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)
"50 mg decrease" » "50 _ decrease" (Expand Search), "50 μg 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.

• Performing a fuzzy search may retrieve terms with similar spellings: (("50 a decrease") OR ((((("5 ppm decrease") OR ("5 nn decrease"))) OR ("50 mg decrease"))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"50 a decrease\") OR (((((\"5 ppm decrease\") OR (\"5 nn decrease\"))) OR (\"50 mg decrease\"))))*".
• Removing quotes may allow a broader search: (( 50 a decrease ) OR ((((( 5 ppm decrease ) OR ( 5 nn decrease ))) OR ( 50 mg decrease ))))*.