Medieval Norwegian hygiene measures backfired and fueled disease

Archaeologists and researchers in Norway identified how medieval hygiene efforts in the city of Nidaros, now known as Trondheim, inadvertently worsened public health.

King Olaf Tryggvason founded the city at the mouth of the Nidelva river around the year 1000. As the city grew rapidly, local authorities attempted to implement sanitary measures based on the contemporary scientific understanding of the time. Researchers compared remains from two medieval cemeteries in the city center and its outskirts.

They found that residents on the periphery suffered from more diseases, had less diverse diets, and lived shorter lives than the elite in the center. More than half of the city's residents experienced physiological stress from poor nutrition during childhood and adolescence, while many died from infectious diseases like leprosy, typhoid fever, and tuberculosis. In 1274, royal officials introduced measures to clean streets and manage waste based on the miasmatic theory, which suggested that foul odors caused illness.

To reduce smells, authorities ordered the transport of waste from city latrines to fields outside the center to be used as fertilizer. However, this practice allowed parasites like tapeworms and roundworms to thrive in the manure and enter the food chain, creating a cycle of intestinal diseases. Environmental changes also affected these efforts.

A decline in wood chips used to mask odors by the late 13th century may have resulted from the Samalas volcano eruption in Indonesia, which reduced forest growth. By 1349, the Black Death arrived in Norway. The population dropped from approximately 500,000 in 1340 to about 200,000 by the start of the 15th century, eventually leading to Norway becoming politically subordinate to Denmark in 1537.