ABSTRACT
The aim of the present study was to assess the impact of chronic exposure to polychlorinated biphenyls (PCBs) and methylmercury on visual brain processing in Inuit children from Nunavik (Northern Québec, Canada). Concentrations of total mercury in blood and PCB 153 in plasma had been measured at birth and they were again measured at the time of testing in 102 preschool aged children. Relationships between contaminants and pattern-reversal visual evoked potentials (VEPs) were assessed by multivariate regression analyses, taking into account several potential confounding variables. The possible protective effects of selenium and omega-3 polyunsaturated fatty acids against methylmercury and PCB toxicity were also investigated. Results indicate that exposure to methylmercury and PCBs resulting from fish and sea mammal consumption were associated with alterations of VEP responses, especially for the latency of the N75 and of the P100 components. In contrast, the concomitant intake of omega-3 polyunsaturated fatty acids was associated with a shorter latency of the P100. However, no significant interactions between nutrients and contaminants were found, contradicting the notion that these nutrients could afford protection against environmental neurotoxicants. Interestingly, significant associations were found with concentrations of neurotoxicants in blood samples collected at the time of testing, i.e. at the preschool age. Our findings suggest that VEP can be used as a valuable tool to assess the developmental neurotoxicity of environmental contaminants in fish-eating populations.
Subject(s)
Diet , Evoked Potentials, Visual/drug effects , Food Contamination , Methylmercury Compounds/toxicity , Polychlorinated Biphenyls/toxicity , Prenatal Exposure Delayed Effects , Animals , Antioxidants/pharmacology , Child , Child, Preschool , Confidence Intervals , Fatty Acids, Omega-3/pharmacology , Female , Humans , Infant, Newborn , Inuit , Male , Pregnancy , Reaction Time/drug effects , Reaction Time/physiology , Regression Analysis , Selenium/pharmacologyABSTRACT
In the neurotoxicology pediatric domain, few neuromotor tests are specifically designed to be sensitive enough for the early detection of subtle deficits in voluntary and involuntary movements. In research and clinical domains, an effort is done to objectify or quantify the qualitative aspects of a movement (pattern of movement) in predicting neurological problems. This study aimed to standardize quantitative motor measures initially developed for adults and adapted to the evaluation of preschoolers. The sample consisted of 110 healthy children aged 4-6. The following quantitative neuromotor tests were selected: alternating movements and pointing movements (DOCO Microsystèmes Inc., Montréal, Canada), postural tremor, postural sway and simple reaction time (Danish Product Development Ltd., Snekkersten, Denmark). Validation measures included global motor tasks and a neurological examination. Results indicate adequate test-retest reliability and complementarities amongst the selected voluntary and involuntary measures. Both the feasibility and relevance of quantitative neuromotor tests in preschool aged children were established. Results also provide a representation of intra-individual and inter-individual variability within this population. Lastly, the results highlight the importance of developmental factors, behavioral factors and testing conditions in the neuromotor evaluation of young children. The proposed tests could help in the early detection of children at risk for motor dysfunctions following neurotoxic exposure. The tests can also be used for the follow up of various conditions relating to motor functions (cerebral palsy, muscular dystrophy, preterm infants) and in the evaluation of the effects of medication.
Subject(s)
Neuromuscular Diseases/diagnosis , Neuropsychological Tests/standards , Neurotoxicity Syndromes/diagnosis , Psychomotor Performance/physiology , Attention/physiology , Child , Child, Preschool , Hair/chemistry , Humans , Individuality , Movement/physiology , Neuromuscular Diseases/etiology , Neurotoxicity Syndromes/complications , Postural Balance/physiology , Psychomotor Performance/drug effects , Reaction Time , Reproducibility of Results , Tremor/diagnosis , Tremor/physiopathologyABSTRACT
The aim of this study was to examine the effects of prenatal and postnatal chronic exposure to mercury (Hg), polychlorinated biphenyls (PCBs) and lead (Pb) on the neuromotor development of preschool children. The study population consisted of 110 preschool Inuit children from Nunavik (Canada). Blood Hg, PCBs and Pb concentrations were measured at birth (cord blood) and at the time of testing. Gross motor functions were evaluated and a neurological examination was performed. Fine neuromotor performance was assessed using quantitative measures of postural hand tremor, reaction time, sway oscillations, as well as alternating and pointing movements. Potential covariates were documented including demographic and familial characteristics, other prenatal neurotoxicants (alcohol, tobacco) and nutrients (selenium (Se), Omega-3 polyunsaturated fatty acids (n-3 PUFA)). Hierarchical multivariate regression analyses were performed, controlling for significant covariates. Gross motor development was not linked to prenatal exposures. However, significant associations were observed between blood Pb concentration at testing time and changes in reaction time, sway oscillations, alternating arm movements and action tremor. For some of these outcomes, neuromotor effects of Pb exposure are observed at blood concentrations below 10 microg/dl. Negative effects of PCBs on neuromotor development were not clearly observed, neither were the potential beneficial effects of n-3 PUFA and selenium. Tremor amplitude was related to blood Hg concentrations at testing time, which corroborate an effect already reported among adults.
