European citizens measure air pollution with their smartphones

iSPEX-EU distributes small devices that can be attached to smartphones [2] to turn them into optical sensors. These add-ons are "spectropolarimeters" that, in combination with the phone's camera, sensors, computing and communications capabilities can be used to measure tiny particles in our atmosphere. These particles can be of natural origin, such as sea salt or tiny ash particles from forest fires or volcanic eruptions, through human-made soot particles produced by traffic and industry, and contribute to air pollution and its impacts on our environment and health in an as-yet poorly understood way. For example, they form one of the largest uncertainties in our current estimates of climate change.

The application of iSPEX is two-fold: 1) It enables crowd-sourced measurements of tiny atmospheric particles, also known as aerosols, at locations and times that are not covered by current air pollution monitoring efforts. 2) It makes atmospheric science accessible to everyone, by active participation in scientific measurements.

The iSPEX app instructs participants to scan the cloud-free sky while the phone's built-in camera takes pictures through the add-on. Each picture taken through the iSPEX add-on contains information on both the spectrum and the linear polarization of the sunlight. The measurements taken using the phone camera can provide unique information about the properties of the particles in the air, including the amount of particles, their size distribution and the type of particles. This type of measurement is crucial in assessing the impacts of atmospheric aerosols on environment and health.

With the advent of smartphones and the development of iSPEX, citizens can now contribute to these crucial measurements and together form a flexible network that can deliver measurements from cities across Europe, even where no specialised equipment is available, and at any daylight hour -- under cloud-free conditions. The active involvement of citizens in an important and real scientific experiment, pioneering a new form of citizen science where participants carry out complex, simultaneous mass-measurements, is the most important aspect of this project.

The citizen science approach was successfully trialled at national level in the Netherlands in 2013. Organised by the Dutch iSPEX-project, the initiative involved three national measurement days with thousands of citizen scientists throughout the country performing measurements of their cloud-free sky. This led to the assembling of atmospheric particle maps of the Netherlands that achieved higher detail than those available from satellite monitoring and filled blind spots of established ground-based atmospheric measurement networks [3]. This success resulted in iSPEX-EU, the European expansion of this citizen science approach in contribution to an improved understanding of air pollution and its various impacts.

For the setup of this campaign the iSPEX-EU team, led by Leiden Observatory [4], works closely with local partners [5] in all cities, including research organisations and environmental protection agencies. These partners are taking up the co-ordination of the citizen science campaign in their city. They play a crucial role in recruiting and motivating citizens to actively participate by performing numerous iSPEX measurements throughout the campaign period, which is the key to a successful iSPEX-EU campaign.

Notes

[1] The iSPEX project is a collaboration between Leiden University (LU), the Dutch Research School for Astronomy (NOVA), SRON Netherlands Institute for Space research, KNMI Royal Netherlands Meteorological Institute, and RIVM National Institute for Public Health and the Environment, all in The Netherlands. The iSPEX add-ons were produced by Bright Led Solutions and the app was programmed by DDQ, both in the Netherlands.

For the initial Dutch campaign of the iSPEX project in 2013, Longfonds, CNG Net, KIJK and Avantes helped recruiting participants. The iSPEX project was first made possible with the support the €100'000 award from the Academische Jaarprijs 2012.

[2] The iSPEX add-on currently fits on the iPhones 4, 4S, 5 and 5S.

[3] The scientific results of the initial campaign of the Dutch iSPEX project in 2013 are published in this article:

"Mapping atmospheric aerosols with a citizen science network of smartphone spectropolarimeters"

[4] Leiden Observatory is part of Leiden University, one of Europe's foremost research universities and lead institute of the iSPEX project. Its astronomical instrumentation researchers have developed the iSPEX smartphone add-on. Leiden Observatory is the world's oldest university observatory and is one of the world's leading astronomical institutes with over 25 faculty and over 70 PdD students.

Leiden Observatory plays an active role in astronomical outreach activities at local, national and international levels. It hosts the Universe Awareness (UNAWE) programme, which educates and inspires young children. With iSPEX add-on and app for the smartphone, Leiden Observatory introduces a new measurement technique for tiny atmospheric particles that make significant part of air pollution, but more important, also a modern measurement philosophy: citizen science.

[5] The iSPEX-EU campaign is organised by the iSPEX and LIGHT2015 projects in close co-orporation with local partners in nine European cities. These partners include the National Observatory of Athens (NOA/IAASARS), ICFO- the Institute of Photonic Sciences, the Centre for Research in Environmental Epidemiology (CREAL), the Institute of Physics Belgrade (IPB), MINT Impuls, Freie Universität Berlin (FUB), the Danish Environmental Protection Agency, The Institute of Physics (IOP), the Science & Technology Facilities Council at the Rutherford Appleton Laboratory (STFC-RAL), the University of Manchester, the Italian Aerosol Society (IAS), Cittadini per l'Aria, the Institute of Atmospheric Sciences and Climate at the National Research Council of Italy (ISAC-CNR).