- Jasmin Hassan, Pauliina Damdimopoulou y Richelle Duque Björvang
- *The Conversation
The birth rate is declining around the world.
In all European countries it is even falling below the levels of the population replacement rate, which refers to the number of children needed per woman to keep the population stable.
Although these drops may be due to many adults intentionally putting off having their first child, or actively choosing not to have them, a growing number of studies suggest that this does not fully explain declining birth rates.
Some research also indicates that lower fertility it is an important factor contributing to this decline.
A factor related to the decrease in fertility is the presence of industrial chemicals found in our environment.
Much is known about the impact of these chemicals on male fertility, but there have not been many studies on how they affect women.
This is what our recent project was looking for.
We found that exposure to common chemical pollutants was associated with a lower countr of ovules in the ovaries of women of reproductive age.
Although these chemicals have been banned ever since, they were once used in household products such as fire retardant productss or mosquito sprays.
And they are still present in the environment and in foods like fatty fish.
We measure the levels of 31 common industrial chemicals, as HCB (an agricultural fungicide) and DDT (an insecticide), in the blood of 60 women.
At the same time, we measured their fertility in relation to the number of reserve eggs they had in their ovaries by counting them in ovarian tissue samples using a microscope.
Because the ovaries are located inside the body and would require surgery to access, the team chose pregnant women who were to undergo a cesarean section, as this allowed access to tissue samples without undergoing additional surgery.
We found that women with higher levels of chemicals in their blood sample also had fewer immature eggs in their ovaries.
We found significant connections between reduced egg numbers and certain chemicals, including PCB (used in refrigerants), DDE (a by-product of DDT), and PBDE (a flame retardant).
More chemicals, fewer eggs
Since female fertility is dependent on age, we make sure to adjust our calculations to that parameter.
This revealed that exposure to these chemicals resulted in lessr number of ovules in women of all ages.
We also found that women with high levels of chemicals in their blood it was harder for them to get pregnant.
For those with the highest levels of chemicals in their blood, it took more than a year.
Unlike men, women are born with a set number of immature eggs in their ovaries and they cannot produce new ones.
That “reserve” (the number of eggs in your ovaries) naturally decreases. with monthly ovulations, as well as with normal follicle death.
When it falls below a critical level, natural fertility ends and menopause begins.
Our findings imply that toxic chemicals can accelerate the disappearance of ovarian follicles, which could lead to reduced fertility and earlier menopause.
We are exposed to industrial chemicals through our food, the products we put on our skin and even as we develop in the womb of our mothers.
The amount of industrial chemicals, as well as their abundance in the environment, has steadily increased since the 1940s, with effects devastating ecosystems, wildlife, and even human fertility.
Many chemicals were introduced to the market with little safety evidence.
This has led to a situation where humans and the environment are exposed to a great “soup” of industrial chemicals.
So far, several chemicals have been found to be harmful to reproduction just by a decade of consumer use.
These include PFAS (the chemical used in Teflon and fire fighting foam), phthalates (used in plastic packaging, medical equipment, and soaps and shampoos), as well as pesticides and other industrial chemicals such as PCBs.
Negative effects include a reduced sperm count in men and damage to women’s ability to get pregnant.
Our study is the first to investigate the link between exposure to chemicals and the number of eggs a woman has.
The chemicals that we studied were all “persistent”, which means that they accumulate in the body over time.
Surprisingly, the chemicals we discovered were associated with a lower egg count they were restricted by an international treaty decades ago.
However, due to their persistence, they still pollute the ecosystem and our food.
Interestingly, PCBs (one of the chemicals we study) have also been linked to decreased sperm count and infertility in men.
The simultaneous drop in male and female fertility It could make it difficult for couples to get pregnant.
In the future, researchers must look at whether the fertility of all women, not just pregnant women, is similarly affected by these chemicals.
But these findings may encourage us to rethink chemical safety to take fertility into account during safety assessments.
Avoid certain foods (like shellfish) and certain products (like the ones we put on our skin and hair) it can also help minimize the negative effects of chemicals on our chances of having a baby.
* Jasmin Hassan, Pauliina Damdimopoulou and Richelle Duque Björvang are PhD students in Reproductive Medicine at the Karolinska Institutet.
This note originally appeared on The Conversation and is published here under a Creative Commons license.
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Eddie is an Australian news reporter with over 9 years in the industry and has published on Forbes and tech crunch.