11/15/2021 at 19:46 CET
Since 1960, the World Bank has collected very precise data on the average number of children of a woman in all countries. This is called the fertility rate.
Its results, backed up by those of many other institutions, revealed a worrying fact: over the past 40 years, we have witnessed an extremely rapid decline in fertility.
As the rapid growth of the human population was not sustainable for the planet’s resources, declining fertility rates were initially seen as good news.
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The low birth rate is no longer so voluntary
Young couples voluntarily reduced the number of children they wanted to have, while delaying the age at which they gave birth to their first babies.
It didn’t sound awkward. If the decline in fertility were due only to voluntary decisions by couples, the trend could easily be reversed.
But gradually it became clear that there is more than voluntary decisions in the low number of children women have.
Indeed, there is a growing scientific evidence showing that much of the low fertility rates of our species is due to a very serious deterioration in reproductive health which is already affecting a large part of humanity.
The data couldn’t be more devastating.
An in-depth meta-analysis of a multitude of laboratory findings over the past decades indicates that in developed countries, nearly all healthy women in their 20s are significantly less fertile than their grandmothers at 35.
And the situation is even worse for men.
Young people in full force produce less than half of their grandparents’ sperm.
An example: in the 70s of the last century, men produced around 99 million sperm per milliliter of semen, while today they barely reach 47 million. Less than half.
Additionally, and to make matters worse, many of these sperm have severe defects in morphology and motility, and in many cases their DNA is fragmented.
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Deterioration at an alarming rate
What worries reproductive medicine experts the most is the extraordinary rate at which this massive loss of fertility is occurring.
Some epidemiologists warn that we are on a dangerous countdown that if we fail to reverse it could lead to extinction. After all, a species can only survive in the long term if it leaves enough offspring.
Science has addressed this loss of fertility by developing extremely innovative assisted reproduction techniques.
Today, up to 15% of babies born in some of the world’s most developed countries (and about one in 10 babies born in Spain) are conceived using assisted reproduction techniques.
These are increasingly sophisticated techniques, with complex hormonal and pharmacological controls, micro-injections of sperm into the oocytes, a selection of embryos to be implanted and exhaustive diagnostic tests that guarantee the viability of the embryos transferred.
Nevertheless, couples must increasingly resort to the donation of oocytes, sperm or embryos from donor banks.
And despite the extraordinary development of these assisted reproduction techniques over the past 40 years, such tremendous progress has by no means compensated for the rapid loss of fertility in our species.
A high percentage of couples do not even manage to have children with such a profusion of techniques
Are pollutants responsible for this rapid loss of fertility?
There is no doubt that the dramatic increase in the age at which couples decide to have their children is a factor to be taken into account. But unfortunately this is not the main cause.
The serious fertility problems that could lead us to a real survival crisis as a species are mainly due to the extremely damaging effect that a long series of diffuse environmental pollutants have on our reproductive system.
And by diffuse pollutants we mean those whose source is not localized at a specific point and generally mainly impact the air and water.
The WHO list
Well, the World Health Organization (WHO) has put together a list of around 800 substances that we are exposed to all the time in our homes and workplaces.
That is, by what the scientific names sound like, phthalates, dioxins, furans, PCBs, bisphenols, alkylphenols, benzophenones, synthetic hormones used to fatten cattle, pesticides and herbicides, metals heavy, UV filters used in sunscreens, food preservatives and mldr;
All of them are endocrine disruptors capable of altering the hormonal system leading to different diseases related to reproductive health.
The effect of these hormone disruptors is cumulative and often irreversible.
Why have such dangerous substances proliferated in this way?
In many countries around the world, companies do not need to prove that chemicals are safe before they are released for sale.
As soon as a substance shows its usefulness, it is launched on the market without having carried out sufficient toxicity checks with it in long-term exposure.
Many of these substances have great commercial success, they become common in our lives and end up displacing sums of money greater than the GDP of most countries.
They are often so present in consumer society that by the time evidence of their toxicity begins to accumulate, their economic weight is so great that their ban would lead to an unprecedented crisis.
Phthalates are almost everywhere
An example of this type of contaminant are esters of phthalic acid, known as phthalates.
This is a group of industrial chemicals widely used as substances added to plastics to increase their flexibility (eg to make PVC more flexible).
From the 50s of the last century, they began to be produced in enormous quantities, assuming that they were harmless without the necessary scientific studies having been done to prove it.
At the start of this century, some 400,000 tonnes of phthalates were being manufactured each year.
Today they are everywhere. And they are an important part of many everyday items such as gels, shampoos, cosmetics, toys, containers, furniture, building materials for our homes & mldr;
But the main route of exposure to phthalates is through food, when food comes in contact with plastic during processing, packaging and storage.
In addition, the diffuse contamination by phthalates in the environment is already so great that they even reach us in the water we drink.
Recent studies show that people who eat in fast food establishments, restaurants or cafeterias, as well as those who consume foods prepared at home, have the highest amounts of phthalates.
What is the danger of phthalates?
When phthalates enter our body, they affect our hormones.
The most important effects occur during the early stages of fetal development, but also during the early years and adolescence. During these phases of our development, phthalates produce alterations in our endocrine system.
The problem is that humans are extremely sensitive to minimal hormonal changes, because during our development hormones are used as regulators of the processes that will follow.
Thus, phthalates alter our sexual differentiation and affect the quality and quantity of our eggs and sperm.
TBT, one of the most dangerous pollutants in the aquatic environment
But phthalates are neither the most abundant nor the worst of the substances that affect our reproductive health. Another example is tributyltin (TBT).
TBT-based antifouling paints were produced in the 1960s. Ten years later, the vast majority of boats (including sports boats) painted their hulls with TBT-based antifouling.
TBT derivatives were subsequently used as stabilizers for plastics and in industrial catalysts.
Its effect as an endocrine disruptor is so important that it is considered one of the most dangerous pollutants in the aquatic environment. We even know that it has already led to the extinction of species of marine snails in the North Sea.
Concentrations of a single nanogram (0 000 000 001) per liter are lethal for species of algae, zooplankton, molluscs and fish, and have even endangered oyster beds in the French basin of Arcachon .
Of course, TBT is just as toxic to humans. And yet, every year we release around 40,000 tonnes of TBT into the environment.
“Eternal chemicals” are even worse
Despite their dangerousness, soluble hormone disruptors (like phthalates or TBT) are less harmful than the so-called “eternal chemicals”. which will remain several decades (probably centuries) in the environment. And when they enter our body, it is impossible to eliminate them.
Many of these perennial chemicals build up in our fat. They can be concentrated in fat in food (often fish).
examples of “eternal chemicals & rdquor; that have serious effects on our endocrine system altering reproductive health would be:
DDT (dichloro diphenyl trichloroethane) which is still used as an insecticide to fight against malaria.
Dioxins, found in dairy products, fish and shellfish.
Certain polychlorinated biphenyls, which are used in sealants, inks, paint additives, refrigerants and lubricants in closed electrical equipment such as transformers & mldr;
Their persistence in the environment, as well as their accumulation in the food chain, makes them extremely dangerous.
And these hormone disruptors often pose a serious threat to reproductive health at doses as low as a single drop of diluted water in a swimming pool.
What will they say about us in the future when they learn that we have used phthalates in our children’s pacifiers and bottles?