Tiny particles, eh? that sounds rather mysterious, do tell:
"...we can only speculate over the relationship between the pollution levels and the cardiac arrests."
And nowhere in the study are coincident events such as experimental vaccines addressed - which are clearly occurring at the same time. It is well known in medicine that often a risk can be magnified and multiplied by the presence of a second or third risk. Until that is addressed, this study is not of much value.