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Paraben



 

Parabens are a group of chemicals widely used as preservatives in the cosmetic and pharmaceutical industries. Parabens are effective preservatives in many types of formulas. These compounds, and their salts, are used primarily for their bacteriocidal and fungicidal properties. They can be found in shampoos, commercial moisturizers, shaving gels, cleansing gels, personal lubricants, topical/parenteral pharmaceuticals and toothpaste. They are also used as food additives.

Their efficacy as preservatives, in combination with their low cost, their long history of safe use—at least to the extent that scientific studies have not proven they are harmful—and the unproven efficacy of natural ingredients like grapefruit seed extract (GSE),[1] probably explains why parabens are so commonplace. They are becoming increasingly controversial, however, and some organizations which adhere to the precautionary principle object to their everyday use.[2]

Additional recommended knowledge

Contents

Chemistry

Parabens are esters of para-hydroxybenzoic acid, from which the name is derived. Common parabens include methylparaben (E number E218), ethylparaben (E214), propylparaben (E216) and butylparaben. Less common parabens include isobutylparaben, isopropylparaben, benzylparaben and their sodium salts. The general chemical structure of a paraben is shown at top right, where R symbolizes an alkyl group such as methyl, ethyl, propyl or butyl.

Occurrence

Some parabens are found naturally in plant sources such as methylparaben from the fruit of the blueberry shrub,[3][4][5] where it acts as an antimicrobial agent.

Synthesis

All commercially used parabens are synthetically produced, although some are identical to those found in nature. They are produced by the non esterification of para-hydroxybenzoic acid with the appropriate alcohol. para-Hydroxybenzoic acid is in turn produced industrially from a modification of the Kolbe-Schmitt reaction, using potassium phenoxide and carbon dioxide.

Toxicology

Parabens are considered to be safe because of their low toxicity profile and their long history of safe use; however, a few recent controversial studies have begun to challenge this view. Studies on the acute, subchronic, and chronic effects in rodents indicate that parabens are practically non-toxic.[6][7] Parabens are rapidly absorbed, metabolized, and excreted.[6] The major metabolites of parabens are p-hydroxybenzoic acid (pHBA), p-hydroxyhippuric acid (M1), p-hydroxybenzoyl glucuronide (M3), and p-carboxyphenylsulfate (M4).[8]

Allergic reactions

In individuals with normal skin, parabens are, for the most part, non-irritating and non-sensitizing. Parabens can, however, cause skin irritation and contact dermatitis in individuals with paraben allergies, a small percentage of the general population.[9]

Breast cancer

One controversial scientific study reports that parabens were found in samples of breast tumors.[10] The validity of the conclusions of this study have been debated in the scientific literature.[11] Nevertheless, this study has fueled the belief that parabens in underarm deodorants or other cosmetics migrated into the breast tissue and contributed to the development of the tumors. However, no causal link with cancer has ever been proven and so far there is no scientific evidence to support any link with any form of cancer. A recent review of the available data[12] has concluded "it is biologically implausible that parabens could increase the risk of any estrogen-mediated endpoint, including effects on the male reproductive tract or breast cancer" and that "that worst-case daily exposure to parabens would present substantially less risk relative to exposure to naturally occurring endocrine active chemicals (EACs) in the diet such as the phytoestrogen daidzein."[13] In addition, the American Cancer Society has concluded that there is no good scientific evidence to support a claim that use of cosmetics such as antiperspirants increase an individual's risk of developing breast cancer.[14]

Estrogenic activity

Animal experiments have shown that parabens have weak estrogenic activity, acting as xenoestrogens.[15] In an in vivo study, the effect of butylparaben was determined to be approximately 100,000 times weaker than estradiol, although this effect was only observed when employing a dose level which was 25,000 times higher than is actually used to preserve products.[16] As the estrogenic effect is dose-related, it may be calculated that the estrogenic effect at normal use concentrations of butylparaben is 100,000 x 25,000, i.e. 2,500,000,000 times weaker than estradiol. In the same study it was shown that the in vivo estrogenic activity of parabens is reduced by about three orders of magnitude compared to in vitro activity probably through the rapid metabolism of the parabens to the non-estrogenic metabolites. In vivo data are accepted as being more relevant than in vitro data.

The estrogenic activity of parabens increase with the length of the alkyl group. It is believed that propylparaben is estrogenic to a certain degree as well,[17] though this is expected to be less than butylparaben by virtue of its less lipophilic nature. Since it can be concluded that the estrogenic activity of butylparaben is negligible under normal use, the same should be concluded for shorter analogs.

Some estrogens are known to drive the growth of tumors; however the estrogenic activity and mutagenic activity of estrogens are not the same with the latter dependent on free radical chemistry and not estrogen receptor activity.[18] Nonetheless, this study has elicited some concern about the use of butylparaben, and to a lesser extent other parabens as well, in cosmetics and antiperspirants. However, there is no evidence that any cosmetics containing parabens pose a health risk, because of the low doses involved and the fact that parabens are unlikely to penetrate into the tissue, remain intact, and to accumulate there.[6]

Nevertheless, the European Scientific Committee on Consumer Products (SCCP) stated in 2006 that the available data on parabens do not enable a decisive response to the question of whether propyl, butyl and isobutyl paraben can be safely used in cosmetic products at individual concentrations up to 0.4%, which is the allowed limit in the EU.[19]

Paraben controversy

The above mentioned studies have resulted in scientific debate that in turn led to popular controversy largely propagated by mass e-mail.[20][21] The controversy has led to some concerns (both over its possible carcinogenicity,[22] as well as its estrogenic effect,[23]) being expressed over the continued use of parabens as preservatives, although the scientific community has found no correlation with cancer and mostly agree that any causation is improbable.[11][24][25][26] There has been consensus that any estrogenic effect caused by the doses of parabens received from consumer products are insignificant compared to natural estrogens and other xenoestrogens.[15]

