Fertility rate declines, environmental pollution should not be "back to the pot"

Declining fertility rates have made the world anxious and worried about many Chinese. Data from the China Statistical Yearbook 2021 show that the national birth rate in 2020 was 8.52 per thousand, the lowest birth rate since the founding of the People's Republic of China. In 2020, China's fertility rate (the average number of children born to each woman during childbearing age) was as low as 1.3, one of the lowest fertility rates in countries and regions.

A study published in The Lancet in July 2021 showed that fertility rates worldwide fell from 4.7 in 1950 to 2.4 in 2017. It is clear that fertility rates have fallen globally and in China. There are many reasons for the decline in fertility, from economic, social, cultural, technological and other aspects. However, the research results recently published in the journal Nature by Professor Nils Scarkerbek of the University of Copenhagen in Denmark have taken a different approach, pointing out that environmental factors are an important cause of the decline in global fertility, and even have a decisive impact on fertility decline. Direct or indirect human exposure to chemicals derived from fossil fuels can lead to today's widespread infertility, resulting in a decline in global fertility.

Only when the fertility rate is greater than 2 can a society achieve sustainable development in human resources and human civilization can pass on the torch. The world's low fertility rate of 2.4 has put social development at risk. Therefore, exploring the causes and coming up with ways to respond to increased fertility rates has become an important task for the current scientific community. In many discussions, the Hypothesis of Danish researchers has emerged - environmental pollution is an important cause of the decline in global fertility rates. However, the current mainstream view in academia is that the decline in fertility rate is attributed to the decline in people's willingness to have children, and there are many factors such as economy and culture behind it.

However, Danish researchers have also proposed a factor that cannot be ignored, that is, environmental pollution has led to an increase in infertility rates, which in turn has led to a decline in fertility rates. The main evidence provided by the study is that more than 20% of Danish men have difficulty conceiving their partner naturally. In Denmark, one in ten babies is born through assisted reproductive technology. In addition, the number of accidental miscarriages in the United States has increased by nearly 2% since 1990, which may also be caused by environmental pollution. At the same time, some previous studies have shown that the quality of human sperm and eggs has gradually declined over the past half century. These factors have led to an increase in infertility rates, which in turn has reduced fertility rates globally.

In fact, Danish researchers are not the only ones who agree with the idea that infertility leads to declining fertility rates. Recently, Professor Shana Swan, an environmental and reproductive epidemiologist at the Icahn School of Medicine in Mount Sinai in New York, pointed out that from 1973 to 2011, the sperm count of Western men has decreased by 59%. Now, this trend shows no signs of reversing, if it continues to develop, the number of male sperm will be reduced to 0 in 2045, men or will be "experiential", human beings may face a situation of no successor. Swann also argues that attributing the decline in fertility to late fertility, personal choices or lifestyle is not entirely accurate, and that chemicals that affect human hormones are also a major factor, but have not been taken seriously.

Whether it is Skackerbek in Denmark, Swan in the United States, or many researchers before them, they have emphasized that the environmental hormones formed by pollutants released into the environment by pollutants in human production processes and industrial products have a negative impact on human fertility, resulting in an increase in infertility rates.

So, what exactly are environmental hormones? Environmental hormones mainly include phthalate plasticizers, bisphenol A, etc., which exist in a large number of industrial products, such as pipes, building materials, packaging materials, cables, imitation leather products, medical materials and products. After entering the environment, phthalates can enter the human body through breathing, diet and skin contact, causing a variety of hazards to human health, the most important of which is to affect reproductive function. When phthalates enter the body, they bind to the corresponding hormone receptors, producing the same effects as hormones, resulting in hormones in the blood that cannot be maintained at normal levels, affecting reproduction, development, and behavior.

Phthalates have a great influence on the developing male reproductive system, which can lead to atrophy of seminal vesicles, a decrease in sperm count, and therefore reduced fertility. At the same time, the substance can also cause precocious puberty in women, and may affect embryonic development through placental lipid and zinc metabolism. The effect of the substance on the fertility of both sexes can lead to infertility, and may also lead to malformations or diseases in the offspring, such as male offspring may have diseases such as decreased sperm count, testicular cancer, prostate cancer, etc.; female offspring may appear endometriosis, vaginal cancer, uterine cancer, ovarian cancer and other diseases.

At present, the infertility rate has reached 20% in Denmark and has climbed to 18% in China, and there is no doubt that the environmental hormones produced by environmental pollution will cause human fertility to decline, but how serious is the decline in fertility caused by environmental pollution?

The clinical diagnosis and treatment of infertility shows that the rise in infertility rates in China and the world is related to factors such as physiological diseases, genetics, environmental pollution, and lifestyle. In China, sperm and semen abnormalities are the main factors leading to male infertility; endometrial abnormalities are the main factors leading to female infertility. Among them, sperm and semen abnormalities caused by environmental hormones are only part of the reason, and lifestyle factors such as smoking, alcoholism and obesity can also lead to a decrease in sperm count, which affects fertility. In addition to infertility induced by endometrial abnormalities in women (e.g., endometriosis, congenital uterine septum), tubal obstruction, ovarian disorders (e.g., polycystic ovary syndrome), and sexually transmitted diseases can also lead to infertility.

In 2020, a report by the American Society of Sleep Medicine and the Sleep Research Association showed that the use of glowing electronic devices at night reduces sperm quality in men. Men who used smartphones or tablets at night had lower sperm concentration, motility, and progressive motility (the normal "swimming" ability of sperm), and a higher proportion of immobile sperm who could not "swim.". This condition can also lead to male infertility.

Therefore, even if environmental pollution is an important cause of infertility, for the current infertility rate of about 20%, only part of the responsibility can be assumed, not all.

Environmental pollution should not be ignored, but while paying attention to the control of environmental pollution, infertility should also be treated for other causes, such as lifestyle, diet, other diseases and genetic factors. In addition, it is also possible to rely on the power of science and technology to increase fertility rates, assisted reproductive technology is one of the most important ways, of which in vitro fertilization, that is, IVF is the most important method.

About 300,000 IVF babies are currently born in China every year. Since the birth of the first IVF in 1978, more than 9 million IVF babies have been born worldwide, completely changing the status quo of infertility and maintaining the global fertility rate while allowing many people to become parents. However, this is only an auxiliary way, and people can only sustain the sustainable development of human beings by having children in a natural way.

There is no doubt that environmental pollution will lead to an increase in infertility rates, and it is also urgent to control environmental pollution. However, if you want to change the current situation of declining fertility rates year by year, the most important thing is to increase people's willingness to have children, which is even more important in China. Some researchers have suggested that the mainland can use 5% of GDP to encourage fertility, and it is clear that this countermeasure is mainly to increase fertility through economic means. If reduced environmental pollution and enhanced assisted reproductive technologies can be added, the decline in fertility is likely to slow down and return to normal.