Validation of the Environmental Kuznets Curve: cases from countries along the Belt and Road

‘One Belt, One Road’ is China’s international strategy, and the countries along its routes are mainly developing countries that face a dilemma between economic growth and serious pollution problems. This paper systematically combs the literature related to the Environmental Kuznets Curve (EKC) in countries along the ‘Belt and Road’ (B&R) for the first time, and collects 87 literature from Web of Science, CNKI and Science Hub. Through the verification of EKC relationship and the theoretical explanation of EKC, the paper focuses on the relationship between economic growth, industrial agglomeration and environmental pollution in countries along the ‘Belt and Road’. Finally, some policy recommendations are put forward.


Introduction
In the context of global warming and increasingly serious environmental pollution, green sustainable development with the minimum cost of environmental resources to obtain the maximum economic benefits has become a global consensus (Huang et al 2023).After Grossman and Krueger (1991) proposed that 'environmental pollution increases with the increase of per capita GDP ', Panayotou (1993) named the inverse U-shaped curve between environmental pollution and economic growth as the Environmental Kuznets Curve (EKC).Since then, related researches around EKC have emerged in an endless stream.China put forward the initiative of jointly building the Belt and Road in 2013.The relevant countries are mainly developing countries in Southeast Asia, South Asia, Central Asia and North Africa, with relatively weak economic foundation, and there is a dilemma between economic growth and environmental pollution.The overall economic development level and the labor productivity of the countries along the Belt and Road is generally low, some countries are still in the stage of promoting economic growth by undertaking industries with serious pollution emissions from abroad, environmental pressure and pollution is intensifying, which seriously affects the sustainable development of the country.Therefore, it is of great significance to study the EKC relationship of the 'Belt and Road' countries.
Based on the systematic review of previous literatures, this paper analyzes the relationship between economic growth and environmental pollution in countries along the Belt and Road from two aspects of EKC verification and theoretical interpretation.We hope to find out the gap between these countries and other countries, such as developed countries in Western Europe, and make some suggestions.Possible innovations in this paper include: First, this paper systematically combs the literature related to EKC in countries along the 'Belt and Road' for the first time, although there are many academic studies on the relationship between EKC in different countries.Secondly, this paper not only verifies the EKC of countries along the Belt and Road from the national level and industry level, It also explains the theory from the aspects of Industrial agglomeration and industrial structure change and National Policy Orientation.

