Men who had high concentrations of parabens in their urine had low testosterone and poor sperm quality.  Parabens are common chemicals that are used in cosmetics, lotions, shampoos, lipstick, sprays, gels, and even some food products.  Parabens are preservatives used to kill bacteria in these products.

When I polled pharmacists, in early the 2000's, many pharmacists proclaimed that parabens were safe given the 50 year history of use.  It is true that parabens are largely safe from a toxicity point of view and cancer causing point of view when taken orally.  When parabens are taken orally, it is claimed that they may or may not be safe from a hormone disruptive point of view. 

However, what the pharmacists did not take into account was that the parabens are APPLIED TOPICALLY.  Anything put on the skin has a 10 times greater potency that what is taken orally.  This is because whatever is put on the skin goes directly into the body.  In contrast, whatever is taken orally is 90% prefiltered by the liver.  Thus, you need to be 10 times more careful about what is put on the body.  Parabens fed to rats had no effect on the rat uteri.  But rats that were given parabens topically in the concentrations typically used by humans had an increase of rat uteri size of 30%.

Back to the Men with Fertility Problems

Men with high concentrations of parabens in their urine compared to men with low concentrations of parabens in their urine had larger percentage of oddly shaped sperm (abnormal morphology, abnormal size or shape).  These men with high concentrations of parabens also had sperm that was slower (low motility). High levels of parabens is also associated with DNA damage in the sperm.  All of these traits are associated with a lower fertility rate.  Sperm that is cannot swim strongly or are misshapen cannot reach the egg.

The 315 men whose sperm and paraben levels were measured were from a Polish infertilty clinic.

The lead study author Joanna Jurewicz of the Nofer Institute of Occupational Medicine in Lodz commented, "We have observed an impact of parabens on semen quality.  To avoid parabens is very difficult because they are widespread, but we can try to minimize the exposure by only using personal care products with label information saying that there are no parabens in the particular product."

However, in my experience, some products that are "paraben free" use in its place an even worse chemical phenoxyethanol.

Some parabens are banned from use in cosmetics by the European Union citing a possible risk of increase in breast cancer.  However, the U.S. FDA has not put any limits on the use of parabens in cosmetics.

Typically several parabens are combined and used in cosmetic products to increase their effectiveness to kill bacteria.  Butyl paraben seems to be associated with oddly shaped and oddly sized sperm as well as decreased sperm motility.  Ethyl paraben was only associated with strange shapes and strange sizes, but not decreased sperm motility.

There are several caveats.  The study was from men coming to a fertility clinic. We do not know if these results apply to "normal" men.  Researchers have not determined the "safe" levels or use of parabens on the skin.

Marisa Bartolomei, co-director of the epigenetics program at the University of Pennsylvania Perelman School of Medicine in Philadelphia stated, "No one really knows the mechanism of action of these compounds."

References:

1.

https://www.researchgate.net/profile/Pawel_Radwan/...

Joanna Jurewicz, PhD, Michał Radwan, PhD, Bartosz Wielgomas, PhD, Emila Dziewirska, MSc, Anetta Karwacka, MD, Anna Klimowska, MSc, Paweł Kałuz˙ny, PhD, Paweł Radwan, PhD, Michał Bochenek, PhD, and Wojciech Hanke, MD, PhD, Human Semen Quality, Sperm DNA Damage, and the Level of Reproductive Hormones in Relation to Urinary Concentrations of Parabens, JOEM, American College of Occupational and Environmental Medicine, Volume XX, Number X, Month 2017, March 2017.