Men who are regularly exposed to dirty air may develop fertility problems due to a pollutant that can reduce sperm production.

In a study presented at an annual meeting of the Endocrine Society 2019 in New Orleans, Louisiana, scientists from Sao Paulo University in Brazil examined the impact of air pollution on sperm production.

Human fertility is fast becoming a serious problem around the world, with an estimated 15 percent of the global population suffering from infertility, according to the World Health Organization. About half of all cases recorded so far involved men.

Researchers believe an air pollutant, known as particulate matter (PM) 2.5, may be the culprit. These fine particles have been found to affect the endocrine system, which plays a crucial role in producing sperm in animals and humans.

Fine Particles In The Air

USP researcher Dr. Elaine Maria Frade Costa led the team in looking at the impact of PM2.5 on fertility.

Particulate matter is formed when solid particles in the air get mixed up with tiny liquid particles. Those that are no bigger than 2.5 micrometers are the ones called PM2.5.

Previous studies have shown how exposure to PM2.5 can lead to health conditions such as simple eye, nose, throat and lung irritations. It can also cause more serious illnesses such as lung infection and worsening of asthma and heart disease.

The fine particles are now being linked to infertility because of how they can disrupt the normal function of the endocrine system.

Dr. Costa and her colleagues selected some laboratory mice and then grouped them into four. One group was exposed to PM2.5 samples before and after they were born, as well as the day they were weaned from their mothers until they became adults. The second group was exposed to the pollutant when they were still going through gestation.

The third group was exposed only after they were born, from weaning until adulthood. The fourth group was exposed to filtered air during their gestation, as well as the day they were weaned until they became adults.

Deterioration In The Mice's Testes

The researchers then examined the mice's testes in order to check sperm production. They also used DNA tests to analyze the subjects' gene expression, or how the proteins in animals receive instructions through the genes in DNA.

Dr. Costa and her team found that all mice that were exposed to PM2.5 had deteriorated tubes in their testes, which are known to produce sperm. Mice that belonged to the first group were in a far worse state, especially when compared to those in the fourth that were not exposed to the pollutant.

PM2.5 affected the animals' gene levels that were related to testicular cell function. Those that were exposed to the pollutant after their birth suffered the most from deterioration in their testicular function.

The researchers said the changes in the mice are epigenetic. This means that they were not caused by any changes in the animals' DNA sequence.

Dr. Costa believes their study is the first to show how exposure to dirty air in highly populated cities can severely affect sperm production through epigenetics. This is particularly true for those that were exposed to PM2.5 after they were born.

"These findings provide more evidence that governments need to implement public policies to control air pollution in big cities," Dr. Costa noted.