Yang said lead enters a body through food, inhalation or contact with skin. A person covered with lead at work, if not properly washed, could bring the substance home and affect his family.

Excessive lead harms the human digestive system, disturbs the blood system and damages the nerve system in serious cases.

Construction of the Guangjin apartment building started in 2004 and residents, mostly migrant workers, said they have suffered smells from factories less than 100 m away.