Air quality significantly improved in European metropolitan areas such as Milan and Madrid because of lockdown restrictions imposed to curb the spread of the coronavirus pandemic, European Union officials said Monday.

The improvements were particularly notable for the pollutant nitrogen dioxide (NO2) and fine particulate matter, which both can have a serious impact on people's health.

An EU report on air quality published Monday showed that among metropolitan areas with the largest NO2 concentrations, Barcelona's levels sank by 59% during the early spring compared to the year before. NO2 levels in Madrid dropped by 47%.

In Italy, NO2 pollution in Milan fell by 54% and in Rome by 39%. Levels in many other metropolitan areas across Europe, especially western Germany, Belgium and the Netherlands, also dropped by significant margins.

"Now we realize that this is, of course, temporary and that we should not be reaching air quality standards by locking down society," said Hans Bruyninckx, the executive director of the European Environmental Agency.

"But it indicates that if we can keep pushing quality standards and if we can keep innovating in those sectors, that indeed serious benefits to society, to human health are there," he added.

Lockdown measures in several EU member states during the first wave of the pandemic had a major impact on economic activity, dramatically reducing road and air transport plus shipping. That all affected the air quality in the regions.