How does your neighbourhood smell? That's not the set-up for a feeble joke; a group of people are genuinely interested. Perhaps your picturesque village has a light floral bouquet. Maybe you live near farmland where there's a whiff of manure if the wind changes direction. If, like me, you live in London, researchers have already plotted our "urban smellscape" onto a map based on data gleaned from exploratory "smell walks", combined with information mined from Flickr, Instagram and Twitter.
According to the map, my part of the world is characterised by strong smells of emissions (I'm guessing exhaust fumes) and food (probably kebab shops). While that sounds about right, I can't say I've ever paid much attention to the odour of my local area. But having seen the map, I resolve to conduct my own sensory exploration at lunchtime.
The research paper, "Smelly Maps: The Digital Life of Urban Smellscapes", was put together by a team including Daniele Quercia (formerly of Yahoo Labs) and Kate McLean (Royal College of Art). While their work aims to celebrate "the complex smells of our cities", it focuses on what they believe is not only a neglected human sense, but also a neglected aspect of urban design.
While New York City is said to have been designed to allow odours to be carried away on the prevailing westerly winds, people living near the noxious steelworks of Port Talbot might not consider themselves so lucky. Indeed, last summer saw a number of British towns plagued by bad smells, with citizens of Wallingford complaining of "grated parmesan and dried vomit", Truro of "the stench of burning animal innards" and Brackley, Northamptonshire, of "sickly rotting meat".
This is nothing, of course, in comparison to the Great Stink of 1858, when the stench from the River Thames was enough to make the government of the day ponder leaving the Palace of Westminster and moving to somewhere more fragrant, namely St Albans. Today, however, as I embark on my own smell walk, London doesn't seem to smell of much at all. As I walk past Raw Gym Fitness I detect nothing. A branch of Halifax has no characteristic pong. There's the odd waft of something I can't quite put my finger on, and the alleyways obviously smell of urine (because they always do). But aside from some "high notes" of solvent from the dry cleaner, garlic from the Chinese takeaway and new leather from the shoe shop, the strongest smells tend to come from the people I walk past; extravagantly applied perfume, or summer armpit.
Perhaps my perception of Walthamstow as relatively odourless is down to the fact that I've got used to the pollution. I can certainly imagine a time-traveller from the early 19th century choking in distress on Lea Bridge Road while pressing a nosegay to their face. "We do become desensitised to common odours in our everyday lives," says McLean, "simply because they're no longer perceived as being a threat, or they're very familiar." But, she adds, some smells can surpass habituation. "The smell of lobster bait (rotten skate) is something the fishermen of Newport, Rhode Island, say they'll never get used to. They still retch as they load it into the lobster pots before lowering them into the ocean."
The maps were generated using a list of 285 terms (cedar, pine, farts, fish, etc) that participants in McLean's smell walks employed to describe various odours. Those words were then used as search terms across social media in order to map smells to locations. And while that may not seem particularly scientific, the researchers found a strong correlation between "smell clusters" and official air quality indicators. If something honks sufficiently badly, we'll express our displeasure on social media, and thus we'll characterise that area as reeking of bleach, badgers or bananas. London and Barcelona have now been mapped; your town may be next.