Environmental Lead Exposure and Otoacoustic Emissions in Andean Children

Abstract

Studies relating sensory hearing impairment to lead (Pb) exposure in children have presented inconsistent results. The objective of this study was to measure distortion product otoacoustic emissions (DPOAE), sounds emanating from the outer hair cells of the inner ear, in Pb-exposed children to determine the effects of Pb poisoning on the inner ear. DPOAE were recorded for 9 f₂ frequencies from 1187 to 7625 Hz on 102 ears of 53 Pb-exposed children (aged 6–16 yr) residing in Pb-contaminated environments in the Andes Mountains of Ecuador where Pb glazing of ceramics is the primary livelihood. Blood lead (PbB) levels ranged from 4.2 to 94.3 μg/dl (mean: 37.7; SD: 25.7; median: 36.4). The median PbB level was markedly higher than the Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) 10-μg/dl action level. Spearman rho correlation analyses of the relation between PbB level and DPOAE amplitude and between PbB level and DPOAE signal-to-noise ratio revealed no significant associations at any of the f₂ frequencies tested. In addition, no significant correlation (Spearman rho) between PbB level and hearing sensitivity for 6 pure-tone test frequencies from 1000 to 8000 Hz was found. Although the study group was found to have abnormally elevated PbB levels, in contrast to some earlier reports, the results of the current study showed no consistent Pb-induced sensory effects on the cochlea of Pb-intoxicated children.

Acknowledgments

The authors thank the Administration of Universidad San Francisco de Quito and the Fundacíon Capacitar of Ecuador for support of this project. We are grateful to Harvard University Biological Laboratories, the David Rockefeller Center of Latin American Studies at Harvard University, the University of Massachusetts Medical School/Shriver Center, and Dr. Jeremy Bloxham of Harvard University for support. We are thankful to Anthony B. Jacobs for excellent technical assistance, and to the Boston Children's Hospital Department of Laboratory Medicine and the Channing Trace Metals Laboratory of the Harvard School of Public Health for laboratory support.