At a population level the main impacts of lead exposure arise from its effects on neurocognitive development in children and on cardiovascular disease in adulthood. In children the greater risk of reduced cognitive ability, IQ, attention and visualmotor and reasoning skills, as well as impacts on social behaviour all contribute to an increased public health and economic burden.
While the estimated IQ decrease in children from lead poisoning is small (6.9 points over the blood concentration range 2.4 to 30 µg/dL), the impact at the population level can be important (Bellinger, 2004b; Lanphear et al., 2005). It is estimated that a mean IQ reduction of 3 points from 100 to 97 would increase the number of individuals with an IQ below 100 by 8% and there would be a 57% increase in individuals with an IQ below 70 (commonly considered the cut-off for identifying individuals with intellectual disability).
There would also be a 40% reduction in potentially high-achieving individuals with an IQ score greater than 130 (Bellinger, 2004b; JECFA, 2011). In the case of blood pressure, a review by Healey et al. (2010) estimated that for the Canadian population a change in blood lead concentrations in adults from 1 µg/dL to 4 µg/dL would be associated with an estimated increase in mean systolic blood pressure of approximately 0.8 mmHg (0.11 kPa) among Caucasian males and 1.4 mmHg (0.19 kPa) in susceptible subpopulations.
While the impact at the individual level is small, increases in blood pressure are associated with age-specific increased mortality rates for both ischaemic heart disease and stroke (Lewington et al., 2002; Fewtrell et al., 2003). Based on 2015 data, lead exposure is estimated to account for 12.4% of the global burden of idiopathic intellectual disability, 2.5% of the global burden of ischaemic heart disease and 2.4% of the global burden of stroke (IHME, 2016).
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