it did, the label wasn’t guaranteed to actually be representative of the contents. The “open it and sniff” method of identification was common. The really brave might take their chances with tasting. Home-brew wine might well be next to the lawnmower fuel, and if they got mixed up, well, it probably wouldn’t be fatal.

Probably.

You know, I’m not sure we ought to be keen to go back to that, even if it does save plastic. Sealed bottles with hard-to-remove child safety caps, nozzles that only dispense small amounts (making it difficult if not impossible to drink the contents, by accident or otherwise) and accurate ingredients lists are, well, they’re safe.

And we’ve all grown used to them. Which means that now, if I pick up a bottle, I expect the label to tell me what’s in it. I trust the label. If I went to someone else’s house and found a bottle of, say, something that looked like washing up liquid by the sink, I’d assume it was what the label said it was. I wouldn’t even think to check.

You might think, well, so what? You fill a bottle, you know what’s in it. It’s up to you. But what about all the other people that might come into contact with that bottle, having no idea of its origins? What if a visitor has an allergy to a particular ingredient? They look at the label, check it doesn’t contain that ingredient, and use it. Only, someone has refilled that bottle with something else, and maybe that something else does contain the thing they’re allergic to.

Even simpler, someone goes to a shop that sells refills, fills a hair conditioner bottle with fabric softener and doesn’t think to label it. They know what it is, right? They leave it in the kitchen, someone else picks up that bottle, and takes it into the shower. They get it in their eyes and… maybe it causes real harm.

Then there are the very real hazards associated with mixing chemicals. One that always worries me is the confusion between toilet cleaner and toilet bleach. Many people have no idea what the difference is. The bottles even look quite similar. But they are not the same substance. Toilet cleaner is usually a strong acid, often hydrochloric acid, while toilet bleach contains sodium hypochlorite, NaClO. Mixing the two is a very bad idea, because the chemical reaction that occurs produces chlorine gas, which is particularly hazardous in a small, enclosed space such as a bathroom.

Okay, fine, toilet bleach and cleaner, noted, check. Is anyone selling those as refills anyway? Probably not. (Seriously, though, if you finish one bottle, make sure you don’t mix them in the toilet bowl as you open the next.)

But it may not be as straightforward as that. Have you ever used a citrus-scented cleaning product? They can be quite acidic. Combine them with bleach and, yep, same problem. What if someone refilled a container that contained traces of a bleach cleaner with one that was acidic, not realising? Not only would it be harmful to them, it could also be harmful for other people around them, including employees, especially if they suffer from a respiratory condition such as asthma.

There are risks associated with the type of container, too. Some plastics aren’t suitable to hold certain substances. Infinity Foods themselves pointed out that some people were trying to find drinking water bottles and plastic milk bottles with cleaning products. These types of bottles are usually made of high-density polyethylene (HDPE). This type of plastic is a good barrier for water, but not oily substances and solvents. Cleaning products could weaken the plastic, resulting in a leak which would be messy at best, dangerous at worst. That’s before we even think about the (un)suitability of the cap.

Plus, think of the poor salesperson. How are they supposed to judge, in a shop, whether a particular bottle is safe for a particular product? I wouldn’t feel at all confident about that decision myself. It’s not even always easy to identify which plastic a bottle is made of, and that’s before you even start to consider the potential risks of mixing substances.

In fact, the more you think about it, the more Infinity Foods’ policy makes sense. If you say that you can only refill a bottle with the exact same substance it originally contained, and you insist that the labels have to match, well, that’s easy to check. It’s easy to be sure it’s safe. Yes, it might mean buying a bottle you wouldn’t have otherwise bought, but if you’re going to reuse it, at least it’s just the one bottle.

These concerns all arise from wanting to make sure the world is a safer and healthy place. We do need to cut down on single-use plastics, but taking risks with people’s health to do so surely misses the point.

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