Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 pa decreased" (Expand Search), "5 ppm 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 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 we decrease" (Expand Search), "50 mg decrease" (Expand Search), "10 ng decrease" (Expand Search), "5 ng decrease" (Expand Search)
"50 nn decrease" » "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 mean decrease" (Expand Search), "50 ns decrease" (Expand Search), "50 n decrease" (Expand Search), "59 nn 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 ((("50 μ decrease") OR ((("50 ng decrease") OR ("50 nn decrease"))))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"50 ppm decrease\") OR (((\"50 μ decrease\") OR (((\"50 ng decrease\") OR (\"50 nn decrease\"))))))*".
• Removing quotes may allow a broader search: (( 50 ppm decrease ) OR ((( 50 μ decrease ) OR ((( 50 ng decrease ) OR ( 50 nn decrease ))))))*.