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Visual functions in 6-year-old children in relation to lead and mercury levels
L Altmann1, K Sveinsson, U Krämer
1Medical Institute of Environmental Hygiene, Heinrich-Heine-University, Düsseldorf, Germany. altmannl@rz.uni-duesseldorf.de
Insights
Environmental toxins like lead and mercury can subtly impact children's developing visual systems. This study measured visual-evoked potentials (VEPs) and contrast sensitivity (CS) in relation to blood lead and mercury levels.
Area of Science:
- Environmental Health
- Neuroscience
- Ophthalmology
Background:
- The developing visual system is sensitive to environmental exposures.
- Lead and mercury are common environmental contaminants with potential neurotoxic effects.
Purpose of the Study:
- To investigate the relationship between environmental lead and mercury exposure and visual system functions in children.
- To assess neurophysiological (visual-evoked potentials) and psychophysical (contrast sensitivity) outcomes.
Main Methods:
- Field experiments involving 384 children in East and West Germany.
- Measurement of blood lead and urinary mercury levels as exposure biomarkers.
- Neurophysiological assessment using visual-evoked potentials (VEPs).
- Psychophysical assessment of contrast sensitivity (CS).
- Linear regression analysis to determine relationships between exposure and outcomes, adjusting for confounders.
Main Results:
- Statistically significant alterations in some VEP interpeak latencies were associated with blood lead concentrations.
- Significant reductions in contrast sensitivity (CS) were observed with increasing urinary mercury levels.
- No significant relationships were found for other measured visual function outcomes and exposure levels.
Conclusions:
- Even low-level environmental exposure to lead and mercury can induce measurable, subtle changes in children's visual system functions.
- VEPs and CS are sensitive indicators for detecting neurodevelopmental effects of environmental toxins.
Abstract:
Within a larger comparative environmental health screening program in East and West Germany we investigated functions of the developing visual system in field experiments in a total of 384 children living in three different areas. Visual functions were assessed neurophysiologically by visual-evoked potentials (VEPs) and psychophysically by measuring the contrast sensitivity (CS). Blood lead concentrations and urinary mercury levels were used as markers of environmental and/or amalgam-derived exposure, respectively. The relationships among lead and mercury concentrations and the neurophysiological and psychophysical outcomes were investigated by means of linear regression analysis. After adjusting for confounding effects, statistically significant lead-related changes were found only for some of the VEP interpeak latencies, while some of the CS values were significantly reduced with increasing mercury concentrations. All other outcome variables were not significantly related to lead or mercury levels. It is concluded that even at blood lead levels in the range of 14 to 174 micrograms/l and at very low urinary mercury levels subtle changes in visual system functions can be measured.