Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 _ decrease" (Expand Search)
"50 ng decrease" » "50 _ decrease" (Expand Search), "10 ng decrease" (Expand Search), "50 μg decrease" (Expand Search)
"5 ng decrease" » "5 _ decrease" (Expand Search), "5 g decrease" (Expand Search), "5 μg decrease" (Expand Search)
"5 mm decrease" » "5 _ decrease" (Expand Search), "2 mm decrease" (Expand Search), "_ mm 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: (("5 ppm decrease") OR ((("50 ng decrease") OR ((("5 ng decrease") OR ("5 mm decrease"))))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"5 ppm decrease\") OR (((\"50 ng decrease\") OR (((\"5 ng decrease\") OR (\"5 mm decrease\"))))))*".
• Removing quotes may allow a broader search: (( 5 ppm decrease ) OR ((( 50 ng decrease ) OR ((( 5 ng decrease ) OR ( 5 mm decrease ))))))*.