[k2enemy]

It depends on how they calculated percent change, but looking at the journal article, you are correct. From the abstract...

> Compared with recirculation, PM2.5 and PM10 were higher by up to 589% (Blantyre) and 1020% (São Paulo), during windows-open and higher by up to 385% (São Paulo) and 390% (São Paulo) during fan-on, respectively.

The headline should read 400% more to reflect the 80% reduction. This is a massive failure of the university press office and I think your comment should be at the top.