Estimated health effects from domestic use of gaseous fuels for cooking and heating in high-income, middle-income, and low-income countries: a systematic review and meta-analyses

Background Exposure to household air pollution from polluting domestic fuel (solid fuel and kerosene) represents a substantial global public health burden and there is an urgent need for rapid transition to clean domestic fuels. Gas for cooking and heating might possibly affect child asthma, wheezing, and respiratory health. The aim of this review was to synthesise the evidence on the health effects of gaseous fuels to inform policies for scalable clean household energy. Methods In this systematic review and meta-analysis, we summarised the health effects from cooking or heating with gas compared with polluting fuels (eg, wood or charcoal) and clean energy (eg, electricity and solar energy). We searched PubMed, Scopus, Web of Science, MEDLINE, Cochrane Library (CENTRAL), Environment Complete, GreenFile, Google Scholar, Wanfang DATA, and CNKI for articles published between Dec 16, 2020, and Feb 6, 2021. Studies eligible for inclusion had to compare gas for cooking or heating with polluting fuels (eg, wood or charcoal) or clean energy (eg, electricity or solar energy) and present data for health outcomes in general populations. Studies that reported health outcomes that were exacerbations of existing underlying conditions were excluded. Several of our reviewers were involved in screening studies, data extraction, and quality assessment (including risk of bias) of included studies; 20% of studies were independently screened, extracted and quality assessed by another reviewer. Disagreements were reconciled through discussion with the wider review team. Included studies were appraised for quality using the Liverpool Quality Assessment Tools. Key health outcomes were grouped for meta-analysis and analysed using Cochrane's RevMan software. Primary outcomes were health effects (eg, acute lower respiratory infections) and secondary outcomes were health symptoms (eg, respiratory symptoms such as wheeze, cough, or breathlessness). This study is registered with PROSPERO, CRD42021227092. Findings 116 studies were included in the meta-analysis (two [2%] randomised controlled trials, 13 [11%] case-control studies, 23 [20%] cohort studies, and 78 [67%] cross-sectional studies), contributing 215 effect estimates for five grouped health outcomes. Compared with polluting fuels, use of gas significantly lowered the risk of pneumonia (OR 0<middle dot>54, 95% CI 0<middle dot>38-0<middle dot>77; p=0<middle dot>00080), wheeze (OR 0<middle dot>42, 0<middle dot>30-0<middle dot>59; p<0<middle dot>0001), cough (OR 0<middle dot>44, 0<middle dot>32-0<middle dot>62; p<0<middle dot>0001), breathlessness (OR 0<middle dot>40, 0<middle dot>21-0<middle dot>76; p=0<middle dot>0052), chronic obstructive pulmonary disease (OR 0<middle dot>37, 0<middle dot>23-0<middle dot>60; p<0<middle dot>0001), bronchitis (OR 0<middle dot>60, 0<middle dot>43-0<middle dot>82; p=0<middle dot>0015), pulmonary function deficit (OR 0<middle dot>27, 0<middle dot>17-0<middle dot>44; p<0<middle dot>0001), severe respiratory illness or death (OR 0<middle dot>27, 0<middle dot>11-0<middle dot>63; p=0<middle dot>0024), preterm birth (OR 0<middle dot>66, 0<middle dot>45-0<middle dot>97; p=0<middle dot>033), and low birth weight (OR 0<middle dot>70, 0<middle dot>53-0<middle dot>93; p=0<middle dot>015). Non-statistically significant effects were observed for asthma in children (OR 1<middle dot>04, 0<middle dot>70-1<middle dot>55; p=0<middle dot>84), asthma in adults (OR 0<middle dot>65, 0<middle dot>43-1<middle dot>00; p=0<middle dot>052), and small for gestational age (OR 1<middle dot>04, 0<middle dot>89-1<middle dot>21; p=0<middle dot>62). Compared with electricity, use of gas significantly increased risk of pneumonia (OR 1<middle dot>26, 1<middle dot>03-1<middle dot>53; p=0<middle dot>025) and chronic obstructive pulmonary disease (OR 1<middle dot>15, 1<middle dot>06-1<middle dot>25; p=0<middle dot>0011), although smaller non-significant effects were observed for higher-quality studies. In addition, a small increased risk of asthma in children was not significant (OR 1<middle dot>09, 0<middle dot>99-1<middle dot>19; p=0<middle dot>071) and no significant associations were found for adult asthma, wheeze, cough, and breathlessness (p>0<middle dot>05). A significant decreased risk of bronchitis was observed (OR 0<middle dot>87, 0<middle dot>81-0<middle dot>93; p<0<middle dot>0001). Interpretation Switching from polluting fuels to gaseous household fuels could lower health risk and associated morbidity and mortality in resource-poor countries where reliance on polluting fuels is greatest. Although gas fuel use was associated with a slightly higher risk for some health outcomes compared with electricity, gas is an important transitional option for health in countries where access to reliable electricity supply for cooking or heating is not feasible in the near term. Copyright Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.