Chemicals in cosmetics, moisturizers linked to DNA damage in human sperm.
Meeker, JD, T Yang, X Ye, AM Calafat and R Hauser. 2010. Urinary concentrations of parabens and serum hormone levels, semen quality parameters, and sperm DNA damage. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.100223.
One type of paraben preservative – butyl paraben (BP) – was linked to DNA damage in men's sperm, according to a study that compared the levels of this compound to several reproductive measures in men. DNA damage in sperm cells can have negative effects on men's reproductive potential.
The findings indicate that the higher the BP levels, the more DNA damage the sperm had. The relationship was even stronger when BP and bisphenol-A (BPA) levels were considered together.
This is the first study to look at the relationship between paraben levels in men and sperm health. A prior study found that the late stages of sperm production were affected in mice fed BP. The results warrant further investigation into effects of parabens on men's sperm health as well as their effects on female reproductive systems and pregnancy and birth measures, given that women typically have higher levels of parabens than men.
Parabens are a group of antimicrobial chemicals often used to preserve cosmetics, pharmaceuticals and sometimes food. They are added to numerous personal care products – including make-up, shaving gels, lotions and creams – and some food and drinks. As a class of compounds, they differ in their chemical structure, often depending on the length of the chemical chain attached to the backbone structure. Different sized parabens have distinct properties that make them useful in various applications. Many cosmetics, lip gels, lotions and cleansers contain BP.
The U.S. Centers for Disease Control and Prevention (CDC) reports that a majority of the population is exposed to these chemicals on a daily basis, yet little is known about their health effects on people. Exposure is likely to occur from both eating the chemicals and absorbing them through the skin.
In this new study, researchers recruited a group of men attending an infertility clinic in Massachusetts between 2000 and 2004. They measured the concentrations of three paraben metabolites in the men's urine – methyl paraben (MP), propyl paraben (PP) and BP – and BPA. About one-third of the men had repeated urine samples taken several weeks apart and analyzed for changes in paraben levels over time. They also measured concentrations of several hormones in the blood. Markers of sperm quality and function were also examined. Paraben levels were then compared to hormone levels, semen quality and sperm DNA damage markers.
Parabens were detected in all samples but amounts varied depending on the chemical's structure. For instance, MP was detected in 100 percent of the samples, PP in 92 percent and BP in 32 percent. Levels of each varied over time. BPA levels in the urine were published in a previous study.
There was a significant positive association between urinary BP levels and DNA damage measured in sperm cells. This effect was also seen for BPA, as reported previously. When considering both compounds together in this study, the authors found a significant dose-dependent increase in DNA damage – more simply, as BP and BPA levels increased, so did the genetic damage.
The authors also found a potential, though somewhat weak, relationship between urinary paraben levels and thyroid hormones. When comparing blood thyroid hormone levels with the urinary paraben concentrations, they observed a negative relationship that was almost significant – thyroid stimulating hormone (TSH) levels decreased as methyl paraben levels increased. No significant associations were observed between urinary paraben concentrations and other hormone measurements.
A small sample size and the preliminary nature of the study limit the conclusions, but the findings do suggest further research is needed to understand the relationship between parabens and DNA damage in sperm and how BPA and BP and other parabens may act together to affect sperm health.
