Major European Cities See Pollution Halved

Levels of air pollution in many European capitals have fallen by half compared to last year, new research has revealed. The drop in concentrations of contaminants such as carbon dioxide (CO2) and nitrogen dioxide (NO2) is being attributed to the lockdown measures implemented by countries in Europe and beyond, which have restricted industrial activity and limited transportation emissions.

The findings were uncovered by the Dutch TROPOMI instrument, attached to the Copernicus Sentinel-5P satellite, which is capable of delivering high spatial resolution images. This allows researchers to analyse the concentrations of pollutants above cities and across larger planes simultaneously, producing a comprehensive overview of the pollution situation.

Over 50% reductions in some cities

As a means of preventing the spread of the virus, many governments across the globe have put in place so-called quarantine controls, which limit the movement of residents. This has meant everyone who can work from home is encouraged to do so, immediately removing a significant chunk of the world’s cars from its roads. Industrial and commercial activity has also declined, which means emissions from places of work are falling, too.

While pollution reductions were first picked up by the Sentinel-5P over China, a similar phenomenon has also been observed in European metropoles, as well. Paris, for example, has enjoyed a 54% drop in levels of NO2 compared to this time last year, while Rome, Milan and Madrid also saw similar slumps in NO2 concentrations that amounted to nearly 50% in each city.

A powerful new technology

While urban air quality monitoring networks have improved significantly in recent years, they are still not omnipresent in cities across the globe. That’s why the data supplied by the TROPOMI instrument is so useful, since it is capable of quantifying a range of different pollutants over a prolonged period of time. By taking readings for longer, scientists can minimise the effects of variables like weather patterns and wind speeds, although they say that a 15% margin of error should still be considered.

“The Dutch TROPOMI satellite instrument measures the concentrations of pollutants such as NO2, CO, CH4, SO2 and HCHO worldwide on a daily basis,” say the Dutch scientists responsible for manning TROPOMI. “This makes it possible to register increases and decreases for different areas and periods. TROPOMI is unique because of its high spatial resolution, with which the larger sources and cities can be studied individually. This instrument does not measure ammonia (NH3).”

A welcome silver lining

The news that NO2 is in decline is especially positive, given that the gas can interact with other particles in the air and create more damaging contaminants, like ozone and particulate matter (PM). Scientists have developed revolutionary monitoring solutions for PM, but it’s still believed to be one of the biggest killers on the planet, so any fall in its concentration levels is hugely welcome.

The findings are a rare snippet of optimism at a time of great sadness and uncertainty, as hundreds of thousands of people have already been lost to the disease and countless more are struggling to stay afloat financially. At least the skies will be a little clearer and the air a little cleaner when the crisis passes and lockdown measures are finally lifted.