Nothing it is totally impossible, but the chances of a harmful ingredient getting into a cosmetic and affecting the health of the people who use it is really really unlikely. Even if the people who formulated them were both stupid and irresponsible, they would kill themselves first. If not, the people making the stuff in the factory would be the ones most at risk and when they started showing symptoms the problem would come to light.
But there is always a chance that a cosmetic ingredient might be harmful to the environment, and it is much harder to safeguard against this risk. A good example is the possible environmental risk of cyclic silicones known as D4 and D5.
These definitely pose no risk to people using them in products. But they have a two properties which make them potentially troublesome to the environment and particularly to water courses. They are very stable, and they are soluble in fat. This means that if they get into a food chain they can accumulate. A small dose in an aquatic insect is harmless. It might well do no damage to the fish that eats a lot of the insects. But by the time a bird of prey has eaten enough of the fish it might well be at a level where it can be harmful.
In fact the propensity to accumulate is really the problem here rather than the toxicity. Most things can be toxic if you have a big enough dose, and if something can accumulate in a food chain it is quite difficult to estimate just how big a dose some animal somewhere is going to end up being exposed to. This is not just a theoretical problem. Several environmental pollutants have been linked to egg shell thinning in birds that eat fish, and although it is hard work to prove beyond doubt which chemical is to blame there is good evidence that DDE used to do so before it was banned, and less good evidence that PCBs did the same.
It has always been my opinion that you need to be very careful with anything that might behave in this way. As I say, it is not always easy to be sure of exactly what is going on in the environment. Finding a dead eagle that happens to have a high level of a particular chemical in it doesn’t necessarily mean that it was that chemical that killed it. And the harm doesn’t necessarily have to manifest itself in obvious symptoms like dying. Changing the behaviour of a wild animal slightly can kill it just as effectively as outright poisoning. And once a chemical is in the environment there is no easy way of getting it out again if it is chemically stable.
So when concerns are raised about D4 and D5 I think we need to be prepared to take action even if the case against these materials has yet to be made fully. Environmental impacts are considered by the European Chemicals Agency, who in 2012 concluded that D4 was a persistent bioaccumulative toxic chemical, even though there was no conclusive evidence to support it. They didn’t put D5 into the same class, but did note that the similarity of the two chemicals meant that D5 might pose the same risk.
It takes quite a while for the wheels to grind on this kind of issue. Concerns have been voiced about these materials for some time. When the SCCS, the scientific committee that advises the EU on cosmetic safety, examined them in 2010 it was able to conclude that they were safe for consumers but did note that the environmental safety was questionable. To my mind the state of play in 2012 was already enough to trigger off regulatory action. But the European Chemicals Agency is still waiting for more data to be submitted.
In the meantime a lot of people in the cosmetic industry are quietly starting to get D4 out of formulations. It is used in hair care products mainly. Its role is to make things lubricious and shiny, so it is a great ingredient. The name that gets used on the ingredient list is cyclomethicone – but that also covers D5 and several other silicones. There is no way of knowing from the ingredient list whether your product poses a risk to the environment. So there is no scope for consumer pressure here.
I am not convinced that the D4 bad D5 okay is the right approach personally. I think it would be better to legislate to get rid of them both. The risk is to birds like eagles and pelicans. I think that they are rather more precious than a shiny hair do, and I don’t want to take the chance.