Which inorganic pollutant is known to cause kidney damage upon long-term exposure?

• A. Arsenic
• B. Lead
• C. Mercury
• D. Cadmium

Answer: (D)

Chronic nephrotoxicity from an inorganic pollutant is most characteristically caused by cadmium because it readily accumulates in the kidneys and has a very long biological half-life. After exposure, cadmium binds to metallothionein and is delivered to proximal tubular cells, where it is released and induces oxidative stress and mitochondrial dysfunction. This damages the proximal tubule, impairing reabsorption and leading to tubular dysfunction. Early signs include loss of low-molecular-weight proteins in urine (like beta-2 microglobulin), aminoaciduria, glycosuria, and phosphate wasting, which reflect the kidney’s inability to reabsorb substances properly. With continued exposure, kidney function can decline further. While other inorganic metals like arsenic, mercury, and lead can also affect the kidneys, cadmium’s pattern of long-term, dose-related proximal tubule damage is a classic and well-established scenario for chronic kidney injury from inorganic pollutants.