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Environmental contaminants linked to male infertility 'crisis'

The World Health Organisation (WHO) recently reported that around one in six couples globally are affected by infertility, which for many years, tended to be blamed on women – especially in African countries.

But it’s now known that male factor infertility contributes about 50% of total cases. And men worldwide, including in Africa, are experiencing a worrying trend of decreased sperm count and quality.

In The Conversation, Daniel Marcu, Liana Maree and Shannen Keyser write that there are multiple causes of male infertility. However, it is clear that environmental contaminants play a large part in declining fertility worldwide.

Concern is rising about substances such as per- and polyfluoroalkyl substances, nanomaterials and endocrine disrupting compounds, all found everywhere in modern, everyday lives.

Most are present in personal-care products like soaps, shampoos and hair sprays, as well as food wrap, water bottles, while other contaminants that are increasing in prevalence and show signs of entering our food chain are pesticides and medication.

Recent research in our laboratory found high traces of these in the near-shore marine environment of False Bay, as well as in rivers and air in agricultural areas of the Western Cape.

Our study suggests these “contaminants of emerging concern” might be contributing to the male infertility crisis in surprising ways.

In our study, we described the effects of contaminants like pharmaceuticals and pesticides on male reproduction. We propose these can affect men’s reproductive fitness either by interacting with their brain, or by targeting the reproductive organs such as the testes directly.

The public needs to be aware of the effects of contaminants in the environment on reproductive health. Our research could assist in finding a possible cause of unexplained infertility. It may also lead to preventive treatments.

Impact on male fertility

Our research suggests that across animals, including humans, most contaminants of emerging concern interfere with hormone function, targeting the hypothalamic-pituitary-gonadal axis.

This is the part of the endocrine system controlling reproductive functions – the ability to produce sperm in men and eggs in women. When the axis is disrupted, reproductive hormones aren’t released as normal, influencing the rate and quality of sperm production.

We report that contaminants of emerging concern can also act directly on testicles by disrupting the blood-testis barrier – which protects developing sperm from harmful substances that may be present in the bloodstream.

Once contaminants cross the barrier, these compounds move into the compartments of the testis where sperm are produced and can interact with the cells involved in sperm production. These cells also play important roles in regulating the production of hormones like testosterone.

Contaminants can either directly damage these cells or interfere with their function.

The contaminants can also directly damage the DNA in the sperm cells, leading to genetic changes that can affect the quality of the sperm and their ability to fertilise an egg. This can result in infertility or compromise the health of the resulting children.

The legacy of fathers

The way environmental factors affect fertility and cause effects over multiple generations may involve the epigenome of sperm. The mechanisms are far from being fully understood. But these epigenetic marks can affect how the genes within sperm work without changing the underlying DNA sequence.

Yet, these changes can be passed down from a parent to their child. This can happen in two ways: when the germ cells that make sperm are exposed to contaminants of emerging concern, and when the sperm itself is affected.

In both cases, epigenetic changes can be passed on to future generations who have not been directly exposed to the contaminants.

One category of compounds whose impact on epigenetic marks that has been extensively studied is non-steroidal anti-inflammatory drugs like paracetamol and ibuprofen, used for managing pain and inflammation.

But our research suggests they also have adverse effects on reproductive health in children. For example, exposure during pregnancy can lead to reduction in testosterone levels and changes in genes involved in neurodevelopment in boys.

Further studies have also suggested that when adults were exposed to insecticides, their sperm carried marks in genes involved in neurological functions, including susceptibility to autism spectrum disorders, schizophrenia and bipolar disorder.

These effects may be particularly significant when exposure to contaminants of emerging concern is cumulative. And that’s often the case. These contaminants can accumulate in the environment and enter our bodies in various ways, through diet, drinking water, and exposure at work or in recreation.

But there might be solutions to limit their exposure.

Taking charge

The numerous pathways in which contaminants of emerging concern contaminate soil, water and air are apparent. But it’s not easy to detect and eradicate these. So how to reduce our exposure to them?

Current control measures include regulatory frameworks to limit the use of certain pesticides or pharmaceuticals, and develop safer alternatives. There are personal protective measures to take, like using air and water filters, and reducing the use of plastic products that may contain contaminants of concern.

Public health campaigns could raise awareness about the risks of exposure, or the development of new technologies that can detect and quantify these contaminants in the environment more accurately.

Individuals, especially men, should be made aware of the rise in male infertility and how improving their own health and avoiding exposure to contaminants can increase their chances of fatherhood.

Daniel Marcu is aPhD researcher in Reproduction and Genetics, University of East Anglia; Dr Liana Maree is a senior lecturer at the University of the Western Cape; Shannen Keyser is a lecturer at the University of the Western Cape.

Study details

Contaminants of Emerging Concern (CECs) and Male Reproductive Health: Challenging the Future with a Double-Edged Sword

Daniel Marcu, Shannen Keyser, Leslie Petrik, Samuel Fuhrimann and Liana Maree.

Published in MDPI on 30 March 2023

Abstract

Approximately 9% of couples are infertile, with half of these cases relating to male factors. While many cases of male infertility are associated with genetic and lifestyle factors, approximately 30% of cases are still idiopathic. Contaminants of emerging concern (CECs) denote substances identified in the environment for the first time or detected at low concentrations during water quality analysis. Since CEC production and use have increased in recent decades, CECs are now ubiquitous in surface and groundwater. CECs are increasingly observed in human tissues, and parallel reports indicate that semen quality is continuously declining, supporting the notion that CECs may play a role in infertility. This narrative review focuses on several CECs (including pesticides and pharmaceuticals) detected in the nearshore marine environment of False Bay, Cape Town, and deliberates their potential effects on male fertility and the offspring of exposed parents, as well as the use of spermatozoa in toxicological studies. Collective findings report that chronic in vivo exposure to pesticides, including atrazine, simazine, and chlorpyrifos, is likely to be detrimental to the reproduction of many organisms, as well as to sperm performance in vitro. Similarly, exposure to pharmaceuticals such as diclofenac and naproxen impairs sperm motility both in vivo and in vitro. These contaminants are also likely to play a key role in health and disease in offspring sired by parents exposed to CECs. On the other side of the double-edged sword, we propose that due to its sensitivity to environmental conditions, spermatozoa could be used as a bioindicator in eco- and repro-toxicology studies.

 

MDPI article – Contaminants of Emerging Concern (CECs) and Male Reproductive Health: Challenging the Future with a Double-Edged Sword (Open access)

 

The Conversation article – Male fertility crisis: what environmental contaminants have got to do with it (Creative Commons Licence)

 

See more from MedicalBrief archives:

 

Infertility affects one in six worldwide, large-scale WHO analysis finds

 

The stigma of male infertility in SA

 

Stringent EPA limits for ‘forever chemicals’ in drinking water

 

US states crack down on toxic ‘forever chemicals’

 

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