The rapid reduction in life spans after noah's flood may be due to reduction in shielding effects of the current atmosphere a change in the properties of the atmosphere increase in radiation after the flood all of the above

ALL OF THE ABOVE. There are multiple factors that may have impacted the rapid reduction of lifespans after the flood as written in the Bible. Genetics, environment, oxygen, and dietary changes all probably had some sort of involvement in how people lived, grew, and survived, thus changing lifespans as a whole over time.