Low levels of two common metals may contribute to hearing loss, according to a study published recently in Environmental Health Perspectives.

Researchers found that lead and cadmium – even at levels below national workplace standards set by OSHA – can damage hearing. At metal concentrations common in the general population, hearing ability dropped 14-19 percent.

Previous studies have shown that the two cause a range of toxic effects on the hearing system; in particular affecting the inner ear where sound is received and sent to the brain.

The study is the first to establish the link between hearing loss and low-level exposures to lead and cadmium in a large sample of men and women in the United States and the first to report cadmium’s effects on hearing in adults.

Hearing loss affects more than 35 million Americans older than 18. Loud noise at work, shooting firearms and environmental and industrial chemicals can damage hearing.

“Lead is banned from gasoline, paint and other products in countries around the world but still lingers in the environment,” notes the study. It is used in electronics and ammunition. In the United States, the most common sources are lead-based paint, contaminated soil, household dust and drinking water.

Cadmium is widely used in products and applications, including batteries, pigments and metal plating. It is also a by-product of ore smelting and may be released in the air from the burning of fossil fuels. Most people are exposed to cadmium through diet, air pollution and smoking.

According to the researchers, “the findings support efforts to reduce environmental cadmium and lead exposures to effectively prevent or delay hearing loss in the general population.”

The researchers are: Choi, Y-H, H Hu, B Mukherjee, J Miller and SK Park.