Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 _ decrease" (Expand Search)
"50 pp decrease" » "50 _ decrease" (Expand Search)
"50 a decrease" » "50 _ decrease" (Expand Search), "50 _ decreased" (Expand Search), "50 _ decreases" (Expand Search), "5 a decrease" (Expand Search), "50 i decrease" (Expand Search)
"5 c decrease" » "5 _ decrease" (Expand Search), "5 _ decreased" (Expand Search), "5 _ decreases" (Expand Search), "45 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 pp decrease\") OR (\"50 a decrease\"))) OR (\"5 c decrease\"))) OR (\"5 ppm decrease\"))~".
• Removing quotes may allow a broader search: (((((( 50 pp decrease ) OR ( 50 a decrease ))) OR ( 5 c decrease ))) OR ( 5 ppm decrease ))~.
• Adding a wildcard symbol may retrieve word variants: (((((("50 pp decrease") OR ("50 a decrease"))) OR ("5 c decrease"))) OR ("5 ppm decrease"))*.