This book raises important issues about cosmetic safety but is a frustrating read in that it fails to provide sufficiently detailed information on these issues.
Take the sections on coal tar colours. On page 25 we read "almost all these colours have been shown to cause cancer". Strong stuff, but what exactly does it mean? Does it mean that these colours have been shown to cause cancer in humans through the normal use of cosmetics - or that these colours have been shown to cause cancer in laboratory animals? We have to wait another 200 pages for the author to clarify - on p219 she states "studies have shown all coal tar colours to cause cancer in animals". However this doesn't clarify things completely. For a start we've moved from "almost all" colours causing cancer on p25 to "all" doing so on p219 and we are not told what was done to the lab animals. Were coal tar colours rubbed on their skin or were they injected with the colours? Perhaps the matter could be clarified by checking the author's references?
Given the strength of the author's claims about coal tar colours, I would have expected her to back them up with a stack of references to the primary literature - but the only reference is to Ruth Winter's book, "A Consumer's Dictionary of Cosmetic Ingredients". How reliable is this book? Is it based on a thorough study of the primary literature? Any reader interested in following up the primary literature is left in the unsatisfactory position of having to hunt down Winter's book to see if this contains the relevant references.
In the next paragraph on p25 we are told that the World Health Organization (WHO) considers coal tar colours to be "probable carcinogens". Why, if earlier up the page we are told that "almost all these colours have been shown to cause cancer", does the WHO consider them only to be "probable" causes of cancer? Does the author mean that on the basis of animal studies, the WHO considers coal tar dyes to be probable causes of cancer in humans? If so, is it just the coal tar dyes ingested in food that are probable causes of cancer? Or is it also coal tar dyes used in cosmetics? If so, what is the evidence cited by the WHO that coal tar dyes can be absorbed through the skin? It would be very helpful if the author had clarified this issue and had referenced the relevant WHO documents. Instead the only reference is again to Winter's book.
On p16, the author does address the question of chemical absorption through the skin, but only in general terms. She quotes Ruth Winter (!) who says "it is now generally accepted that all chemicals penetrate the skin to some extent and many do in significant amounts". However, no specific evidence is presented about the coal tar dyes.
But such information is easily available in the public domain. Frustrated with the limited information in this book I had a look at the FDA website and found an article on hair dyes which states
"Several coal-tar hair dye ingredients have been found to cause cancer in laboratory animals. In the case of 4-methoxy-m-phenylenediamine (4-MMPD, 2,4-diaminoanisole) which had also been demonstrated in human and animal studies to penetrate the skin, the agency considered the risk associated with its use in hair dyes a "material fact" which should be made known to consumers."
However, in another FDA article it is pointed out that whilst 4-MMPD has caused cancer when fed to laboratory animals in large doses, it has not caused cancer when rubbed onto their skin. It states
"In other studies, when investigators painted 4MMPD on the skin of rodents, there was no evidence that the compounds caused cancer in the animals. But critics claim that not enough of the chemical penetrates the skin from the small areas on which it's applied to accurately assess the compound's ability to prompt cancers in a limited number of animals."
It is shame that the author did not include such easily available information as it would have helped clarify the issue.
On p25 the author describes how in 1960 the FDA put coal tar colours on a provisional list allowing their continued use pending the FDA's conclusions on their safety. The author claims (again referencing Winter) that "only a handful of colours have been tested for safety, and the bulk of colours remain on the list 30 years later". (Given the book was published in 2002, shouldn't this be 40 years later!) This claim led me, again, to the FDA's website where I read
"From the original 1960 catalog of about 200 provisionally listed colours, which included straight colors and lakes, only lakes of some colours remain on the provisional list. Industry withdrew or the FDA banned many, whilst the rest became permanently listed and are still used".
Now I've no idea where the truth lies but I would have thought it is incumbent on the author to explain the seeming anomaly between her claim and the position of the FDA, especially when the FDA's position so easy to establish.
One more example of the frustration this book causes. On p19 the author states that "plastic bottles...may contain dioxins that can leach into the shampoos, body washes and skin creams we use every day". Given that the author describes dioxins as "the most potent carcinogen ever studied" this claim about plastic bottles is a very serious one. However no references whatsoever are given in support. Does her claim apply to all plastics? Should we avoid any cosmetics in plastic containers? We are not told.
Don't get me wrong, I'm as worried as the author about the (potentially) harmful effects of cosmetic chemicals. It's just that her case would have been strengthened if she had made her arguments clearer, provided more information and demonstrated a familiarity with the primary literature.