[anigbrowl]

Unless they have a completely sterile, sealed container that is open only at certain altitudes to collect material in a filter, they will have nothing to stand on.

That is exactly their claim (with detailed method), and they did a control as well, in which the container was not opened, to validate their anti-contamination protocols. I'm all for critiques of the paper, but I do think you might have gone to the bother of looking at it first.