‘We were playing with plastic optics that you could put in front of your eye. At some point we put it in front of a smartphone and it turned out it worked surprisingly well,’ says Dr Frans Snik, an astronomer at the University of Leiden in the Netherlands, whose iSPEX team developed a small spectrographic sensor to use on smartphones.
Spectrographs separate light into a frequency spectrum and record the signal. Light frequencies can tell scientists about the chemical composition of distant planets or, as with Snik’s project, identity the small particles – aerosols – present in the Earth’s atmosphere.
‘We developed an attachment for smartphones and an app. Then we recruited 5,000 participants,’ says Snik. ‘These dust particles have an impact on health, and the smallest particles have the biggest impact. Some particles, like soot, have a big impact while others like sea salt have no impact at all,’ he adds.
Aerosols can aggravate asthma symptoms and the particles also penetrate tissues, causing heart disease. ‘Life expectancy is decreased by at least nine months in the Netherlands due to aerosols. In China it is much worse,’ says Snik.
On average iSPEX’s 10,000 measurements from citizen scientists matched professional results from satellites and ground stations. ‘A satellite only comes over once a day, so it complements the satellite. We can fill in the blind spots,’ adds Snik.
The research also has implications for climate change. ‘The role of CO2 in climate change is understood quite well, but this is not the case for aerosols,’ says Snik. Dust particles scatter light back into space and generate clouds, processes that cool the planet. Black particles like soot absorb heat and trap it in the atmosphere. ‘There are a lot of unknowns, and to really understand climate change we have to measure these particles,’ adds Snik.
Extra data for the project will come this year as iSPEX is released in several European countries.