Welcome to Photrio.
That does look like lot of dust!
But then again, scanners reveal dust better than any other piece of equipment or technique I have ever worked with.
The dust won't have originated in the camera. It almost looks like the film was dried in a dust filled room.
A couple of suggestions:
- see if you can see the dust itself on the negatives, using a magnifier;
- scan a negative. Remove the negative from the scanner, dust it off with the blower brush only, re-insert the negative into the scanner turned 180 degrees around (but not turned over) and scan the negative again. Compare the two scans to see if the dust has moved;
- if your scanner and software offers dust removal options, try to use them to see if there is improvement
The first two suggestions will help you determine if the dust is in the scanner and not the film, as well as determining if the dust is embedded rather than on the surface of the film.
I would be careful with a microfiber cloth - personally I use a jet of air and a camel hair brush.
Your lab should be happy to discuss issues of dust with you.
Good luck.