Barcelona's beaches might be best known for their bars and nightlife, but they also have a reputation for something more pernicious - unpleasant smells from rubbish, sewage, and factory emissions.
Now, an app-based project aims to snuff out those scents using the collective power of crowdsourcing.
The D-Noses project, which was officially piloted in 2018, lets local residents report their complaints through the free OdourCollect app.
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Sponsored by the European Commission, with a budget of 3 million euros, the project is designed as a tool to "empower citizens who are suffering from regular odour nuisance".
Odour pollution is the second most common cause of environmental complaints in Europe after noise, according to the website for the project.
The three-year pilot involves eight European countries.
In Spain, the app is being tested in Poblenou, a newly gentrified district in the northeast of Barcelona.
The area is a hotspot for offensive odours smells, due to the factories left over from its time as the biggest industrial zone in Catalonia and its vicinity to the industrial facilities of the neighbouring Sant Adria de Besos district.
"I have the misfortune of living 400 metres from one of the industrial plants that emits the odours," said Enric Navarro, a long-standing resident.
The 65-year old said the smells have been around for decades but have become more of a nuisance in the last four years or so, because of rising temperatures.
When the app collects enough information for the area, residents can use the map to put pressure on politicians to combat the smells, said Rosa Arias, a Spanish chemical engineer and the app's designer.
There has been limited research into the impact of odour pollution on cities and their residents.
Some studies have looked into the physical and psychological impact of unpleasant odours, with medical experts saying frequent exposure can cause a number of ailments including headaches, stress and respiratory problems.
"If a person experiences sleep deprivation as a result of environmental odours, (that) produces psychological effects in terms of (lowered) alertness, ability to deal with stimuli and hypertension," said Dennis Shusterman, a medical professor at the University of California, San Francisco.
Mar Viana Rodriguez, a senior researcher at the Barcelona-based Institute of Environmental Assessment and Water Research agreed that crowdsourcing apps are more useful for raising awareness than gathering high-quality data.
"But for odour pollution, there is not much data around, so a little bit of subjective data is better than nothing," she said.