Preliminary verification of EKC: national level
In the B&R and non the B&R countries, academic circles have different views on the relationship between income and economic growth and environmental pollution (as shown in table 2).Some scholars believe that increasing income and economic growth will lead to a continuous decline in environmental quality.Al-Mulali et al (2015) and Kim (2020) believes that economic growth exacerbated environmental pollution in Vietnam and South Korea.Economic growth often increases economic complexity, which further exacerbates environmental pollution in low-and middle-income countries (Akbostancı et al 2009, Effiong and Iriabije 2018, Doğan et al 2019).The increase in per capita income will cause changes in the economic activity structure of developing countries, leading to intensified pollution such as water pollution in some African countries worsen (Kukla-Gryz 2009, Orubu andOmotor 2011).Environmental pollution can also hurt household income and significantly widen the urban-rural income gap, leading to income inequality issues (Wang and Lv 2012, Kasuga and Takaya 2017, Zhu and Zhang 2019, Alharthi et al 2022).In addition, income inequality has to some extent increased carbon emissions and SO2 emissions, which means that an increase in income distribution inequality will worsen national environmental pollution (Uzar and Eyuboglu 2019, Ehigiamusoe et al 2022b, Persson et al 2023).Idrees and Majeed (2022) used a nonlinear autoregressive distributed lag model to analyze that income inequality has worsened the environment in Pakistan.
Income, economic growth, and pollution are not always positively correlated, and there may also be an inverted U-shaped relationship between the environmental pollution index and per capita income (Başar and Yilanci and Ozgur 2019, Tosun 2021, Gosztonyi Á et al 2023).Although there is an inverted U relationship between pollution and income, water pollution may continue to increase at higher income levels (Lawell et al 2018).In China, with the economic growth, the problem of environmental pollution first worsened and then gradually improved ( Wang 2010, Fujii Managi 2016, Hao et al 2021).Fodha and Zaghdoud (2010) used cointegration analysis and found that there is also an inverted U-shaped relationship between Tunisia's SO2 emissions and economic growth.Even if appropriate pollutants are chosen, the EKC hypothesis may not be valid.For example, Maneejuk et al (2020) found that among the seven international economic communities, only the economic growth and environmental degradation of the EU, OECD, and G7 countries conform to the EKC hypothesis, showing an inverted U-shape.However, in South Korea, the relationship between economic growth and water pollution is consistent with the EKC hypothesis (Choi et al 2015).In addition to the inverted U-shaped relationship, there may also be a U-shaped and N-shaped relationship between income, economic growth, and pollution (Alvarez-Herranz et al 2017, Arnaut andLidman 2021, Simionescu et al 2023).
Can increasing income and economic growth help improve environmental pollution issues?If viewed as a whole, environmental inefficiency will decrease with the increase of per capita income, which means that the increase in income has to some extent improved environmental quality (Halkos et al 2016).In addition, income inequality caused by differences in income growth rates is generally negatively correlated with environmental degradation and does not worsen the environment, it can even improve environmental quality (Chu & Hoang 2021, Ghazouani et al 2022, Safar 2022).In addition, in the long run, economic growth also contributes to improving the environmental quality of a country (Rahman et al 2021).
In summary, based on existing research results, in the B&R co-construction countries, economic and income growth has a greater negative impact on national environmental quality.Numerous data indicate that in the process of economic growth and income improvement in B&R countries, the increase in emissions of greenhouse gases, sulfur dioxide, industrial waste, and other pollutants has worsened the country's environmental quality and exacerbated national pollution.In addition, the inverted U-shaped relationship of EKC has also been well validated in co construction countries.When using gases such as SO2 and CO2 to evaluate pollution levels, the inverted U-shaped relationship between national income, economic growth, and environmental pollution is more significant.However, it should be noted that even if pollution and income show an inverted U-shaped trend, after income crosses the EKC turning point, it does not necessarily mean that the higher the income, the lower the degree of environmental pollution.Different from the co construction  countries, more data show that in non the B&R countries, the increase of income and economic growth will help to improve national environmental pollution and alleviate environmental inefficiency.
Possible reasons for this difference include: First, the economic development level and per capita income of the B&R countries are generally lower than those of non the B&R countries.At present, many the B&R countries are still or may continue to be on the left side of the EKC curve for a long time in the future, while the economic development level of some non the B&R countries may have reached the EKC inflection point or even the right side of the EKC curve.Therefore, from the existing data, in the process of increasing income levels and economic growth, the likelihood of co-construction countries with increased pollution is greater.Secondly, some the B&R countries have taken advantage of their abundant labor force to undertake some industries with low added value in non the B&R countries.Although this has led to employment and economic growth, the development of these industries is likely to be at the expense of the environment.Therefore, environmental efficiency may continue to decline while national economic growth and income levels improve.

