It can be man-made, but it is also a naturally occurring substance that is produced by cosmic ray action and by the decay 
(It; can be; man-made) (it; is also; a naturally occurring substance that is produced by cosmic ray action and by the decay) (a naturally occurring substance; is produced; by cosmic ray action and by the decay)
It it a naturally occurring substance
can be is also is produced
man-made
a naturally occurring substance that is produced by cosmic ray action and by the decay
by cosmic ray action and by the decay