Heavier air pollution in the southern provinces of Noord-Brabant and Limburg appears to have worsened the impact of coronavirus, according to a study by British scientists.

Researchers at the University of Birmingham found there was ‘compelling evidence of a positive relationship between air pollution … and Covid-19 cases, hospital admissions and deaths’ after analysing data from 355 Dutch municipalities.

Fine dust particles known as PM2.5, caused by pollution from vehicles reacting with ammonia emissions from cattle farming, were identified as the main culprit. An increase of 1 microgram per cubic metre can result in a 13 to 21% increase in the number of Covid-19 deaths, the researchers found.

The concentration of PM2.5 particles in Noord-Brabant and Limburg is around 12 micrograms per m3, compared to 8 micrograms in northern provinces.

The researchers said there was evidence of air pollution affecting Covid-19 infection and death rates even once other factors such as the ‘superspreading effect’ of Carnaval at the end of February were taken into account.

Noord-Brabant has the most recorded Covid-19 deaths in the Netherlands, with 25% of the total and 19.3% of all infections, according to the public health agency RIVM. Limburg has the highest infection and death rate per head, with 439 cases and 67 deaths for every 100,000 inhabitants.