Environmental Cadmium and Lead Exposures and Hearing Loss in US Adults: The National Health and Nutrition Examination Survey, 1999 to 2004

BACKGROUND: Although cadmium and lead are known risk factors for hearing loss in animal models, few epidemiologic studies have been conducted on their associations with hearing ability in the general population. OBJECTIVES: We investigated the associations between blood cadmium and lead exposure and hearing loss in the U.S. general population while controlling for noise and other major risk factors contributing to hearing loss. METHODS: We analyzed data from 3,698 U.S. adults 20-69 years of age who had been randomly assigned to the National Health and Nutrition Examination Survey (NHANES) 1999-2004 Audiometry Examination Component. Pure-tone averages (PTA) of hearing thresholds at frequencies of 0.5, 1, 2, and 4 kHz were computed, and hearing loss was defined as a PTA > 25 dB in either ear. RESULTS: The weighted geometric means of blood cadmium and lead were 0.40 [95% confidence interval (Cl): 0.39. 0.42] mu g/L and 1.54 (95% CI: 1.49, 1.60) mu g/dL, respectively. After adjusting for sociodemographic and clinical risk factors and exposure to occupational and nonoccupational noise, the highest (vs. lowest) quintiles of cadmium and lead were associated with 13.8% (95% Cl: 4.6%, 23.8%) and 18.6% (95% Cl: 7.4%, 31.1%) increases in PTA, respectively (p-trends < 0.05). CONCLUSIONS: Our results suggest that low-level exposure to cadmium and lead found in the general U.S. population may be important risk factors for hearing loss. The findings support efforts to reduce environmental cadmium and lead exposures.