"The recent study focuses on the amount of lithium left behind from a single rocket reentry. Previous studies have already shown that lithium, aluminum, copper, and lead left behind from the reentry of spacecraft already exceeds the cosmic dust influx of those metals to the atmosphere.
It’s not clear yet how exactly this change in the atmospheric chemistry would affect life on Earth, but the researchers behind the new study believe that there is enough reason for concern. Still, more research is needed to narrow down the impact on our planet.
“There are many elements present inside spacecraft which are not very present in our atmosphere due to natural causes,” Wing said. “We know very little about what metals actually exist in the atmosphere and how that relates to re-entry pollution.”"
https://gizmodo.com/study-confirms-reentering-spacex-rockets-are-peppering-the-upper-atmosphere-with-metal-pollution-2000723932
