Objective To investigate the relationship between the level of heavy metal and metalloid in blood and intelligence level of adolescents aged 11 to 15 years in an area of Zibo.
Methods 839 adolescents aged 11 to 15 were selected by stratified cluster sampling. The demographic, behavioral and lifestyle data of the subjects were obtained through questionnaire survey. At the same time, the intelligence level of the subjects was evaluated by Combined Raven's test (CRT). Fasting venous blood was collected, and four elements of blood, including Pb, Cd, Cr and As, were detected by inductively coupled plasma mass spectrometry (ICP-MS). Linear regression single factor analysis was used to investigate the correlation between the levels of four elements and intelligence level. Multiple linear regression model was used to further analyze the relationship between internal exposure level of four heavy metals in blood and intelligence level of adolescents by controlling related confounding factors.
Results The geometric mean values of four elements in the whole blood of 839 adolescents were 16.12 μg/L(Pb), 0.17 μg/L(Cd), 0.50 μg/L(Cr), 1.68 μg/L (As), respectively. Both linear regression single factor analysis and multiple linear regression analysis after controlling confounding factors showed that under the combined exposure of environmental lead, cadmium, chromium and arsenic, only blood lead was significantly negatively correlated with adolescents' intelligence (P < 0.05). An increase of blood lead level from the lower quartile (12.80 μg/L) to the upper quartile (19.76 μg/L) was associated with a decrease of 1.59 points in intelligence test scores of adolescents.
Conclusion Low dose exposure to environmental lead and other heavy metals may increase the risk of intellectual impairment and affect intellectual development of adolescents in the study area.
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