Assessment of Environmental Risks from Pollution by Toxic Emissions in Heat Treatment Process of Electrode Production

Metallurgy is one of the main branches of the Ukrainian economy, because it creates about 30% of the GDP and provides 40% of foreign currency income to the economy. The importance of the metallurgical industry in the country’s economy is due to the fact that this industry produces raw materials for the engineering, transport and construction industries. One of the main metallurgical centers of Ukraine is the city of Zaporizhzhia. It is a large metallurgical center of Ukraine and is part of the Dnipro region, on its relatively small area (631.9 thousand m² or 5.3% of the area of Ukraine) 40% of the ferrous and non-ferrous metallurgical industry, 20.5% of the chemical and machine-building industry are located industry, 41% energy. Therefore, for the city of Zaporizhzhia, as well as for many other industrial cities of Ukraine, which have a significant number of sources of atmospheric air pollution, the substantiation of safe for health volumes of emissions of pollutants into the atmospheric air is more relevant [1, 2]. Atmospheric air pollution significantly affects people’s health because breathing is the basis of vital activity of any organism. As a result of constant and repeated effects on a person through the air, they can change the quality of life and the state of health of the population, even to an increase in the mortality rate, the appearance of genetic disorders, and the growth of oncological diseases.

Since enterprises of the metallurgical industry are significant suppliers of toxic emissions of carbon monoxide, during the production of graphite electrodes in the city of Zaporizhzhia, gaseous waste contains carbon monoxide in the amount of 47% [3]. In Ukraine, the total amount of carbon monoxide emissions is 704,344.218 t/year, or 31% of the total emissions of pollutants and greenhouse gases other than carbon dioxide [4]. Therefore, the prevention of environmental pollution with toxic gases directly in the process of industrial production is undoubtedly relevant and necessary as a way to improve people’s quality of life.

The polluted atmospheric air of large cities worldwide has always been and remains an important risk factor for the health of the population, as evidenced by numerous studies [5, 6]. There is a growing understanding that atmospheric pollution affects medical and demographic indicators – mortality, morbidity, and life expectancy of the population [7, 8], and in some cases, it is the cause of increased social tension and a decrease in the attractiveness of the city as a place of permanent residence. Pollution of the city’s atmospheric air with chemical substances causes adverse changes in people’s health [9], which in certain cases can provoke the further development of pathological conditions and complications of chronic diseases [10, 11]. In connection with the harmonization with international standards, the technology of risk assessment and management in the field of environmental protection and improvement of public health is being implemented in our country according to the methodology of risk analysis approved by the World Health Organization in the document “Health Risk Assessment from Air Pollution. General Principles” and is used in several countries. The tool undoubtedly provides greater targeting of actions and optimization of financial costs to achieve the main management goals [12].

Every year, about seven million people worldwide die from diseases caused by dirty air. Inhalation of harmful substances causes deterioration of the health of all age categories of the population; decrease in life expectancy, worsening conditions for the development of the health care system [13]. Damage to health is considered as a source of direct losses from environmental pollution, which are supplemented by indirect losses (increased costs and loss of income as a result of pollution, expenses for restoring the health of accident victims, etc.) [14].

Due to the global deterioration of the air in 2021, the WHO revised the air quality standards for the first time since 2005 [15]. Thus, the organization lowered the permissible content of solid particles (PM), ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide (SO₂) and carbon monoxide (CO). Exceeding these standards can lead to extremely negative health consequences, while compliance with the new standards can save millions of lives. Therefore, today in Ukraine more and more attention is paid to the timely detection of risk and its analysis [16].

The purpose of the work is to assess the risks to the health of the population living in the zone of influence of emissions of pollutants into the atmospheric air from the operating enterprise “Ukrgrafit”, the city of Zaporizhzhia after the introduction of catalytic methods of carbon monoxide purification in calcination and graphitization furnaces, to generalize the experience of applying the assessment procedure risks and damage to public health in the system of new mechanisms for air quality monitoring and management.

