A study conducted by researchers at the University of Illinois focused on the reproductive impact of phthalate DINP exposure in female mice returned interesting results that could shed light on certain types of human female infertility. In the study, female mice were given small oral doses of the phthalate DINP over the course of a ten-day period of time. The data returned found that the chemical compound disrupted the reproductive cycles of the mice. It also decreased their ability to become pregnant for up to nine months after the exposure.
The study’s findings were originally published in the Journal of Toxicological Sciences. It adds to a rapidly growing body of research which specifically links phthalates, with other reproductive abnormalities. This type of compound is commonly used as a plasticizer in a wide range of everyday products.
Where Are Phthalates Found?
Phthalates are often added to materials like plastic and vinyl to both soften them and make them more flexible. In certain formulations, it can also make items more durable. This degree of versatility makes them very popular with various types of consumer goods. Phthalates are often found in things like the packaging for foods and beverages, as well as vinyl flooring, a wide range of medical devices and even in many popular cosmetics.
There have been several research studies conducted in the past that found a wide variety of health risks associated with the phthalates DINP and DEHP which were given to the female mice. The list of related studies includes a Jodi Flaws’ University of Illinois, College of Veterinary Medicine study, conducted in 2015 which found that DEHP clearly disrupted hormone signaling and the growth and functioning of the rodent’s ovaries. The data and results were initially published in the journal Toxicology and Applied Pharmacology.
The Impact Of Realistic Exposure Levels
One other thing to keep in mind is that a significant amount of previous research on phthalates involved relatively high dosages. Most were in amounts that may not necessarily reflect the kind of exposure levels that humans or even mice are likely to experience.
To more accurately replicate potential real-world exposure amounts the Flaw’s study fed female mice a solution of corn oil with a smaller dosage of phthalate. The mice were administered concentrations of DEHP or DiNP that ranged from 20 micrograms up to 200 milligrams per kilogram of an individual mouse’s body weight. This dosage level is much more comparable to the kind of exposure that a mouse or human being might experience at work or in their own home.
Once the 10-day dosing was over, each of the female mice was paired with a male mouse. Another group of female mice was also paired with untreated males to serve as a control group. They were then provided with the appropriate conditions and exposure to encourage breeding behavior.
The Long-Term Impact Of Exposure
Three months after the phthalate dosing roughly a third of the female mice who received appropriate doses of DEHP and DINP were still incapable of conception after mating. This is in stark contrast to the female mice in the untreated control group who had an astounding 95% conception rate!
The overarching concern that this data set reflects, is that the fertility of the treated female mice was still significantly impaired long after the 10-day exposure period.
The study’s findings also suggest that steroid hormone production and hormone signaling were disrupted in the treated female mice. When measured at three months and again at nine months after the dosing period, the female mice that had been exposed to low-dose DiNP still had an estrous cycle that differed from the comparable female mice in the control group.
One thing it noted was that the proestrus stage, which is when the ovarian follicles develop was shorter, resulting in decreased fertility and a shorter window where the mouse was capable of conceiving. At the same time the later stages of the cycle, including the metestrus and diestrus stages were longer. This phase of the female mouse’s reproductive cycle involves the ovaries producing progesterone and the formation of the uterine lining.
Another interesting fact the researchers noted was that immediately following the 10-day dosing period, the uterus of the phthalate treated mice weighed significantly less than the uterus of the females in the untreated control group. Yet they didn’t find this uterine weight difference in the females they sampled at the three-month and nine-month intervals.
There was also a significant decrease in the number of pups birthed by the treated females who were able to conceive after receiving low doses of DEHP or DiNP. This was reflected and confirmed when compared with the control group mice.
All of this lends to the theory that the steroidal hormones made in the uterine lining of the phthalate treated mice were less receptive to embryo implantation. There is a narrow window of time where the endometrial lining in the uterus is fully receptive to implantation. The female mouse’s steroid hormones need to be well regulated for it to occur.
Can Phthalates Affect Reproductive Lifespan?
Another theory to consider is that there is a distinct chance that phthalate exposure effectively accelerates the end of the mouse’s reproductive lifespan. This could ultimately reduce the female’s chances of becoming pregnant.
It’s also worth bearing in mind that there have been other studies that looked into the effects of phthalate exposure on humans through cosmetic products. Many of them found that there is some evidence indicating that it could promote reproductive aging. This could also cause women to enter menopause earlier in life.
The study conducted by the University of Illinois, College of Veterinary Medicine has yet to be replicated in human females. However, the evidence likely warrants further research into DEHP’s and DINP’s potential impact on reproductive hormone and the ovaries.
For the time being the jury is still out on this effect in humans. The overarching concern is that phthalates are relatively common in modern day life. There are certain things an individual can do to reduce or perhaps limit their exposure to DEHP’s and DINP’s. However, it would be a pretty difficult challenge to completely eliminate phthalate exposure to your body.
Source – Science Daily