Abstract
Metals are one of five major categories of carcinogenic or toxic constituents in tobacco and tobacco smoke. Cadmium is highly volatile and a higher percentage of the total tobacco cadmium content is efficiently transferred to mainstream tobacco smoke than many other toxic metals in tobacco. Inhaled cadmium bioaccumulates in the lungs and is distributed beyond the lungs to other tissues, with a total body biological half-life of one to two decades. Chronic cadmium exposure through tobacco use elevates blood and urine cadmium concentrations. Cadmium is a carcinogen, and an inducer of proinflammatory immune responses. Elevated exposure to cadmium is associated with reduced pulmonary function, obstructive lung disease, bronchogenic carcinoma, cardiovascular diseases including myocardial infarction, peripheral arterial disease, prostate cancer, cervical cancer, pancreatic cancer, and various oral pathologies. Cadmium and zinc have a toxicologically inverse relationship. Zinc is an essential element and is reportedly antagonistic to some manifestations of cadmium toxicity. This review summarizes associations between blood, urine, and tissue cadmium concentrations with emphasis on cadmium exposure due to tobacco use and several disease states. Available data about zinc and cadmium/zinc ratios and tobacco-related diseases is summarized from studies reporting smoking status. Collectively, data suggest that blood, urine, and tissue cadmium and cadmium/zinc ratios are often significantly different between smokers and nonsmokers and they are also different in smokers for several diseases and cancers. Additional biomonitoring data such as blood or serum and urine zinc and cadmium levels and cadmium/zinc ratios in smokers may provide further insight into the development and progression of diseases of the lung, cardiovascular system, and possibly other organs.
Highlights
Tobacco users are exposed to numerous toxic constituents, including toxic metals, from oral use of smokeless tobacco or inhalation of tobacco smoke [1,2]
Morgan reported significantly elevated mean serum cadmium concentrations and suppressed mean serum zinc concentrations as distinct characteristics of patients with bronchogenic carcinoma, a leading cause of death in the U.S population associated with almost 85% of pulmonary cancer cases, and a disease commonly associated with smoking [84,85]
In a prostate cancer study, Ogunlewe and Osegbe reported that the mean (11 μmol/L) and range of serum zinc concentrations were lower and the mean (24.2 μmol/L) and range of plasma cadmium concentrations were higher in patients with prostate cancer than in healthy men (14.9 μmol/L zinc, 15.2 μmol/L cadmium). They concluded that the molar ratios of cadmium/zinc in plasma of prostate cancer patients under their observation were elevated versus patients who did not have prostate cancer, and that plasma cadmium/zinc ratios could be used as a marker for prostate cancer [100]
Summary
Tobacco users are exposed to numerous toxic constituents, including toxic metals, from oral use of smokeless tobacco or inhalation of tobacco smoke [1,2]. This review examines cadmium and zinc levels in smokers and assesses associations between cadmium concentrations in blood, urine, and tissues with tobacco-related diseases. Though present at lower concentrations in tobacco than some other metals [24], cadmium readily transfers to mainstream smoke in concentrations higher than most other metals due to the volatility of the transported form [2,27]. Counterfeit U.S cigarettes had mainstream smoke cadmium levels (ISO 3308 smoking regimen) [31] that were much higher than legal products, ranging. Zinc levels in tobacco are not reported as frequently as cadmium, but one study reported a range spanning 16.8 to 30.5 μg/g tobacco in 12 U.S cigarette varieties [35]. The levels of zinc in tobacco smoke relative to physiological concentrations suggest that biological levels of zinc would be negligibly affected by the small amount transported in tobacco smoke
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