Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search), "50 pa decreased" (Expand Search), "50 026 decrease" (Expand Search), "5 ppm decrease" (Expand Search)
"5 nn decrease" » "5 _ decrease" (Expand Search), "5 mean decrease" (Expand Search), "5 gy decreased" (Expand Search), "5 non decrease" (Expand Search), "59 nn decrease" (Expand Search), "5 nm decrease" (Expand Search)
"10 a decrease" » "10 _ decrease" (Expand Search), "10 _ decreased" (Expand Search), "10 _ decreases" (Expand Search), "10 μ decrease" (Expand Search), "19 a 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 ("10 a decrease"))) OR ("5 nn decrease"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"50 ppm decrease\") OR (\"10 a decrease\"))) OR (\"5 nn decrease\"))".
• Removing quotes may allow a broader search: (((( 50 ppm decrease ) OR ( 10 a decrease ))) OR ( 5 nn decrease )).
• Adding a wildcard symbol may retrieve word variants: (((("50 ppm decrease") OR ("10 a decrease"))) OR ("5 nn decrease"))*.