You may have read reports of a new study from Denmark claiming a link between some substances used in everyday products, including toothpastes and sunscreens, and the health of human sperm, which you may understandably have found worrying. The authors are suggesting this is evidence of an endocrine disrupting effect - that is, our hormonal system or cells may be affected.
We would like to stress that this study does not reflect real life and the cosmetic ingredients mentioned in the study are not endocrine disruptors. There is a wealth of scientific information that supports the safety of these ingredients. Cosmetic products are subject to strict European laws that mean they are some of the most studied products on the market and go through numerous tests before they are deemed safe to go on sale.
What the study says
The authors studied human sperm under "test tube" conditions (known as in vitro testing). They looked to see if a range of substances could affect the swimming ability of the sperm. Some substances (30%) enhanced swimming ability, some reduced swimming ability.
It is important to remember that when any cell is isolated in this way and exposed to any substance it is highly likely that normal function will appear to be affected. This does not mean that in real life conditions any such effects will happen. Crucially, because the authors have only tested substances they believe are capable of endocrine disruption, we are unable to see whether the isolated sperm would be affected by a wider range of substances.
So although this laboratory-based study is interesting science, it is far removed from what actually happens in the human body and does not mean that substances used in cosmetic products will be affecting sperm levels or how sperm works.
What is an endocrine disruptor?
The World Health Organisation (WHO) defines an endocrine disruptor as follows:
An endocrine disruptor is an exogenous substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub)populations.
The key point is that an endocrine disruptor produces adverse health effects in a whole body. It is true that certain substances may mimic some of the properties of our hormones or may, under experimental conditions, show a potential to interact with parts of the endocrine system, but these conditions are not related to real life.
Confidence in safety
There is a legal obligation for manufacturers and importers to carry out a rigorous safety assessment performed by a qualified, scientific expert before placing a cosmetic product on the market. The assessment takes into account the finished product, all of the ingredients, how and where the product is to be used, how often and by whom. The assessment covers all potential risks, including possible endocrine disruption.
A common misconception is the so-called 'cocktail effect' - the idea that when different chemicals combine, their total effect is greater than might be expected. Scientists make sure they investigate whether substances will have additive effects or synergistic effects or even cancel one another out when formulating a product. These findings are taken into account when assessing the safety of a product.
No matter how emotional the issue, the science remains the same and if safety cannot be demonstrated, the substance cannot and will not be used in cosmetics - it is as simple as that.