Andy Zhang's arm is cased in skin-coloured bandages that mask the reality of the mangled flesh beneath.

It hangs by his side, lifelessly, as a permanent reminder of the six months he worked as a machine operator on a 457 visa in Melbourne's west, when he was allegedly exploited by his bosses and exposed to grave danger.

Injured: Chinese migrant Andy Zhang, whose arm was mangled in a work accident. Credit:Jesse Marlow

The Chinese migrant is like thousands of temporary overseas workers in Australia, who are feared to be at a greater risk of on-the-job accidents due to poor language, less training and vulnerability to mistreatment.

But a system to better protect 457 visa holders - by tracking their workplace injuries and monitoring employers - was quietly shelved in Australia despite concerns of exploitation.