Citizens in major European cities are being requested to get out on the streets to help scientists measure air pollution using their smartphones.

The iSPEX-project started on Tuesday and will last until Oct. 15. Participating cities include Athens, Barcelona, Belgrade, Berlin, Copenhagen, London, Manchester, Milan and Rome.

The International Year of Light, a worldwide celebration of light and light-based technologies, is also behind this project on air pollution awareness. It plans to raise awareness and let people become involved in the research process through a mobile phone application that can record the level of atmospheric aerosols in an area.

"The point of the project is to measure the concentration of very fine particles in the atmosphere and these can be from natural sources, things like forest fires or volcanic eruptions, through to manmade factors like burning diesel," said Toby Shannon, the UK national coordinator of the International Year of Light, according to The Guardian.

An iSPEX sensor is distributed to individuals who wish to participate. This device can be attached to smartphones, turning them into optical sensors. It works by combining the "spectropolarimeters" of the iSPEX sensor with a phone's camera sensor. As a result, it can measure and compute the amount of tiny particles found in the atmosphere.

Through this project, crowd-sourcing measurements can be made on a greater scale, as it has the capacity to reach areas that are currently not covered by air pollution monitoring. It also makes atmospheric science accessible to everyone, by active participation in scientific measurements, Science Daily reported.

The iSpex sensors can be requested by email from coordinators within participating cities. You can check out the official website of the project for details.