In depth verification of EKC: industry level
Next, we look at the micro level, that is, only consider the relationship between the development of a certain industry and environmental pollution, what will the results be different?The relevant studies are shown in table 3.
Firstly, in energy-consuming industries.Hanif I. (2017) found that fossil fuel consumption and oil imports are important factors leading to environmental degradation in developing countries in Latin America and the Caribbean.In Malaysia, energy consumption in the transportation and industrial sectors has led to an increase in carbon dioxide emissions.Although energy consumption in the agricultural sector has reduced emissions, its impact is relatively small, so sector energy consumption still deteriorates the country's environment (Shaari et al 2022).In order to reduce the pollution caused by fossil energy consumption, new energy sources such as clean energy have emerged, but this is not a panacea.In the long run, the production of clean energy has actually promoted carbon dioxide emissions (Kahia and Ben Jebli 2021).Su C et al (2023) used quantile to quantile analysis to find that the improvement effect of new energy development on the environment is also negligible.This may be because the industry is still in its early stages of development and technology needs continuous improvement, or increasingly serious environmental pollution has suppressed the development of the industry (Liu 2023).In order to reduce the negative impact of fossil fuel combustion on the environment, people are paying more attention to the research and development of new energy sources such as clean energy and renewable energy.However, in fact, the research and development of energy efficiency can better suppress carbon emissions and optimize environmental quality (Bilgili F et al 2021).Hu Y et al (2023) found that the construction of free trade zones can reduce environmental pollution in the city and surrounding cities by promoting industrial structure upgrading and improving innovation levels, and the improvement effect is more pronounced in non-resource-based cities and central cities Secondly, there is a bidirectional causal relationship between industrialization and environmental pollution (Sumaira and Siddique 2023).In Thailand, industrial expansion is the main cause of environmental conflicts (Soytong and Perera 2017).Akinsola F et al (2022) used an autoregressive distributed lag model to analyze that the increase in industrialization has accelerated environmental degradation in African countries.In addition, industrialization has increased the output of the industrial sector and further promoted carbon dioxide emissions in middle-income economies and newly industrialized countries, exacerbating environmental pollution (Sohag K et al 2017, Parveen S et al 2023).
Finally, in the financial services industry, network industry, import and export trade and other industries.After reaching a certain stage of industrial development, the profit margin of capital decreases, so more capital flows to the tertiary industry, promoting the development of industries such as finance and tourism.Financial development will exacerbate environmental pollution in South Asian countries such as Bangladesh and Nepal, and the improvement of development level is not conducive to improving the environment (Islam 2022), a possible explanation is that financial development supports the development of the secondary and tertiary industries, leading to increased pollution (Xu X et al 2021).Mesagan E et al (2022) and Aminu N et al (2023) argue that in the long run, financial integration has seriously worsened the environmental problems of African countries, and Ehigiamusoe et al (2022b) found that the output of the financial sector has also shown a relationship of first promoting and then inhibiting carbon dioxide emissions in Malaysia.Altinoz and Aslan (2022), Azam et al (2018) and Hassan S et al (2021) found that the accelerated development of tourism has worsened the air quality.The reduction of export diversification will worsen the country's air quality (Sharma R et al 2021).FDI(Foreign direct investment) has also significantly promoted carbon dioxide emissions and worsened environmental quality (Bakirtas and Cetin 2017, Destek and Okumus 2019, Azam et al 2022).Gong and Kong (2022) used the spatial Durbin model to find that the impact of real estate development on environmental pollution presents an inverted U-shape.Li S et al (2011) found that the overall development of

CD test
The relationship between foreign direct investment and environmental pollution presents a U-shaped pattern in emerging industrialized countries the environmental protection industry can improve regional environmental quality.Ike G et al (2022) analyzed the impact of Internet access on the global environment and found that there was an inverted U relationship between Internet access and CO emissions.However, the research findings of Demiral M et al (2023) are contrary to the inverted U-shaped pattern.
From the above analysis, it can be found that the development of the financial industry, tourism and other industries has brought a greater negative impact on the environment of the B&R countries.The financial development of most of the B&R countries is still at a relatively early stage, with a relatively slow pace of development and insufficient supervision, which worsens the waste of resources brought about by industry development, thus having a negative impact on the environment of the B&R countries.In addition, financial transactions need computers, communication networks, data centers, etc.The operation of these facilities needs to consume a lot of fuel and electricity, which will inevitably increase the emissions of sulfur dioxide, carbon monoxide and other toxic gases as well as greenhouse gases, further exacerbating the environmental pollution of the B&R countries.Therefore, financial institutions should enhance their environmental awareness, actively promote green financial products, guide funds to invest in the environmental protection industry, and reduce the negative impact of industry development on the environment of the jointly built country.
The development of tourism may worsen the environmental quality of the B&R countries for the following reasons: Firstly, in the development process of the tourism industry, it is necessary to construct facilities such as hotels, parking lots, and roads, which may lead to excessive land development and water resource utilization, disrupt regional ecological balance, and increase national environmental pressure.Secondly, uncivilized behaviors of passengers, such as littering, trampling on lawns, and diving into the seabed with makeup, can directly damage the environment and even threaten the survival of marine life, which is not conducive to maintaining ecosystem stability.Finally, some countries along the B&R have used tourism to drive economic development, which may have ignored the importance of government regulation and failed to reasonably limit the scale of tourism development, leading to the negative impact of excessive tourism development on the environment.
In addition, in the B&R countries, the EKC relationship has also been well verified in real estate, Internet and other industries.In the early stages of real estate development, it is inevitable that it will affect the national ecological environment.On the one hand, in order to build new buildings, it is often necessary to renovate the land on a large scale and remove some naturally growing vegetation, which can easily lead to environmental problems such as loose land and soil erosion.On the other hand, during the construction of houses, a large amount of dust and noise will inevitably be generated, which seriously affects the regional air quality and the normal life of surrounding residents.But in the later stage, in order to attract buyers, real estate developers may build parks, green belts, etc, which will help expand the green area of the B&R countries and improve the national air quality.Therefore, countries along the Belt and Road should attach importance to reducing the impact of real estate development on the ecological environment and realizing the sustainable development of real estate.
The possible reasons for the EKC relationship between Internet access and pollution are as follows.First of all, Internet access will enhance residents' willingness to eliminate old mobile phones, computers, televisions and other electronic devices, which will produce a large amount of electronic waste.In addition, the operation of the Internet needs to consume a lot of energy and electricity, which will inevitably increase the environmental burden of the B&R countries.However, with the popularization of the Internet, the national environmental quality will be improved.On the one hand, the Internet has realized paperless reading, which helps to protect the ecological environment.On the other hand, the Internet enables remote office work and learning, which helps relieve traffic pressure and reduce exhaust emissions, thus reducing the emissions of carbon monoxide, carbon dioxide, nitrogen oxides and other pollutants and reducing the negative impact on the environment.

