The first point is that breast cancer is on the increase in recent decades. This review basically sets out to propose chemicals in cosmetics as an explanation for why breast cancer rates are increasing.
There are a number of possible explanations which aren’t discussed. It could for instance simply be that as we now live longer, we have more time in which to develop breast cancer. It could be improved rates of diagnosis, or even that the introduction of screening has just increased awareness of breast cancer so that it is more easily recognised.
But the fact that there might be an alternative explanation isn’t proof that a particular explanation is not true. Looking at the reference Dr Darbre cites, the rise is about 40% over the years from 1979 to 1992. This is a big rise to explain and even if cosmetic chemicals are only making a small contribution to this rise, that still equates to a lot of suffering.
On the other hand,a great many things have changed over that time period which might prove to be factors. Also looking at the detail it looks like the increase is concentrated in older women – suggestive that whatever the cause it might well be quite long term. Increased consumption of alcohol, rising obesity and a more sedentary lifestyle all sound like much stronger candidates than parabens to explain the rise.
Looking at more recent data from the cancer research website, breast cancer rates are continuing to rise, though not dramatically. This is consistent with more money being spent on personal care products over that period, but it is consistent with lots of other things as well. As cancer rates overall are going down, the reason why breast cancer rates are going up is both puzzling and something that really does need to be explained.
Could the use of parabens be that explanation. It doesn’t seem likely, but it can’t be dismissed out of hand. Something clearly is causing breast cancer rates to increase, and we don’t know what it it is. The current rate has now reached 120 per 100,000 of the population in Europe, so that represents are pretty major public health issue that really does need to be taken seriously.
Evidence that endocrine disruption can cause cancer
So how well do we understand the causes of breast cancer? A quick digression about hormones. Oestrogen is the hormone that controls a great many aspects of reproductive behaviour. It is not difficult to imagine that disrupting it might cause problems. But there is no need to leave it to the imagination – the link between oestrogen and breast cancer is supported by extensive evidence. Hormone replacement therapy – which is basically a deliberate increase in oestrogen has been shown to cause an increase in the onset of breast cancer. It is even being considered whether there might be some kind of oestrogen reduction treatment that might work as a way of preventing breast cancer.
A point that has to be remembered about hormones is that they are simply chemical messengers the body uses. They trigger off processes rather than directly taking part in them. So it is easy to imagine that very small concentrations, or small changes in concentration, could have a very large effect.
Knowing this, it is clear that synthetic chemicals that mimic oestrogen or alter the way it works, could potentially have very serious health effects. It is a very specific risk with a well understood mode of action. In principle, a chemical that is absorbed through the skin that is similar enough to oestrogen to fool the body that it is the real thing could have profound effects on the body’s processes.
This is a worrying theory for a couple of reasons. First off, hormonal effects are not necessarily going to be quick to come about. So the chain of cause and effect may not be at all easy to spot. Also the quantities involved don’t have to be very great. A straight forward toxic effect like that of arsenic can be studied in animals and calculations can be made about how the same effect would manifest itself in humans. Hormonal imbalances simply aren’t that easy to study or predict.