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A robust sense of smell is a key component of a healthy and enjoyable life.

“Your sense of smell enriches your experience of the world around you. Different scents can change your mood, transport you back to a distant memory, and may even help you bond with loved ones,” stresses the National Institute of Health in the United States.

“Your ability to smell also plays a key role in your health. If your ability to smell declines, it can affect your diet and nutrition, physical well-being, and everyday safety,” it warns.

Yet our sense of smell is on the wane as a result of an insidious threat to our health: airborne pollution.

Scientists are finding that anosmia, a loss of the sense of smell, is becoming a widespread malady among people of all ages who are exposed to chronic levels of PM2.5 pollutants, which are tiny particles that can enter our bodies with every breath we take.

The reason, they posit, is that the olfactory bulbs, which are located above our nasal cavities and are packed with nerve endings for our sense of smell, are affected by exposure to air pollution. The tiny airborne particles might trigger inflammation either in the bulbs themselves or in the brain, impeding our sense of smell over time.

“Our data show there’s a 1.6 to 1.7-fold increased [risk of] developing anosmia with sustained particulate pollution,” Murugappan Ramanathan Jr, a rhinologist at the Johns Hopkins School of Medicine in Baltimore, told Tim Smedley, the author of Clearing The Air: the Beginning and the End of Air Pollution.

Ramanathan is an author of a recent study of nearly 2,700 patients at Johns Hopkins Hospital, a fifth of whom had anosmia despite many of them not having been smokers (who are at higher risk of developing the condition). When the rhinologist and his colleagues looked into the backgrounds of the affected patients they found that these patients invariably lived in neighborhoods with significantly higher levels of air pollution.

“Even small increases in ambient PM2.5 exposure may be associated with anosmia,” Ramanathan and his colleagues say. This is concerning as a loss of the sense of smell “has profound implications for patient safety, well-being, and quality of life, and it is a predictor of patient frailty and mortality.”

This finding reinforces other studies with similar findings, Smedley notes.

One of these studies, conducted in the town of Brescia in northern Italy, found that the more than 200 teenagers and young adults between the ages of 15 and 25 who were examined had suffered olfactory impairments as a result of exposure to nitrogen dioxide, a common component in traffic fumes.

“We observed a significant negative association between NO2 and olfactory threshold score; a 14% decrement (approximately 2 score points) for each 10 unit increase in NO2,” the scientists write.

Nor is it only our sense of smell, of course, that is adversely affected by airborne pollutants. They have been linked to a whole host of chronic conditions from cardiovascular disease to dementia. Alarmingly, even relatively low levels of air pollution can be deadly.

Yet the loss of a sense of smell is a condition that is often overlooked albeit it can lead to numerous adverse health outcomes, including dementia. A sense of smell is intricately linked to memory as well and life is a lot less fun without it.

“People don’t remember what that pastry looked like that they ate in France, but they remember what the shop smelled like,” Ramanathan says.

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