Medical radioisotopes in wastewater. Environmental problem or environmental tracer?

Routine surveillance of wastewater and wastewater treatment sludge show a nationwide, continuous input of radioisotope characteristic for nuclear medicine procedures. The main isotopes are 99mTc for diagnostics and 131I for therapy. Applied activites are in the Gigabecquerel range. A systematic study at a wastewater treatment plant covering in- and outflow and primary sludge shows characteristic time patterns for both isotopes. Values for 131I coincide well with estimates published by the German Commission on Radiological Protection (SSK). Investigations of river sediment detected 131I over a river length of 40 km, with a maximum at the outlet of the treatment plant. The values agree well with simple models, and a detailed modelling appears feasible. Calculated external and internal doses are in the Nanosievert to Microsievert range. (orig.)