Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 a decrease" (Expand Search), "5 pa decreased" (Expand Search), "5 026 decrease" (Expand Search)
"5 nn decrease" » "5 a 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)
"50 c decrease" » "50 c decreased" (Expand Search), "50 a decrease" (Expand Search), "50 rc decreased" (Expand Search), "5 c decrease" (Expand Search), "50 μ decrease" (Expand Search), "20 c decrease" (Expand Search)

You may be able to get more results by adjusting your search query.

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