Inverse association between intelligence quotient and urinary retinol binding protein in Chinese school-age children with low blood lead levels: Results from a cross-sectional investigation

Abstract

Objectives: Examine the relationship between blood lead concentration and children’s intelligence quotient (IQ) in Chinese children 8–12years old. Participants and methods: This is a cross-sectional study, and participants included 446 children from three primary schools in Jiangsu, China. We collected environmental and genetic information from questionnaires. Blood lead (Pb), manganese (Mn), cadmium (Cd) and selenium (Se) concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS). IQ was assessed using the Combined Raven’s Test and then converted to a standard IQ score according to Chinese children’s norm. Morning urine samples were collected to measure retinol binding protein (RBP). Results: The average blood lead concentration was 33.13μgL−1 (geometric mean), and the blood lead concentration (BoxCox transform) was inversely and significantly associated with IQ (r=−0.11, p=0.02). The geometric mean of blood Mn, Cd and Se was 7.02μgL−1, 0.18μgL−1 and 94.77μgL−1, respectively. Blood Mn, Cd and Se showed no association with IQ, but all of them associated with urinary RBP. Urinary RBP was identified as a new factor associated with IQ (β=−6.49, p=0.011). Conclusions: Urinary RBP was recognized as a new indicated factor associated with children’s IQ. Mn, Cd and Se exposure might affect urinary RBP concentration and further IQ. Findings also support that blood lead concentrations in 8–12years old children, even <44μgL−1, have a negative association with IQ.