Table 4.

Random-effects meta-analysis for the association between a $10\text{-}{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$ increase in exposure to particulate matter with an aerodynamic diameter below $2.5\mathrm{\mu }\mathrm{m}$ (${\mathrm{PM}}_{2.5}$) and breast cancer onset: main analyses, sensitivity analyses (SA, based on the main analysis not corrected for publication bias), and supplementary analyses according to the menopausal status or the hormonal receptor subtype.

Meta-analysis	$n$ effect estimates	$n$ cases	$n$ participants	RR (95% CI)	$I^2$ (%)	Heterogeneity $p$-valuea
Main analysis (not corrected for publication bias)b	14	111,758	2,959,079	1.014 (0.929, 1.106)	37.4	0.13
Main analysis (corrected for publication bias)b	17	112,371c	2,974,306c	1.006 (0.941, 1.076)	34.3	0.12
SA1. Leave-one-out meta-analysisd	13	111,130	2,945,692	1.017 (0.970, 1.067)	7.7	0.50
SA2. Restricted to prospective cohort studies	12	19,447	392,303	1.012 (0.883, 1.159)	42.2	0.072
SA3. Restricted to European populations	9	5,223	84,549	1.084 (0.730, 1.608)	42.4	0.084
SA4. Restricted to North American populations	5	106,535	2,874,530	1.012 (0.957, 1.070)	34.1	0.29
SA5. Restricted to studies with adjustment for main reproductive factorse	4	8,452	198,823	0.958 (0.856, 1.073)	3.3	0.47
SA6. Restricted to studies with adjustment for socioeconomic contextf	12	109,448	2,933,766	1.013 (0.910, 1.128)	46.3	0.066
SA7. Restricted to effect estimates reported in “all women” onlyg	7	108,845	2,899,843	1.014 (0.970, 1.059)	12.8	0.52
SA8. Excluding CECILE case–control study (not published yet)	13	110,593	2,956,643	1.011 (0.922, 1.109)	41.8	0.096
SA9. Restricted to studies with exposure assessment based on precise home addressesh	13	20,612	394,739	1.017 (0.895, 1.155)	38.9	0.095
SA10. Restricted to studies with exposure assessment based on residential historyi	5	99,598	2,763,163	1.000 (0.935, 1.070)	13.6	0.42
SA11. Restricted to studies with exposure assessment based on modeling dataj	10	8,043	131,982	1.071 (0.798, 1.437)	41.9	0.11
SA12. Restricted to studies with recruitment starting in 2000 or laterk	4	95,199	2,616,140	1.024 (0.990, 1.059)	0.2	0.61
In premenopausal women	5	4,078	NAl	1.110 (0.976, 1.263)	2.6	0.51
In postmenopausal women	12	13,021	NAl	0.931 (0.770, 1.126)	46.8	0.035
Hormone responsive positive ($\text{ER}+/\text{PR}+$)	4	5,917	NAl	0.978 (0.862, 1.110)	0.0	0.83
Hormone responsive negative ($\text{ER}-/\text{PR}-$)	4	1,336	NAl	0.967 (0.742, 1.259)	0.0	0.79

Note: Studies included in sensitivity analyses (SA): SA1: All but VHM&PP; SA2: CEANS, CNBSS, DCH, DNC, EPIC-NL, EPIC-Oxford, EPIC-Turin, HUBRO, MEC, NHSII, Sister Study, VHM&PP; SA3: CEANS, CECILE, DCH, DNC, EPIC-NL, EPIC-Oxford, EPIC-Turin, HUBRO, VHM&PP; SA4: CNBSS, MEC, NHSII, ONPHEC, Sister Study; SA5: CECILE, DNC, MEC, NHSII; SA6: CEANS, CNBSS, DCH, EPIC-NL, EPIC-Oxford, EPIC-Turin, HUBRO, MEC, NHSII, ONPHEC, Sister Study, VHM&PP; SA7: CECILE, CNBSS, DNC, MEC, NHSII, ONPHEC, Sister Study; SA8: All but CECILE; SA9: CEANS, CECILE, CNBSS, DCH, DNC, EPIC-NL, EPIC-Oxford, EPIC-Turin, HUBRO, MEC, NHSII, Sister Study, VHM&PP; SA10: CECILE, DNC, MEC, NHSII, ONPHEC; SA11: CEANS, CECILE, DCH, DNC, EPIC-NL, EPIC-Oxford, EPIC-Turin, HUBRO, Sister Study, VHM&PP; SA12: CECILE, HUBRO, ONPHEC, Sister Study; In premenopausal women: CECILE, CNBSS, DNC, NHSII, Sister Study; In postmenopausal women: CEANS, CECILE, CNBSS, DCH, DNC, EPIC-NL, EPIC-Oxford, EPIC-Turin, HUBRO, NHSII, Sister Study, VHM&PP; On hormonal receptor subtypes: CECILE, MEC, NHSII, Sister Study. CI: confidence interval: .

^aCochrane’s heterogeneity Q test.

^bEffect estimates reported in studies led in postmenopausal women only were included in the main meta-analysis in addition to the effect estimates reported in “all women” (i.e., irrespective of menopausal status).

^cEffectives simulated by trim-and-fill analysis.

^dI.e., excluding the study contributing the most to the between-study heterogeneity (see Figure S3).

^eAge at menarche, age at the first full-term pregnancy, and parity.

^fAt the area level.

^gI.e., irrespective of menopausal status.

^hI.e., excluding studies in which air pollutant levels were assessed at the postal code scale.

ⁱI.e., excluding studies in which air pollutant levels were assessed for a single home address.

^jI.e., from land-use regression (LUR), dispersion model (DM), or chemistry-transport model (CTM).

^kBecause of stronger potential for exposure misclassification in studies recruiting subjects before 2000.

^lSample size could not be calculated due to missing information in source studies.