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. Author manuscript; available in PMC: 2020 Sep 1.
Published in final edited form as: Environ Int. 2019 Jun 22;130:104935. doi: 10.1016/j.envint.2019.104935

Table 4.

Associations between near-roadway air pollution (NRAP) exposure and NEFA-related metabolomic principal component (PC)1 scores stratified by sex and race/ethnicity among adolescents and young adults in the Children’s Health Study.

NRAP Exposure Males
(N=94)		 Females
(N=79)		 Interaction
p3 		Non-Hispanic
Whites
(N=50)		 Hispanic
Whites
(N=97)		 Interaction
p4
β2 p β2 p β2 p β2 p
Long-term exposure5
 Freeway NRAP −0.13 0.55 0.52 0.0 42 0.049 −0.30 0.63 0.17 0.35 0.27
 Non-freeway NRAP 0.31 0.08 0.50 0.032 0.21 0.24 0.39 0.39 0.044 0.62
 Total NRAP −0.05 0.83 0.65 0.008 0.049 −0.05 0.93 0.23 0.21 0.29
Short-term exposure6
 Freeway NRAP −0.15 0.51 0.71 0.008 0.033 −0.40 0.55 0.24 0.16 0.49
 Non-freeway NRAP 0.32 0.09 0.45 0.06 0.44 0.31 0.30 0.32 0.11 0.75
 Total NRAP −0.07 0.76 0.74 0.005 0.036 −0.06 0.92 0.27 0.12 0.52
1.

NEFA-related metabolomic PC (also known as PC2 in this paper) represents non-esterified fatty acids (NEFA) and NEFA oxidation by-products including long-chain acylcarnitines, acetylcarnitine (C2) and 3-Hydroxybutyrylcarnitine (C4-OH), which explains 10.2% variance of concentrations of all 63 metabolites analyzed in the study samples.

2.

Mixed effects model was used to estimate regression associations between freeway, non-freeway and total NRAP exposure with the outcome variables of metabolomic factor scores after adjusting for confounders including age, sex, race/ethnicity, parental education levels as a proxy for social economic status, whether or not smoked cigarettes during the last week, ever/never smoked electronic cigarettes, season of the study visit and random intercepts for CHS communities and metabolomics analytical batches. NRAP exposure was scaled by two standard deviations. Association estimates (β) and p-values for significance of statistical tests are presented in the table.

3.

Interaction p-values <0.05 represent statistically significant differences in effect sizes for the associations between NRAP exposure and PC2 score comparing males to females.

4.

Interaction p-values <0.05 represent statistically significant differences in effect sizes for the associations between NRAP exposure and PC2 score comparing Non-Hispanic Whites to Hispanic Whites.

5.

Long-term air pollution exposure was estimated by cumulative averages of monthly exposure concentrations over one year prior to the study visit and were weighted by time spent at each different address.

6.

Short-term air pollution exposure was estimated by one-month exposure concentrations prior to the study visit.