Table 3.

Pooled difference in leukocyte count ($\mathrm{\Delta }$; $\text{cells}/\mathrm{\mu }\mathrm{L}$) per $10{\text{-}\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$ increase in PM concentrations among $n=\mathrm{165,675}$ participants, Women’s Health Initiative (1993–2002) and Atherosclerosis Risk in Communities (1986–1998) study.

PM exposure	Model 1a		Model 2b		Model 3c
	$\mathrm{\Delta }$ (95% CI) $\text{cells}/\mathrm{\mu }\mathrm{L}$	$p_{\text{Cochran}’\mathrm{s}Q}$d	$\mathrm{\Delta }$ (95% CI) $\text{cells}/\mathrm{\mu }\mathrm{L}$	$p_{\text{Cochran}’\mathrm{s}Q}$d	$\mathrm{\Delta }$ (95% CI) $\text{cells}/\mathrm{\mu }\mathrm{L}$	$p_{\text{Cochran}’\mathrm{s}Q}$d
${\mathrm{PM}}_{10}$ (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)
2-d mean	$-6$ ($-12$, 0)	0.89	$-7$ ($-12$, $-1$)	0.90	$-7$ ($-13$, $-1$)	0.91
7-d mean	$-10$ ($-19$, $-1$)	0.49	$-10$ ($-20$, $-1$)	0.53	$-11$ ($-20$, $-2$)	0.42
1-month mean	22 ( 3, 41)	2.5$\times {10}^{–3}$	8 ($-8$, 25)	0.08	$-2$ ($-18$, 14)	0.08
12-month mean	65 (26, 103)	6.5$\times {10}^{–4}$	32 (4, 59)	0.37	8 ($-17$, 33)	0.56
${\mathrm{PM}}_{2.5}$ (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)
1-month mean	33 (9, 56)	0.21	21 (0, 43)	0.51	12 ($-9$, 33)	0.45
12-month mean	114 (65, 163)	0.59	64 (15, 114)	0.99	28 ($-20$, 75)	0.99
${\mathrm{PM}}_{2.5–10}$ (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)
1-month mean	18 ($-8$, 44)	0.01	$-1$ ($-24$, 21)	0.13	$-13$ ($-36$, 9)	0.12
12-month mean	67 (8, 127)	6.5$\times {10}^{–6}$	18 ($-30$, 66)	0.04	$-5$ ($-47$, 36)	0.15

Note: ARIC, Atherosclerosis Risk in Communities; CI, confidence interval; PM, particulate matter; ${\mathrm{PM}}_{10}$, $\mathrm{PM}\le 10\mathrm{\mu }\mathrm{m}$ in diameter; ${\mathrm{PM}}_{2.5}$, $\mathrm{PM}\le 2.5\mathrm{\mu }\mathrm{m}$ in diameter; ${\mathrm{PM}}_{2.5–10}$, $\mathrm{PM}>2.5$ and $<10\mathrm{\mu }\mathrm{m}$ in diameter; WHI, Women’s Health Initiative.

^aModel 1 adjusted for race/ethnicity, age, sex (in ARIC), randomly assigned treatment group (in WHI), mean temperature, mean dew point, mean barometric pressure, season, and a restricted cubic natural spline function of calendar time with one knot per calendar year.

^bModel 2 adjusted for all covariates in Model 1 and additionally for individual-level education and neighborhood socioeconomic status.

^cModel 3 adjusted for all covariates in Model 2 and additionally for smoking status, alcohol use, body mass index, and physical activity.

^dHomogeneity of associations among strata was tested using Cochran’s Q-test statistic, where a $p_{\text{Cochran}’\mathrm{s}Q}<0.10$ suggests there is evidence to reject the null hypothesis of homogeneity.