The assessment of the risk of impact on the environment from stationary sources of emissions of pollutants into the atmospheric air of the operating enterprise PJSC “Ukrgrafit” was carried out in accordance with the raw and energy resources existing at the time of the calculation, improved by eco-modernization of technological processes of production, assortment, and volume of products; qualitative and quantitative composition of pollutant emissions into atmospheric air; the potential influence of other influencing factors on the environment and public health; taking into account the existing planning infrastructure of industrial and settlement areas [17] using the report on the inventory of sources of emissions of pollutants into the atmosphere from stationary sources of PJSC “Ukrgrafit” [18]. The basis for determining the risk assessment of the impact of the planned activity on the environment is the methodological recommendations “Assessment of the risk to public health from atmospheric air pollution” [9], requirements for the composition and content of the environmental impact assessment section in the design documentation for new construction, reconstruction, and overhaul of buildings and structures of any purpose and their complexes [19], the procedure for determining the values of background concentrations of pollutants in atmospheric air [20].

PJSC “Ukrgrafit” is located on four production sites, the distance between which is less than 500 m, therefore the enterprise was considered as one production site. 159 stationary emission sources were included in the study. Expected harmful components: substances in the form of suspended particles undifferentiated by composition, emissions after the afterburning of pungent gases (nitrogen oxides, sulfur oxides, carbon oxides), benzene, styrene, benzapyrene, naphthalene, dibutyl phthalate, phenol and some others.

Graphitization furnaces are resistance furnaces (Acheson furnaces), where the heater is the heatinsulation charge located between the workpieces. The operating mode of the ovens is cyclic. Acheson’s furnaces emit a large amount of pollutants. Therefore, it was proposed to implement the Kastner method, which consists in heating the workpieces with a current that is passed directly through the workpiece. This will make it possible to reduce emissions of dust, carbon oxides, and sulfur into the atmosphere and to reach the standards of maximum permissible emissions of pollutants into the atmosphere during graphitization.

The materials do not consider the influence of industrial emissions of other enterprises. The results of establishing the level of average concentrations of priority pollutants in the surface layer of the atmosphere are generated by the program of dispersion of pollutants in the surface layer of the atmosphere “EOL 2000” in DBF format. This system made it possible to calculate pollution fields for a point model of a source of emission of harmful substances with a round or rectangular mouth of the pipe. When assessing the impact of enterprises undergoing reconstruction on atmospheric pollution, the calculation was made taking into account background concentrations.

The risk assessment of the impact of the planned activity on the health of the population from atmospheric air pollution was carried out based on the calculations of the risk of the development of non-car-cinogenic and carcinogenic effects [9, 10].

Characterization of the risk of development of non-carcinogenic effects in the case of combined and complex action of chemical compounds is carried out based on the calculation of the hazard index (HI). The danger index for conditions of simultaneous intake of several substances by the same route (for example, inhalation or oral) is calculated according to the following formula: 1HI=HQi, where HQ_i– hazard coefficients for individual substances, which are determined in accordance: 2HQi=Ci/RfCi, where C_i – estimated annual average concentration of the i-th substance, mg/m³; RfC_i – reference (safe) concentration of the i-th substance, mg/m³ (in the absence of reference doses/concentrations (according to the list), the maximum permissible concentration (MPC) can be used as an equivalent; HQ_i = 1 – the limit value of the accepted risk.

The calculation of hazard indices is carried out considering critical organs and systems that are negatively affected by the investigated substances. As evidenced by the results of scientific research, when the components of the mixture affect the same organs or systems of the body, the most likely type of combined effect is summation [9, 10].

With HQ equal to or less than 1, the risk of harmful effects was considered to be quite low. With an increase in HQ, the probability of the development of harmful effects should increase, however, it is impossible to accurately indicate the value of this probability (Table 1).

The risk of developing individual carcinogenic effects (ICR) from substances with carcinogenic effects is calculated according to: 3ICR=Ci·URi,

where C_i – estimated annual average concentration of the i-th substance, mg/m³; UR – the unit carcinogenic risk of the i-th substance, mg/m³.

The unit risk is calculated using the value of SF (mg/kg·day), the standard value of human body weight of 70 kg, and daily air consumption of 20 m³ [9, 10]: 4UR=SFi/(70·20).

Hazard ratios were calculated separately for each substance at each calculation point and differentiated for different conditions (acute and chronic exposure). The danger factor is a multiple of the reference concentration for acute or chronic exposure to the maximum or average annual calculated concentration of a toxic substance in the surface layer of the air. The hazard index is the sum of these hazard coefficients from individual pollutants.

