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