Neurotoxicity may occur in children exposed to methylmercury during early life, but dose-response relationships are uncertain. Toxicokinetic factors affect the precision of the exposure assessment, as does the timing in relation to susceptible periods of brain development. Outcome variables vary in their psychometric properties and sensitivity at different ages and cultures. Confounders and other potential sources of bias may also hamper interpretation. In a large prospective study in the Faroe Islands, we measured mercury exposures at birth. At a follow-up examination of 917 children (90% of the cohort) 7 years later, mercury-related neuropsychological dysfunctions were seen, especially in attention, language and memory. In addition, delays were seen on evoked potentials as well as changes in heart rate control and blood pressure. Significant associations remained after confounder adjustments and exclusion of children with high exposures to mercury or increased concomitant exposures to PCB. In a new prospective cohort in the Faroes, more detailed documentation on organochlorine exposures is available. Preliminary results up to age 4.5 years confirm that prenatal methylmercury exposure is associated with decreased function on neurological assessment, and that organochlorines cause little confounding or interaction. In conjunction with cross- sectional studies on the island of Madeira and in the Amazon Basin, these studies demonstrate that widespread effects on nervous system function are associated with prenatal methylmercury exposure, even at exposure levels previously considered safe. Decisions on preventive actions should recognize that some uncertainties will remain that may not be fully resolved in the short term.
Learning Objectives: 1. Recognize methylmercury as one of several risk factors for developmental neurotoxicity 2. Identify the most important uncertainties in current knowledge on the dose-response relationship for methylmercury neurotoxicity 3. Discuss preventive approaches
Keywords: Environmental Exposures, Toxicants
Presenting author's disclosure statement:
Organization/institution whose products or services will be discussed: None
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.