Co-exposure to environmental lead and manganese affects the intelligence of school-aged children.
BACKGROUND
Exposure to environmental levels of lead (Pb) and manganese (Mn) has been associated with detrimental effects to neurodevelopment. However, little is known about the potential association between environmental levels of Pb and Mn on intelligence of children. The aims of the study were to investigate the association of community level of Pb and Mn with the intelligence of school-aged children, and to explore the implications of joint exposure to these two heavy metals.


METHODS
A cross-sectional examination of blood Pb and Mn concentrations was performed, and the intelligence quotient (IQ) was determined for 261 Korean children aged 8-11 years.


RESULTS
The mean blood concentrations of Pb and Mn were 1.73 microg/dL (SD=0.8; median=1.55; range=0.42-4.91) and 14.3 microg/L (SD=3.8; median=14.0; range=5.30-29.02), respectively. Both Pb and Mn showed significant linear relationship with full-scale IQ (Pb, beta=-0.174, p=0.005; Mn, beta=-0.123, p=0.042) and verbal IQ (Pb, beta=-0.187, p=0.003; Mn, beta=-0.127, p=0.036). Blood Pb (DeltaR(2)=0.03) and Mn (DeltaR(2)=0.01) explained 4% of the variances of the full-scale IQ and 5% of the variances of the verbal IQ. When Pb and Mn levels were entered as predictive variables, additive increase in the explained variances was observed. Finally, full-scale IQ and verbal IQ of the children with blood Mn>14 microg/L showed significant association with Pb, whereas group with Mn<14 microg/L did not, suggesting effect modification between Pb and Mn.


CONCLUSIONS
The present study suggests the presence of additive interaction and effect modification between Pb and Mn on the intelligence of school-aged children, suggesting more attention should be paid to preventing the exposure of disadvantaged children to various combinations of toxic materials.
Kim
Yeni
Y
Division of Child & Adolescent Psychiatry, Department of Psychiatry and Institute of Human Behavioral Medicine, Seoul National University College of Medicine, 28 Yeongun-Dong, Chongno-Gu, Seoul, 110-744, Republic of Korea.
Kim
Bung-Nyun
BN
Hong
Yun-Chul
YC
Shin
Min-Sup
MS
Yoo
Hee-Jeong
HJ
Kim
Jae-Won
JW
Bhang
Soo-Young
SY
Cho
Soo-Churl
SC
D002648:Child; D003430:Cross-Sectional Studies; D004781:Environmental Exposure; D004785:Environmental Pollutants / Q000633:toxicity*; D005260:Female; D006801:Humans; D007360:Intelligence / Q000187:drug effects* / Q000502:physiology; D007361:Intelligence Tests; D007854:Lead / Q000097:blood / Q000633:toxicity*; D007855:Lead Poisoning / Q000503:physiopathology*; D008297:Male; D008345:Manganese / Q000097:blood / Q000633:toxicity*; D020149:Manganese Poisoning / Q000503:physiopathology*; D009483:Neuropsychological Tests
D004785:Environmental Pollutants; D007854:Lead; D008345:Manganese