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)
"a point decrease" » "_ point decrease" (Expand Search)
"a fold decrease" » "_ fold decrease" (Expand Search), "5 fold decrease" (Expand Search), "a food decrease" (Expand Search)

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("5 ppm decrease") OR ((((("a fold decrease") OR ("a point decrease"))) OR ("5 nn decrease"))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"5 ppm decrease\") OR (((((\"a fold decrease\") OR (\"a point decrease\"))) OR (\"5 nn decrease\"))))*".
• Removing quotes may allow a broader search: (( 5 ppm decrease ) OR ((((( a fold decrease ) OR ( a point decrease ))) OR ( 5 nn decrease ))))*.