Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 _ decrease" (Expand Search)
"50 nn decrease" » "50 _ decrease" (Expand Search)
"50 ng decrease" » "50 _ decrease" (Expand Search), "10 ng 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 nn decrease") OR ("5 ppm decrease"))) OR ("50 a decrease"))) OR ("50 ng decrease"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((((\"50 nn decrease\") OR (\"5 ppm decrease\"))) OR (\"50 a decrease\"))) OR (\"50 ng decrease\"))*".
• Removing quotes may allow a broader search: (((((( 50 nn decrease ) OR ( 5 ppm decrease ))) OR ( 50 a decrease ))) OR ( 50 ng decrease ))*.