Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 nn decrease" (Expand Search)
"5 ppm decrease" » "5 _ decrease" (Expand Search), "5 a decrease" (Expand Search), "5 nn decrease" (Expand Search)
"5 ng decrease" » "5 nn decrease" (Expand Search), "5 _ decrease" (Expand Search), "5 a decrease" (Expand Search), "5 n_ decrease" (Expand Search), "5 na decrease" (Expand Search), "5 ngy decreased" (Expand Search), "5 mg decrease" (Expand Search), "5 nm decrease" (Expand Search), "5 kg decrease" (Expand Search)
"5 g decrease" » "5 _ decrease" (Expand Search), "5 a decrease" (Expand Search), "5 gy decreased" (Expand Search), "5 mg 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 ng decrease") OR ("5 g decrease"))))) OR ("5 ppm decrease"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"50 ppm decrease\") OR (((\"5 ng decrease\") OR (\"5 g decrease\"))))) OR (\"5 ppm decrease\"))".
• Removing quotes may allow a broader search: (((( 50 ppm decrease ) OR ((( 5 ng decrease ) OR ( 5 g decrease ))))) OR ( 5 ppm decrease )).
• Adding a wildcard symbol may retrieve word variants: (((("50 ppm decrease") OR ((("5 ng decrease") OR ("5 g decrease"))))) OR ("5 ppm decrease"))*.