Are these white spots in my cats brushed fur flea eggs or dander?
It is not possible to say from your picture so to be sure you need to bring your cat to a vet for a diagnosis and treatment.
It might be lice too,A quick way to see if it is is to hold your hand at one point on the back of your cat for a couple of minutes,This will atract the lice so you will be able to see it crawling in the fur of your cat.
You will still have to visit your vet to be sure,Cat lice if this is what it is can not live on people but if you have other cats they needs to be treated at the same time to get rid of the problem.
This answer is only one of several things it might be so i might be wrong on this one.
If you take the cat to the vet,Your vet will look at this in a microscope and be able to tell you what it is and recoment a treatment if it is lice or if it is dander.