Why Polluted Air Contributes To Infertility In men

Inability to father a child could be a big problem
in AfricaMany people think that air pollution affects only the lung. But the effects of pollution is far more than this as experts have warned that it could be a reason more men may become infertile, reports Sade Oguntola.

Infertility is a big problem that is on the rise worldwide and experts are now linking its incidence to exposure to fumes and soot from power plants and vehicle exhaust in our towns and cities. Many people tend to think that air pollution only affects the lungs, but a Health Canada-led study of mice confirmed that pollution most especially from the highways and out of steel mills, affects a man’s fertility, triggering sperm mutations that are passed to the next generation. According to the study published in the U.S. Proceeding of the National Academy of Sciences, the polluted air near Hamilton Harbour was said to significantly increase sperm mutations in the mice that breathed the dirty air for 10 weeks. The study was a follow-up to a 2004 study led by McMaster University biologists that showed male mice that breathed Hamilton’s air passed on twice as many mutations to their offspring as mice that inhaled air stripped of the fine particles in air pollution, known as particulates, produced by vehicles and fossil-fuel burning industrial plants.

Carole Yauk, of the department’s environmental and occupational toxicology division, working with several Canadian scientists and a colleague associated with U.S. National Centre for Toxicological Research, looked at mice that spent 10 weeks housed in a shed two kilometres from two steel mills and one kilometre from a major highway on Hamilton Harbour. The researchers compared the rodents’ mutation rates with another group of mice living in a chamber equipped with a HEPA filter that removed 99.97 per cent of the particulates from the air. Their study revealed a 1.6 fold (or 60 per cent) increase in sperm mutation frequency’ in mice breathing air near the mills and highway for 10 weeks, compared to mice breathing filtered air. They reported that many of the mutations in the sperm DNA persisted even after the mice were no longer exposed to the pollution, indicating the changes were in germ-line cells that produce sperm.

While mice are not humans, the study adds to mounting evidence that fine particulate pollution is not only affecting people’s lungs, but may also affect their unborn children and grandchildren. According to the study, “Increased germ-line DNA mutation frequency may cause population-level changes in genetic composition and disease incidence in the descendants of exposed individuals. The level of particulates that triggered the sperm mutations in mice in Hamilton was said to be similar to levels in several polluted areas across Canada and was common to many of the world’s largest cities. “Combustion of fossil fuels results in the production of complex mixtures of chemical that are released into the environment and potentially affect millions of people globally,” the scientists said.

Previous studies had established a contributory link between air pollution and heart disease and they pin-pointed specific mechanisms on how this happens. They showed that air pollution could be particularly damaging when coupled with a high-fat diet, according to new research published in the December 2005 issue of JAMA. Another group of experts, in a study presented at the American Thoracic Society International confrence demonstrated that when people with specific diseases such as diabetes, heart attack, chronic obstructive pulmonary disease and inflammatory diseases such as rheumatoid arthritis, are exposed to particulate air pollution, or soot, for one or more years, their risk of death is increased. A 2008 study published in American Journal of Epidemiology suggests that kids who live in neighbourhoods with heavy traffic pollution have lower Intelligent Quotients (IQs) and score worse on other tests of intelligence and memory than children who breathe cleaner air.

Another study subtitled in the 2003 issue of the Journal of Allergy and Clinical Immunology says that diesel exhaust particles alone may be enough to induce acute asthma attacks. Meanwhile, Dr. Adekola Adebayo an urologist formerly at the Ring Road State Hospital, Ibadan, said air pollutants are generally toxic to tissues of the body, including the brain, kidney and liver. According to him, “There are a lot of pollutants around now and some of them are toxic. That is why environmentalists talk more about its implications on health. Just as it can affect organs of the body such as the heart, the testes is not exempted because it is an organ which produces rapidly dividing cells. In the course of development, if they come in contact with agents that are toxic, this can change their genetic makeup, what is referred to as genetic mutation.”

Many air pollutants can cause health problems according to Dr. Godson Ana, a lecturer and consultant at the Department of Environmental Health, Faculty of Public Health at the University of Ibadan. Some of these according to the environmental health expert include heavy metals like lead that have neuro-toxic effects on the cells of the body and organic compounds such as polycyclic aromatic hydrocarbons. These chemical substances form part of the aerosol from the exhaust of power plants and vehicle exhaust in our towns and cities. He declared that polycyclic aromatic hydrocarbons are products of incomplete combustion of fuels and wood. Also of importance are dioxins, which are products of complete combustion from electrical industry such as transformers as well as pesticides.

Dr. Ana said the toxic effects of these pollutants on the nerves and its effects on the reproductive organs had been demonstrated in animals. While some toxic substances target specific organs in the body, some also elicit specific responses in the different body functions. “Dioxin and pesticides were linked with brain toxicity just as poly aromatic hydrocarbons were linked to cancers of the colon and skin in animals. For ethical reasons, these were extrapolated to what could happen in humans. So in a way animal studies may help us guess how it may affect the sperm as well," he concluded.