Cadmium & kidneys

Townsend Letter for Doctors and Patients,  Oct, 2005  by Jule Klotter

• E-mail
• Print
• Link

Swedish researchers discovered that renal tubular damage may occur at lower levels of exposure to cadmium than previously expected (Occup Environ Med 2000;57:668-672). When inhaled or ingested, the heavy metal cadmium tends to accumulate in the kidneys where it damages tubules and glomeruli in the kidneys' nephrons. Cadmium is released into the air and waterways during metal refining, the production of nickel-cadmium batteries and, perhaps most importantly, the production and use of artificial phosphate fertilizers. Food crops and tobacco absorb cadmium from the soil. The cadmium then enters those who eat the crops or who breathe the contaminated tobacco smoke. Shellfish, mussels, lobsters and other water creatures--contaminated by run-off from fertilized fields and industrial pollution that enters surface water--can also accumulate cadmium.

This study measured cadmium and protein HC ([+ or -]1-microglobulin) in the urine of 1021 people living in two Swedish communities with nickel-cadmium battery factories. (One plant had closed in 1974; the other was still operating.) Protein HC, a low molecular weight protein, indicates the development of cadmium-induced renal lesions in the renal tubules. Over time, tubular dysfunction can lead to glomerular damage and a decreased glomerular filtration rate. After making an adjustment for age-related protein in the urine, the Swedish researchers found "a positive, highly significant, linear relation ... between dose (cadmium in urine) and effect (urinary protein HC)." They discovered that people with urine-cadmium levels of 1 nmol/mmol creatinine (the upper part of normal range) showed a "threefold increase in risk of having increased urinary protein HC." (Creatinine, formed from the metabolism of creatine, is an indicator of kidney function used in blood and urine tests.) An expert group at the World Health Organization set a 'health-based limit' of about 5 nmol Cd/mmol creatinine.

The researchers also found that bone density decreased as urinary cadmium and urinary protein HC increased. They state that other studies have found an increased incidence of kidney stones, osteoporosis, and urinary excretion of calcium among cadmium-exposed workers. Because of the health consequences of cadmium intake, the researchers believe that "measures should be taken to reduce exposure to cadmium in the general population, including lowering of current standards for intake of cadmium in food."

Jarup, Lars et al. Low level exposure to cadmium and early kidney damage: the OSCAR study. Occup Environ Med 2000;57:668-672 [downloaded from www.oem.bmjjournals.com on 13 July 2005]

Cadmium (Cd)--Chemical properties, Health and Environmental effects. www.lenntech.com/Periodic-chart-elements/Cd/en.htm (accessed 13 July 2005)

COPYRIGHT 2005 The Townsend Letter Group
COPYRIGHT 2005 Gale Group