(CNN) It was supposed to be one of those routine ceremonial appearances that politicians make all the time.
Show up at a 20K race, wave to the crowd and cheer as the runners bolt from a starting line and dash through the streets of Brussels.
But for Charles Michel, Prime Minister of Belgium, Sunday's 20 kilometer de Bruxelles event has proven to be a little thorny. Michel says he has been suffering hearing loss since a starter pistol, signaling the beginning of the race, was fired near his left ear.
The moment was captured in a photo showing Princess Astrid of Belgium's royal family firing the gun into the air. Next to her is a wincing Michel, who appears to be recoiling at the sound.
The Prime Minister's spokesman, Barend Leyts, confirmed that Michel is suffering from an ear injury caused by the pistol's firing.
Michel, 41, is following a series of treatments for the injury and is still coming to work between doctor appointments, Leyts said.
The Prime Minister had to cancel a meeting at Parliament on Tuesday morning, but his schedule has not been cleared and his office is going about things as normally as possible, Leyts said.
A 2013 study published in the International Journal of Audiology found that typical starter pistols produce a noise exceeding 140 decibels -- roughly equivalent to an airplane taking off -- and could cause hearing loss among "unprotected officials and others in the immediate vicinity of the shooter."
The annual race attracted some 40,000 runners and came four days after Michel met with US President Donald Trump in Brussels on his foreign tour.