An Air Cleaner Intervention Study of Air Pollution and Children's Cognitive Development: The Ulaanbaatar Gestation and Air Pollution Research (UGAAR) study

Prenatal exposure to fine particulate matter (PM2.5) may impair children's neurodevelopment. Effects of indoor PM2.5 on neurodevelopment, and the neurodevelopmental benefits of using portable high efficiency particulate air (HEPA) filter air cleaners to reduce PM2.5, have not been evaluated. My research aimed to (1) evaluate the impact of HEPA filter air cleaner use during pregnancy on neurodevelopment, (2) identify characteristics of children who benefitted the most after their mothers used HEPA filter air cleaner during pregnancy, and (3) examine the association between indoor PM2.5 concentrations during pregnancy and neurodevelopment in childhood. Study staff assigned 540 nonsmoking pregnant women to receive 1-2 portable HEPA filter air cleaners or no air cleaners during pregnancy. Health, demographic, and lifestyle data were collected through home and clinical visits and from clinic records. Maternal hair samples were analyzed for cortisol and dehydroepiandrosterone (DHEA). The primary outcome was full-scale intelligence quotient (FSIQ) measured by using the Wechsler Preschool and Primary Scale of Intelligence, Fourth Edition (WPPSI-IV), when children were a median of 48 months old. I estimated the effect of the intervention on mean FSIQ using multiple imputation with chained equations (MICE) in an intention to treat analysis. I also evaluated potential modifiers of the intervention-FSIQ relationship. Finally, I examined the relationship between indoor PM2.5 averaged over the full pregnancy and each trimester and FSIQ. The mean FSIQ among children in intervention group was 2.5 points (CI: −0:4, 5.4 points) higher than that of children in the control group. The largest between-group difference in the intervention's effect was a 7.5-point (95% CI: -0.7, 15.7) larger increase in mean FSIQ among children whose mothers did not take vitamins than among children whose mothers did take vitamins. A 9.4 µg/m3 increase in indoor PM2.5 concentration over the full pregnancy was associated with a reduction of 1.1 points (95% CI: -3.7, 1.5) in mean FSIQ. A 20.7 µg/m3 increase PM2.5 concentrations during first trimester was associated with a reduction of 3.5 points (95% CI: 0.7, 6.6) in mean FSIQ. Indoor PM2.5, particularly during early pregnancy, may impair children's brain development but reducing exposure improved mean FSIQ scores. This benefit was more pronounced for children of mothers who did not take vitamins during pregnancy.