Theoretical explanation: industrial agglomeration and industrial structure change
In the process of economic growth, there is a close autocorrelation between Industrial agglomeration and industrial structure change and environmental pollution (Cui M et al 2015).The transfer of manufacturing, agricultural resource-based industries and heavy chemical industries will significantly exacerbate environmental pollution, so the transfer of technology-intensive industries and consumer durables industries is more welcome (Kong F et al 2017, Shi M et al 2017).With comparative advantages such as low labor costs and abundant natural resources, countries along the 'Belt and Road' have undertaken many manufacturing, agriculture and energy industries, which have promoted industrial agglomeration and industrial structure upgrading to a certain extent, and the relationship between them and environmental pollution has also changed (see table 4).
Many scholars have verified the inverted U-shaped relationship between industrial agglomeration, structural changes, and environmental pollution (Li W 2010, Tan and Zhang 2015, Gan J and Liu X 2016, Mao and Yuan 2020).Yuan and Xie (2015) found that there is an inverted U-shaped relationship between industrial agglomeration and pollution, and the vast majority of provinces in China are located on the left side of the curve, which means that agglomeration exhibits negative externalities on the environment.Wang et al (2018) used the generalized least squares method to analyze the overall relationship between the agglomeration of renewable resources industry and environmental pollution, showing a 'non-standard inverted U-shaped' relationship.The pollution effects of agglomeration vary at different development stages.Zhou et al (2019) found that there is also an inverted U-shaped relationship between tourism agglomeration and pollution, which is promoted first and then suppressed.In addition, when considering the three industrial structures, it can be found that when the primary and tertiary industries are dominant, the pollution situation is relatively light and even improved.However, when the secondary industry is dominant, pollution will continue to deteriorate.Therefore, there is also an inverted U relationship between industrial structure adjustment and pollution (Li 2015).
Industrial agglomeration and structural adjustment also contribute to alleviating environmental pollution.In the early stages of industrial agglomeration, environmental efficiency may be low, but as the level of agglomeration increases, environmental efficiency will also improve, which helps to improve environmental pollution Li (2017).Yan et al (2011) used a panel error correction model to find that industrial agglomeration is beneficial for reducing pollution in the short term.Overall, agglomeration can also improve the efficiency of industrial development and improve environmental pollution in the local and neighboring areas (Lin 2022).In addition, agglomeration can promote the rationalization and advancement of industrial structure, thereby improving resource allocation efficiency, reducing resource waste, helping to optimize the ecological environment, and suppressing environmental pollution (Li 2018, Gong andLiu 2020).Zheng et al (2021) found that the higher the match between financial structure and industrial technology structure, the more conducive it is to reducing pollution.Nkwatoh (2022) found that in West African countries, agriculture, services, and renewable energy have a positive impact on the environment, and even manufacturing and industrial sectors are not sufficient to disrupt the environment.
Some industries in the B&R countries are still dominated by primary industries, with low added value of products, and some industries even need to consume a lot of natural resources, which seriously affects the national environmental quality.However, agglomeration helps enterprises to make better use of resources and technology, improve production efficiency and reduce waste of resources, and help reduce pollution in the B&R countries.In addition, agglomeration has significantly reduced the cost of transportation and communication, and exchanges and cooperation between enterprises have become more convenient, which will help reduce greenhouse gas and harmful gas emissions and promote the improvement of environmental quality in the B&R countries.
To sum up, the evolution of the relationship between industrial agglomeration and environmental pollution in countries along the Belt and Road is as follows.At the beginning of the agglomeration, the environmental pollution of the B&R countries may increase, but when the agglomeration reaches a certain level, the improvement of the agglomeration level will help to improve the environmental quality of countries.The possible reasons for the negative impact of agglomeration development on the environment in the early stage are as follows.On the one hand, in the early stage of agglomeration, enterprises have not yet gained profits from it.Therefore, driven by a profit seeking mentality, various enterprises will compete for limited resources in the area, resulting in resource waste, imbalance of the regional ecosystem, and exacerbation of pollution.On the other hand, the agglomeration of industrial industries helps to increase departmental output, and an increase in output will inevitably lead to an increase in industrial exhaust emissions.In addition, in the early stage of agglomeration, technology needs to be upgraded and production efficiency needs to be further improved, so the positive externality of industrial agglomeration on the environment is difficult to manifest in the initial stage.

