Fall in fertility rates may be linked to fossil fuel pollution, finds study


Danish scientists urge more research into impact of exposure to toxic chemical pollutants from fossil fuels

A decrease in fertility appears to have started at the beginning of industrialisation.

 Photograph: acilo/Getty


Sofia Quaglia
Wed 15 Dec 2021 

Decreasing fertility rates may be linked to pollution caused by fossil fuel burning, a review of scientific studies has found.

Over the past 50 years childbirth has steadily decreased. The study focused on Denmark, but the trend is also seen in other industrialised nations. One in 10 Danish children are born with assisted reproduction and more than 20% of men never have children, according to the researchers. This decrease seems to have started at the beginning of industrialisation. Experts have warnedthe trend could lead to an unbalanced demographic with too few younger people to support the older generations.

“We have to realise that we know all too little about infertility in the population so the next step forward would really be to find out why so many young couples do not have children,” said Niels Erik Skakkebæk, a professor at the University of Copenhagen, Denmark, and lead author of the study published in the journal Nature Reviews Endocrinology.

Falling birthrates are often chalked up to cultural and socioeconomic factors, such as the rise of access to planned parenthood, contraception and abortion, and the changing role of women in society, as education and participation in the workforce has delayed childbearing, for example. But data shows that pregnancies were already declining before the rollout of the contraceptive pill, overall abortion numbers are decreasing over the years, and unintended pregnancy loss has been increasing by 1-2% since 1990.

Instead, a growing body of research has shown growing rates of human infertility due to biological reasons including 74,000 yearly cases of testicular cancer, insufficient sperm and egg quality, premature puberty in young women, and an increase in the number of congenital malformations in male infant genitalia .


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Such a trend cannot be explained genetically because evolution takes place over longer periods of time and more generations, so Skakkebæk and his colleagues are urging the scientific community to look at the impact of environmental exposure to toxic chemical pollutants from fossil fuels, which have been around since the Industrial Revolution.

“What has struck me in this study was the finding that so much of modern life originates from fossil fuels,” said Skakkebæk. “We don’t think about it that way. When we buy a pair of shoes made of chemicals originally produced from fossil fuels.”

Fossil fuels are ubiquitous and they have been found in people’s blood, urine, semen, placenta and breast milk, as well as their fatty tissue. Many fossil fuel pollutants are endocrine disruptors, meaning they interfere with the body’s hormonal systems and have a negative effect on reproductive health.

“We know from numerous experimental animal studies that plastics, chemicals, and so forth can cause problems in animal reproduction,” said Skakkebæk. “We cannot do such exposure studies in humans, that would not be ethical, but we know enough from animal studies to be concerned.”

Studies show that, for example, rats and mice undergo genetic changes affecting their reproductive abilities when exposed to endocrine disruption by toxic chemicals. Research on humans is still sparse, but some studies have shown that endocrine-disrupting chemicals might be substantially linked to male reproductive diseases.

Animal data has shown female and male reproductivity is affected differently with the same levels of exposure, and that early gestation is a particularly sensitive time for these chemicals to have a disruptive effect.

However, these links will have to be systematically examined and assessed for causality. Changes in lifestyle such as less physical activity, smoking, growing rates of obesity, alcohol consumption and changes in diet also must be kept into account.