Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search)
"5 ppm decrease" » "5 _ decrease" (Expand Search)
"5 wt decrease" » "5 _ decrease" (Expand Search), "_ wt decrease" (Expand Search), "5 ht decrease" (Expand Search), "2 wt decrease" (Expand Search)
"10 a decrease" » "10 _ decrease" (Expand Search), "10 _ decreased" (Expand Search), "10 _ decreases" (Expand Search), "19 a decrease" (Expand Search), "1 a decrease" (Expand Search)

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (((("50 ppm decrease") OR ("5 ppm decrease"))) OR ((("10 a decrease") OR ("5 wt decrease"))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"50 ppm decrease\") OR (\"5 ppm decrease\"))) OR (((\"10 a decrease\") OR (\"5 wt decrease\"))))*".
• Removing quotes may allow a broader search: (((( 50 ppm decrease ) OR ( 5 ppm decrease ))) OR ((( 10 a decrease ) OR ( 5 wt decrease ))))*.