When I first started working in a cosmetic science lab there was a big brown bottle of triethanolamine on the end of the bench. We used it a lot. It is used as a neutralising agent to adjust the pH of formulations which you need to do a lot.
Nearly every chemical you handle when you make cosmetics is intended ultimately to go on the skin so most of them are fairly easy to handle. Triethanolamine is one of the few exceptions. If the neat stuff touches you it doesn’t take long to irritate it. This is mainly because pure triethanolamine has a very high pH. This is made much worse by the fact that it is a thick oily liquid that stays put when it gets there. (Viscosity isn’t usually considered relevant to safety by people who concerns themselves with these things, but it is in real life.)
It isn’t a problem when included in a formulation of course, because it is added specifically to bring the pH back into balance. In fact as a neutralising agent it is one of the milder ones.
It seemed like a very straight forward and uncontroversial material. And so it was until some time in I think the early nineties when there was a television programme in Germany. A green group called Oekotest had measured the levels of nitrosamines in Timotei shampoo and presented the results. Nitrosamines, or at least some of them, are known to be carcinogenic. Timotei’s sales plummeted.
In fact it turned out that there was nothing particularly unusual about Timotei. It had a few parts per billion of nitrosamines which newly developed highly sensitive chemical assay methods were able to detect. But so did many other shampoos. And many other cosmetics. And in fact, many other things altogether. Nitrosamines could be detected in rooms where a smoker had been. Electrical arcs from loose connections in poorly wired plugs would produce measurable nitrosamines from the nitrogen in the atmosphere nearby.
But the really rich seam of nitrosamine was found in food. A survey in Germany showed that the average German male was eating about a microgram of nitrosamines a day. Teutonic favourites cured meat and beer were particularly rich sources. It made the traces found in shampoo seem a bit tame. But the damage was done and the process of getting nitrosamines out of cosmetic products started. And lets face it, turning down a beer or a sausage is hard. Passing legislation about cosmetics is easy. So that was what was done.
It wasn’t too obvious at first where the nitrosamines came from. They weren’t being added as an ingredient, so they had to be being produced in the products themselves. Almost any source of nitrogen can give rise to nitrosamines if the conditions are right. Even the nitrogen that makes up 80% of the air we breathe can be transformed into them. Soon it had been surmised that the nitrosamines were coming from a small number of nitrogen containing ingredients which belonged to the family known as secondary amines. Triethanolamine isn’t one of them – it is a tertiary amine. But it does often contain diethanolamine as an impurity, and diethanolamine is a secondary amine.
In fact the diethanolamine was added deliberately. It lowered the melting point, and this meant it was liquid at room temperature all of the time. Pure triethanolamine melts at around 20°C, so has the inconvenient property of being liquid on a warm day and solid on a cold one. So sooner or later you are going to weigh out a neat pile of crystals and come back the next day to find they have become a puddle. That brown bottle I remember from my first cosmetic laboratory was 85% triethanolamine and 15% diethanolamine.
Nonetheless, following all the talk about nitrosamines everyone switched over to pure triethanolamine. The EU followed on with some purity and use level restrictions. The legislation has a bit of a twist to it which makes triethanolamine itself illegal if used with a couple of other materials which are fine if used on their own. This has led to a tendency to switch away from using it altogether. Other raw materials that do the same job don’t have any restrictions so why burden your brain with an extra factor. It is true enough that you can avoid it easily enough when you are formulating, though as the risk it poses is to all intents and purposes non-existent it seems a bit of waste of everybody’s time.
I imagine that in the long run triethanolamine will gradually disappear from cosmetics but for now it still appears on a great many ingredient lists including new ones. I can see no reason whatever to avoid it as a consumer and I use plenty of products that contain it myself.
If you like raw material posts, here are a couple more.