Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 _ decrease" (Expand Search)
"5 nn decrease" » "5 _ decrease" (Expand Search), "k nn decrease" (Expand Search), "_ nn decrease" (Expand Search)
"5 we decrease" » "5 _ decrease" (Expand Search), "_ we decrease" (Expand Search)
"50 a decrease" » "50 _ decrease" (Expand Search), "50 _ decreased" (Expand Search), "50 _ decreases" (Expand Search), "5 a decrease" (Expand Search), "50 i decrease" (Expand Search)

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"5 ppm decrease\") OR (((((\"5 nn decrease\") OR (\"5 we decrease\"))) OR (\"50 a decrease\"))))~".
• Removing quotes may allow a broader search: (( 5 ppm decrease ) OR ((((( 5 nn decrease ) OR ( 5 we decrease ))) OR ( 50 a decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (("5 ppm decrease") OR ((((("5 nn decrease") OR ("5 we decrease"))) OR ("50 a decrease"))))*.