Relationship between environmental phthalate exposure and the intelligence of school-age children.
BACKGROUND
Concern over phthalates has emerged because of their potential toxicity to humans.


OBJECTIVE
We investigated the relationship between the urinary concentrations of phthalate metabolites and children's intellectual functioning.


METHODS
This study enrolled 667 children at nine elementary schools in five South Korean cities. A cross-sectional examination of urine phthalate concentrations was performed, and scores on neuropsychological tests were obtained from both the children and their mothers.


RESULTS
We measured mono-2-ethylhexyl phthalate (MEHP) and mono(2-ethyl-5-oxohexyl)phthalate (MEOHP), both metabolites of di(2-ethylhexyl)phthalate (DEHP), and mono-n-butyl phthalate (MBP), a metabolite of dibutyl phthalate (DBP), in urine samples. The geometric mean (ln) concentrations of MEHP, MEOHP, and MBP were 21.3 microg/L [geometric SD (GSD) = 2.2 microg/L; range, 0.5-445.4], 18.0 microg/L (GSD = 2.4; range, 0.07-291.1), and 48.9 microg/L (GSD = 2.2; range, 2.1-1645.5), respectively. After adjusting for demographic and developmental covariates, the Full Scale IQ and Verbal IQ scores were negatively associated with DEHP metabolites but not with DBP metabolites. We also found a significant negative relationship between the urine concentrations of the metabolites of DEHP and DBP and children's vocabulary subscores. After controlling for maternal IQ, a significant inverse relationship between DEHP metabolites and vocabulary subscale score remained. Among boys, we found a negative association between increasing MEHP phthalate concentrations and the sum of DEHP metabolite concentrations and Wechsler Intelligence Scale for Children vocabulary score; however, among girls, we found no significant association between these variables.


CONCLUSIONS
Controlling for maternal IQ and other covariates, the results show an inverse relationship between phthalate metabolites and IQ scores; however, given the limitations in cross-sectional epidemiology, prospective studies are needed to fully explore these associations.
Cho
Soo-Churl
SC
Department of Psychiatry and Institute of Human Behavioral Medicine, Seoul National University College of Medicine, Republic of Korea.
Bhang
Soo-Young
SY
Hong
Yun-Chul
YC
Shin
Min-Sup
MS
Kim
Boong-Nyun
BN
Kim
Jae-Won
JW
Yoo
Hee-Jung
HJ
Cho
In Hee
IH
Kim
Hyo-Won
HW
D000704:Analysis of Variance; D002648:Child; D003404:Creatinine / Q000652:urine; D004781:Environmental Exposure; D004785:Environmental Pollutants / Q000633:toxicity* / Q000652:urine; D005260:Female; D006801:Humans; D007360:Intelligence / Q000187:drug effects*; D008297:Male; D010795:Phthalic Acids / Q000633:toxicity* / Q000652:urine; D012044:Regression Analysis; D056910:Republic of Korea; D014888:Wechsler Scales
D004785:Environmental Pollutants; D010795:Phthalic Acids; C032279:phthalic acid; D003404:Creatinine