The mainstream cosmetic industry believes that parabens, like most cosmetic ingredients, are safe based on their long term use and safety record and recent scientific studies.[26] Public interest organizations which raise awareness about cosmetic ingredients believe that further research is necessary to determine the safety of parabens (see also precautionary principle).[22] The concerns have led to a significant minority shift from their usage by natural personal care companies seeking alternatives.[27]

References

  1. ^ von Woedtke T; Schluter B; Pflegel P; Lindequist U; Julich WD. Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained. Institute of Pharmacy, Ernst Moritz Arndt University, Greifswald, Germany. Pharmazie (1999) June;54(6):452-6. Abstract
  2. ^ New York State Breast Cancer Support and Education Network, Cancer and the Environment: A Case for the Precautionary Principle.
  3. ^ Antimicrobial Agents From Higher Plants. Antimicrobial Agents From Peganum harmala Seeds A. Al-Shamma, S. Drake, D. L. Flynn, L. A. Mitscher, Y. H. Park, G. S. R. Rao, A. Simpson, J. K. Swayze, T. Veysoglu, and S. T.-S. Wu. J. Nat. Prod.; 1981; 44(6) pp 745 - 747. doi:10.1021/np50018a025
  4. ^ Harsh Pal Bais, Ramarao Vepachedu and Jorge M. Vivanco, Root specific elicitation and exudation of fluorescent beta-carbolines in transformed root cultures of Oxalis tuberosa, Plant Physiology and Biochemistry, Volume 41, Issue 4, , 1 April 2003, Pages 345-353. doi:10.1016/S0981-9428(03)00029-9
  5. ^ In Vitro Cellular and Developmental Biology - Plant Volume 37, Issue 6 , 2001, Pages 730-741
  6. ^ a b c Soni, M. G.; Carabin, I. G.; Burdock, G. A. Safety assessment of esters of p-hydroxybenzoic acid (parabens). Food and Chemical Toxicology (2005), 43(7), 985-1015.
  7. ^ Soni, M. G.; Taylor, S. L.; Greenberg, N. A.; Burdock, G. A. Evaluation of the health aspects of methyl paraben: a review of the published literature. Food and Chemical Toxicology (2002), 40(10), 1335-1373.
  8. ^ Elder, R. L. (1984). Final report on the safety assessment of methylparaben, ethylparaben, propylparaben, and butylparaben. J. Am. Coll. Toxicol. 3, 147–209.
  9. ^ Nagel JE, Fuscaldo JT, Fireman P. Paraben allergy. JAMA. 1977, Apr 11; 237(15):1594-5. Abstract
  10. ^ Darbre PD, Aljarrah A, Miller WR, Coldham NG, Sauer MJ, Pope GS. Concentrations of parabens in human breast tumours. J Appl Toxicol. 2004 Jan-Feb;24(1):5-13. Abstract
  11. ^ a b Harvey, Philip W.; Darbre, Philippa. Endocrine disrupters and human health: Could estrogenic chemicals in body care cosmetics adversely affect breast cancer incidence in women? A review of evidence and call for further research. Journal of Applied Toxicology (2004), 24(3), 167-176.
  12. ^ Parabens in deodorants and antiperspirants linked to breast cancer (NICNAS Search page)
  13. ^ Golden, Robert; Gandy, Jay; Vollmer, Guenter. A Review of the Endocrine Activity of Parabens and Implications for Potential Risks to Human Health. Critical Reviews in Toxicology (2005), 35(5), 435-458.
  14. ^ The American Cancer Society Antiperspirants and Breast Cancer Risk
  15. ^ a b Byford JR, Shaw LE, Drew MG, Pope GS, Sauer MJ, Darbre PD. Oestrogenic activity of parabens in MCF7 human breast cancer cells. J Steroid Biochem Mol Biol. 2002 Jan;80(1):49-60. PMID 11867263
  16. ^ Edwin J. Routledge, et al. Some Alkyl Hydroxy Benzoate Preservatives (Parabens) Are Estrogenic. Toxicology and Applied Pharmacology. 153(1), 12-19. doi:10.1006/taap.1998.8544
  17. ^ Cashman AL, Warshaw EM. Parabens: a review of epidemiology, structure, allergenicity, and hormonal properties. Dermatitis. 2005 Jun;16(2):57-66; quiz 55-6. PMID 16036114
  18. ^ Int J Cancer. 2006 Apr 15;118(8):1862-8. PMID 16287077
  19. ^ SCCP: Opinion on Parabens. Colipa No P82 10 Oct 2006.
  20. ^ Can Rumors Cause Cancer Journal of the National Cancer Institute, Vol. 92, No. 18, 1469-1471, September 20, 2000
  21. ^ Antipersperants do not cause breast cancer. www.breastcancer.org.
  22. ^ a b Cosmetics, Parabens, and Breast Cancer. Organic Consumers Associtation.
  23. ^ Environmental Working Group Review of Parabens: concerns regarding estrogenic effect
  24. ^ Antiperspirant Use and the Risk of Breast Cancer Journal of the National Cancer Institute, Vol. 94, No. 20, 1578-1580, October 16, 2002
  25. ^ www.breastcancer.org Antiperspirants Do Not Increase Breast Cancer Risk
  26. ^ a b The Truth about Antiperspirants and Breast Cancer. Unilever.
  27. ^ Signers of the Compact for Safe Cosmetics. The Safe Cosmetics Campaign.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Paraben". A list of authors is available in Wikipedia.
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