Chapter 5 Male Fertility and Infertility: Environmental Pollution and the Definition Criteria of Infertility
Male fertility and infertility
Why has environmental pollution become a "sperm killer"?
Environmental pollution is one of the main culprits behind the significant decline in sperm quality. With the rapid development of industrial modernization, environmental pollution has become increasingly serious, a major global concern. Naturally, men who work in polluted environments for extended periods will likely have lower sperm quality than the average person, as they inhale pollutants daily; pollution on roads remains severe. Over the past few decades, the types and quantities of environmental pollutants, including combustion soot, vehicle exhaust, food additives and pesticide residues, chemical disinfectants, and physical electromagnetic radiation, have increased significantly. The harm of environmental factors to human reproductive health is increasingly attracting the attention of reproductive professionals. In the past, medical research focused primarily on the acute toxicity, tumorigenicity, and teratogenicity of environmental pollution. In recent years, however, research has begun to focus on the reproductive toxicity and genotoxicity of environmental pollution, and research on reproductive toxicity has shifted towards reproductive health, especially male reproductive health.
Prolonged exposure to high temperatures can damage male spermatogenesis. Studies have confirmed that temperature affects sperm quality. Under normal circumstances, a man's testicular temperature is lower than his body temperature. Sometimes, when the external temperature is too high, the scrotum needs to sweat to lower its temperature, ensuring sperm quality. A constant temperature of 34-35℃ is ideal for normal sperm development. However, prolonged exposure to high-temperature work environments and unhealthy lifestyle habits, such as frequent saunas or hot baths, can place the testicles in a relatively high-temperature environment, thus affecting sperm production and development. Generally speaking, the testicles need a temperature slightly lower than body temperature to produce sperm; high temperatures are detrimental to sperm production. Men who enjoy saunas, where room temperatures can reach 70-80℃, are particularly susceptible to damaging the sperm's growth environment, potentially leading to excessive "dead sperm" and infertility. Therefore, young men should be cautious about sauna use and avoid prolonged exposure to excessively hot water during baths to prevent artificially disrupting the normal sperm growth environment. Of course, there are no clear medical guidelines on how long one should stay in hot water. Therefore, taking a sauna once in a while is probably fine, but frequent sauna use will definitely affect fertility. So be sure to keep the water temperature from getting too high and the time spent in the sauna from getting too long.
In addition, some unhealthy lifestyle habits may allow spermicides to take advantage of healthy men, such as frequently wearing tight jeans. Clinical observations show that under normal circumstances, the temperature of a man's testicles varies with body temperature, generally being about 2°C lower. Because tight jeans are made of thick material, they have poor breathability and heat dissipation, making the testicular temperature closer to the body's temperature, thus damaging the environment for sperm survival. Furthermore, the tightness of jeans can compress the male reproductive organs, affecting normal testicular development.
People must strive to create a relatively better environment for themselves, cherish the environment, and remember that ecology is something we borrow, not something we inherit. Regular physical activity is essential. It's especially important to remind men who spend long hours sitting in offices that this not only easily causes nerve compression but also raises local temperature and impairs blood circulation. They should get up and walk around or stand still every hour. Walking is the best form of exercise. Moderate exercise is better than prolonged sitting.
What is infertility?
Infertility refers to couples who are capable of conceiving and have a history of pregnancy, but who do not have a live birth due to miscarriage (including recurrent spontaneous abortion), ectopic pregnancy, molar pregnancy, premature birth, stillbirth, or stillbirth. While both infertility and sterility involve not having children after marriage, infertility refers to the inability to conceive after two years of unprotected intercourse, while sterility refers to the inability to conceive despite past pregnancies due to miscarriage, premature birth, or stillbirth. Generally speaking, infertility is often due to problems with sperm or egg formation, resulting in obstructed fertilization or implantation; sterility is often due to problems with embryonic or fetal development after implantation. The two have distinct causes. However, because early miscarriages are often difficult to identify, strictly defining the boundary between infertility and sterility can sometimes be challenging.
There are many different opinions regarding the definition of male infertility, especially concerning the time standard for infertility. Most scholars believe that male infertility is defined as the inability to conceive after two years of regular, unprotected sexual intercourse, where the cause is attributed to the male partner. However, in 1995, the WHO published the "Manual of Standard Examination and Diagnosis for Infertile Couples," which established a more scientific and internationally unified standard: "At least 12 months of unprotected sexual intercourse without the ability to conceive." This standard, in its wording, is well-considered and possesses a certain degree of scientific validity.
First, regarding the time standard for infertility. There has never been a unified standard in China; some say 3 years, others 2 years, and still others 1 year. Later, some surveys showed that with regular sexual activity and no contraception, approximately 80% of women can conceive within 12 months of marriage (or cohabitation), and 10% can conceive within the 24th month. Therefore, the International Federation of Gynecology and Obstetrics set the time standard for infertility at 2 years. Domestic scholars have largely followed this standard in recent years. However, the *Standard Examination and Diagnosis Manual for Infertile Couples* sets it at "at least 12 months." Comparatively, the WHO's view is more scientific. The "at least 12 months" has several implications: firstly, it establishes a lower limit for diagnosing infertility; secondly, it uses months instead of years, based on the woman's ovulation cycle and allowing for cumulative calculations, not based on the length of marriage, but on the number of months of effective sexual activity. This includes premarital sexual activity and excludes months of separation due to various reasons after marriage.
Second, "unprotected sexual activity history" refers to the number of months in which effective ejaculation occurred in the vagina between a man and a woman, excluding the time of sexual activity involving oral contraceptives, contraceptive devices, withdrawal, masturbation, etc.
Furthermore, the terms "couple" and "after marriage" have both been used in previous definitions of male infertility. Because there are unmarried cohabiting couples, the "Standard Examination and Diagnosis Manual for Infertile Couples" uses "male and female" instead of "couple," thus eliminating the "after marriage" issue, which is more appropriate.
How are sperm produced?
Sperm are male reproductive cells produced by the testes, the gonads of men. They are shaped like tadpoles in water, with an oval head at the front and a thread-like tail at the back. By wagging their tails, sperm can move forward at an astonishing speed, much like tadpoles swimming in water.
The male testicles are the "factories" that produce sperm. There is one testicle on each side, each weighing 10.20g, with a medium texture and an oval shape. If the volume of the testicles is less than 11 cubic centimeters and the texture is as soft as a human lip, it often indicates poor testicular function. The seminiferous tubules in the testicles are the base for sperm production. It takes about 74 days for spermatogonia to develop into sperm. An adult can produce about 10 million sperm per day per gram of testicular tissue.
How long does it take for humans to conceive?
Studies show that human eggs only live for a maximum of 12-24 hours after ovulation. Sperm motility is largely influenced by the environment within the female reproductive tract. If sperm remain in the vagina after ejaculation, they will die within 8 hours; if sperm enters the cervix, and the cervical mucus has a suitable pH level, sperm can survive for 3 days (and possibly 5 days). Therefore, the maximum fertile window for humans is 4 days. It is generally recommended to enter the female reproductive tract a few days in advance to await the egg and increase the chances of fertilization.