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