The Relationship between Population Aging and Air Pollution in Iran: Application of GMM

Nowadays, environmental problems, especially air pollution, are one of the major issues in the world's metropolises with increasing its dimensions and side effects. Humans are one of the main sources of air pollution. The age structure of the population is an important indicator in the progress of societies. It can be said that one of the effective factors in economic growth and long-term socio-economic development plans is the age structure of the population (youth or aging population). In working-age (provided that the labor market has the capacity to absorb more workforce in activities), increasing labor supply leads to economic growth.In general, the age structure of population is important because economic activities and energy consumption vary by age or stage of life. On the other hand, the age of household head is related to household size (people over 65 usually have smaller households than middle-aged people). Studies conducted in Iran have mostly focused on examining Kuznets' environmental hypothesis, the impact of income and population changes on carbon dioxide emissions, and so far have not examined the effect of aging on carbon dioxide emissions. Therefore, this article examines the effect of aging on air pollution in Iran. This article uses the GMM to investigate the dynamic effect of population aging on air pollution during 1981-2020.

To collect information for this study, a documentary method was used. The research was conducted based on annual data from 1982 to 2020 in Iran's economy. EViews software was used to estimate the model. It should be noted that data related to research variables were extracted from various sources such as the Central Bank of Iran Statistical Center of Iran, and Energy Balance Sheets.To estimate the model, a time series econometric method called GMM was used because the model used in this study is dynamic and satisfies generalized moment conditions. In fact, GMM is used for time series models that are linear and also provide generalized moment conditions and instrumental variable properties. This method have many advantages.

In this study, the impact of population aging on air pollution was investigated using the GMM in Iran during the period of 1981-2020. The estimation of the model indicates that increasing the age of the population and the transition of the age structure of the population to the aging stage has a negative effect on air pollution. As it is predicted, Iran will face the problem of population aging in the next few years. According to the results, with increasing population, it can be expected that air pollution and environmental degradation will decrease. Due to the negative coefficient of the per capita income squared, the Kuznets environmental hypothesis is confirmed by considering the age structure of the population. In addition, urbanization, industrialization, trade openness, pollution of the previous period have positive and significant effects on air pollution.The results indicate an inverted U-shaped EKC pattern between environmental degradation (pollution emissions) and per capita income (economic growth); therefore, it can be concluded that environmental degradation initially increases with increasing per capita income in a country, but after reaching a certain level of economic growth, environmental degradation stops and then decreases. Therefore, the results confirm the Kuznets environmental hypothesis for Iran. Based on this, it is recommended that the government design its plans with environmental considerations, especially air pollution. The results indicate that population aging has a significant negative effect on air pollution emissions. Population aging is detrimental to a country's economy and although it is inevitable for any country, policies to increase the number of elderly people in the population mix cannot be formulated and implemented even though it reduces air pollution levels. However, the harm caused by population aging outweighs this benefit. Of course, recently topics such as "active aging" have been raised to deal with population aging logically and should be on policymakers' agenda given the transition of age structure and movement towards aging in future years.

Based on the evidence of Iran's population age distribution during the period under study, it can be said that in future decades, older individuals will make up a higher percentage of the total population. This will lead to a reduction in carbon dioxide pollution automatically without government intervention or any other actions. The results of this study also show that urbanization and industrialization have positive impacts on air pollution. This result indicates that with the increase in the number of industrial enterprises and the trend towards urbanization in Iran, air pollution has increased. The reason for this is that most industries in Iran are energy-intensive and use fossil fuels. Another reason is the outdated technology with low efficiency in production. Other research findings show that pollution from previous periods and trade liberalization have positive effects on air pollution. The policy of economic liberalization by creating division of labor and using advantages, increasing capacity utilization in industries, increasing capital formation rates, changing technology, and creating competition in international markets lead to higher productivity levels for all production factors at a higher level.