Spatiotemporal Dynamics, Source Apportionment, and Stochastic Health Risk Assessment of Volatile Organic Compounds in Almaty, Kazakhstan

Urban air pollution in Central Asia remains a critical challenge, with volatile organic compounds (VOCs) posing significant threats to public health and regional climate stability. This research integrates studies conducted in Almaty, Kazakhstan, between 2015-2023 to characterize VOC concentrations, identify emission sources, and quantify human health risks [1-4].

In Almaty, the COVID-19 lockdown period in 2020 provided a unique opportunity to observe air quality under traffic-free conditions. While traffic-related pollutants (CO and NO₂) decreased by 49% and 35%, benzene and toluene levels remained 2–3 times higher than in the same seasons of 2015-2019. These results indicate that VOC pollution is dominated by non-traffic sources, such as coal-fired combined heat and power plants (CHPs) and residential heating systems. During the lockdown, people remained at home, potentially increasing coal combustion for private heating and public bathhouses (saunas) [1].

Throughout 2020, VOC concentrations in Almaty displayed significant seasonal and spatial variability. In total, 9 of 19 VOCs showed significant seasonal fluctuations, peaking during the winter heating season. Total VOC (TVOC) concentrations in January (233-420 µg/m³) weresubstantially higher than in summer. Spatially, TVOC levels correlated with Almaty’s northward-declining topography, increasing from southern upper to northern lower districts, closer to CHPs and characterized by stagnant conditions and persistent temperature inversions [2].

Consequently, a stochastic human health risk assessment for Almaty residents revealed concerning long-term implications. Median non-carcinogenic Hazard Indices (HI-s) were generally within acceptable limits (<1.0), but 95^th percentile HIs exceeded 3–5 in winter, indicating exceeded exposure margins for a non-negligible population fraction. More critically, lifetime carcinogenic risk exceeded the 10^-6 threshold in all scenarios. Median risks ranged from 10^-5 to 10^-4, while worst-case winter scenarios reached 10^-3, indicating significant cancer risk primarily driven by benzene [3].

Following these assessments, a year-long study (2022–2023) utilized sorbent tubes for active 24-hour air sampling to characterize Almaty’s air quality. An annual average benzene concentration (8.25 µg/m³) exceeded European Union and Canadian standards by factors of 4.9 and 13.8. HYSPLIT backward trajectory modeling identified that stagnant winter conditions facilitate local VOC accumulation, while additional transboundary contributions from Kyrgyzstan and Uzbekistan. Reactivity analysis showed that xylenes, toluene, and pseudocumene contribute over 80% of ozone formation potential, highlighting their role in urban smog [4]. These findings highlight an urgent need for targeted regulatory interventions, including annual benzene limits, CHP infrastructure modernization, and transitioning to cleaner fuels to mitigate the air quality crisis in Central Asia.

Acknowledgments

This research was funded by the Science Committee of the Ministry of Higher Education and Science of the Republic of Kazakhstan (Grant No.AP22785481,2024-2026).

References

[1]A.Kerimray et al. Assessing air quality changes in large cities during COVID-19 lockdowns: The impacts of traffic-free urban conditions in Almaty, Kazakhstan. STOTEN (2020),730,139179.

[2]O.P.Ibragimova et al. Seasonal and Spatial Variation of VOCs in Ambient Air of Almaty City, Kazakhstan. Atmosphere, (2021),12(12),1592.

[3]A.Alibekov et al. Severe health risks from ambient VOCs in a Central Asian city: Source attribution and probabilistic risk assessment. Atmos.Environ.X (2025),28,100378.

[4]O.P.Ibragimova et al. Urban atmospheric volatile organic compounds pollution in Kazakhstan: Trends, sources identification, and health risk assessment. Atmos.Pollut.Res. (2025),102761.