Could Pollution Be Causing Infertility in Men?
By Jill Horn
Infertility is a common problem faced by couples who are trying to conceive. While infertility is often associated with women, it is important to note that 40% of all infertility is attributed to male factors. In fact, over the past 50 years, there has been a decline in semen quality, with reduced sperm count, smaller ejaculate volume, decreased sperm motility, and changes in sperm morphology. A significant body of research links a range of lifestyle factors and environmental factors to decreased sperm quality. These factors include behavioral factors like smoking or drinking, as well as various chronic diseases and exposure to pollutants and toxic chemicals including air pollution, bisphenol A, and glyphosate. This article discusses the most recent scientific literature on the effects of pollution on male fertility parameters, particularly semen quality.
“With regards to fertility, research has found that air pollution was associated with increased DNA fragmentation in sperm, as well as decreased sperm motility and a change to normal sperm morphology.”
Air pollution is known to have adverse health effects on human health, including cardiovascular and respiratory diseases, lung cancer, and problems with neurodevelopment. With regards to fertility, research has shown that air pollution is associated with increased DNA fragmentation in sperm, as well as decreased sperm motility and a change to normal sperm morphology. These findings are consistent across several studies, as shown in a recent review. Possible mechanisms of how air pollution may negatively affect reproductive health include reactive metabolites of airborne particles (referred to as PM) that pollute the air, and are larger (PM10) or smaller (PM2.5) in diameter, respectively. As shown in several studies, when PM10 reacts with sperm DNA during the later stage of spermatogenesis, DNA fragmentation could occur. DNA fragmentation has then been observed to subsequently affect sperm morphology and motility. The smaller pollutants, PM2.5 have also been associated with DNA fragmentation in sperm in animal studies.
Other air pollutants that have been found to negatively affect sperm quality include heavy metals such as lead, however lead concentration in the air is much lower than it has been in previous years, so this concern may not be as timely. Ozone further has also been associated with decreased sperm quality, which could be due to its oxidative power, resulting in the production of oxidative stress and disruptions in DNA integrity. Importantly, most of the studies investigating the effects of air pollution on sperm quality were observed at pollution levels that were within the legal limit (with only very few investigating higher levels of air pollution). Yet the majority of them still found that air pollution is significantly associated with decreases in sperm quality, regarding the parameters discussed.
“Overall, the study results showed a weak association of high urinary BPA levels and low sperm motility. In the case of long-term BPA exposure at high levels, the researchers observed a statistically significant decrease in sperm viability, as well as DNA damage.”
Bisphenol A (BPA), which is found in cans and plastics, has been shown to have endocrine-disrupting effects. However, despite the evidence of such a negative health effect being confirmed by a large body of animal research, clinical research on the association with sperm quality has only shown a weak connection between urine BPA levels and decreases in male fertility. A recent, high-quality meta-analysis looked at 9 out of 90 studies on this topic that met the strict inclusion criteria for a quantitative analysis. Overall, the results showed a weak association of high urinary BPA levels and low sperm motility. In the case of long-term BPA exposure at high levels, the researchers observed a statistically significant decrease in sperm viability, as well as DNA damage. However, even though statistically significant, the associations found in this study were weak. It has been speculated that the primary action of BPA on central estrogen receptors may result in slight alterations in the production of sperm, a process known as spermatogenesis. Spermatogenesis is dependent on the concentration of male sex hormones, the production of which is reduced by stimulation of estrogen receptors and subsequent expression and systemic circulation of female sex hormones, such as FSH and LH. Though there is extensive literature on the mechanisms of BPA on the estrogen system and endocrine disruption in animal studies, it will be important to perform more quality studies on the clinical implications of BPA exposure and its effects on infertility mechanisms.
“A few recent high-quality studies have looked at the association of glyphosate and sperm quality, all of which showed negative effects of the herbicide on fertility in males.”
Glyphosate is the active ingredient of the notorious chemical “Roundup”, which is a pesticide and herbicide that has been used intensely in large amounts until 2014 in the United States as part of GMO production of food. In studies conducted in the last twenty years, glyphosate exposure has been associated with several different cancers, neurodegenerative disease, and gut dysbiosis with chronic inflammation. A few recent high-quality studies have looked at the association of glyphosate and sperm quality, all of which showed negative effects of the herbicide on fertility in males. One study found that the motility of sperm was reduced one hour after glyphosate treatment, when compared to the collection time. Another study confirmed this finding, and further found a decrease of sperm viability and mitochondrial function. Exposure to glyphosate has also been associated with a decrease in testosterone levels in the blood in several animal studies, and given the importance of testosterone in spermatogenesis, this could be a critical contributor to the effects of glyphosate on sperm quality. Both the production of sperm and its viability has therefore been shown to be negatively affected by glyphosate exposure, even though studies on glyphosate’s effect on male fertility are still small in number and fairly new.
In conclusion, it is important to consider several environmental factors affecting sperm quality and count when making decisions to increase fertility in males. From a public health perspective, education on these associations is essential to enable individuals to make informed decisions when it comes to the purchasing of foods, and the containers in which the foods are packaged. Unfortunately, it is much harder for people living in big cities, closer to polluting industries, to avoid the exposure to heavily polluted air.
Even though environmental factors have received recent attention as a potential cause of male infertility, other largely unknow mechanisms may be at play, including alterations in the gut microbiome, dietary factors and an increase in chronic stress. Even though it should be obvious to everybody that the current trends are a threat to many industrialized societies, the topic has not received sufficient urgent attention.
Jill Horn is a recent UCLA graduate with a degree in Neuroscience. She is deeply interested in the interconnectedness of body, mind, and spirit takes an integrative approach to health and well-being. She aspires to the public about a research-based lifestyle and mindset that promote health. Jill also deeply resonates with the One Health concept, which emphasizes the interdependence of the health of people and the health of our planet, given the climate crisis we are facing.