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Increased ERG a- and b-Wave Amplitudes in 7- to 10-Year-Old Children Resulting from Prenatal Lead Exposure

¹ From the National Institute of Public Health, Cuernavaca, Mexico; ² Environmental Research Center and Department of Anesthesiology, Charles R. Drew University of Medicine and Science, Los Angeles, California; the ³ National Institute of Perinatology, Mexico City, Mexico; the ⁴ U.S. Environmental Protection Agency, Division of Neurotoxicology, Research Triangle Park, North Carolina; and ⁵ College of Optometry, Departments of Biology and Biochemistry, and Pharmacology and Pharmaceutical Sciences, University of Houston, Houston, Texas.

PURPOSE. To determine the dose–response relationship between blood lead concentration ([PbB]) and scotopic ERG amplitude in 7- to 10-year-old children with lifetime lead exposure.

METHODS. Full-field flash scotopic ERGs were recorded over a 4-log-unit range in 45 dark-adapted children with normal visual acuity. [PbB] was measured throughout pregnancy and postnatal development, and the subjects’ [PbB] levels were grouped at each age by tertiles.

RESULTS. The median [PbB] during pregnancy was, from lowest to highest tertile, 2.5 to 5.0, 7.5 to 9.0, and 14.0 to 16.5 µg/dL, and after birth was 4.0 to 8.0, 6.0 to 14.5, and 7.5 to 21.0 µg/dL. Only maternal [PbB] at 12 weeks of pregnancy showed a significant dose–response relationship with the ERG measures, so that with increasing [PbB] there were significant increases in leading-edge a-wave amplitude, peak a-wave amplitude, and b-wave amplitude and sensitivity, with no changes in implicit times. Data analyses showed that children whose mothers had [PbB] of 10.5 µg/dL or more at 12 weeks of pregnancy had relatively increased a- and b-waves.

CONCLUSIONS. Lead exposure during the first trimester of pregnancy produces dose-dependent increases in scotopic a- and b-wave amplitudes in 7- to 10-year-old children. The results suggest that the increases in a- and b-wave amplitudes originate from rods; however, the increased b-wave amplitude and sensitivity may also originate in the inner retina. These alterations occurred at maternal [PbB] at or below currently accepted safe levels. These novel findings reveal that the developing retina is a sensitive target for lead and suggest that lead-exposed children be examined for possible future visual system deficits.

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