Environmental risk assessment for the widely used iodinated X-ray contrast agent iopromide (Ultravist)

Iodinated X-ray contrast media are diagnostic pharmaceuticals that are applied to enhance the contrast between organs or vessels examined and surrounding tissues during radiography. These substances are applied in doses up to ca. 200 g per person (corresponding to approx 100 g iodine) and are rapidly excreted. In the sewage system they contribute to the burden of adsorbable organic halogens (AOX). To assess the potential environmental impact of this release, studies on environmental fate and effects were conducted for a risk assessment of the frequently used X-ray contrast medium iopromide (brand name: Ultravist). A screening test for biological degradation (OECD Screening Test 301 E) led to iopromide being classified as not readily biodegradable. Therefore, the predicted environmental concentration (PEC) in surface water was calculated in a first step. The resulting concentration of 2 microgram/liter was then compared in a second step with the predicted no-effect concentration as derived from a battery of ecotoxicity tests. In short-term toxicity tests with bacteria (Vibrio fisheri, Pseudomonas putida), algae (Scenedesmus subspicatus), crustaceans (Daphnia magna), and fish (Danio rerio, Leuciscus idus) no toxic effects were detected at the highest tested concentration of 10 g/liter. In a chronic toxicity test with D. magna no effect was observed at the highest tested concentration of 1 g/liter. Using an assessment factor of 100 the ratio between the predicted environmental concentration (PEC) and the predicted no-effect concentration (PNEC) was calculated to be