Table 1

Effect size of COPD associated with solid fuel smoke exposure

Reference	Country	Types of study	Fuel type	Sample size	Exposure measured	Types of diagnosis	Sample type	Effect size
Reference	Country	Types of study	Fuel type	Sample size	Exposure measured	Types of diagnosis	Sample type	%	OR (95% CI)
Dossing et al 199420	Saudi Arabia	CC study defined by diseases	Wood	50 cases, 71 controls	No direct measurement	FEV₁/FVC <70% and FEV₁<70% of predicted value; <15% or <250 ml absolute reduction of FEV₁ after inhalation of 200 μg aerosolised salbutamol	Adults with COPD	88 vs 34	17.42 (10.58 to 28.68)
Dennis et al 1996³¹	Columbia	CC study defined by diseases	Wood and gasoline	104 cases, 104 controls	No direct measurement	FEV₁/FVC <70% and FEV₁<70% of predicted value	Women ≥35 years with COPD	85 vs 62	3.92 (1.7 to 9.1)
Orozco-Levi et al 200616	Spain	CC study defined by diseases	Wood (W), charcoal (C) or both (B)	60 cases (hospitalised), 60 control	Duration of exposure reported.	FEV₁/FVC <70% and FEV₁<80% of predicted value; <12% change in FEV₁ after inhalation of 400 μg inhaled salbutamol	Women >50 years with COPD	95 vs 72	W: 1.8 (0.6 to 6.0), C: 1.5 (0.5 to 4.6)), B: 4.5 (1.4 to 14.2)
Regalado et al 2006³²	Mexico	CS study	Biomass and gas	Biomass 778, gas 67	PM₁₀ measured for 1 h during cooking	GOLD (G) criteria for diagnosis of COPD	Non-smoking adult women	Biomass	Biomass: G I
								G I: 13.5 G II: 2.7	1.5 (0.5 to 4.3)
								Gas G I: 9.1
Liu et al 200714	China	CS study	Biomass (BM), coal (C) and LPG	Combined BM 1306	Measured SO₂, NO₂, CO and PM₁₀ directly	GOLD criteria for diagnosis of COPD	Adults ≥ 40 years	12.0 (BM)	BM: 1.72 (1.27 to 2.35)
				C 172				12.2 (C)	C: 1.55 (0.74 to 3.22), LPG=reference
				LPG 1808				7.3 (LPG)	C: 1.55 (0.74 to 3.22), LPG=reference
				LPG 1808			Non-smoking women ≥40 years	7.3 (BM)	BM: 3.11 (1.63 to 5.94)
				Non-smoking women BM 744 C 90 LPG 995				6.7 (C)	C: 2.77 (0.83 to 9.26), LPG=Reference
				Non-smoking women BM 744 C 90 LPG 995				2.5 (LPG)	C: 2.77 (0.83 to 9.26), LPG=Reference
Zhong et al 200722	China	CS study	Biomass	10 661 (never exposed); 9 584 (ever exposed)	Not measured directly	GOLD criteria for diagnosis of COPD	Adults ≥ 40 years	9.3 (ever exposed),	1.35 (1.20 to 1.52)
Zhong et al 200722	China	CS study	Biomass	10 661 (never exposed); 9 584 (ever exposed)	Not measured directly	GOLD criteria for diagnosis of COPD	Adults ≥ 40 years	7.3 (never exposed)	1.35 (1.20 to 1.52)
Caballero et al 2008³³	Columbia	CS study	Wood exposed ≥10 years	2175 (not exposed); 3364 (ever exposed)	Not measured directly	FEV₁/FVC ratio<70% after bronchodilator (200 μg salbutamol)	Adults ≥ 40 years	13.4% (exposed for ≥10 years)	2.42 (2.0 to 2.92) (exposed for ≥10 years)
Xu et al 200715	China	CC study defined by exposure to solid fuel and smoking	Electricity/gas,coal, firewood/straw	1743 cases, 1743 controls	No direct measurement	Hospital diagnosed	Adults ≥35 years	74.1 (electricity/gas), 2.7 (coal) and 23.2 (firewood/straw)	1.32 (0.79 to 2.20) (coal user) and 0.71 (0.46 to 1.10) (firewood/straw)
Chapman et al 2005³⁴	China	Retrospective cohort study (switched to chimney stove)	Coal	20453	No direct measurement	Hospital diagnosed	16606 (81.2%) had chimney stove and 3847 (18.8%) no chimney stove	19.4% (no chimney stove) and 4.5% (changed to chimney stove)	5.15 (4.62 to 5.74)
Sezer et al 2004³⁵	Turkey	CC study defined by diagnosis of COPD	Biomass	74 COPD cases and 74 non-COPD cases (healthy)	No direct measurement	Hospital diagnosed	Non-smoking women ≥38 years	75.7% cases and 70.3% controls exposed to biomass	6.61 (2.17 to 20.18) in women exposed to biomass ≥30 years
Ekici et al 2005³⁶	Turkey	CC study defined by fuel types	Biomass and LPG	Biomass (cases)=397 LPG (control)=199	No direct measurement	BMRC criteria for the diagnosis of CB and CAO defined by FEV₁/FVC<70	Non-smoking women > 40 years	23.1	2.5 (1.4 to 4.0)
Kiraz et al 200321	Turkey	CC study defined by fuel types	Biomass and LPG	Biomass=242 and non-biomass=102	No direct measurement	ATS and BMRC	Adult women	12.4 vs 3.9	28.9 (8.7 to 95.9)

ATS, American Thoracic Society; BMRC, British Medical Research Council; CAO, chronic airway obstruction; CB, chronic bronchitis; CC, case–control; COPD, chronic obstructive pulmonary disease; CS, cross-sectional; DS, descriptive study; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; GOLD, Global Initiative for Obstructive Lung Disease; LPG, liquefied petroleum gas; PM₁₀, particles of ≤10 μm.