THURSDAY, Aug. 28 (HealthDay News) -- The metal cadmium plays a major role in causing emphysema, and even low-level exposure through secondhand smoke and other sources can increase the risk of lung disease, a new study says.

The University of Michigan School of Public Health research also suggests that people with high levels of cadmium in their bodies may have as much as double the risk of developing a pulmonary disease such as emphysema or chronic bronchitis.

In this study, principal investigator Howard Hu and his colleagues tested the lung function of 96 men. Those with higher levels of cadmium in their urine had a reduced ability to exhale. This association was most evident among current and former smokers.

"The study suggests that the critical ingredient in smoking that may be causing emphysema is cadmium, a well-known contaminant of cigarette smoke. The worry is if you are exposed to this (cadmium) through other sources, you can also be at risk for emphysema," Hu said in a university news release.

Nonsmokers can be exposed to cadmium through secondhand smoke, by eating contaminated foods, or in the workplace. Cadmium is widely used in batteries and pigments, and is present in sludge and crop fertilizers, the researchers said.

Cadmium is difficult for the body to expel, because the kidneys tend to retain cadmium, which is recycled into the body, said Hu, chairman of the School of Public Health's department of environmental health sciences.

The next phase of this research will involve a much larger, population-based study with more people and multiple measurements of cadmium exposure and lung function over an extended period of time.

"With a larger population, we will be able to better disentangle the independent effects of cadmium and smoking, and whether dietary cadmium or other non-cigarette sources may also influence lung function," Hu said.

The study findings are published in the September issue of the journal Environmental Health Perspectives.

More information

The American Cancer Society has more about secondhand smoke.