For the past three years , Zheng has been fixing photocopy machines at various factories in China 's manufacturing heartland . China has more than 260 million migrant workers . Survey suggests many may suffer from mental health problems . Leaving behind children and elderly parents an emotional and financial burden . Comment:
China has more than 260 million migrant workers . Survey suggests many may suffer from mental health problems . Leaving behind children and elderly parents an emotional and financial burden . Comment: