Impact of prenatal methylmercury exposure on neurobehavioral function at age 14 years

Abstract

A cohort of 1022 consecutive singleton births was generated during [1987][1988] in the Faroe Islands, where increased methylmercury exposure occurs from traditional seafood diets that include pilot whale meat. The prenatal exposure level was determined from mercury analyses of cord blood, cord tissue, and maternal hair. At age 14 years, 878 of 1010 living cohort members underwent detailed neurobehavioral examination. Eighteen participants with neurological disorders were excluded. Blood and hair samples obtained from the participants were analyzed for mercury. The neuropsychological test battery was designed based on the same criteria as applied at the examination at age 7 years. Multiple regression analysis was carried out and included adjustment for confounders. Indicators of prenatal methylmercury exposure were significantly associated with deficits in finger tapping speed, reaction time on a continued performance task, and cued naming. Postnatal methylmercury exposure had no discernible effect. These findings are similar to those obtained at age 7 years, and the relative contribution of mercury exposure to the predictive power of the multiple regression models was also similar. An analysis of the test score difference between results at 7 and 14 years suggested that mercury-associated deficits had not changed between the two examinations. In structural equation model analyses, the neuropsychological tests were separated into five groups; methylmercury exposure was significantly associated with deficits in motor, attention, and verbal tests. These findings are supported by independent assessment of neurophysiological outcomes. The effects on brain function associated with prenatal methylmercury exposure therefore appear to be multi-focal and permanent.

Total imprecision of exposure biomarkers: implications for calculating exposure limits

“…Further, the results agree with independent regression analyses, where cord blood tended to be the best predictor of neurobehavioral deficits at age 7 years. The recently completed 14-year examinations also confirmed these findings [Debes et al, 2006].…”

Selenium as a Potential Protective Factor Against Mercury Developmental Neurotoxicity

“…Mercury-related neuropsychological dysfunctions were most pronounced in the domains of language, attention, and memory, and to a lesser extent, in visuospatial and motor functions. In addition, delayed peak latencies in the brainstem auditory evoked potentials (BAEP) were associated with prenatal and recent MeHg exposure (Debes et al, 2006;Grandjean et al, 1997;Murata et al, 2004). Impaired performance on behavioral tasks, such as the differential reinforcement of low rates task (DRL), has been found among children prenatally exposed to low-level MeHg and other environmental contaminants (Stewart et al, 2006).…”

Expressing urine from a gel disposable diaper for biomonitoring using phthalates as an example

“…Another example of a particularly susceptible subpopulation of children is children whose families (e.g. indigenous peoples) rely on marine mammals and fish, which may be heavily contaminated with persistent organic pollutants (POPs) or heavy metals, for subsistence food (Damstra, 2002;Barr et al, 2006;Debes et al, 2006). WHO considers social, cultural, and economic factors to be major determinants of ill-health, the "causes behind the causes" of morbidity and mortality.…”