What Is a ‘Smellfie’ and How Can it Help with Pollution?

The human nose has a role to play in sniffing out inner-city pollution, according to a new report on the relationship between urban life and odours.

By creating “smelly maps” of London and Barcelona, the authors of the report have demonstrated that there is a direct correlation between the smells we are able to perceive on our daily commute, the words we use to describe photographs on social media and the amount of pollution in any given area.

Following your nose

The study, which was published online and discussed at the International Conference on Web and Social Media (ICWSM) 2017, was an international collaboration and focused on creating smell maps of two of Europe’s biggest and busiest metropolises.  

Volunteers were asked to conduct walks around the centres of each city and record their olfactory experiences – the words they used to describe the smells they detected were collated into an “urban smell dictionary”. The team then analysed millions of photographs on Flickr, Instagram and other social media channels, scouring them for matches with words from the dictionary. These smell-related images, dubbed “smellfies”, helped them to build up a picture of how certain regions of the city smell.

Armed with this information, the team created a smell map of the city and cross-referenced this against air monitoring data taken from stations and sites across both locations. The results showed that the smell maps were largely accurate in pinpointing the worst-affected areas in terms of air pollution.

“Some people might say you're using social media, it’s biased so you're just capturing most of the hipsters in East London,” explained Daniele Quercia, the Bells Lab computer scientist who authored the study. “To double check we collected air quality indicators for each street sector for London and we looked at the relationship between these indicators and the profile from the smelly maps.”

“We found that when there's a lot of nitrogen dioxide, then there are a lot of traffic emission-related words. So, more or less the methodology works - there is a relationship between air pollution and the smelly maps.”

Technology and olfactory working hand in hand

So these maps might help us understand pollution, but how can they improve our daily lifestyle? By allowing us to see at a glance which streets suffer from the highest levels of pollution and tailor our routines accordingly. Whether this means using a different route to get to work or planning out an exercise circuit free from fumes, the smell maps can reduce our exposure to poor air quality.

“If you go for a run next to a street full of traffic, it’s the worst possible thing you can do - when you run your blood pressure goes up and your ability to absorb air pollution is far higher than if you were walking,” Quercia continued.

“But you could have technologies that would design a run for you next to nature based smells, and maybe smells that are more energising than calming. If you want to rest a bit you can do that on a public bench, where you have lavender which is a more calming smell.”

Meanwhile, Kate McLean from the Royal College of Art, who co-authored the study, said that the nasal maps can help support technological monitoring of pollution in an urban environment.

“The technical equipment is always going to be valuable for odour monitoring, for pollution control for large factories, but in terms of the moving, shifting smell-scape which most cities are, then the human nose can contribute just as much if we decide to contribute in the same we do to traffic reports,” explained McLean.

“We can all become smell-meisters, there's nothing specialist about it, any single one of us can do it. Just get out there - go sniff!”