Perhaps just noisy, not dusty?
If you look at the black areas on the mural behind the Budda, you'll see the noise more clearly perhaps.
Using a popular noise reduction program with the default settings, I reduced the noise considerably. With more time, you could tinker with the settings to get a better result.
If you're interested in seeing the result, send me a message along with your email. I'll fire it off to you.
Edit: Here, I'll include it. I had to reduce the quality to fit under the 200 kb limit.
Any better? The difference is more pronounced when examining under an electronic loupe at 300%. Anyway, it is there for your consideration.