Previous studies have suggested adverse effects of arsenic and lead exposure (even at low levels) on children's cognitive function, including lower IQ scores, impaired attention and memory, and behavioural problems (Lanphear et al., 2005; Rosado et al., 2007). Copper deficiency during gestation can negatively affect motor function, balance and coordination (Georgieff, 2007), whilst excessive free copper may play a role on adult cognitive decline (Salustri et al., 2010). Methylmercury is a known neurotoxicant that can be found as a contaminant in fish. However, it has been difficult to assess its effects on cognitive ability independently of the beneficial effects of fish intake (Daniels et al., 2004).

Aims: To examine the role of prenatal and postnatal levels of metals on the cognitive development of children. We will use genetic variants robustly associated with serum concentrations of arsenic, copper, lead and mercury, identified through genomewide association studies (GWAS), as proxies for these exposures and investigate their association with offspring IQ scores and school test results.Hypotheses: We hypothesise that alleles which increase levels of circulating toxic metals such as arsenic, lead and mercury will be associated with a worse performance in cognitive tests. With respect to copper, both high and low serum levels could potentially lead to an adverse cognitive outcome.