Srimad Bhagavatam Canto 12, Chapter 02, Text 11

SB 12.2.11

trimsad vimsati varsani
 paramayuh kalau nrnam
 
Translation: 
 
The maximum duration of life for human beings in Kali-yuga will become fifty years.
Srimad Bhagavatam Canto 12, Chapter 02, Text 10
Srimad Bhagavatam Canto 12, Chapter 02, Text 12-16