Table 2.

Household air pollution exposure of daily means summary statistics on control and intervention groups in rural Peru.

	Control					Intervention					Relative difference
Follow-up visit (months)a	$n$ b	Mean (SD)	Median (25th, 75th)	GM (GSD)	$<\text{WHO}$	$n$ b	Mean (SD)	Median (25th, 75th)	GM (GSD)	$<\text{WHO}$	$p$-Valuec
Kitchen ${\mathrm{PM}}_{2.5}$
Baseline	89	1,220 (1,010)	970 (390, 1,790)	770 (3)	1%	89	1,190 (880)	990 (500, 1,880)	800 (3)	0%	0.865
3	89	1,140 (980)	840 (320, 1,730)	670 (3)	1%	90	82 (52)	71 (40, 140)	61 (2)	18%	$<0.001$
6	88	1,180 (1,130)	770 (330, 1,830)	670 (3)	0%	90	50 (30)	62 (21, 72)	39 (2)	28%	$<0.001$
12	89	1,420 (1,220)	1,080 (430, 2,230)	830 (3)	0%	87	41 (59)	21 (8, 41)	22 (3)	59%	$<0.001$
18	88	63 (183)	17 (8, 41)	22 (3)	67%	87	447 (649)	74 (70, 635)	150 (5)	14%	$<0.001$
24	84	34 (74)	14 (8, 23)	17 (3)	76%	84	561 (1,251)	74 (70, 708)	140 (6)	17%	$<0.001$
Personal ${\mathrm{PM}}_{2.5}$
Baseline	90	126 (214)	71 (44, 127)	76 (2)	8%	90	104 (100)	77 (37, 137)	73 (2)	11%	0.782
3	87	92 (186)	57 (29, 85)	53 (3)	21%	90	26 (18)	25 (16, 32)	22 (2)	50%	$<0.001$
6	90	96 (111)	61 (28, 113)	60 (3)	23%	89	35 (55)	16 (15, 33)	22 (2)	65%	$<0.001$
12	90	103 (108)	71 (33, 117)	65 (3)	18%	87	26 (34)	15 (8, 23)	16 (2)	76%	$<0.001$
18	90	16.7 (15.1)	8.8 (8, 18.9)	13.2 (2)	84%	88	46 (102)	16 (16, 38)	25 (2)	59%	$<0.001$
24	85	17 (15)	11 (8, 16)	13 (2)	84%	84	35 (38)	17 (16, 43)	24 (3)	58%	$<0.001$
Kitchen CO
Baseline	84	53.4 (48.5)	38.8 (21.3, 71.8)	33.5 (3.1)	12%	85	50.2 (40.8)	42.1 (17.8, 69.1)	32.5 (3)	12%	0.874
3	84	46.4 (37.4)	38.4 (18.7, 67.1)	28.5 (3.4)	17%	80	4.6 (6)	2.5 (1, 5.4)	2.6 (2.8)	89%	$<0.001$
6	86	49.9 (43)	40.9 (18.3, 67.8)	30.5 (3.3)	12%	82	5.1 (5.5)	2.9 (1.4, 5.7)	3.2 (2.6)	82%	$<0.001$
12	86	48.7 (38.6)	41.2 (15.2, 70.5)	29.9 (3.4)	17%	77	8.1 (13.2)	4.1 (1.8, 8.3)	4.1 (3.1)	78%	$<0.001$
18	83	7.1 (10.6)	3.1 (1.1, 7.9)	3.3 (3.4)	77%	79	21.3 (25.8)	12.8 (1.9, 30.3)	8.6 (4.6)	46%	$<0.001$
24	80	5.7 (6.2)	4.1 (1.2, 6.7)	3.3 (2.9)	84%	79	23 (28.2)	12.4 (3.3, 33.3)	10.2 (4.1)	47%	$<0.001$
Personal CO
Baseline	81	6.6 (8.2)	3.2 (1.6, 8)	3.9 (2.7)	79%	79	7.1 (8.4)	4.4 (1.9, 8.7)	4.3 (2.7)	77%	0.526
3	79	6.3 (8.7)	3.5 (1.7, 7.5)	3.7 (2.7)	81%	76	2.5 (3.3)	1.2 (0.9, 2.6)	1.7 (2.2)	96%	$<0.001$
6	81	7 (8.1)	4.3 (1.8, 8.8)	4.2 (2.7)	75%	79	1.7 (2.6)	1 (0.8, 1.3)	1.2 (1.9)	97%	$<0.001$
12	81	6.7 (8.9)	3.8 (1.8, 7.8)	4.1 (2.7)	80%	79	2.7 (3.9)	1.2 (0.8, 2.1)	1.6 (2.4)	91%	$<0.001$
18	75	2.6 (4.2)	1.2 (0.8, 2.2)	1.6 (2.4)	95%	80	4.5 (7.3)	1.6 (0.8, 4.9)	2.2 (3)	88%	0.033
24	73	2.7 (4.4)	1.1 (0.8, 2.5)	1.6 (2.4)	93%	76	3.9 (5.4)	1.6 (0.9, 5)	2.1 (2.8)	91%	0.042
Kitchen BC
Baseline	89	180 (120)	170 (90, 270)	130 (3)	—	89	210 (150)	170 (80, 330)	140 (3)	—	0.672
3	89	200 (130)	210 (110, 290)	130 (3)	—	90	7.6 (4.2)	10.4 (2.3, 10.7)	5.6 (2)	—	$<0.001$
6	88	200 (140)	160 (100, 290)	130 (3)	—	90	5.8 (4.5)	2.8 (1.3, 10.8)	3.8 (3)	—	$<0.001$
12	89	220 (150)	210 (100, 300)	150 (3)	—	87	3 (5.7)	1.2 (1.2, 2.2)	1.8 (2)	—	$<0.001$
18	88	4.4 (9.5)	1.6 (1.6, 1.7)	2.3 (2)	—	87	99 (133)	15 (14, 147)	31 (6)	—	$<0.001$
24	84	2.7 (4.8)	1.6 (1.6, 1.7)	1.9 (2)	—	84	82 (124)	14 (14, 127)	23 (6)	—	$<0.001$
Personal BC
Baseline	90	19.1 (16.7)	15.2 (6.1, 26.8)	12.5 (2.7)	—	90	21.3 (22.3)	15.6 (5.9, 31.3)	13.4 (2.8)	—	0.646
3	87	14.4 (15.3)	9.1 (2.4, 21.5)	8.8 (2.8)	—	90	2.2 (1.2)	2.3 (1.2, 2.4)	2 (1.5)	—	$<0.001$
6	90	14.7 (18.3)	8.8 (2.6, 14.8)	8.5 (2.8)	—	89	2.3 (4.5)	2 (1.2, 2.4)	1.8 (1.6)	—	$<0.001$
12	90	17.6 (18.9)	12 (4.5, 20.9)	10.8 (2.8)	—	87	1.9 (2.6)	1.2 (1.2, 1.3)	1.4 (1.7)	—	$<0.001$
18	90	2.2 (3.6)	1.6 (1.6, 1.7)	1.8 (1.5)	—	88	7.9 (11.2)	3.2 (3.1, 7.4)	4.7 (2.4)	—	$<0.001$
24	85	2.1 (1.7)	1.6 (1.6, 1.7)	1.9 (1.5)	—	84	5.9 (6.1)	3.2 (3.1, 5.9)	3.9 (2.6)	—	$<0.001$

