Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search)
"_ w_ decrease" » "_ _ decrease" (Expand Search), "_ _ decreased" (Expand Search), "_ _ decreases" (Expand Search), "_ wt decrease" (Expand Search), "_ we decrease" (Expand Search), "_ w decrease" (Expand Search)
"5 e decrease" » "5 _ decrease" (Expand Search), "5 _ decreased" (Expand Search), "5 _ decreases" (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)

Try widening your search to All Fields.

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 e decrease") OR ("_ w_ decrease"))))) OR ("50 a decrease"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"50 ppm decrease\") OR (((\"5 e decrease\") OR (\"_ w_ decrease\"))))) OR (\"50 a decrease\"))".
• Removing quotes may allow a broader search: (((( 50 ppm decrease ) OR ((( 5 e decrease ) OR ( _ w_ decrease ))))) OR ( 50 a decrease )).
• Adding a wildcard symbol may retrieve word variants: (((("50 ppm decrease") OR ((("5 e decrease") OR ("_ w_ decrease"))))) OR ("50 a decrease"))*.