Monthly Archives: April 2018

This week’s blog post features four citizen initiatives that are taking action to reduce air pollution – in Belgium Kosovo, Bulgaria and Great Britain. Better air quality information enables us to fight for better air in where we live: Get inspired by these stories – and share with us what you are up to!

Help – I can’t breathe: Parents take action on air pollution around schools in Belgium 

On March 14, 2018 a report in Belgian national television informed the public about the dangerous levels of air pollution around schools. This documentary showed the results of a large scale study on air quality and used two schools as examples. 

The next day, the first protest actions happened at school streets. Filter Cafe Filtre was born.

The invitation is simple and powerful: “Close off the street where your school is to traffic every Friday morning before school starts. Have a cup of coffee together and let the children play in the car-free street. Invite local politicians to come and join you for a coffee.”

The initiative is growing: on April 20, 60 parent groups across Belgium took part. The mission is to raise awareness and change mindsets of parents and children, and to convey the urgency to policymakers.

Get data – Drive change: Youth-led air quality campaign in Kosovo

Kosovo is one of the most polluted regions in Europe. The project “Science for Change Kosovo” is a youth-led environmental movement, investigating air pollution in Kosovo and mobilizing people to take actions. The project was one of the partners in the Making Sense project. 

It works with local youth around environmental policy issues, how to collect data about air quality, and how to use this data to advocate for change. Their approach was documented in the Making Sense toolkit for citizen science initiatives – have a look!

Bulgaria: New collaboration between citizen activists and government to reduce air pollution

Air pollution is much worse in Eastern Europe. In Sofia, air pollution norms were exceeded on 70 days between October 2017 and March 2018. Government and activists are working hand-in-hand to improve the situation. The citizens’ group “AirBG.info” was founded in April 2017 and has rapidly expanded their network in the first year of their activities.

This initiative maps air quality with low-budget sensors, built by citizens. The open data from this citizen science project are collected at the luftdaten platform. Currently, 600 air quality sensors are operating in Bulgaria, nearly 300 of them in the capital. AirBG.info has been very successful in establishing a close collaboration with the Bulgarian government and with the environmental executive agency. This collaboration led to the decision that Bulgaria will integrate all existing air quality monitoring systems. The Environment Minister said: “We are trying to integrate all [air quality monitoring] systems: those of non-government organizations, of which there is a myriad but are less precise, and those of the Executive Agency for Environment, which are fewer but are more precise, in order to get a clear picture about the quality of air we breathe.”

Parents campaign for clean air in London

Mums for Lungs is a London based group of parents who are seriously concerned about the dangerous impact air pollution is having on children’s health. They have set up air quality campaigns in various contexts.

In March 2018, they campaigned for the extension of the Ultra Low Emission Zone in London. Within this zone, most vehicles will have to meet emissions standards or pay a daily charge. In London, around half of emissions of particulate matter (PM) come from transport. The Ultra Low Emission Zone will reduce the most harmful emissions generated by road traffic. Mums for Lungs, together with a number of local partners, has been calling to extend this zone so that more inhabitants of London can benefit from cleaner air.

In the ongoing local elections, Mums for Lungs has proposed a number of pledges to local parties – raising awareness about air quality. The pledges are also a way to hold policy makers accountable – after the elections.

Have you taken a sky photo with the hackAIR app? Are you curious how the app estimates the air quality, based on your photo? Do you want to know more about the science behind this feature?

Even with your bare eyes, you can see that the cloudless sky is not always the same blue. The color of the sky changes with the time of the year and time of the day, but it also changes when particles are present in the atmosphere. In very polluted cities the sky often does not appear very blue, while it can be deep blue when it has rained recently and it is very windy and it can also be deep blue in remote locations.

The feature

Once you have taken a sky photo with your hackAIR mobile app, the image is uploaded to the hackAIR server where we analyse the colour of the sky and estimate the current air quality. When the calculations have completed, the picture is shown on the hackAIR map with an estimate of the air quality.

Behind the scenes

• Step 1: A computer algorithm detects the portion of blue sky in the photo. As the lower parts of photos often show buildings or landscape, this part is discarded by the hackAIR system. From the recognised sky, the upper third is used for further analysis.
  
• Step 2: Using the average colour detected, hackAIR then calculates the ratio between red and green light bands (R/G ratio).
  
• Step 3: We then look up this ratio in a table that lists the corresponding air quality value in relation to the location and time of day at which the photo was taken.
  
• Step 4: The estimated rating of the air quality, together with the photo, is shown on the hackAIR platform.
  

The scientific background

The main idea is that the ratio of red and green band of the light (R/G) depends on the amount and type of aerosols in the atmosphere (R/G increases with increasing AOD).

Aerosols, which are tiny particles suspended in the atmosphere, are emitted by natural (e.g., volcanoes, desert dust, forest fires, sea salt) as well as human activities (e.g., biomass burning, combustion of fossil fuel, industrial activities). Aerosols affect the levels of surface solar radiation by scattering and absorbing the light coming from the sun reducing the visibility in the atmosphere.

By measuring the radiation that reaches the ground at specific wavelengths we can assess the degree to which aerosols prevent the transmission of light by absorption or scattering. This is expressed as aerosol optical depth (AOD). AOD is unitless and usually reported at a wavelength of 550 nm. A value of 0.01 corresponds to an extremely clean atmosphere (air quality = very good), and a value of 0.4 would correspond to a very hazy condition (air quality = bad).

To control for varying atmospheric conditions, we produced a set of look-up tables using a  radiative transfer model (RTM). RTMs calculate the intensity of the light transferred within the atmosphere under different user-input scenarios that include information about the position of sun (solar zenith angle) relative to Earth and various atmospheric parameters (e.g., clouds, aerosols, water vapour, ozone, surface albedo, etc.).

We then compare the measured light intensities with those expected conditions to retrieve an estimate of the current aerosol optical depth.

A similar approach has been used to examine the atmospheric effects of volcanic eruptions in historical paintings¹. Instead of the painter’s eyes, hackAIR uses mobile images and publicly available images from Flickr and webcams. We performed a number of tests to check the effect of the camera type on R/G ratios – as previous studies indicate, this is not a major issue.

Future potential

This analysis of sky photos makes it possible to monitor air quality in urban and rural environments with easily available tools: digital and mobile cameras. This estimation of air quality supports citizens in collecting more valuable information about the quality of the air: e.g. in their neighbourhood, around schools, in busy streets.

hackAIR uses the sky photo analysis not only for images provided by users through the mobile app. This image analysis is also used by the hackAIR tech team to analyse a very large number of photos from Flickr and webcams.

¹ Zerefos, C. S., Gerogiannis, V. T., Balis, D., Zerefos, S. C., and Kazantzidis, A.: Atmospheric effects of volcanic eruptions as seen by famous artists and depicted in their paintings, Atmos. Chem. Phys., 7, 4027-4042, https://doi.org/10.5194/acp-7-4027-2007, 2007.