Risk Assessment for the Population of Kyiv, Ukraine as a Result of Atmospheric Air Pollution

Background. According to the World Health Organization, 92% of the world's population lives in places where air quality levels exceed recommended limits. Recently, Ukraine had the most deaths per every 100,000 people (out of 120 countries) attributed to atmospheric air pollution. High levels of atmospheric air pollution have been observed not only in typically industrial regions, but in Ukraine's capital, Kyiv, as well. Objectives. The aim of the present study was to establish the state of air pollution in Kyiv and perform a risk assessment of associated human health effects. Methods. Using official statistics and state monitoring data, the study aimed to identify and analyze risks to the health of Kyiv's population associated with air pollution. The following methods were used: systematic, functional and comparative analysis, risk theory, mathematical modeling, probability theory and mathematical statistics, as well as geographic information system technologies for digital map design and objective-oriented methodology for software design systems. Results. The risk values across different areas of the city varied significantly, indicating that atmospheric air quality remains unstable. Areas with the highest and lowest risk values were identified. Conclusions. The environmental state of atmospheric air in Kyiv requires greater attention and additional research to identify the causes of air pollution, along with implementation of measures to improve air quality. Competing Interests. The authors declare no competing financial interests.


Introduction
Air pollution is a large problem in many countries around the world. The main sources of atmospheric air pollution are transportation, power companies, chemically hazardous enterprises, metallurgy, machinebuilding, metal-processing enterprises and industries, building materials industries, and lumber operations, among others. 1 Atmospheric pollution is considered to be the most dangerous form of pollution by volume, as pollution of industrially developed cities by toxic agents becomes irreversible and has negative impacts on the health of the population.
According to the World Health Organization (WHO), 92% of world population breathes air polluted beyond the acceptable limits. 2 Ukraine is no exception and recently (in September, 2017) ranked first (out of 120 world countries) in deaths caused by atmosphere air pollution, per 100,000 people. Air pollution in Ukraine causes four times more deaths per capita than the five cleanest countries altogether, according to the WHO. 3 The main sources of pollution in Kyiv are motor transport and energy enterprises (thermal stations), enterprises of the construction industry, mechanical engineering, chemical-pharmaceutical, and the food industry. In 2015, the total amount of pollutants in the atmosphere from stationary and mobile sources in Kyiv amounted to 144.3 thousand tons. More detailed data on emissions from stationary technogenic facilities in Kiev are presented in Table 1. 4 The air monitoring system in Ukraine is currently ineffective and has significant problems. There is no data collection and analysis center and Research monitoring results are stored in paper form. Most atmospheric scientific research results with some elements of statistical and comparative analysis do not consider the environmental risks to public health. Therefore, a risk assessment of the health of Kyiv`s population due to air pollution supported by data and analysis is urgently needed. The aim of the present study was to establish the state of air pollution in Kyiv and perform a risk assessment of associated human health effects.

Methods
Kyiv, the capital of Ukraine, is one of the biggest and oldest cities in Europe. Kyiv is situated in the south of Ukraine, on the border of Polissya. The Dnipro River runs through the city and there is forest steppe on either side of the river. Kyiv has an area of 836 km². The climate is moderately continental, with mild winters and warm summers. The average monthly temperature in January and July is −3.5°C and +20.5°C, respectively, with an average annual precipitation of 649 mm. Forests, parks and gardens make up more than half of the almost 80 000 hectares. The population in Kyiv was 2.9 million in December 2017, according to data of the General Statistics Department. 5 The present study was conducted from September 2016 till September 2018.
In Ukraine, programs monitoring the quality of atmospheric air are aimed at the control of primary pollutants at stationary and mobile stations. In Kyiv, the Central Geophysical Observatory systematically monitors the content of pollutants in atmospheric air at 16 stationary (but manual) pollution observation stations (POS) with samples taken every 6 days, 3-4 times a day. These stations collect data on suspended substances, sulfur dioxide, carbonic oxide, hydrogen sulfide, phenol, hydrogen fluoride, ammonia, formaldehyde, and eight heavy metals. Their composition is defined depending on the emissions of pollutants in atmospheric air from enterprises located in the area of the observation stations. The distribution of POS in Kyiv is shown in Figure 1. In order to assess atmospheric air pollution levels, the air pollution index was used, following Equation 1.

