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" » "5 _ decrease" (Expand Search), "5 a decrease" (Expand Search), "5 pa decreased" (Expand Search)
"5 nn decrease" » "5 _ decrease" (Expand Search), "5 a decrease" (Expand Search), "5 mean decrease" (Expand Search), "5 n_ decrease" (Expand Search), "5 na decrease" (Expand Search), "5 n_ decreased" (Expand Search), "5 non decrease" (Expand Search), "59 nn decrease" (Expand Search), "5 nm decrease" (Expand Search)
"50 n decrease" » "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 _ decreased" (Expand Search), "50 ns decrease" (Expand Search), "50 ng decrease" (Expand Search), "50 μ decrease" (Expand Search)

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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 n decrease"))) OR ((("5 ppm decrease") OR ("5 nn decrease"))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"50 ppm decrease\") OR (\"50 n decrease\"))) OR (((\"5 ppm decrease\") OR (\"5 nn decrease\"))))".
• Removing quotes may allow a broader search: (((( 50 ppm decrease ) OR ( 50 n decrease ))) OR ((( 5 ppm decrease ) OR ( 5 nn decrease )))).
• Adding a wildcard symbol may retrieve word variants: (((("50 ppm decrease") OR ("50 n decrease"))) OR ((("5 ppm decrease") OR ("5 nn decrease"))))*.