Hong Kong was not a healthy place in the late 19th century. For decades after the British founded the colony in 1842, the Chinese settlement of Sheung Wan struggled with overcrowding and chronic disease.
Things were especially bad in Tai Ping Shan, a hillside enclave of tenement houses packed with coolies who worked as manual laborers. In 1881, the colonial government hired Oswald Chadwick, a British engineer, to conduct a survey of the district's homes. He was alarmed by what he found. In some buildings, 80 tenants crammed into a single flat. People shared space with chickens and pigs. Drains were built haphazardly, so they clogged and became septic, toxic sludge leaking into the surrounding soil.