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)
"_ e decrease" » "_ _ decrease" (Expand Search), "_ _ decreased" (Expand Search), "_ _ decreases" (Expand Search)
"_ a decrease" » "_ _ decrease" (Expand Search), "_ _ decreased" (Expand Search), "_ _ decreases" (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: "((\"5 ppm decrease\") OR (((\"50 ng decrease\") OR (((\"_ e decrease\") OR (\"_ a decrease\"))))))~".
• Removing quotes may allow a broader search: (( 5 ppm decrease ) OR ((( 50 ng decrease ) OR ((( _ e decrease ) OR ( _ a decrease ))))))~.
• Adding a wildcard symbol may retrieve word variants: (("5 ppm decrease") OR ((("50 ng decrease") OR ((("_ e decrease") OR ("_ a decrease"))))))*.