Lead contamination and child neurodevelopment: a review of biochemical mechanisms and cognitive health outcomes

Lead contamination is a longstanding environmental health issue worldwide and continues to threaten children by contaminating soil, household dust, drinking water, food, industrial waste, informal recycling processes, and maternal-fetal transfer. Children are especially vulnerable due to an increase in gastrointestinal absorption, hand-to-mouth, poor detoxification mechanisms and rapid neurological development, hypocritical, foetal life, infancy and early childhood. This report was a systematic review of a study on the association between child neurodevelopment and lead contamination, focusing on biochemical pathways and cognitive health. The review was conducted according to the PRISMA 2020 guidelines. 80 records were identified, 12 of which were duplicates, and 68 distinct research papers were analysed. After the eligibility assessment, 61 studies were included in the core qualitative synthesis, and 7 were retained as supporting contextual literature. The studies included were prospective cohort studies, cross-sectional studies, neuroimaging studies, mechanistic reviews, systematic reviews and meta-analyses. The findings indicated that lead exposure in children is multi-environmental and aggravated by developmental toxicokinetics, including increased absorption, placental transfer, and bone retention. The lead neurotoxicity was mediated biologically by oxidative stress, calcium pathway interference, mitochondrial impairment, apoptosis, neuroinflammation, synaptic impairment and epigenetic modification. Developmental delay, lower intelligence quotient, executive dysfunction, attention and behavioural issues, language and learning difficulties, motor impairment, and altered brain connectivity were the most commonly reported, and some studies suggest they persist into adult mental and structural brain functions. Childhood lead exposure is a severe, preventable, and life-course neurodevelopmental risk that needs increased environmental control, biomonitoring and protection of vulnerable populations.