Associations of prenatal and early childhood mercury exposure with autistic behaviors at 5 years of age: The Mothers and Children’s Environmental Health (MOCEH) study

Science of The Total Environment
Volumes 605–606, 15 December 2017, Pages 251-257

Associations of prenatal and early childhood mercury exposure with autistic behaviors at 5 years of age: The Mothers and Children’s Environmental Health (MOCEH) study

Author
JiaRyu a,Eun-HeeHa a,Boong-Nyun Kim b, Mina Ha c, Yangho Kim d, Hyesook Park e, Yun-Chul Hong f, Kyoung-Nam Kim f g
a Department of Occupational and Environmental Medicine, School of Medicine, Ewha Womans University, Seoul, Republic of Korea
b Division of Child & Adolescent Psychiatry, Department of Psychiatry and Institute of Human Behavioral Medicine, College of Medicine, Seoul National University, Seoul, Republic of Korea
c Department of Preventive Medicine, College of Medicine, Dankook University, Cheonan, Republic of Korea
d Department of Occupational and Environmental Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Republic of Korea
e Department of Preventive Medicine, School of Medicine, Ewha Womans University, Seoul, Republic of Korea
f Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea
g Institute of Public Health and Medical Service, Seoul National University Hospital, Seoul, Republic of Korea
Received 26 April 2017, Revised 24 June 2017, Accepted 26 June 2017, Available online 28 June 2017.

https://doi.org/10.1016/j.scitotenv.2017.06.227

Highlights
• We explored the associations between blood mercury levels and autistic behaviors.

• This study involved an ongoing multi-center prospective birth cohort.

• Blood mercury levels were repeatedly measured from early pregnancy to 3 years.

• Autistic behaviors were assessed at 5 years with the Social Responsiveness Scale.

• Prenatal and early childhood mercury levels were associated with autistic behaviors.

Abstract
Background
Although mercury is an established neurotoxin, only few longitudinal studies have investigated the association between prenatal and early childhood mercury exposure and autistic behaviors.

Methods
We conducted a longitudinal cohort study using an ongoing prospective birth cohort initiated in 2006, wherein blood mercury levels were measured at early and late pregnancy; in cord blood; and at 2 and 3 years of age. We analyzed 458 mother-child pairs. Autistic behaviors were assessed using the Social Responsiveness Scale (SRS) at 5 years of age. Both continuous SRS T-scores and T-scores dichotomized by a score of ≥ 60 or < 60 were used as outcomes.

Results
The geometric mean of mercury concentrations in cord blood was 5.52 μg/L. In adjusted models, a doubling of blood mercury levels at late pregnancy (β = 1.84, 95% confidence interval [CI]: 0.39, 3.29), in cord blood (β = 2.24, 95% CI: 0.22, 4.27), and at 2 years (β = 2.12, 95% CI: 0.54, 3.70) and 3 years (β = 2.80, 95% CI: 0.89, 4.72) of age was positively associated with the SRS T-scores. When the SRS T-scores were dichotomized, we observed positive associations with mercury levels at late pregnancy (relative risk [RR] = 1.31, 95% CI: 1.08, 1.60) and in cord blood (RR = 1.28, 95% CI: 1.01, 1.63).

Conclusion
We found that blood mercury levels at late pregnancy and early childhood were associated with more autistic behaviors in children at 5 years of age. Further study on the long-term effects of mercury exposure is recommended.