WordNet records no synonym and no antonym for overexposure. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the act of exposing film to too much light or for too long a time
the act of exposing someone excessively to an influencing experience
“an overexposure to violence on television”
Synonyms, antonyms and the broader and narrower relations for overexposure come from Princeton University’s WordNet. Full sources and licences.