Visual functions in 6-year-old children in relation to lead and mercury levels.

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.