Note: —, no data; BC, black carbon; CO, carbon monoxide; GM, geometric mean; GSD, geometric SD; $<\text{WHO}$, percent of samples $<\text{World}$ Health Organization daily guidelines (${\mathrm{PM}}_{2.5}$ $<25{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$, $\mathrm{CO}<9.4\text{\hspace{0.17em}ppm}$) (There is no current guideline for BC.). LOD, limit of detection; ${\mathrm{PM}}_{2.5}$, fine particulate matter with aerodynamic diameter of $\le 2.5\mathrm{\mu }\mathrm{m}$; SD, standard deviation.

^a During the second year (follow-up visits:18- and 24 months) the control participants received the LPG stove intervention and vouchers for 1-y supply of free fuel and intervention participants stopped receiving free fuel but kept the LPG stove.

^b n: Represents nonmissing samples in each time point; each sample represents the daily mean metric defined as the mean of the two consecutive 24-h average concentrations, where available.

^c $p$-Values obtained using Student’s $t$-test on the log-transformed exposure concentrations comparing intervention and control groups. Samples $<\text{LOD}$ were replaced by $\text{LOD}/\sqrt{2}$: 7 and $1\mathrm{\mu }\mathrm{g}$ for ${\mathrm{PM}}_{2.5}$ and BC gravimetric integrated samples, respectively; and $0.7\text{\hspace{0.17em}ppm}$ for direct reading CO measurements.