Environmental Toxins Likely Cause of 50% Decline in Global Sperm Count
Sperm count
A new study has mapped a massive decline in sperm count – environment primary suspect.

A worldwide decline in sperm counts of more than 50% over the past 46 years has been identified by a team of international researchers, and the decline has accelerated since the year 2000, according to an article in the journal Human Reproduction Update published on Tuesday.

The article updates a previous study published in 2017, providing strong evidence for the first time of a decline in sperm count and total sperm concentration in men from South and Central America, Asia and Africa.  A previous study showed a similar decline in North America, Europe and Australia. 

Threat to human survival?

“We have a serious problem on our hands that, if not mitigated, could threaten mankind’s survival,” said Professor Hagai Levine of the Hebrew University- Hadassah Braun School of Public Health, who led the study in collaboration with a team of scientists from Denmark, Brazil, Spain and the United States.

Levine described the findings as a “canary in the coal mine – a red flag. There is a loss of biological diversity around the world. We know that reproduction is very sensitive to the environment and it is essential for future existence.”

A mom and her newborn baby in Dhaka, Bangladesh.  Exposures to environmental toxins in the womb could be one of the reasons for reduced sperm count, researchers say.

Data from 53 countries was included in the meta-analysis, including Australia, Bangladesh, Belgium, Brazil, Canada, Chile, China, Cuba, Czech Republic, Denmark, Egypt, Estonia, Finland, France, Germany, Greece, Greenland, India, Indonesia, Iran, Iraq, Ireland, Israel, Italy, Japan, Jordan, Kenya, Latvia, Libya, Lithuania, Malaysia, Mexico, Netherlands, New Zealand, Nigeria, Norway, Pakistan, Peru, Poland, Russia, Singapore, Slovenia, South Africa, Spain, Sweden, Taiwan, Tanzania, United Republic of Thailand, Tunisia, Turkey, Ukraine, United Kingdom and the United States.

The previous study focused only on countries in North America, Europe and Australia and was based on samples collected between 1973 and 2011. The latest study includes seven additional years of sample collection. 

Levine told Health Policy Watch that the data shows a decline of around 2.5% each year in mean sperm concentration since the year 2000, which is “a clear signal that something is wrong with men’s sperm count around the world, something that cannot be explained by genetics.”

Sperm count
Dr Hagai Levine

Sperm count is the total number of sperm a man produces. Sperm concentration is the number of sperm per millilitre of semen. 

These are not the only predictors of fertility. Another predictor is total motile sperm, which looks at what percentage of sperm are able to swim and move. Infertility is generally defined as a couple’s inability to get pregnant for one year despite regular intercourse. 

Sperm concentration and count are not only good markers of men’s ability to participate in conception, but have also been linked to men’s general health, including premature mortality and morbidity risks.

In other words, men with lower sperm counts have higher chances of becoming sick or dying at a younger age, Levine said.

He noted that the worldwide decline in sperm concentration and count is consistent with other adverse trends in men’s health, including increasing rates of testicular cancer and genital birth defects.

Primary suspect: mother’s exposure to environmental toxins in pregnancy

Heavy metals, toxic gasses, urban air pollution and unhealthy lifestyles may all lower sperm count; portrayed here, air pollution in Cairo, Egypt

While the study does not aim to prove the cause of the decline in sperm count and concentration, Levine said animal research points to a connection between environmental toxins and hormonal disruptions or imbalances, which in turn impede reproductive capacity. 

Growing evidence that plasticisers, pesticides, herbicides, heavy metals, toxic gasses, air pollution and poor lifestyle choices such as sedentary behaviour, poor diet and smoking all are tied to abnormal sperm count. 

“The primary suspect is a mother’s exposure to man-made chemicals during pregnancy,” Levine told Health Policy Watch. “We also know exposure in adult life and lifestyle choices such as smoking and poor nutritional habits can be associated with poor sperm count.”

He stressed, however, that the research is neither definitive nor does it establish which chemicals specifically may be causing the decline.

Dr Ryan Smith, associate professor of urology at the University of Virginia, confirmed Levine’s assessment. After reviewing the paper, he said that “the impact of reproductive toxins on male infertility deserves further investigation and there is cause for concern”. 

Environmental toxins a threat to reproductive health

Microplastics collected from the Rhode River, Maryland, whose tributeries feed into the Chesapeake Bay.

“Environmental toxin exposure represents a clear threat to our global reproductive and general health. Increased public awareness and advocacy that leads to more careful monitoring and regulation will be critical to protect our future global health and our environment,” Smith said. 

He added that while the authors acknowledge that sperm count is an imperfect assessment of fertility and point out that a higher sperm count does not necessarily imply a higher probability of conception, “the authors should be commended for this work and their prior investigations into the decline in male reproductive health.”

The 2017 study that focused primarily on developed countries was well received. However, there were some researchers who pushed back at the report, including a team from Harvard’s GenderSci Lab led by Sarah S. Richardson, which called the previous assessment “overblown” and noted that separate research contradicted the assumption that there was a causal link between declining sperm counts and declining fertility and between exposure to certain chemicals and lower sperm counts. 

Health Policy Watch reached out to Richardson and asked her to evaluate the updated study, but Richardson could not respond by press time.

Levine said that in his own country and in the US there are a growing number of theoretically healthy couples who struggle to conceive and require assistance. “This is not something that is supposed to be,” he said. “Our species is supposed to be able to reproduce.”

New study includes meta-analysis of over 10,000 publications

To develop the analysis, Levine and team systematically reviewed all the relevant studies published until 2019 that they could find according to a strict protocol. Then, using sophisticated modelling they adjusted the data from different places and studies to get one estimate about the global trend in sperm count and concentration.

“This requires enough data, and so we screened over 10,000 publications that gave data on sperm count,” Levine explained. “We read the papers, and with a large team of researchers and according to a strict protocol, identified which studies met our criteria and then, from those studies, extracted the relevant data.”

While he said that relying on modelling was not foolproof nor a substitute for additional research of specific populations at specific points in time, Levine noted that modelling is a good way to evaluate long-term trends. 

“We are seeing the forest from the trees,” he said. “We aim to look at the overall picture.”

Urgent call for action to promote healthier environments

Healthier lifestyles and environments reduce exposure to environmental toxins.

“As clinicians, we can educate our patients and advocate for continued research and public health support,” Smith said. 

He said the topic should be given attention not only by clinicians and scientists but also from decision-makers and the general public.

“Men need to be aware that their health and lifestyle choices can impact their reproductive health and that lifestyle changes, such as increased exercise and a healthy diet can have positive impacts,” Smith concluded. 

Added Levine “We urgently call for global action to promote healthier environments for all species and reduce exposures and behaviors that threaten our reproductive health.”

Image Credits: Photo by Nadezhda Moryak, UN Photo/Kibae Park/Flickr, Avi Hayon Hadassa, Kim Eun Yeul / World Bank, Will Parson/Chesapeake Bay Program, WHO.

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