In "Photoshop CS Book" by Scott Kelby :
1. Open the file
2. Convert image to to Lab color thru Image>Mode>Lab Color
3. Goto Channels & select channel "a"
4. From menu, go under Filter menu, under Blue, choose Gaussian Blue
5. In Gaussian Blur dialog box, increase radius (amount of blur) until the dots starts to disappear
6. Now select channel "b" & repeat step 5
7. Now go under Image menu, Image>Mode> RGB to return to RGB mode
8. The noise should be less pronounced