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)
"50 mg decrease" » "50 _ decrease" (Expand Search), "50 we decrease" (Expand Search), "50 mean 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: "((((\"50 ppm decrease\") OR (\"5 nn decrease\"))) OR (((\"50 a decrease\") OR (\"50 mg decrease\"))))~".
• Removing quotes may allow a broader search: (((( 50 ppm decrease ) OR ( 5 nn decrease ))) OR ((( 50 a decrease ) OR ( 50 mg decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (((("50 ppm decrease") OR ("5 nn decrease"))) OR ((("50 a decrease") OR ("50 mg decrease"))))*.