Low-Level Exposure to Cadmium, Lead Linked to Hearing Loss

Researchers have found that low-level cadmium and lead exposure is linked to hearing loss. Both dangerous heavy metals, cadmium and lead have been linked to myriad health reactions.

The researchers reviewed data from 1999 to 2004 from the National Health and Nutrition Examination Survey (NHANES), said MedPageToday. The team found that those people who tested with the highest quintile of blood cadmium levels were significantly likely to have hearing loss at speech frequencies versus those in the lowest quintile, said Sung Kyun Park, ScD, MPH, of the University of Michigan in Ann Arbor, Michigan, and colleagues. Findings appear online in Environmental Health Perspectives.

“The present study supports the hypothesis that environmental cadmium and lead exposures at levels currently observed in the U.S. may increase the risk of hearing loss, the third leading chronic condition experienced by adults ages 65 and older,” the team wrote. “Our findings support efforts to reduce environmental cadmium and lead exposures to effectively prevent or delay hearing loss in the general population.”

From 1999 to 2004, a subset of about 5,000 NHANES participants underwent hearing tests; this, in addition to other NHANES testing on which the team utilized, said MedPageToday. Park and colleagues used data for some of their study from 3,698 participants, after excluding people with unilateral hearing loss or missing information on critical, potential confounders (for instance, firearm noises). When participants were grouped into quintiles of blood cadmium and lead levels, a clearly defined relationship appeared between the levels and hearing impairment, noted MedPageToday. Park and colleagues also pointed out that prior animal studies revealed that these heavy metals cause a number of toxic effects in the auditory system, added MedPageToday.

We recently wrote that, cadmium has been linked to breast cancer. The results of that study reveal that post-menopausal women with a fairly high daily dietary intake of cadmium also have a 21 percent increased risk for developing breast cancer. The main source for cadmium in women’s diets, according to the study, were foods broadly considered healthy, such as whole grains and vegetables, which accounted for 40 percent of the cadmium ingested; cadmium is often found in fertilizer. It is also believed that cadmium can lead to the same adverse health effects as estrogen, a female hormone. Estrogen has long been linked to the development of some breast cancers.

We have long written that the federal government is concerned about toxic metals. And, as regulations regarding toxic metals have increased, cadmium has shown up in a wide variety of children’s products, specifically jewelry. On the U.S. Centers for Disease Control’s (CDC) priority list of 275 most hazardous substances in the environment, cadmium ranks No. 7.

Cadmium, considered an even more dangerous toxic metal than lead, is a known carcinogen and can interfere with brain development in very young children and can lead to kidney, bone, lung, and liver disease.

We have also written that lead can accumulate in the body over time and pregnant women, infants, and young children, especially, should avoid exposure to lead. Lead exposure in children and unborn children can lead to brain and nervous system damage; slowed growth; headaches; mental and physical retardation; and behavioral, learning, hearing, and other health problems. The developing brain is of particular concern because lead exposure can have long-lasting effects that can continue well into puberty and beyond. Once poisoned, no organ system is immune. Also, as we’ve written, lead bans prompted many Chinese manufacturers to switch to the equally toxic heavy metal, cadmium, in products they import to the United States. A known carcinogen, cadmium interferes with brain development in very young children. As with lead, cadmium’s longer-term effects are not always immediately evident.

We also wrote that another study  revealed that childhood exposure to lead dust is linked to violence. Lead is also known to cause cancer and reproductive harm and, in adults, can damage the nervous system.

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