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

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 (((\"_ we decrease\") OR (\"_ e decrease\"))))) OR (\"50 a decrease\"))~".
• Removing quotes may allow a broader search: (((( 50 ppm decrease ) OR ((( _ we decrease ) OR ( _ e decrease ))))) OR ( 50 a decrease ))~.
• Adding a wildcard symbol may retrieve word variants: (((("50 ppm decrease") OR ((("_ we decrease") OR ("_ e decrease"))))) OR ("50 a decrease"))*.