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