In mid-December, when news emerged that the number of newborn babies in Japan in 2016 would likely fall below 1 million for the first time since the government started collecting data in 1899, it sparked a renewed debate on how to reverse the downtrend in the fertility rate.

While the usual spade of issues dominated the policy talk — such as increasing state support for child care and reining in excessive overtime to help parental work-life balance — Danish pediatrician Niels E. Skakkebaek had a completely different perspective. For him, the news was a wake-up call for Japan to take a harder look at what has long been ignored and considered taboo: male infertility.

“My main message is that, although we don’t know why birthrates are so low, it should be taken into consideration that perhaps poor semen quality contributes to it,” Skakkebaek told The Japan Times last month during a visit to Tokyo, where he delivered a lecture at the annual convention of the Japan Pediatric Society. “And that is almost never said in newspapers and other media. They always blame women’s work or social factors. But those who work in fertility (treatment) know that infertility is very important.”

Skakkebaek, a professor at the department of growth and reproduction at the University of Copenhagen, is a leading authority in the research of testicular cancer and other male reproductive disorders, including low sperm quality. Research overseas has shown that semen quality has declined over the last several decades, with sperm counts dropping, their swimming ability waning and more of them having abnormally-shaped heads or tails.

The situation in Japan is not rosy either, though research so far has been limited.

Dr. Teruaki Iwamoto, a male infertility expert at the center for human reproduction at Sanno Hospital in Tokyo, says that the sperm count among many young men in Japan is also at subpar levels, though there is not enough data to nail down its causes and judge to what degree it contributes to infertility.

In a 2013 paper published in the journal BMJ Open, Iwamoto and co-researchers, with the guidance of Skakkebaek, studied the semen quality of 1,559 young men in four cities — Kawasaki, Osaka and Kanazawa and Nagasaki. The study, which was funded by the health ministry, concluded that the Japanese men appeared to have a higher sperm count than men from Northern Europe, but slightly lower than men from Spain.

What is most worrisome, however, is that nearly 10 percent of the subjects had a sperm count below the World Health Organization reference level of 15 million sperm per millimeter of semen, or a total of 39 million semen per ejaculation. Furthermore, nearly one-third of men had a sperm concentration of less than 40 million per millimeter, a level said to affect the ability to reproduce.

Skakkebaek has for years advocated the concept that poor semen quality is part of a bigger phenomenon, which he calls the “Testicular Dysgenesis Syndrome.”

Sperm dysfunction, as well as testicular cancer, cryptorchidism (a condition in which one or both testicles are lodged inside a boy’s body and remain undescended) and hypospadias (a birth defect where the opening of the urethra is halfway down the penis instead of at the tip) are all interlinked, he has argued.

Though the exact causes of these problems are unknown, Skakkebaek suspects the industrialization of many countries after World War II and their increased exposure to chemical pollutants, including endocrine disrupting chemicals (EDCs), may have had a role in impairing male reproductive health.

EDCs are found in pesticides, metals, additives or personal care products. They are known to be passed on from pregnant women to the fetus and child through the placenta and breast milk.

“We think that environmental exposures can influence a whole life in all ages, but the particular vulnerable time is fetal life,” Skakkebaek said. “When a woman is pregnant, her baby, or a boy, is particularly sensitive to exposures. This has been shown in animal studies.”

He points to the increasing incidence worldwide of testicular cancer as a reason for suspecting environmental factors.

In Denmark, the testicular cancer rate has risen 400 percent since the early 1940s, he says, a trend also observed in other industrialized European countries. According to the European Cancer Observatory, Norway and Denmark lead Europe in testicular cancer cases, with age-standardized rates of 12.7 and 12.5 per 100,000, respectively, as of 2012.

“When you see a phenomenon like testicular cancer in Denmark increasing 400 percent over a couple of generations, it cannot be genetics,” he said. “It’s not inherited. It’s something from the environment.”

Indeed, instances of man-made chemicals causing male reproductive dysfunctions have been widely documented.

According to a 2013 European Environmental Agency report, the pesticide Dibromochloropropane (DBCP) was widely used against roundworms or threadworms in banana and other tropical fruit plantations from the 1960s through the 1980s. As a result, tens of thousands of plantation workers in Latin America, the Philippines and elsewhere are alleged to have become sterile after being exposed to DBCP.

Dioxin is another EDC linked to reproductive health. A study published in the journal Lancet in 1996 reported that an explosion at a chemical factory in the Italian town of Seveso in 1976 led to massive dioxin contamination of the area’s residents. Children born to affected parents between 1977 and 1984 had a highly skewed sex ratio, with only 26 boys born against 48 girls, the researchers found.

Skakkebaek is cautious not to rush linking environmental pollution with Japan’s low fertility rate, but decries the lack of interest among health authorities and politicians to investigate the issue further, despite the fact infertility is an increasingly serious issue.

Japan’s testicular cancer rate — estimated at 1 or 2 in 100,000 men — is much lower than in the West, but data are not comprehensive enough because the estimate is based on regional studies, he said. (It was only in January 2016 that Japan launched a nationwide cancer registry.)

“Stop blaming women for not having children — because having children is a biological process, not just a social process,” he said. “It’s also a matter of biology. If something is not functioning, you should look for causes in both men and women. And I see few signs in Europe or Japan that people do that.”

Iwamoto, a urology specialist, agrees, saying that the government needs to boost research into this area and assess semen quality continually.

Monitoring incidence of undescended testicles and hypospadias should be stepped up, and a detailed analysis on semen samples’ exposure to EDCs is also necessary, Iwamoto argued.

“Infertility is believed to afflict 10 percent of married couples in Japan, with men and women equally contributing to the problem,” he said. “It is often the case that women spend millions of yen in fertility treatment, only to find afterward that the causes of infertility were in men. Male infertility is an area that deserves more attention, as it could help us discover causes of infertility and possibly offer solutions to Japan’s birthrate decline.”

A Matter of Health is a weekly series on the latest health research, technology or policy issue in Japan. It appears on Thursdays.

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