Sobirjon S. Ruziyev

Type of the article: Research Article

Abstract
Central Asian countries face acute air quality challenges, with PM2.5 concentrations in major cities exceeding World Health Organization guidelines several times over, while industrial CO₂ emissions continue to rise alongside economic development. Understanding the empirical linkage between these pollutants is essential for designing integrated environmental policies. The purpose of this study is to assess the impact of industrial CO₂ emissions on PM2.5 air pollution in five Central Asian countries – Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan – using balanced panel data for the period 2000–2020 (N = 105) obtained from the World Bank’s World Development Indicators. Pooled OLS, fixed effects, and random effects estimators were applied, with GDP per capita, urbanization, and energy intensity as control variables. Model selection was based on the Hausman test, and robustness was verified through ten alternative specifications. The random effects model (Hausman χ2 = 0.412, p = 0.521) reveals a statistically significant positive relationship: a one million metric ton increase in industrial CO₂ emissions is associated with a 0.87–0.89 µg/m3 rise in mean annual PM2.5 concentration (p < 0.01). The coefficient remains stable across all robustness checks (0.823–0.923). GDP per capita shows a significant negative effect (−1.92, p < 0.05), supporting the Environmental Kuznets Curve hypothesis, while energy intensity has a positive effect (p < 0.05). Country-specific effects reveal substantial heterogeneity, with Tajikistan exhibiting the highest baseline PM2.5 (+26.25 µg/m3 above Kazakhstan) and Turkmenistan the lowest (+7.49 µg/m3). These findings confirm the co-pollutant hypothesis and justify integrated climate-air quality policies with country-specific strategies.

Acknowledgments
The authors would like to thank the anonymous reviewers for their constructive comments and suggestions that helped improve this manuscript.