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S. Allen Counter,^1,2 Marie Vahter,³ Göran Laurell,⁴ Leo H. Buchanan,⁵ Fernando Ortega,⁶ and Staffan Skerfving⁷

¹Department of Neurology/Biological Laboratories, Harvard University, Cambridge, MA 02138 USA; ²Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
³Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden; ⁴Department of Otolaryngology, Karolinska Hospital, Karolinska Institute, Stockholm, Sweden; ⁵Department of Audiology, Shriver Center/Harvard University Health Services, Waltham, MA 02154 USA; ⁶Department of Medicine, Universidad San Francisco De Quito, Quito, Ecuador; ⁷Department of Occupational and Environmental Medicine, University Hospital, Lund, Sweden

Abstract
We investigated blood lead (B-Pb) and mercury (B-Hg) levels and auditory sensory-neural function in 62 Andean school children living in a Pb-contaminated area of Ecuador and 14 children in a neighboring gold mining area with no known Pb exposure. The median B-Pb level for 62 children in the Pb-exposed group was 52.6 µg/dl (range 9.9-110.0 µg/dl) compared with 6.4 µg/dl (range 3.9-12.0 µg/dl) for the children in the non-Pb exposed group ; the differences were statistically significant (p<0.001) . Auditory thresholds for the Pb-exposed group were normal at the pure tone frequencies of 0.25-8 kHz over the entire range of B-Pb levels. Auditory brain stem response tests in seven children with high B-Pb levels showed normal absolute peak and interpeak latencies. The median B-Hg levels were 0.16 µg/dl (range 0.04-0.58 µg/dl) for children in the Pb-exposed group and 0.22 µg/dl (range 0.1-0.44 µg/dl) for children in the non-Pb exposed gold mining area, and showed no significant relationship to auditory function. Key words: auditory, brain stem evoked response, hearing, lead, mercury. Environ Health Perspect 105:522-526 (1997)

Address correspondence to S. A. Counter, Harvard University, The Biological Laboratories, Cambridge, MA 02138 USA.

This study was conducted under the auspices of the Universidad San Francisco De Quito Medical School in Quito, Ecuador. The study was approved by the Human Studies Committee of Universidad San Francisco De Quito Medical School. We appreciate the support of Ing. Luis Parodi V., Miguel Falconi Puig, and Gonzalo Mantilla. We thank Anthony B. Jacobs, Paola Calozzi, Titiana Rodriguez, and Magdalena Terneux, for technical assistance and Andrejs Schütz for laboratory analysis. We are also grateful to Erik Borg, Keith Chiappa, and Raymond D. Adams for helpful advice and comments. The study was supported by Harvard University, Fundacíon Capacitar, the Swedish Medical Association, and the Medical Faculty, Lund University.

Received 7 November 1996 ; accepted 15 January 1997.