Observation of changes in urinary excretion of thorium in humans following ingestion of a therapeutic soil

The study investigated the changes in urinary thorium excretion by humans following ingestion of a therapeutic soil, which contains about 10 ppm of thorium. This well-known healing earth in Germany has been considered as an alternative medicine for diarrhoea and gastric hyper-acidity. Six adult volunteers ingested this therapeutic soil in varying quantities for 1–15 days at levels approximating those described in the package insert of the medicine (10–60 g of soil per day). The subjects ingested about 0.1–0.6 mg of thorium daily, which is 100–600 times higher than the normal daily intake of about 1 μg thorium in Germany. All 24-h urine samples collected from the subjects during pre-ingestion, ingestion and post-ingestion periods of the soil were analyzed for 232Th using inductively coupled plasma mass spectrometry (ICP-MS). The measured excretion values varied in a wide range. Apparently, the high thorium amounts administered did not increase the 232Th excretion in urine as expected, suggesting that this soil ingestion will not result in a considerably higher and harmful uptake of thorium into the human body.