Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 _ decrease" (Expand Search), "5 nn decrease" (Expand Search), "5 pa decreased" (Expand Search)
"50 ng decrease" » "50 nn decrease" (Expand Search), "50 _ decrease" (Expand Search), "50 gy decreased" (Expand Search), "50 mg decrease" (Expand Search), "10 ng decrease" (Expand Search), "5 ng decrease" (Expand Search)
"50 we decrease" » "50 _ decrease" (Expand Search), "50 nn decrease" (Expand Search), "50 mean decrease" (Expand Search)
"5 a decrease" » "5 _ decrease" (Expand Search), "5 _ decreased" (Expand Search), "5 _ decreases" (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 a decrease\"))) OR (((\"50 ng decrease\") OR (\"50 we decrease\"))))~".
• Removing quotes may allow a broader search: (((( 5 ppm decrease ) OR ( 5 a decrease ))) OR ((( 50 ng decrease ) OR ( 50 we decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (((("5 ppm decrease") OR ("5 a decrease"))) OR ((("50 ng decrease") OR ("50 we decrease"))))*.