The article did refer to published research about one aspect covered in the article, namely the impact of air pollution on performance of professional footballers in Germany.

The study was carried out by three economists at the ‘Institute of Labor Economics’ (IZA) in Bonn, Germany. 

The claim is based on the established fact that physical exercise increases breathing rates and volumes, and links this with knowledge that long-term exposure to air pollution can have detrimental impacts on health. The claim has then been extended to sport and refers to the collapse of a tennis player at the Australian Open and to a research study of professional German footballers. The study presented evidence supporting the claim that even moderate air pollution had a negative impact on professional footballer’s performance. Because the study was published in a peer-reviewed journal (Labour Economics) it means that the data and methods used should be reliable. However, although evidence-based, the study was relatively small, so analyses of data from other sports and from different countries would be needed before the claim could be extended to ‘sport’ in general and to other parts of the world.  

Although the impact of Australian bushfires was considered, the only data that was analyzed was from Germany. 

The study considered professional footballers from 18 teams across Germany, for over 300 games per year during a 12-year period. The air pollution data were hourly monitor readings for PM10 and ozone concentrations within ten kilometers around each stadium.