People with higher levels of cadmium in their urine—evidence of chronic exposure to the heavy metal found in industrial emissions and tobacco smoke—appear to be nearly 3.5 times more likely to die of liver disease than those with lower levels, according to a study by researchers at Johns Hopkins.
The findings do not show that cadmium directly causes liver disease, the scientists caution, but do suggest an association that needs more investigation.
Reviewing information from a large population-based survey, the Johns Hopkins investigators say the cadmium-liver disease link disproportionately affects men. The gender differences could occur because of the protective effects of menopause chemistry, which may redistribute stored cadmium from liver and kidneys, where it can do more damage, and into bones where it remains more stable.
Cadmium accumulates in the body over time because of the metal's long chemical half-life, according to the researchers, who reported their findings online in the Journal of Gastrointestinal Surgery.
"We already know about the health hazards of heavy metals like lead and mercury, but we don't know much about what cadmium does to the body," says study leader Omar Hyder, a postdoctoral fellow in the Department of Surgery at the Johns Hopkins University School of Medicine. "In mice, chronic cadmium exposure has been shown to cause liver failure, but we need to understand more about the factors that may cause liver disease in humans, and whether we can do anything to prevent it."
Cadmium is found widely in the environment, with tobacco smoke the most important, single source of exposure in the general population. Other environmental sources of human exposure include fossil fuel combustion and the incineration of municipal waste. For many years, most of the batteries in the United States were made with cadmium, and it is also found in pigments and plastics.
Hyder says long-term exposure is known to cause kidney disease and has been linked to lung cancer. Studies have shown an increase in all-cause mortality and cancer mortality in populations exposed to low levels of cadmium for long periods of time.
For their study, Hyder and his colleagues analyzed data from 12,732 participants in the National Health and Nutrition Examination Survey.
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