BLOOD MERCURY AND AUDITORY NEURO-SENSORY RESPONSES IN CHILDREN AND ADULTS IN THE NAMBIJA GOLD MINING AREA OF ECUADOR

This study investigated blood mercury (B-Hg) levels and the auditory n euro-sensory status of children and adults in the remote Andean settle ment of Nambija, Ecuador where Hg is used in the extensive gold mining operations. The mean B-Hg level in 75 Nambija (Study Area) inhabitant s (36 children and 39 adults) was 17.5 mu g/L (SD = 11.0) vs 3.0 mu g/ L (SD = 1.6) in a second group of 34 subjects (15 children and 19 adul ts) in a non-gold mining area (Reference Area), the difference being s tatistically significant (p < 0.0001). Neuro-otological examinations r evealed 34 subjects (45%) with complaints of headaches and/or memory l oss, 3 cases of severe neurological impairment and 4 cases of middle e ar pathology. Audiological tests on 40 persons in the Study Area (21 c hildren and 19 adults) showed hearing thresholds ranging from normal t o mildly abnormal at 2, 3, 4, 6 and 8 kHz for children, and normal to severely abnormal for adults. Correlation coefficients showed a signif icant relationship between B-Hg level and hearing level in children at 3 kHz in the right ear, and at no frequency for adults. Auditory brai nstem evoked responses (ABR) on subjects in the Study Area showed a si gnificant correlation between B-Hg and the I-III interpeak latency on the right side. The results indicated that the study population of the Nambija gold mining area had abnormally elevated B-Hg levels, and may be at neurological risk from exposure to methylmercury (MeHg) from th e consumption of contaminated food and possibly from elemental Hg vapo rs inhaled during amalgam burning in the gold extraction process. (C) 1998 Intox Press, Inc.