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 we decrease" (Expand Search), "50 mg decrease" (Expand Search), "10 ng decrease" (Expand Search), "5 ng decrease" (Expand Search)
"5 nm decrease" » "5 nn decrease" (Expand Search), "5 _ decrease" (Expand Search), "5 we decrease" (Expand Search), "5 mm decrease" (Expand Search), "5 cm decrease" (Expand Search)
"50 a decrease" » "50 _ decrease" (Expand Search), "50 _ decreased" (Expand Search), "50 _ decreases" (Expand Search), "50 μ decrease" (Expand Search), "50 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 (((((\"50 a decrease\") OR (\"50 ng decrease\"))) OR (\"5 nm decrease\"))))~".
• Removing quotes may allow a broader search: (( 5 ppm decrease ) OR ((((( 50 a decrease ) OR ( 50 ng decrease ))) OR ( 5 nm decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (("5 ppm decrease") OR ((((("50 a decrease") OR ("50 ng decrease"))) OR ("5 nm decrease"))))*.