Study Links Hearing Loss to Low Levels of Lead and Camium Exposure

Exposure to extremely low levels of Lead and Cadmium can lead to hearing loss of up to 20% according to a new study published on Monday.

"The metal levels found to influence hearing were below national workplace standards set by the Occupational Safety and Health Administration. Although the study does not establish causality, the results support previous animal and humans studies that link these heavy metals to hearing loss.

Animal studies show lead and cadmium have a wide array of toxic effects on the hearing system. Both can affect the inner ear where sound is received and sent on to the brain.

Human studies are limited, but exposure to high levels of lead has been linked to hearing loss in children and males exposed at work. Studies in teens have also linked cadmium exposure to hearing loss."

Lead is used in electronics and ammunition, and of course can be found in the fallout of lead smelters like the one in Frisco that Exide Corporation operated until recently. In the United States, the most common sources are old building with lead-based paint, contaminated soil, household dust and drinking water.

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

Hearing was tested at sound frequencies of normal speech so a loss could make it harder to hear conversations. Lead and cadmium were measured in blood samples.

When lead levels were higher, so were cadmium levels. Higher levels of the metals either alone or together related to more hearing loss, especially in older adults.

Adults with the highest lead and cadmium exposures had more hearing loss. Lead levels above 2.8 micrograms per deciliter of blood related to an 18.6 percent rise in PTA and cadmium levels above 0.8 micrograms per liter had a 13.8 percent increase in PTA.

The CDC recently recommended an "action level" of lead in blood of 5 micrograms per deciliter based on the last decade of research, most of which suggests there is no safe level of exposure to lead. This study certainly points in that direction.

Despite banning lead from gasoline and paint, ongoing testing shows that the average concentration of lead in the American bloodstream is still two orders of magnitude higher than natural human levels.