2.1. Theoretical basis
Studies have shown that the combustion of wood, coal, and other traditional fuels will generate airborne pollutants(Ou et al., 2020; Zhao et al., 2019), such as carbon monoxide, airborne particulates, and toxic elements, all of which adversely affect indoor air quality and cause health problems(Fajersztajn et al., 2013; Simkovich et al., 2019). Environmental Stress Theory considers that the cause of these health problems lies in individuals’ adaptive responses to the pollutants, and affects people physiology, psychology, and behavior(Martin et al., 1996; Zhang and Tielbörger, 2020).
The physiological responses occur in three stages: the short and rapid abstinence response stage under sympathetic action; the adaptive stage under parasympathetic action, which reassesses the stimulus and prepares to address the danger it poses; and the exhaustion stage, which is a result of the stress caused by the large amounts of the body’s energy used to deal with the pollutants, which can exceed the body’s endurance limit. Therefore, when using traditional energy, we argue that although our body can resist the effects of limited amounts of pollution on health in the initial stage, in the long term the pollutants can cause an irreversible decline in people’s physiological health. There is also a psychological response: facing the threat of pollution caused by poor air quality, individuals will have a negative evaluation of their health, according to their individual cognitive capabilities(Ellis et al., 2009), meanwhile, Behavioral Constraint Theory (Prosser et al., 2007) provides further evidence. When fuel combustion adversely affects indoor air quality and individuals’ health, their first reaction will be psychological resistance; they will try their best to improve the indoor air quality. This can be achieved in two ways: changing their own behavior or alleviating their unhealthy surroundings. From this perspective, the act of replacing traditional energy sources with clean energy becomes an effective way of alleviating an unfavorable environment by checking the sources of pollution and also improving their sense of control over the air they breathe.
Therefore, based on the Environmental Stress Theory and the Behavioral Constraint Theory, and the responses to physiological and psychological stress, this study considers that when individuals use clean energy to replace traditional energy, it will reduce adverse impacts on their physiological health, enhance their sense of psychological well-being, and their sense of control over the air they breathe, resulting in an overall improvement of their health.
2.2. Literature review
The existing literature discussing energy use in rural households has mainly focused on analyzing its influencing factors and how to make it greener(Chen et al., 2016; Tao et al., 2018). Ravindra et al. (2019)found five major factors that influence households’ use of clean energy: household characteristics, energy costs, cognitive level, government policy, and external conditions. Deng et al. (2020)revealed that families with elderly people are more willing to use clean energy. Environmental values, marital status, the influence of others, demonstration of the alternatives, and the perception of utility improvements significantly affect people’s willingness to use clean energy. Dong (2017) analyzed solar energy and found that economic considerations and rural households' awareness of the benefits of low carbon emissions were the main factors affecting the uptake of solar energy. Li et al. (further investigated the influence of national subsidies and the peer effect on rural green energy transformation, then put forward more specific suggestions to promote clean energy use. These include: financial incentives, expanding the demonstration effect, generating new sources of income for farmers, and cultivating awareness of the need to conserve energy. It is clear that rural households' standard of living, their awareness of energy use, government promotion, neighborhood behavior, and other factors are all key influences on rural households’ clean energy use.
From scholars’ investigation of how China's energy consumption has developed, it can be observed that the use of clean energy in China is still at a low level(Carter et al., 2020), the main reason being rural households' lack of understanding of the risks posed by the use of traditional energy sources(Elie et al., 2019; Wang et al., 2019). Current research into the relationship between clean energy and health mainly focuses on analyzing the impact of air pollution on public health(Fann et al., 2013; Nel, 2005; Shaddick et al., 2020; Sofiev et al., 2018). Some scholars have looked at physiological data in their investigation of the relationship between energy substitution and middle-aged and elderly rural residents' health(Liu et al., 2018). However, overall, there have been few studies on this topic in China, with most of the research having been conducted in other countries. For example, Sattler et al. (2018)found that replacing coal-fired power plants with clean energy in Illinois could improve the residents’ health. Baumgartner et al. (2011)found that air pollution resulting from traditional energy use may raise the risk of hypertension and cardiovascular diseases. Haines et al. (2007) pointed out that the current pattern of fossil fuel using causes substantial health problems. Therefore, a comprehensive clean energy application plan should strongly emphasize the health benefits of improved air quality.
