The car is a white Toyota Camry 2012.
As you can see there are many tiny black dots on the roof. I can't remove them by scratching by hand or with a high water pressure cleaner.
What caused these dots? What can I do to remove them?
The cause can be one of many possibilities:
or worse paint overspray
The first two should come off - good cleaner / polish and lots of work, but the paint may mean that you need a re-spray at the worst - there may be a professional treatment that could do it. So go and see a good paintshop and see what they say.
My guess is tree sap that then takes in road dust which hardens over time. Just today I’ve tried iron spray and tar remover , no joy, used clean slate by chemical guys too. Gonna finish cleaning the rest of the car and set aside a day or two for this. Going forward I’d recommend getting a good wax or sealant or coating on the roof and keep on top of maintenance.
Her is a good news video explaining the source of the problem: https://www.wdbj7.com/content/news/Black-spots-on-your-car-could-be-from-a-nearby-fungus-in-your-mulch-509250841.html