Fetal Exposure to Air Pollution in Late Pregnancy Significantly Increases ADHD-Risk Behavior in Early Childhood

Abstract

Background: Air pollution nowadays has seriously threatened the health of the Chinese population, especially in the vulnerable groups of fetuses, infants and toddlers. In particular, the effects of air pollution on children’s neurobehavioral development have attracted widespread attention. Moreover, the early detection of a sensitive period is very important for the precise intervention of the disease. However, such studies focusing on hyperactive behaviors and susceptible window identification are currently lacking in China. Objectives: The study aims to explore the correlation between air pollution exposure and hyperactive behaviors during the early life stage and attempt to identify whether a susceptible exposure window exists that is crucial for further precise intervention. Methods: Based on the Longhua Child Cohort Study, we collected the basic information and hyperactivity index of 26,052 children using a questionnaire conducted from 2015 to 2017, and the Conners’ Parent Rating Scale-revised (CPRS-48) was used to assess hyperactive behaviors. Moreover, the data of air pollution concentration (PM10, PM2.5, NO2, CO, O3 and SO2) were collected from the monitoring station between 2011 to 2017, and a land-use random forest model was used to evaluate the exposure level of each subject. Furthermore, Distributed lag non-linear models (DLNMs) were applied for statistic analysis. Results: The risk of child hyperactivity was found to be positively associated with early life exposure to PM10, PM2.5 and NO2. In particular, for an increase of per 10 µg/m3 in PM10, PM2.5 and NO2 exposure concentration during early life, the risk of child hyperactivity increased significantly during the seventh month of pregnancy to the fourth month after birth, with the strongest association in the ninth month of pregnancy (PM10: OR = 1.043, 95% CI: 1.016–1.071; PM2.5: OR = 1.062, 95% CI: 1.024–1.102; NO2: OR = 1.043, 95% CI: 1.016–1.071). However, no significant associations among early life exposure to CO, O3 and SO2 and child hyperactive behaviors were observed. Conclusions: Early life exposure to PM10, PM2.5 and NO2 is associated with an increased risk of child ADHD-like behaviors at the age around 3 years, and the late-prenatal and early postnatal periods might be the susceptible exposure windows.

Prenatal Exposure to Air Pollutants and Attentional Deficit Hyperactivity Disorder Development in Children: A Systematic Review

“…Yorifuji et al (2016, 2017) [ 55 , 56 ] also found NO 2 exposure during pregnancy to be strongly correlated with ADHD symptoms, such as interrupting people [aOR = 1.02, 95% CI (0.95, 1.09)], inability to wait his/her turn during play [aOR = 1.00, 95% CI (0.87, 1.14)] or failure to pay attention when crossing the street [aOR = 1.10, 95% CI (1.02, 1.19)]. Liu et al (2022) [ 65 ] found a significant increase in hyperactivity in children when exposed to NO 2 [OR = 1.04, 95% CI (1.06–1.07)] during the seventh month of pregnancy and up to four months after birth, but a peak was observed at nine months of pregnancy. However, the remaining four studies by Gong et al (2014) [ 52 ], Fuertes et al (2016) [ 54 ], Forns et al (2018) [ 57 ], and Oudin et al (2019) [ 59 ] did not find any significant or clear evidence to support the association between NO x and the risk of developing ADHD.…”

“…Chang et al (2022) [ 64 ] found that ADHD was significantly associated with a 10 μg/m 3 increase in PM 2.5 during the first trimester [OR = 1.26, 95% CI (1.13–1.40)], and increased at PM 2.5 over 16 μg/m 3 . Furthermore, Liu et al (2022) [ 65 ] found a significant increase in hyperactivity in children when exposed to PM 10 [OR = 1.04, 95% CI (1.06–1.07)] and PM 2.5 [OR = 1.06, 95% CI (1.02–1.10)] during the seventh month of pregnancy and up to four months after birth but the peak is observed at nine months of pregnancy, whereas the remaining four studies by Forns et al (2018) [ 57 ], Gong et al (2014) [ 58 ], Shih et al (2020) [ 62 ], and Peterson et al (2022) [ 63 ] did not find an association between PM and ADHD.…”

“…Two out of the four studies found an association between prenatal SO 2 exposure and ADHD symptoms; however, an elevated exposure effect was observed at the age of 2.5 years for interrupting people [aOR = 1.04, 95% CI (1.00, 1.08)], inability to wait for his/her turn during play [aOR = 1.03, 95% CI (0.94, 1.12)], and failure to pay attention when crossing the street [aOR = 1.06, 95% CI (1.01, 1.11)] [ 54 , 55 ], whereas Shih et al (2020) [ 62 ] and Liu et al (2022) [ 65 ] did not find significant results in relation to SO 2 and hyperactivity.…”

Prenatal exposure to ambient air pollution is associated with neurodevelopmental outcomes at 2 years of age

“…Studies assessing children younger than school age report that prenatal exposure to NO 2 is associated with poorer cognitive development at ~14 months [ 19 ] and poorer global psychomotor development [ 17 ] between 1–6 years while prenatal PAH exposure is associated with poorer cognitive development at age 3 [ 18 ]. In addition, PM 10 , PM 2.5 , and NO 2 exposure in the late-prenatal and early postnatal periods have been associated with an increased risk of ADHD-like behaviors in children around age 3 [ 22 ].…”

“…Many of these processes occur throughout gestation where neurogenesis can begin as early as week six and end by mid-gestation while others, such as circuit formation and myelination, are not observed until mid-gestation and continue beyond birth at rapid pace [ 23 – 26 ]. Additionally, a substantial body of work highlights how disruptive events (environmental, immunological, stress) during pregnancy negatively impact neurodevelopment [ 27 – 29 ], where air pollution research has primarily implicated the mid-late gestational periods, when migration, synaptogenesis, myelination, and circuit formation begin to occur [ 24 , 26 , 29 , 30 ], as critical windows of exposure [ 16 , 21 , 22 ].…”