Spatial variability of the effect of air pollution on term birth weight: evaluating influential factors using Bayesian hierarchical models

Table 1 Statistics for the means of the target and individual-level variable across Census tracts

Type	Variable	Category	Mean	Median	Inter quartile range (IQR)^a
Target variable	Term birth weight (g)		3393	3392	58 (3363,3421)
Pollution indicator	Spatiotemporal NO₂ (ppb)^b		25.00	24.14	11.43 (18.74, 30.17)
Pollution indicator	Spatiotemporal NO_x (ppb)^c		17.32	26.31	31.32 (15.48, 46.80)
Individual- level variable	NDVI		0.26	0.25	0.09 (0.21, 0.30)
	Maternal age		28.8	28.1	4.1 (26.7, 30.8)
	Length of gestation		277	276	12 (271,283)
	Infant gender (percentage)	Male	49 %	49 %	6 % (46–52 %)
	Infant gender (percentage)	Female	51 %	51 %	6 % (48–54 %)
	Race/ethnicity (percentage)	Hispanic	54 %	57 %	57 % (26–83 %)
		White	24 %	12 %	43 % (2–45 %)
		Black	6 %	3 %	5 % (0.8–6 %)
		Asian	13 %	8 %	14 % (2–16 %)
		Others	2 %	1 %	2 % (1–3 %)
	Maternal educational level (percentage)	Less than 8th grade	10 %	8 %	15 % (1–16 %)
		9th grade to high school	42 %	47 %	36 % (24–60 %)
		Less than 4 years of college	29 %	20 %	43 % (6–49 %)
		4+ of college	19 %	19 %	11 % (13–24 %)

^aIQR for the mean (continuous variables) or percentage (categorical variables);
^bEstimates of NO₂ by the spatiotemporal model; ^cEstimates of NO_x by the spatiotemporal model

ISSN: 1476-069X