The human race could be in danger as sperm counts continue to fall, an epidemiologist said, according to Axios.

Mt. Sinai Medical School epidemiologist Shanna Swan co-authored an analysis back in 2017 that found total sperm count in the Western world had decreased by 59% between 1973 and 2011.

Swan has now authored a new book called “Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, And Imperiling the Future of the Human Race,” which draws on earlier conclusions of her sperm count study.

“If you look at the curve on sperm count and project it forward–which is always risky–it reaches zero in 2045,” Swan said, noting that the average man would have no viable sperm, according to Axios. “That’s a little concerning, to say the least.”

The dire findings could leave the world struggling to procreate.

Between 1964 and 2018, the global fertility rate has fallen from 5.06 to 2.04. To make matters more concerning, many countries across the world, including the U.S., have fertility rates below replacement levels, according to a study from Yale Global. The affected nations account for about half of the world’s population, according to the study.

“In some parts of the world, the average twenty-something woman today is less fertile than her grandmother was at 35,” Swan wrote, according to the New York Post (NYP).

Still, there are other factors that contribute to falling fertility rates aside from sperm count, like birth control, personal choice and the rising costs of raising a child. These other factors, however, do not close the gap for people who say they want children but then don’t have them, according to Swan.

Swan said increasing rates of miscarriages and other signs point to the fact that there are biological factors at play, according to Axios.

Testosterone levels have also dropped in young adults and teens, according to a report from the Urology Times Journal. To combat the decreasing levels, prescriptions for testosterone therapies more than doubled between 2010 and 2013, according to Forbes.

Swan says that “90 percent of men can have their sperm counts drop to zero while they’re on [testosterone replacement therapies],” according to the NYP.

“If women want to have a baby, they are often told, ‘Clean up your act,'” Swan writes, according to the NYP. “But it’s probably more important for men to do so.” (RELATED: The United States Had Fewer Babies This Year Than In The Past 30 Years: Report)

She notes that there is an increase in boys with gender abnormalities and earlier signs of puberty among girls, according to Axios. These findings, Swan reportedly said, shows there are endocrine-disrupting chemicals in everyday items that could be affecting fertility.

“Chemicals in our environment and unhealthy lifestyle practices in our modern world are disrupting our hormonal balances, causing various degrees of reproductive havoc,” Swan wrote, according to Axios.

These chemicals include phthalates and bisphenol-A, which are found in ordinary items like plastics, pesticides, cosmetics and even some receipts, according to Axios. Phthalates, which can make plastics flexible and allow beauty products to absorb scents have been linked to a decrease in the production of hormones like testosterone, according to a 2015 study from the National Library of Medicine.

Other factors like smoking tobacco and marijuana and obesity could also affect fertility rates among both men and women, according to Axios. Some scientists have criticized studies that link endocrine-disrupting chemicals to fertility problems, according to Science Media Centre. But as Swan notes, there are other factors at hand.

“The current state of reproductive affairs can’t continue much longer without threatening human survival,” Swan writes, according to Axios.

The Daily Caller has reached out to Swan but did not receive a response at the time of publication.