Comparative Hygienic Assessment of the Composition of Ash and Dust Fractions in Ambient Air of the Area Affected by Emissions from a Thermal Power Station: Improving the Accuracy of Human Health Risk Assessment

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Introduction: The relevance of the study is determined by a great number of functioning thermal power stations that operate using solid fuels (40 %) and are a source of ambient air pollution posing human health risks. Objective: A comparative hygienic assessment of the component, disperse, and morphological composition of fly ash and airborne particles in the area surrounding a coal-fired power station for the purpose of increasing the accuracy of human health risk assessment. Materials and methods: We have used unified and approved methods for hygienic assessment of ambient air quality; hazard identification and health risk assessment; scanning electron microscopy and micro-X-ray fluorescence spectroscopy of component, disperse, and morphological structure of fly ash and airborne particulate matter. Results and discussion: Large coal-fired thermal power plants emit about 36 chemicals. Over 59 % of brown coal ash particles are calcium, magnesium, iron, silicon, aluminum, sodium, potassium, sulfur, and phosphorus compounds. Particles found in fly ash and ambient air of the surrounding area have similar components and dispersion, are predominantly less than 10 µm in diameter with the sphericity index ranging from 0.4 to 1.0. Maximum allowable concentrations (MAC) of seven chemicals are exceeded in the study area: up to 3.3 single MAC, up to 1.4 average daily MAC, and up to 1.5 average annual MAC, with the estimated contribution of the thermal power stations of about 40 %. We have also established increased non-carcinogenic health risks with the dust fractions alone generating risk levels as high as 5.5 HQac, 2.4 HQch, and 6.9 HIch, which are rated as “high” and “alerting”. Identified solid particles (aluminum, magnesium, calcium, etc.) are more significant risk factors compared to unidentified particulate matter and can cause respiratory and circulatory diseases, diseases of the eye, etc., which requires their quantification. These chemicals are not included in air emissions inventory lists and are, therefore, not monitored. As a result, health risks posed by economic activities of thermal power stations may be underestimated.