Apollo Constellation Engine designed their propulsion systems for mega constellations to use mercury, which is what got PEER involved in this. Popular Mechanics also reported on their plans. Even if Apollo changed their minds since, that's a pretty significant 'near miss'.
https://ecfsapi.fcc.gov/file/111998371507/11_19_18_FCC_compl...
https://www.popularmechanics.com/space/rockets/a25242578/apo...