Although this is a small sample, it suggests that man-made dust particles predominate over naturally occurring ones.

ECONOMIST: Orbital debris

However, if a man's PSA looks high, doctors will often recommend removal of a tissue sample for further tests.

BBC: NEWS | Health | Prostate cancer danger predicted

"The man in Canada has a diagnosed medical condition and we need the permission of those treating him to take a DNA sample - to do this we are seeking the assistance of the Canadian authorities, " said Det Supt Langley.

BBC: News | UK | Murder hunt heads for Canada