Marshall lives in west Jackson, in the US state of Mississippi - a predominantly black and poor part of the city. He has no choice but to drink the tap water that Jackson residents have been told to avoid. When he turns the tap on - the water runs brown. He says it's been like this for about eight months and he has no choice but to drink it. "Yes ma'am. I been drinking it." He smiles when we ask whether it worries him. "I turn 70 later this month," he says.