"Excessive" means more than your body needs to carry out metabolic functions. When you take in more than you need, your body either discards the excess through urination (putting strain on the kidneys proportionate to the amount of excess), or stores it in fat deposits,which can lead to other toxic effects.
To a certain extent, your body is equipped with a sophisticated system for eliminating excess trace nutrients... but stressing those systems with large excesses can have very deleterious effects.
It is impossible to put numerical values on what constitutes "adequate" or "excessive" trace nutrient intake. Like calorie intake, these are very individual.
Well...gee....isn't that what I have been saying? People are different....some may need MORE vitamins/supplements than others....It is NOT like "oxygen."