Humans shed their epidermis at the rate of 0.001-0.003 ounces of skin flakes every hour. That is roughly 0.024-0.072 ounces per day 9-27oz/year , or 0.55-1.6 pounds per year. According to the WHO , 70 years was the average life expectancy at birth of the global population in 2012
So , 70 times 1.6 is 112 pounds of skin cells shed over a lifetime