Use the Despeckle command to remove single-pixel specks that are mostly white or black. This command analyzes the brightness of each pixel and compares it to the surrounding pixels to determine if it should be removed.
To remove single-pixel specks in an image:
Select the area that contains the specks. See Using the Selection Tools.
Choose Adjust > Add/Remove Noise > Despeckle. The selection is despeckled.
Removing Multiple-Pixel Black and White Specks
Removing Noise While Preserving Edge Details
Removing Noise While Preserving Texture Details