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Neurocognitive screening of mercury-exposed children of Andean gold miners

Abstract:

Performance on Raven's Coloured Progressive Matrices (RCPM) test of visual-spatial reasoning was used to evaluate the effects of mercury (Hg) exposure on 73 Andean children aged 5 to 11 years (mean: 8.4) living in the Nambija and Portovelo gold mining areas of Ecuador, where Hg is widely used in amalgamation. Mean levels of Hg found in blood (HgB), urine (Hg U), and hair (HgH) samples were 5.1 μg/L (SD: 2.4; range: 1-10 μg/L), 13.3 μg/L (SD: 25.9; range: 1-166 μg/L), and 8.5 μg/g (SD: 22.8; range: 1-135 μg/g), respectively. Of the children in the Nambija area 67-84.9% had abnormal RCPM standard scores (i.e., ≤ 25%tile), depending on the test norm used in the data analysis. Higher standard scores for Peruvian (t = 4.77; p = < 0.0001) and Puerto Rican (t = 4.51; p = < 0.0001) norms than for U.S. norms suggested a linguistic influence. No difference was found between Peruvian and Puerto Rican norms (t = 0.832; p = < 0.408), which showed a significant positive correlation (r = 0.915, p = < 0.0001). Children with abnormal HgB and HgH levels had significantly lower scores on the RCPM subtest B than did children with nontoxic Hg levels (t = -2.16; p = < 0.034). These results suggest that a substantial number of Hg-exposed children in the Nambija study area have neurocognitive deficits in visual-spatial reasoning.