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Our sense of smell is one of our richest and wide-ranging windows into the world around us, playing a vital role in what we taste, our social interactions and even helping us detect potential dangers. But a threat in the air we breathe may be eroding our olfactory powers.
For many people, a bout of Covid-19 gave a first taste (or rather a lack of it) of what it is like to lose their sense of smell. Known as “anosmia”, loss of smell can have a substantial effect on our overall wellbeing and quality of life. But while a sudden respiratory infection might lead to a temporary loss of this important sense, your sense of smell may well have been gradually eroding away for years due to something else – air pollution.
Exposure to PM2.5 – the collective name for small airborne pollution particles, largely from the combustion of fuels in vehicles, power stations and our homes – has previously been linked with “olfactory dysfunction”, but typically only in occupational or industrial settings. But new research is now starting to reveal the true scale – and the potential damage caused by – the pollution we breathe in every day. And their findings have relevance for us all.
On the underside of our brains, just above our nasal cavities, lies the olfactory bulb. This sensitive bit of tissue bristles with nerve endings and is essential for the enormously varied picture of the world we get from our sense of smell. It’s also our first line of defence against viruses and pollutants entering the brain. But, with repeated exposure, these defences slowly get worn down – or breached.
“Our data show there’s a 1.6 to 1.7-fold increased [risk of] developing anosmia with sustained particulate pollution,” says Murugappan Ramanathan Jr, a rhinologist at the Johns Hopkins School of Medicine, Baltimore. He has become one of the few experts in this field after he started to wonder if there was a link between the large numbers of patients he was seeing with anosmia and the environmental conditions where they lived.