Cadmium (Cd) is a food-chain contaminant that has high rates of soil-to-plant transference. This phenomenon makes dietary Cd intake unavoidable. Although long-term Cd intake impacts many organ systems, the kidney has long been considered to be a critical target of its toxicity. This review addresses how measurements of Cd intake levels and its effects on kidneys have traditionally been made. These measurements underpin the derivation of our current toxicity threshold limit and tolerable intake levels for Cd. The metal transporters that mediate absorption of Cd in the gastrointestinal tract are summarized together with glomerular filtration of Cd and its sequestration by the kidneys. The contribution of age differences, gender, and smoking status to Cd accumulation in lungs, liver, and kidneys are highlighted. The basis for use of urinary Cd excretion to reflect body burden is discussed together with the use of urinary N-acetyl-β-d-glucosaminidase (NAG) and β2-microglobulin (β2-MG) levels to quantify its toxicity. The associations of Cd with the development of chronic kidney disease and hypertension, reduced weight gain, and zinc reabsorption are highlighted. In addition, the review addresses how urinary Cd threshold levels have been derived from human population data and their utility as a warning sign of impending kidney malfunction.

The present review aims to provide an update on health risks associated with the low-to-moderate levels of environmental cadmium (Cd) and lead (Pb) to which most populations are exposed. Epidemiological studies examining the adverse effects of coexposure to Cd and Pb have shown that Pb may enhance the nephrotoxicity of Cd and vice versa. Herein, the existing tolerable intake levels of Cd and Pb are discussed together with the conventional urinary Cd threshold limit of 5.24 μg/g creatinine. Dietary sources of Cd and Pb and the intake levels reported for average consumers in the U.S., Spain, Korea, Germany and China are summarized. The utility of urine, whole blood, plasma/serum, and erythrocytes to quantify exposure levels of Cd and Pb are discussed. Epidemiological studies that linked one of these measurements to risks of chronic kidney disease (CKD) and mortality from common ailments are reviewed. A Cd intake level of 23.2 μg/day, which is less than half the safe intake stated by the guidelines, may increase the risk of CKD by 73%, and urinary Cd levels one-tenth of the threshold limit, defined by excessive ß₂-microglobulin excretion, were associated with increased risk of CKD, mortality from heart disease, cancer of any site and Alzheimer’s disease. These findings indicate that the current tolerable intake of Cd and the conventional urinary Cd threshold limit do not provide adequate health protection. Any excessive Cd excretion is probably indicative of tubular injury. In light of the evolving realization of the interaction between Cd and Pb, actions to minimize environmental exposure to these toxic metals are imperative.

A peer-reviewed open access journal published by the National Institute of Environmental Health Sciences

Cadmium (Cd) is an environmental toxicant of widespread exposure and pervasive toxicity. Absorption, systemic transport and uptake of Cd are mediated by metal transporters that the body uses for acquisition of physiologically-essential elements, notably of iron, zinc and calcium. Currently, human exposure to Cd is known to damage the kidneys, especially the proximal tubular cells that actively reabsorb Cd along with zinc, glucose and amino acids in the glomerular filtrate. Severe kidney damage, glycosuria and proteinuria are known outcomes after high dietary Cd intake (> 200 µg/day). Dietary Cd intake of 10-30 µg/day has been linked with reduced tubular reabsorption, chronic kidney disease, hypertension, coronary arterial and peripheral arterial diseases, macular degeneration, obesity-independent diabetes, and cancer. The links between diabetes, hypertension and end stage kidney disease (ESKD) are indisputable. ESKD requires dialysis or kidney transplant, an immense health care cost. This review adds to these connections by presenting the synergism of kidney Cd toxicity on blood pressure control and glucose homeostasis. Blood pressure control is mediated at least in part by cytochrome P450 (CYP) enzymes such as CYP4A11 and CYP4F2 that produce 20-hydroxyeicosatetraenoic acid (20-HETE), involved in salt balance in the kidney, and all are known to be altered during Cd exposure. The potential effects of Cd exposure on glucose reabsorption, inflammation, oxidative stress, and heme oxygenase activity are highlighted. The information presented offers strategies for mitigation of toxic effects of Cd through minimization of the food-chain transfer of Cd, and modulation of mechanistic pathways altered by Cd exposure.