The large population in Antananarivo and the high density of its residential zones pose challenges to public health, sanitation, and access to clean drinking water. Processing and disposal of industrial and residential waste is inadequate. Waste water is often discharged directly into the city's waterways. Air pollution from vehicle exhaust, residential coal-burning stoves, and other sources is worsening. While the city has set up clean water pumps, they remain inadequate and are not distributed according to population density, with poor access in the poorest and most populous parts of the city. Antananarivo is one of the two urban areas in Madagascar where bubonic plague is endemic.