In connection with the fact that multicomponent chemical pollution of environmental objects was analyzed in the studied territories, the total risks caused by the simultaneous action of several chemical compounds were evaluated.

The characterization of the carcinogenic risk was carried out in the following stages: summarization and analysis of all available information about harmful factors, features of their effects on the human body, exposure levels; calculation of the carcinogenic risk for each substance entering the human body; calculation of the carcinogenic risk for each carcinogenic component of the investigated mixture of chemicals, as well as the total carcinogenic risk for the entire mixture; calculation of total carcinogenic risks for each of the analyzed routes of entry, as well as the total summarized carcinogenic risk for all substances and all routes of their entry into the body; summarizing and presenting the results of risk characterization.

The calculation of the carcinogenic risk was carried out only for the range of doses of the chemical substance that corresponds to the linear portion of the “dose-response” dependence. The characteristics of the “dose-response” dependence, which are most often used to assess carcinogenic risk, have been sufficiently studied in epidemiological studies. Among them is the factor of carcinogenic potential (ICS), which reflects the probability of the development of a harmful reaction when the dose (concentration) increases by 1 mg/kg or 1 mg/m³ per exposure level, associated with a certain probability of effect (the indicators of this group are used for the establishment of reference, i.e., reference doses and concentrations) [9, 10].

The carcinogenic risk due to the combined effect of several chemical compounds is considered additive, and the combined effect of several carcinogenic substances polluting the atmosphere (CR_a) is determined according to: 5CRa=∑ ICRi,

where ICR_i – the carcinogenic risk of the i-th substance.

The calculation of hazard indices was carried out taking into account critical organs and systems that are negatively affected by the investigated substances. Individual carcinogenic risk characterizes the limit of carcinogenic risk during the period corresponding to the average life expectancy of a person (within 70 years) (Table 2).

The calculation of climatological, meteorological coefficients and indicators of the dispersion of pollutants in the atmosphere were carried out taking into account the maximum and average annual concentrations using the unified program for calculating atmospheric pollution “EOL 2000”, which allows you to calculate surface concentrations of pollutants in the atmosphere following [20], given in Table 3.

To calculate and assess non-carcinogenic risks based on hazard ratios (HQ), individual carcinogenic risks for the health of the exposed population exposed to atmospheric air pollution by emissions from stationary sources of the operating enterprise PJSC «Ukrgrafit», according to the provided materials, stationary sources were included in the study emissions of PJSC “Ukrgrafit”.

Taking into account the criteria for the selection of pollutants emitted into the atmospheric air by stationary sources of the operating enterprise of PJSC “Ukrgrafit”, namely: analysis of volumes (g/s) of pollutants entering the atmospheric air; assessment of the toxicity of polluting chemical substances capable of affecting the health of the population; data analysis regarding hazard parameters and “dose-response” dependencies (reference concentrations; factors of carcinogenic potential; current domestic regulations (limit-permissible maximum single and average daily concentrations); estimates of the directionality of the impact on the organs and systems of the human body; the number of the population exposed from the company’s emissions, a list of pollutants necessary for researching the assessment of the risk to public health from air pollution by emissions from stationary sources of PJSC “Ukrgrafit” was formed.

PJSC “Ukrgrafit” is a Ukrainian enterprise in the field of graphite processing and production of electrical equipment from it, today it produces electrodes for electrometallurgical enterprises, graphite anodes for the magnesium industry, as well as graphite blocks for the aluminum and metallurgical industries. On the territory of the production site, there are firing shops and graphitization shops, where innovative technologies of catalytic neutralization of toxic carbon monoxide using metal oxide catalysts on zeolite (Fig. 1) and fibrous carriers (Fig. 2) were introduced [21, 22].

Figure 1.

Design features of catalytic reactors arrangement with modified zeolite in the fire channels of the firing furnace

Figure 2.

Scheme of laying modified ceramic fiber in a metal frame on top of thermal insulation of the graphitization furnace

The main task in hazard identification was to identify specific chemical substances that could negatively affect the health of the local population. Considering the criteria for the selection of pollutants emitted into the atmosphere by stationary sources of the operating enterprise PJSC “Ukrgrafit” after the introduction of catalytic systems on furnaces, a list of 25 pollutants necessary for further research on the assessment of the risk to public health from air pollution was formed by emissions from stationary sources of the operating enterprise PJSC “Ukrgrafit” (Table 4).

