Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search)
"5 wt decrease" » "5 _ decrease" (Expand Search), "_ wt decrease" (Expand Search), "5 ht decrease" (Expand Search), "2 wt decrease" (Expand Search)
"50 a decrease" » "50 _ decrease" (Expand Search), "50 _ decreased" (Expand Search), "50 _ decreases" (Expand Search), "50 i 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: "((((\"50 a decrease\") OR (\"5 a decrease\"))) OR (((\"50 ppm decrease\") OR (\"5 wt decrease\"))))~".
• Removing quotes may allow a broader search: (((( 50 a decrease ) OR ( 5 a decrease ))) OR ((( 50 ppm decrease ) OR ( 5 wt decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (((("50 a decrease") OR ("5 a decrease"))) OR ((("50 ppm decrease") OR ("5 wt decrease"))))*.