> After the Napoleonic Wars, Notre-Dame was in such a state of disrepair that Paris officials considered its demolition.
> The stone masonry of the cathedral's exterior had deteriorated in the 19th and 20th century due to increased air pollution in Paris, which accelerated erosion of decorations and discolored the stone. By the late 1980s, several gargoyles and turrets had also fallen off or become too loose to remain in place.
https://en.wikipedia.org/wiki/Notre-Dame_de_Paris#Restoratio...
> After the Napoleonic Wars, Notre-Dame was in such a state of disrepair that Paris officials considered its demolition.
> The stone masonry of the cathedral's exterior had deteriorated in the 19th and 20th century due to increased air pollution in Paris, which accelerated erosion of decorations and discolored the stone. By the late 1980s, several gargoyles and turrets had also fallen off or become too loose to remain in place.