Other deep-seated factors: national policy orientation
Due to differences in development level, cultural background, political system and other factors (table 5), national policies such as the quality of corporate supervision, government efficiency, corruption control and rule of law in countries along the Belt and Road are crucial to improving environmental quality (Nguyen and Su 2021).
Firstly, from the perspective of environmental harmfulness theory.In the process of continuous social development, the proportion of urban population is gradually increasing, while the proportion of rural population is continuously decreasing.This is a manifestation of urbanization.Although urbanization is beneficial for narrowing the income gap between urban and rural areas, it increases environmental pollution to a certain extent (Azam and Raza 2022).The higher the level of urbanization in a country, the faster its economic growth, and the greater its likelihood of maintaining democracy.Agbede et al (2023) found that democracy has increased carbon dioxide emissions in countries such as Mexico and Indonesia, exacerbating environmental pollution.At the same time, fiscal decentralization, as a manifestation of democracy, has brought certain negative impacts to the environment and reduced environmental efficiency (Li 2019, Xiao and Xiao 2019).Fiscal decentralization not only exacerbates regional environmental pollution, but may also breed local corruption, making it more difficult for countries to control corruption.However, Usman et al (2022) found that controlling corruption can lead to an increase in carbon dioxide emissions, which may further worsen the environmental quality in Africa.Secondly, from the perspective of environmental benefits theory.Unlike the previous text, in Cambodia, controlling corruption helps to reduce carbon dioxide emissions and improve the national environment (Ozturk and Al-Mulali 2015).In addition to controlling corruption, the implementation of clean energy subsidy policies by the government can also effectively improve the energy consumption structure, reduce the emission intensity of major pollutants, and slow down national environmental pollution (Xu 2018).
To sum up,controlling corruption, improving government efficiency and regulatory quality can improve national environmental quality and alleviate national environmental pollution caused by fiscal decentralization and democracy in countries along the Belt and Road.Firstly, the national government can formulate laws and regulations to protect the environment, providing legal guarantees for optimizing the national environmental quality, such as China's Air Pollution Prevention and Control Law, Zambia's Environmental Management Law, and Uganda's National Environmental Law.Secondly, the national government has the responsibility to supervise and inspect the implementation of environmental protection work, ensure that environmental pollution control work is implemented in practice and the effective implementation of relevant laws and regulations.Finally, the government can provide technical and financial support for environmental protection work, encourage enterprises to actively research and develop green and beneficial products, and minimize environmental pollution while promoting economic growth.

