Infertility affects roughly one in six people worldwide, and with more than half of the global population now residing in urban areas, researchers are increasingly investigating whether urban living—specifically exposure to traffic noise and air pollution—may contribute to infertility. A recent study conducted in Denmark has provided new insights into this potential link, using nationwide data to examine how long-term exposure to these environmental factors affects reproductive health.
The study found that prolonged exposure to air pollution and traffic noise may be associated with a higher risk of infertility, with different impacts observed between men and women.
The effects of pollution and noise on the body
The detrimental effects of traffic pollution on both the environment and human health are well-documented, with connections to various diseases, including cancer and heart disease. Polluted air contains chemicals that can travel through the bloodstream to the reproductive system, potentially disrupting hormones and damaging eggs and sperm.
While the health effects of traffic noise are less clearly defined, some research indicates that noise can elevate stress hormone levels, which in turn may negatively impact fertility.
Study design
The Danish study leveraged nationwide data to analyze potential links between environmental exposures and infertility. Denmark maintains comprehensive databases that track information about each resident’s health, occupation, education, and family life, making it possible to perform detailed “data linkage” studies.
Researchers focused on individuals likely to be attempting to conceive and, therefore, at risk of receiving an infertility diagnosis. The study identified more than two million men and women of reproductive age, narrowing the sample to those who:
Were aged 30-45,
Lived together or were married,
Had fewer than two children, and
Lived in Denmark between January 1, 2000, and December 31, 2017.
Exclusions included individuals diagnosed with infertility before age 30, those living alone or in registered same-sex partnerships, and those with incomplete address information.
The final sample included 377,850 women and 526,056 men. Rather than surveying participants, the study cross-referenced detailed residential data with infertility diagnoses recorded in the Danish National Patient Register. The researchers also estimated the level of exposure to road traffic noise (in decibels) and air pollution, specifically particulate matter (PM2.5), at each individual’s residence.
Key findings
Infertility was diagnosed in 16,172 men and 22,672 women within the study group. The findings revealed that men exposed to PM2.5 levels 1.6 times higher than World Health Organization recommendations had a 24% greater risk of infertility. For women over the age of 35, exposure to traffic noise at levels 10.2 decibels above average (between 55 and 60 decibels) was associated with a 14% increase in infertility risk.
These risks remained consistent regardless of whether individuals lived in urban or rural areas, and after adjusting for education and income levels.
Implications of the study
The research highlights the immediate and long-term effects of environmental exposure, emphasizing that these factors may impact male and female fertility differently. For men, who produce sperm continuously, environmental changes can rapidly influence sperm count and quality. In contrast, women are born with a finite number of eggs, and their bodies employ mechanisms to protect these eggs from environmental damage over time.
However, the study’s five-year exposure period may not be long enough to fully capture the potential impact on women’s reproductive health. Longer-term studies could provide further insights into how air pollution and noise exposure affect female fertility.
The role of data linkage in fertility research
While data linkage enables large-scale studies like this one, there are inherent limitations. The research relied on assumptions about whether couples were actively trying to conceive and calculated noise and pollution exposure based on residential addresses, without accounting for time spent outside the home.
More comprehensive studies, which include surveys on sleep disturbances, stress, and lifestyle factors, as well as direct biological measurements, could offer a clearer understanding of how environmental exposures affect fertility.
Despite its limitations, this large-scale Danish study is a crucial step toward exploring the connection between air pollution, traffic noise, and infertility. Further research involving more precise exposure measurements will be essential to deepen our understanding of these complex relationships.
