[leamangaarandia (OP)]

What is a paraben and why it can cause cancer?

[chiralSPO]

Parabens are esters of 4-hydroxybenzoic acid. As far as I know this class of compounds is not particularly carcinogenic, although they can interfere with some hormone pathways, and perhaps thereby indirectly increase risks of some cancers.

https://en.wikipedia.org/wiki/Paraben

[leamangaarandia (OP)]

thank you for your answer.. but i was so concern about the different cosmetics that is into the market which you can buy anywhere..most of them or 99% of them contains paraben then the study show that using of it may cause cancer,how come it is still used as a content for beauty products?

[chiralSPO]

can you provide a link (or reference) to the study showing that parabens cause cancer?

There have been many studies indicating parabens to be safe (http://www.fda.gov/Cosmetics/ProductsIngredients/Ingredients/ucm128042.htm).

One must be very skeptical of research relating to toxicity and carcinogenicity:

Assessing the toxicity of chemicals is notoriously difficult to do because researchers are prohibited from purposefully poisoning people, they must rely on studies using human cells or tissues (which will not address systemic toxicity or identify toxic metabolites, or will misidentify compounds as highly toxic when in fact the liver metabolizes them so quickly that they are not toxic to whole humans), or they subject other animals (like mice, rats, guinea pigs, or even dogs) to doses of these compounds (and these animals aren't necessarily good analogs--imagine the FDA declared chocolate toxic because of a study done on dogs!!)

It is even more difficult to assess whether compounds are carcinogenic (essentially a subset of toxic). Usually exposures to carcinogens are long-term at low dose. Impatient researchers won't treat their subjects with low doses of suspected carcinogens for 30-year studies, and so instead they often give 30x higher doses for 1 year (or 300x higher doses for 5 weeks). This is not great science...

[leamangaarandia (OP)]

i've read several articles about paraben and its effect..here are some.

4. Parabens are carcinogenic. Past research has focused on how parabens fuel the growth of existing cancer cells through their estrogenic activity. But in a second study published earlier this year, Dr. Darbre found that parabens may be carcinogenic, meaning they can transform healthy cells into cancer cells.

this is from Wellandgood.com/good-looks/paraben-update-theres-new-research-on-beautys-most-problematic-preservatives/

you may also want to read the article from livestrong.com/article/194949-what-are-the-side-effects-of-parabens/

[chiralSPO]

Thanks for the lead. The scientific articles referred to in the first link you provided are:

http://onlinelibrary.wiley.com/doi/10.1002/jat.1786/abstract
Which shows that parabens were found in breast cancer tumors. I agree that this is a cause for suspicion, and indicates that more study is needed. However, there is certainly no causal link shown in this paper. Additionally, this paper only looked at cancerous breast tissue. I hope that there is also a study in the works looking for concentrations of parabens in healthy breast tissue. If they are able to observe a trend showing that there are higher concentrations of parabens in cancerous tissue than in healthy tissue, and are able to rule out the possibility that tumors just happen to concentrate parabens for some reason, then there is some cause for concern. Even better, if they can show that higher levels of parabens in healthy breast tissue are a predictor of increased chance of developing breast cancer in the future, then that will be very clear evidence implicating parabens as causitive (but still not conclusive...)

http://onlinelibrary.wiley.com/doi/10.1002/jat.2753/abstract
Which shows that parabens, like estrogen, enable growth of colonies of breast epithelial cells in vitro (in a glass dish). This is also evidence that there *might* be a causative link, but definitely not proof.

At this point (speaking as someone from a family with a history of skin cancer) I would still advise you to wear sun lotion, even if it contains parabens. It might be advisable to reduce use of makeup, or switch to brands that use other preservatives like BHT or tocopherols (vitamin E)...

[Bored chemist]

It's grounds fo concern, but then again
"Breast cancer[edit]
There is no evidence that application of consumer products containing parabens cause cancer.[11] Investigations by the American Cancer Society and FDA found that current levels of parabens in consumer products were not dangerous.[12][13] A 2005 review 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 "worst-case daily exposure to parabens would present substantially less risk relative to exposure to naturally occurring endocrine active chemicals in the diet such as the phytoestrogen daidzein."[3]"
from
https://en.wikipedia.org/wiki/Paraben#Breast_cancer