Reading some of the advertisements for electrostatic air filters you'd think that they would be the perfect choice. But there's more to it.
An electrostatic air filter collects particles on the principle that the filter is charged one way and the dust particles are charged the other way, causing the dust particles to stick to each other. (opposites attract).
In practice this works well.
The problems is when the surfaces of the electrostatic air filter are coated in dust. New dust now coming through the filter doesn't stick that well.
Still, you can pull out the filter, wash it off and now it's back in business attracting dust again.