According to [23], the main production relates to chemical enterprises (enterprises for the processing of coal) with a sanitary protection zone of 1000 m. Calculation of the dispersion of pollutants in the atmosphere for methane and hydrocarbons of the C12-C19 range was not carried out, as the sum of the maximum groundlevel concentrations in fractions of MAC (Maximum Allowable Concentration) is less than 0.1. The list of priority chemical substances emitted by stationary sources of PJSC “Ukrgrafit” after reconstruction is presented in Table 5, where the direction of impact on the organs of vision (OV), immune system (IS), skeletal system (SS), nervous system (NS), respiratory organs (RO), reproductive system (RS), parenchymal organs (PO), cardiovascular system (CVS), central nervous system (CNS), carcinogenic effects (CE), congenital malformations (CM), liver (L), kidneys (K), nasal cavity (NC), blood (B), demographic indicators (DI) – increase in mortality rate – is justified.

Based on the calculated exposure levels, the characteristics of the risk of atmospheric air pollution caused by the emissions of the operating enterprise PJSC «Ukrgrafit» were established, which included the calculations of the hazard indices for individual HQ substances (non-carcinogenic risks) and for the combined effect of HI (Table 6) and calculations of carcinogenic individual of ICR risks and by the combined effect of CRa (Table 7). The assessment of non-carcinogenic risks was carried out based on the calculation of the HQ hazard indices, which are the ratio between the exposure values and the safe (reference) action level.

The assessment of long-term effects at the level of the average annual concentration on human health of the studied substances, which will allow assessment of the chronic inhalation effect of the occurrence of negative effects on the health of the exposed population during life for the assessment and characterization of multistage risk, showed that the HQ hazard indices do not exceed the norm.

Calculations of acute and chronic inhalation hazard indices resulting from emissions from the operating enterprise PJSC “Ukrgrafit” after the implementation of catalytic purification showed that the hazard indices HQ for the impact of substances in the form of suspended solid particles, mercury, and its compounds in terms of mercury, ammonia, fluorine, and its gaseous and vaporous compounds in terms of hydrogen fluoride, styrene, phenol, nitrogen oxides (nitric oxide and nitrogen dioxide) in terms of nitrogen dioxide, carbon monoxide, sulfur dioxide (sulfur dioxide and trioxide) in terms of sulfur dioxide, manganese, and its compounds in terms of manganese dioxide, hydrogen sulfide, naphthalene, acenaphthene, dibutyl phthalate, dimethyl sulfide, iron, and its compounds in terms of iron, hydrocarbon homologues C12-C19, and mineral oil in the atmospheric air can be considered permissible, with an extremely low risk of adverse effects occurrence.

During the analysis of air pollution levels by chemical carcinogens emitted into the atmosphere by the sources of PJSC “Ukrgrafit” after reconstruction, namely: benzo(a)pyrene, benzene, lead and its compounds in terms of lead, chromium and its compounds in terms of chromium trioxide, it was established that the values of individual carcinogenic risk ICR during the entire stay of a person in the area of the nearest residential development are as follows: –

benzo(a)pyrene ICR = 5.69×10⁻⁹;

Such risks do not require additional measures to reduce them.

In assessing the health risks to the population of Zaporizhzhia from emissions of PJSC “Ukrgrafit”, priority pollutants were identified: carbon oxide, nitrogen oxides, sulfur oxides, and substances in the form of undifferentiated suspended solid particles. Hazard indices were determined for individual substances HQ (non-carcinogenic risks) and for combined action HI, calculated carcinogenic individual risks (ICR), and for combined action (CRa).

Evaluation of the long-term effects (at the level of average annual concentration) on human health of the investigated substances, allowing assessment of the chronic inhalation impact and the occurrence of negative health effects in the exposed population over a lifetime for assessing and characterizing the multi-stage risk, showed that hazard indices (HQ) do not exceed the norms.

Analyzing the above, it is necessary to note that the assessment of emissions from PJSC “Ukrgrafit”, taking into account their toxicity, which is used in the methodology for assessing the health risk to the population, allows determining the environmental situation, provides a sufficiently reasoned, objective assessment of the harmfulness of emissions into the atmosphere, developing a rational, scientifically based approach to mitigating the impact of emissions on public health regarding the urgency and priority of implementing environmental tasks facing the enterprise and the local authorities of the city.