At the DuPont warehouse, Amazon workers with such injuries took an average of 103 days to heal, Washington state found. Workers' compensation payouts to Amazon workers with musculoskeletal disorders are often in the tens of thousands of dollars — some exceed $100,000, data from Washington state shows. But because musculoskeletal disorders take months to develop and aren't as visible as other, more catastrophic injuries, even some Amazon workers write them off. Williams was out of work for more than 150 days because of her shoulder injury, internal Amazon injury logs show. The company needs to become "Earth's Safest Place to Work," Amazon's founder, Jeff Bezos, said in his final letter to shareholders last year.

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