Hospital-Use Pharmaceuticals in Swiss Waters Modeled at High Spatial Resolution

A model
to predict the mass flows and concentrations of pharmaceuticals
predominantly used in hospitals across a large number of sewage treatment
plant (STP) effluents and river waters was developed at high spatial
resolution. It comprised 427 geo-referenced hospitals and 742 STPs
serving 98% of the general population in Switzerland. In the modeled
base scenario, domestic, pharmaceutical use was geographically
distributed according to the population size served by the respective
STPs. Distinct hospital scenarios were set up to
evaluate how the predicted results were modified when pharmaceutical
use in hospitals was allocated differently; for example, in proportion
to number of beds or number of treatments in hospitals. The hospital scenarios predicted the mass flows and concentrations
up to 3.9 times greater than in the domestic scenario
for iodinated X-ray contrast media (ICM) used in computed tomography
(CT), and up to 6.7 times greater for gadolinium, a contrast medium
used in magnetic resonance imaging (MRI). Field measurements showed
that ICM and gadolinium were predicted best by the scenarios using
number of beds or treatments in hospitals with the specific facilities
(i.e., CT and/or MRI). Pharmaceuticals used both in hospitals and
by the general population (e.g., cyclophosphamide, sulfamethoxazole,
carbamazepine, diclofenac) were predicted best by the scenario using
the number of beds in all hospitals, but the deviation from the domestic scenario values was only small. Our study demonstrated
that the bed number-based hospital scenarios were
effective in predicting the geographical distribution of a diverse
range of pharmaceuticals in STP effluents and rivers, while the domestic scenario was similarly effective on the scale of
large river-catchments.