More recently, the relationship between clean energy use and health and, in particular, the impact of kitchen fuel on health, is beginning to attract academic attention(Imelda, 2020; Yun et al., 2020). For example, Yun et al. (2020)has confirmed that ultra-fine particulate matter produced by the combustion of solid fuel poses potential health risks to people. Alexander et al. (2017)having conducted a randomized trial in Nigeria, concluded that replacing the solid fuel used in household stoves by ethanol may reduce pregnant women's diastolic blood pressure and hypertension: the use of clean cooking fuels may, therefore, reduce the overall harmful health effects caused by household air pollution. Imelda (2020)estimated the carcinogenic risk of hetero-cyclic amines inhaled by women under different cooking conditions by simulating the process of typical household solid fuel combustion. The results showed that when the smoke could not be effectively discharged, women had higher health risks when bituminous coal, straw, and wood were used. Most scholars, therefore, have found that the type of fuel used for cooking has a significant impact on health. Along with scholars, the general public is also now beginning to pay more attention to health issues, Khandelwal et al. (2017) found that improved stoves that reduce negative impacts on health and the environment are receiving considerable attention in India.
However, studies of this issue have reached different conclusions. For example, Rosenthal et al. (2018) argued that improved biomass stoves could only incrementally improve air quality and provide few health benefits. Having followed the progress of 10,750 children in rural Malawi, Mortimer et al. (2017) also found no evidence that cleaner fuel stoves were effective in reducing their risk of contracting pneumonia.
It is clear, then, that scholars have different views on the health effects of clean energy use in the kitchen. However, when studies on the impacts of the wider environment are focused on the health of women, the evidence of adverse health impacts of poor air quality is more conclusive. These include the impacts on blood pressure problems during pregnancy; the risk of cancer caused by hetero-cyclic amines; certain physiological diseases including those of the respiratory tract, eyes; lung cancer; and others. From these studies, therefore, it can be safely inferred that the use of traditional energy sources for cooking has a negative impact on women’s health.
To sum up, scholars have confirmed that there is likely to be a positive relationship between the use of clean energy and health, but when the health benefits of clean energy use in kitchen are specifically examined, the matter is unsettled. Chinese scholars mainly focus on verifying whether the particulate matter and soot produced by fuel combustion has negative effects on health from the perspective of environmental science. Other countries' scholars have focused more on the effects of stoves using different fuels on air quality and health. However, owing to different sample populations, the analyses have reached different conclusions and, while most studies investigating the environment and medicine use objective data, there has been little analysis of women's subjective view of their own health. In other words, there is still a lack of quantitative research into the health effects of women's cooking energy choices outside the environmental and medical fields; in China, in particular, such research simply does not exist.
Therefore, considering that the vast majority of people cooking for Chinese rural families are women, and considering rural women's health as its research object, this paper innovatively investigates changes in rural women's self-evaluation of their health following the replacement of traditional energy by clean energy in their households. At the same time, through heterogeneity analysis, this study examines the health differences between rural women with different characteristics following their uptake of clean energy, filling the research gap that exists due to the absence of studies that focus solely on the relationship between energy substitution and women's health in China. In doing so, this study attempts to include the female perspective into the debate among scholars regarding energy use in the kitchen and women’s health.
This study therefore proposes two hypotheses:
The use of clean energy in rural areas will affect women's health, but whether this impact is positive or negative is not yet known.
Women with different characteristics may experience different health effects following their uptake of clean energy.