Main argument
Since most of the countries along the Belt and Road are facing the dilemma of economic growth and environmental pollution, the research on their EKC is of great significance for them and for China, which is preparing to enter the market of these countries.Some interesting points were found in this review.
First, the EKC relationship of countries along the Belt and Road is confirmed, but the income level of most countries is still on the left side of the curve, indicating the existence of significant negative environmental externalities.The scale effect shows that the negative impact of economic growth on environmental quality is mainly manifested in two aspects: on the one hand, economic growth requires increased investment, which in turn increases the use of resources such as oil and natural gas; On the other hand, more output is often accompanied by an increase in pollution emissions.This provides a perspective to explain the deterioration of the ecological environment in the process of realizing economic growth in the 'Belt and Road' countries.In addition, per capita income in most countries is still at a low level, and the demand for environmental quality is low, which exacerbates the deterioration of the environment.In fact, when the economic income develops to a certain extent, the EKC hypothesis can not necessarily be verified.For example, Maneejuk et al (2020) found that in 44 countries (the European Union, Organization for Economic Co-operation and Development, and Group of Seven), only nine countries have validated the EKC hypothesis.This may be closely related to the significant differences in the level of financial development, industrial development and urbanization.Therefore, countries along the Belt and Road should deepen the reform of financial and other sectors.
Secondly, the conclusion that energy consumption and industrialization will worsen a country's environmental quality is more in line with expectations.It should be noted that the development of new energy such as clean energy in some countries along the Belt and Road is in the initial stage, and the technology is not yet mature, which has little effect on the improvement of the environment, and may even increase regional pollutant emissions.Therefore, in the B&R countries, there may be an inverted U-shaped relationship between the generation of new energy and environmental pollution.
Thirdly, the negative impact of industrial agglomeration and structural upgrading on the environment is relatively small.Industrial agglomeration can improve industrial operation efficiency, reduce resource misallocation, reduce exchange costs, and even help reduce environmental pollution in surrounding areas (Liu and Xu 2021, Dou et al 2022, Igibah et al 2023).In addition, technological innovation and coordinated development of two-way FDI can promote the optimization of industrial structure, improve the rationalization and advanced level of structure, and thus help to optimize the ecological environment and improve environmental pollution.Finally, political system, fiscal decentralization and corruption will have a certain impact on the evolution of EKC in countries along the Belt and Road.For example, clean energy subsidy policies can effectively improve the energy consumption structure and optimize the ecological environment.In addition, the government can also guide funds through policies to invest in pollution reduction (Liu et al 2022).There is no doubt that improving the environment requires sufficient investment in reducing pollution, but this is based on the accumulation of sufficient capital in the process of economic development.Therefore, the change from insufficient to sufficient investment in pollution abatement forms the basis of the inverse U-shaped relationship between environmental quality and income.

Policy Implications
The evolving relationship between economic growth and environmental pollution in the countries along the Belt and Road has policy implications not only for the countries themselves, but also for China.
Firstly, countries along the 'Belt and Road' should strengthen the use of clean energy and new energy.The government should increase investment in science and technology, encourage enterprises to strengthen technological innovation, develop advanced technologies such as clean energy and resource recycling, make full use of technological innovation to improve resource utilization efficiency in the production process, and promote high-quality economic development with technological progress.
Secondly, the Belt and Road countries should dynamically address the relationship between industrial agglomeration and environmental pollution.In the early stages of agglomeration, due to uncoordinated development and rapid increase in energy consumption in a short period of time, agglomeration development may worsen the national environment.Therefore, in regions with lower levels of agglomeration, governments can actively introduce foreign direct investment and advanced technology, and adopt stricter environmental regulations to minimize the adverse effects of agglomeration on the environment in the early stages.However, in the later stage, when agglomeration develops to a higher level and resource competition among enterprises in the same industry is no longer fierce, the government should actively guide enterprises to innovate, change traditional low-end processing models, improve the rationalization and upgrading level of industrial structure, and thereby enhance the environmental improvement effect of agglomeration development on the country and even neighboring countries.
Finally, countries along the 'Belt and Road' should actively play the role of government policy guidance.For example, we will guide the flow of capital and better leverage the role of finance in low-carbon transformation and reducing environmental pollution.It is necessary to increase support for clean energy and climate adaptation projects, and speed up the integration of green investment and financing standards.

Conclusion
Due to the limitation of time and resources, this paper may have the following research defects and deficiencies.First of all, some references may be outdated, lack innovative viewpoints, and have some differences from the status quo.Secondly, it is difficult for references to cover all countries jointly built under the Belt and Road Initiative, and EKC relationship studies in some countries may be lacking or difficult to obtain data.Finally, the analysis of references may not be advanced enough and lack a deeper understanding.

Table 1 .
Quality assessment of all studies.

Table 2 .
Relationship between economic growth and pollution in countries along the B&R.
Başar and Tosun (2021) of PM2.5 in the atmosphere can have a negative impact on household incomeBaşar and Tosun (2021)28 OECD countriesWeighted establishment of seven pollutant environmental pollution indicesSystem-GMM There is an inverted U-shaped relationship between environmental pollution index and per capita income 7 Environ.Res.Commun.6 (2024) 062001 X Xu et al

Table 3 .
Relationship between development of specific industries and pollution in the B&R countries.

Table 4 .
Relationship between industrial agglomeration of the B&R countries and pollution.

Table 5 .
The relationship between national policies of the B&R and pollution.