Here's an interesting new patent application from Canon uncovered by Canon News, it details a new anti-static coating for lens elements. Canon seems to think there is a potential dust issue on the rear element of RF lenses and their close proximity to the image sensor.
The solution? Create an anti-static coating for the rear element of RF lenses so less dust adheres to the lens that could potentially end up on the image sensor during shooting.
From Japan Patent Application 2019-008147 (Google translated)
When distance becomes short, the influence concerned may become for example, less minor [ even if garbage has adhered to the lens in the case of an interchangeable lens, if the distance from an imaging surface to a lens is a comparatively long lens, the influence of the garbage to the image quality of the photoed image is minor, but ]. For example, garbage is easily reflected in a taken image.
Also in the imaging device disclosed in the Patent document 1, if the distance from an imaging surface to a lens becomes short, a possibility that the garbage which did not adhere to a solid state imaging element surface will adhere to a lens will become high.