MATERNAL MERCURY LEVELS ARE RELATED TO NEURO-COGNITIVE DEVELOPMENT AT AGE 6 MONTHS

Abstract

ISEE-79 Introduction: Coal-burning in Poland is a major source of environmental mercury exposure, via air pollution or bio- accumulation in the food chain. Aim: The purpose of the study was to assess the neuro-cognitive status of 6-month-old infants whose mothers were exposed to low but varying amounts of mercury during pregnancy. Methods: Mercury levels in maternal blood at delivery were used to assess environmental exposure to mercury; and the Fagan Test of Infant Intelligence (FTII) assessed visual recognition memory (VRM). The cohort consisted of 233 infants of mothers who gave birth to babies at 33–42 weeks of gestation, between January 2001 and March 2003. None of the children manifested obvious neurological abnormalities at the development check-up. Results: VRM in 6-month-olds, as measured by novelty scores from the FTII, was inversely related to maternal blood mercury levels. The estimated risk of scoring in the suspected or at risk groups for developmental delay (FTII risk group classifications 2+3) due to higher mercury blood levels (above 0.50 μg/L) was threefold greater (OR = 3.21, CI = 1,12 to 9.20), than for lower mercury blood levels (≤ 0.5 μg/dL), after adjusting for potential confounders such as gestational age, gender of the child, maternal education, exposure to environmental tobacco smoke and lead. Conlcusion: The results of the study suggest that the Fagan Test may be a sensitive end-point for low level mercury exposure and that the group of infants at risk of delayed neuro-cognitive development may be defined by a maternal blood mercury level exceeding 0.5 μg/L at delivery. As the risk of reduced VRM attributable to this exposure level is 63%, a large portion of developmental delay could be prevented by reducing maternal blood mercury level below 0.5 μg/L.