## 1 Introduction
used the linear mixed effects model to analyze PM2.5 and LE and found that a decrease in PM2.5 was related to an increase in LE, and the strict implementation of the Action Plan for Air Pollution Prevention and Control had significant benefits for LE [22]; however, because the LE in each period is the average of the past LE, the LE index is lagging behind. Some scholars try to study the time lag and spatial lag effects of environmental factors on LE. In terms of a time lag, [PERSON] et al. used the distributed nonlinear lag model to fit the time relationship between air pollution and LE [23]; [PERSON] et al. used the nonlinear autoregressive distribution lag model to reveal the long-term relationship among environmental quality, public environmental expenditure, and LE [24]; In terms of spatial lag, [PERSON] et al. found that neighborhood characteristics have an impact on the spatial lag of LE in a study area [25]. However, at present, studies on the combination of time lag, spatial lag, and LE have not been reported. With the national emphasis on environmental health, research on the relationship between environment and health in China have gradually increased, but most of the work focuses on the impact of various types of pollution on health. For example, [PERSON] et al. studied the impact of air pollution on Chinese public health [26]; [PERSON] et al. used the spatial econometric model to analyze the impact of air pollution, economic development, and other factors on public health in the cities of the Yangtze River Economic Belt. The results showed that there was a significant spatial correlation between air pollution and public health in the cities of the Yangtze River Economic Belt [9]; [PERSON] et al. studied the potential risk of heavy metal pollution on the health of residents in Hanzhong City, Shaanxi Province [27]; [PERSON] et al. studied the harm of mineral mining pollution on human health in China [28]. However, there are few studies on the relationship between the environment and health in mainland China under the B&R. With the development of remote-sensing technology, the indicators and methods of ecological environment quality evaluation are constantly improving and perfecting. The establishment of the indicator system is the key to using it for evaluation. Assessing environmental quality is a complex and challenging task. In 2006, the Technical Specifications for Ecological Environment Assessment (Trial) issued by the Ministry of Environment of the People's Republic of China stipulated the indicator system for ecological environment status assessment and the calculation methods for each indicator, including biological abundance index [29], land surface temperature (LST) [30], plant coverage index, and other indicators. These indicators only reflect the ecological quality from a single aspect, such as soil and vegetation. However, the interaction between each environmental component in the ecosystem will affect the entire ecological environment. Therefore, it is best to use comprehensive, ecological-environment-quality indicators for this type of evaluation [27; 31; 32]. For example, [PERSON] et al. selected five indicators, i.e., impermeable surface, normalized difference vegetation index, land surface temperature, greenness, and brightness, and constructed comprehensive evaluation factors through a factor analysis method [33]; [PERSON] et al. selected the normalized difference vegetation index (NDVI), water use efficiency (WUE), and leaf area index (LAI) to calculate weight using the projection pursuit model (MEQ-PPM) to obtain the comprehensive ecological quality index [34]; [PERSON] et al. used the analytic hierarchy process (AHP) to study the ecological quality evaluation of hilly areas with red soil by integrating nine factors, including water resources and vegetation coverage [35]. However, for the land area of China under the B&R, there has been no relevant research to select comprehensive evaluation indicators regarding the ecological environment.