Table 4 Significant determinants of outdoor air concentrations from mixed modeling.

From: Characterization of outdoor air pollution from solid fuel combustion in Xuanwei and Fuyuan, a rural region of China

	ln-PM_2.5			ln-BaP			ln-NAP			SO₂				ln-NO₂
	β	95% CI	GMR^a	β	95% CI	GMR	β	95% CI	GMR	β	95% CI		OR	β	95% CI	GMR
Coal type
Smokeless coal	Ref		1.00	Ref		1.00	Ref		1.00	Ref		1.00
Smoky coal	0.31	− 0.31, 0.93	1.36	1.02	0.29,1.76	2.79	0.89	0.04,1.75	2.44	− 0.85	− 1.58, − 0.12	0.43		Not included
Proportion of chimney stoves in a village
≤ 50%	Ref		1.00	Ref		1.00	Ref		1.00
> 50%	− 0.02	− 0.39, 0.35	0.98	0.40	0.01, 0.79	1.49	0.06	− 0.53, 0.64	1.06		Not included			Not included
Season
Autumn	Ref			Ref		1.00	Ref		1.00					Ref		1.00
Spring/summer^b	0.19	− 0.18, 0.56	1.21	0.52	0.21, 0.84	1.69	0.29	− 0.14, 0.71	1.33		Not included			− 0.04	− 0.21, 0.14	0.96
Winter	0.62	0.25, 0.99	1.86	0.38	0.04, 0.72	1.46	1.15	0.65,1.65	3.17					0.17	0.00, 0.33	1.18
Population, per 1,000
	0.46	− 0.04, 0.95	1.58	Not included			Not included			Not included				Not included
Use firepit to cook, 10%
Not included				Not included			Not included			0.20	− 0.31, 0.71		1.22	Not included
Averaged indoor NO₂, µg/m³
Not applicable				Not applicable			Not applicable			Not applicable				0.010	0.006, 0.014	1.01
Coal deposit
20,27	Ref			Ref		1.00	Ref		1.00	Not included				Ref		1.00
1, 2, 4, 7, 8	− 0.17	− 0.79, 0.44	0.84	− 0.22	− 0.85, 0.41	0.80	− 0.16	− 0.95, 0.63	0.85					0.18	0.01, 0.35	1.20
9	− 0.74	− 2.13, 0.66	0.48	− 0.16	− 0.91, 0.59	0.85	− 0.04	− 1.17,1.08	0.96					0.51	0.21, 0.81	1.66
10	− 0.11	− 0.98, 0.77	0.90	0.08	− 0.81, 0.96	1.08	−	−	−					0.31	− 0.01, 0.62	1.36
LS	− 1.40	− 2.88, 0.09	0.25	− 0.81	− 1.61,− 0.01	0.44	− 0.38	− 1.53, 0.76	0.68					0.15	− 0.16, 0.46	1.16
12, 13, 14, 38	− 0.18	− 0.84, 0.48	0.83	− 0.30	− 0.94, 0.34	0.74	0.59	− 0.31,1.50	1.81					0.21	− 0.01, 0.44	1.24
16, 17, 19	− 0.32	− 0.95, 0.30	0.72	− 0.48	− 1.12, 0.17	0.62	0.04	− 0.79, 0.86	1.04					0.08	− 0.10, 0.25	1.08
Intraclass correlation
Between villages		1			1			0.86			1				1
Reference value^c	3.24 ln-µg/m³			0.97 ln-ng/m³			5.38 ln-ng/m³			–				3.67 ln-µg/m³

NAP naphthalene, BaP Benzo(a)pyrene, SO₂ sulfur dioxide, NO₂ nitrogen dioxide.
^aGMR = geometric mean ratio = GM (estimate)/GM (reference) = Exp (β), number is bold if β is significantly different from zero (p < 0.05). ^bMerged due to few outdoor measurements in summer. ^cReference value represents log transformed value for the reference model entry.

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Table 4 Significant determinants of outdoor air concentrations from mixed modeling.

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