## 2 Literature Review and Theoretical Analysis  
A systematic review of current research shows that the relevant research results of producer service agglomeration are mainly manifested in the level of agglomeration, agglomeration characteristics, influencing factors, and the economic and social effects of agglomeration [8]. The research in these areas has achieved relatively rich research results. The impact of industrial agglomeration on environmental pollution is derived from the research on the relationship between economic development and environmental pollution [9]. Economic development is one of the core issues of economic research. Therefore, academia has produced a lot of theoretical and empirical research on the relationship between economic development and environmental pollution. [PERSON] and [PERSON] produced the famous environmental Kuznets curve in 1992, which has become a classic theory to study the relationship between economic development and environmental pollution [10]. Environmental Kuznets reflects economic development through income, studies the relationship between income and environmental pollution, and finds that this relationship shows the characteristics of an inverted U shape [11]. With the increase in income, environmental pollution will gradually become worse and more serious, but when it reaches a certain inflection point, environmental pollution will decrease with the continuous increase in income [12]. This lays an important foundation for studying the impact of industrial agglomeration in economic development on environmental pollution. Since then, many experts and scholars have conducted in-depth and extended research on the Kuznets curve [13]. They have obtained real experimental data and proposed theoretical hypotheses for analysis and verification. Based on the above research, some scholars have begun to pay attention to the relationship between industry and environmental pollution, especially the impact of industrial agglomeration on environmental pollution, which is an extension and expansion of the research on the relationship between economic development and environmental pollution [14]. Due to the differences in the methods, data, and research areas used, scholars' research conclusions are not the same. The impact of industrial agglomeration on environmental pollution can be roughly divided into three conclusions, which are described as follows. One conclusion is that industrial agglomeration will have an impact on environmental pollution and may lead to environmental degradation. For example, based on data from different countries, scholars have found that industrial agglomeration has a significant positive impact on environmental pollution. The increase in the degree of industrial agglomeration will bring about an increase in the level of environmental pollution, resulting in a decline in environmental quality [15]. Some scholars conduct research from different cities or regions within a country and find that industrial agglomeration may indeed bring about environmental pollution [16]. Moreover, this influence relationship may show a linear or nonlinear relationship. In addition, some scholars have begun to explore the path and mechanism of industrial agglomeration affecting environmental pollution, further improving the level of academic research [17]. The second conclusion is that industrial agglomeration will not bring about environmental pollution, and even improve environmental quality through industrial competition, technological progress, and innovation spillovers, etc., thus having a negative inhibitory effect on environmental pollution. For example, some scholars have selected specific industries and analyzed that industrial agglomeration will reduce the level of environmental pollution, and even improve environmental quality by affecting industrial structure, production efficiency, and technological spillovers [18]. In this regard, domestic and foreign scholars have conducted extensive and in-depth research.