today’s topic is one that has sparked craaaaazy hysteria in the general public and is basically the idea that cosmetics containing parabens are going to give you cancer. let’s take a look at this “claim” and see if it’s actually a genuine concern or a result of irresponsible science reporting/scientific journalism gone wrong!
what are parabens? structurally, they look like this:
chemical structures of commonly used parabens
their current use is mainly as a preservative in cosmetics, certain foods, and pharmaceutical drugs. why do we need to use preservatives? because many of the product we use day-to-day are made up of tons of organic (carbon-based, not the other meaning) molecules and these molecules decompose of time, faster if exposed to heat and/or light. preservative like parabens help inhibit microbial and fungal growth in these products, making for longer shelf-lives. parabens are types of molecules called esters, known to be hydrolyzed by esterases (enzymes) in human bodies to para-hydroxybenzoic acid which is excreted out of the body, and also metabolized via different pathways and then excreted out of the body like through urine. let’s first take a look at the supposed paper that started to whole paraben-free craze: Darbre, P. D. et al. J. Appl. Toxicol. 2004, 24, 5-13.
in this paper, the data collected shows that in 20 human breast tumor samples, a mean of 20.6 ± 4.2 ng of parabens per gram of tissue sample was obtained. no comparison was made for non-cancerous breast tissue, which would be the scientifically responsible thing to do if you’re going to publish something like this, instead of pushing it off to “future outlooks”. they make claims like:
“It is therefore not inconceivable that the levels of parabens measured in this study could exert oestrogenic effects on epithelial cells in the human breast.”
let’s look at this statement. according to routledge and coworkers (Toxicol. Appl. Pharmacol. 1998, 153, 12-19), their finding showed that parabens were approximately 2,500,000 to 10,000 times (from methylparaben to butylparaben) less potent in producing an in vitro estrogenic response compared to 17-β-estradiol (subcutaneous administration of the paraben). this means that the amount of paraben per volume needs to be 2,500,000 time more in the case of methylparaben, 150,000 times more in the case of ethylparaben, 30,000 times more in the case of propylparaben, and 10,000 times more in the case of butylparaben to have the same estrogenic response as one equivalent amount of 17-β-estradiol per volume. so assuming that most of the parabens collected was methyparaben (they report over 60% to be), that mean you take 20.6 ng and (roughly) divide by 2,500,000 to get the amount of 17-β-estradiol that would was an estrogenic response. that’s a crazy small number yo! can you even measure an estrogenic response with a dose of 8.24 x 10^-15 g; if not, how can you claim that it’s “not inconceivable that the levels of parabens measure in this study could exert oestrogenic effects…”?
moreover, the journal that the Dabre data was published in is a journal with an impact factor (i.f.) of 2.478 compared to science (i.f. of 31.201 for 2011) or nature (i.f. of 36.280 for 2011)…if this research was so cutting edge and important (which it would be if the experiments were thoroughly done and data interpreted correctly), wouldn’t it have received critical acclaim from the scientific community and gone through the peer-review process in a high impact journal? instead the Dabre paper received at least 3 different scathing responses from the scientific community raising questions about the thoroughness of the experiments and interpretation. then some journalist who hadn’t really thought out the scientific interpretations decided to write an article disseminating the “dangers” of parabens and now we’re here…living in fear of parabens.
now the fda and the european medicines agency have both spoken on parabens. the fda states that through the cosmetics ingredients review, the acceptable safe concentration of parabens in cosmetics is set as 25%. currently, most cosmetics contain levels of parabens ranging from 0.01 to 0.3%. what does that really mean though? in a scientific review paper by golden and coworkers (Crit. Rev. Toxicol. 2005, 35, 435-458 [impact factor of 5.160]), they write that the estimated amount of parabens that an average woman (60 kg) comes into contact with/uses is 0.307–1.02 mg/kg/day through “bath products, colognes and toilet waters, powders, hairsprays, shampoos, tonics and other hair grooming aids, blushers, foundations, lipstick, makeup bases, bath soaps and detergents, deodorants, skin cleansers, depilatories, face preparations, body moisturizers, skin fresheners, and sun products”. assuming that 40% (number taken from another paper) of the “worst paraben (butylparaben)” is absorbed through the skin, that her enzymes are faulty and cannot process parabens to the excretable para-hydroxybenzoic acid before absorption, and that the woman uses all her products every day, the dose of paraben per day would be 0.12–0.41 mg/kg/day. compare this value to ones reported in another scientific study of parabens on rodents and adjusted for humans: the value would be 440 times less, according to cook et. al., than the value needed produce effects in humans similar to estrogen in rodents or 240-830 times less for adverse effects in offspring in utero (Toxicol. Sci. 1998, 44, 155-168). the review (Crit. Rev. Toxicol. 2005, 35, 435-458) concludes that:
“Based on highly conservative assumptions (i.e., worst case) pertaining to total daily exposures to parabens and dose/potency comparisons with both human and animal NOELs and LOELs for estrogen, it is biologically implausible that parabens could increase the risk of any estrogen-mediated endpoints, including effects on the male reproductive tract or breast cancer. While not explicitly considered in these comparisons, an additional margin of safety is provided by the fact that potency differences between parabens and estrogen are even greater due to the inability of parabens to produce estrogen like effects comparable to estrogen, no matter what dose is employed[…]Based on the estrogenic potency differences between parabens and estrogens, there is no scientific basis for concluding that in utero exposure to parabens might cause adverse effects on a developing fetus. Similarly, given the large differences in potency between estrogen and the three parabens that have weakly estrogenic activity in vivo, there is no basis for hypothesizing that parabens play any role in the etiology of breast cancer. The implication of the Darbre et al. (2004) study that parabens might be causally associated with breast tumors is biologically implausible. It has now been established that studies with other weakly estrogen-active chemicals that may bioaccumulate in breast tissue do not provide credible evidence that they are etiologically associated with increased risk of breast cancer. Consequently, there is no scientific basis for hypothesizing or inferring that parabens are etiologically linked to the development of breast cancer[…]While there is no question that in utero or adult exposure to sufficient doses of estrogen can cause a number of adverse effects in humans, the presumption that exposure to chemicals that are many orders of magnitude less potent than estrogen will cause similar effects has never been demonstrated.”
so there you have it! you can now use your beauty products (even ones with parabens) at ease…enjoy~