# In-vivo toxicokinetics of chromium in human blood and urine after intravenous injection of chromate

## TL;DR

A rare case of chromium poisoning helped scientists determine how long red blood cells live and how chromium is stored in the body.

## Contribution

This case provides the first direct evidence of red blood cell lifespan and chromium storage in humans.

## Key findings

- The average red blood cell lifespan was calculated as 111 days.
- Chromium in plasma remained elevated long after injection.
- Chromium in red blood cells returned to background levels after 24 weeks.

## Abstract

Although intoxication with hexavalent chromium [Cr(VI)] compounds can be fatal to humans, reliable data on chromium toxicokinetics are largely missing. We report on a rare case of intravenous Cr(VI) poisoning and its impact on the scientific understanding of chromium toxicokinetics and red blood cells’ (RBCs’) lifespan in the human body. The approximate amount of injected chromium was between 0.33 and 0.66 g. Laboratory findings were collected over a half-year period from the time of injection. We monitored kidney function, liver function, RBC parameters, and chromium concentration in RBCs, plasma, and urine. In all samples, the total chromium concentration was quantified by inductively coupled plasma-mass spectrometry. By injecting Cr(VI) into his vein, the patient inadvertently labeled all his RBCs with chromium. This gave us the unique opportunity to calculate the RBC lifespan rather than just to estimate it. Based on RBC breakdown rates, the average lifespan was calculated to be 111 days, and the maximum lifespan to be 141.4 days. At about 24 weeks post-injection, the RBC chromium concentration approached background-exposure values, whereas chromium in plasma reached a plateau considerably higher than the reference value. These results confirm that there is a long-term storage compartment for chromium in the human body, which releases chromium into plasma but leaves the RBC chromium concentration unaffected. Therefore, this singular case of Cr(VI) poisoning provides us with the long-awaited scientific proof that chromium in the RBC fraction is a specific monitoring parameter for exposure to the carcinogen Cr(VI) in occupational and environmental settings.