Equation 1
where, API is the air pollution index; С і is the average concentration of і-additive in time (per month or per year) calculated for the station, city or a group of cities; MPC a.d.i is the maximum permissible daily average concentration of a pollutant in the air; and β і is the dimensionless constant of reducing the damage of і-substance to the damage of sulfur dioxide which accepts the values of 1.7; 1.3; 1.0; 0.9 for 1, 2, 3, 4 classes of hazard of pollutants, respectively.
The above-mentioned health standards characterize only the level of chemical air pollution of a territory under investigation and do not define the impact of pollution on human health. Therefore, a risk assessment was conducted to determine the probability of negative effects on human health for individuals or groups of people affected by a particular chemical reagent. It is characterized by the value that lies within (0…1) interval, where 0 indicates the absence of effect and 1 indicates the greatest effect.
In order to assess the negative impact of anthropogenic air pollution on the health of a population which may manifest itself in immediate or chronic toxic effects (carcinogenic and immunotoxic), two groups of models have been introduced: threshold and non-threshold. 6 Acute toxicity (immediate toxic manifestations) has a definite threshold character. In order to assess the risk of immediate toxic effects (RITE), the model of personal impact thresholds is used. In terms of air pollution, this model is defined by where, a, b are the parameters depending on toxicological properties of the substance; C is the toxicant concentration in the air (mg/m 3 ); and MPC m.s. is the maximum permissible single concentration of a pollutant in the air. To find RITE, it is necessary to calculate a defined exponential function integral: exp(-τ 2 /2) = e -τ2 / 2 (number e = 2,71), where, τ is an integration variable that takes a value from -∞ д a + b lg(C/MPC m.s. ) and dτ is a differential variable τ.
The risk of chronic intoxication (RCI) is defined for a certain time period using Equation 3.

Equation 3
where, β is the coefficient that takes into account toxic properties of the substance; K is the parameter depending on the class of hazard of the substance; C is the pollutant concentration in the air over time (t) (mg/m 3 ); and MPC a.d. is the maximum permissible daily average concentration.
The values of a, b, β, and K depend on the substance hazard classification and are given in Table 2.
In order to define the level of air pollution attributed to a certain substance, average concentration values along with the highest values of concentration at a certain period of time are identified.
The level of integral risk from simultaneous impact of all investigated substances was calculated with the formula in Equation 4:

Equation 4
where, R ∑ is the level of integral risk from simultaneous impact of all investigated substances; R i is the health risk value as a result of the impact of і-substance; and n is the number of substances under investigation.
In Ukraine, according to applicable instructional guidelines of the Ministry of Health of Ukraine, the individual carcinogenic risk, hazard coefficient for exposure to i-substance, level of noncarcinogenic risks and hazard index are defined. 7 The carcinogenic risk was calculated using Equation 5: where, CR is the carcinogenic risk; LADD is the average daily dose over a lifetime (mg/(kg·day)); and SF is the slope factor (mg/(kg·day)) -1 .
The average daily dose over a lifetime is defined by Equation 6:

Equation 6
where, C a is the concentration of the substance in the ambient air (mg/ m 3 ); C h is the concentration of the substance in the room air (mg/m 3 ); T out is the time spent outdoors (h/day); T in is the time spent indoors (h/day); V out is the breathing rate outdoors (m 3 /hr); V in is the rate of breathing indoors (m 3 / hr); EF is the frequency of exposure (days/year); ED is the duration of exposure (years); BW is body weight (kg); and AT is the exposure average period (years).
The hazard coefficient is defined using Equation 7:

Equation 7
where, HQ i is the hazard coefficient for exposure of i-substance; C і is the level of exposure to i-substance (mg/m 3 ); and RfC i is the safe exposure level of i-substance (mg/m 3 ).
The hazard index is defined using

Research
Equation 8 where, HI is the hazard index; НQ і is the hazard coefficients for individual components of the solution of chemical reagents that produce an effect.
The main parameter determining the types of risk considered in this analysis is the concentration of pollutants in atmospheric air, which is measured by the monitoring system or in cases where measurements are absent, modeling is based on data on emissions and meteorological conditions. All other parameters listed in the above formulas are either selected from the relevant reference literature tables, for example Popov et al., for each substance respectively (MPC, slope factor, safe exposure level), or were set in accordance with study conditions. 8 The authors of the present study have designed a software-modeling complex (SMC) to solve problems of environmental pollution in technogenic loaded territories. 8-10 The essential advantages of this SMC above other models are the wide range of investigated environmental problems, the presence of a universal database monitoring the sources of pollution and pollutants, POS data, different environmental health values (demographics, population morbidity, etc.) and the existence of a module of environmental risks calculation, which is thought to be the most objective hazard assessment. The SMC database obtained data from different monitoring sources in Ukraine from 2005 to 2017.
The designed SMC makes it possible to observe the spatial distribution of atmospheric air pollution levels and individual risk distributions for a population (risk maps). The risk assessment completes the process of modeling anthropogenic pollution loads on a city's population and defines the criteria for managerial decisions. Figure 2 shows the module structure of the risk assessment system that is a part of the SMC. The input modeling data are POS data, pollutant characteristics, sources of pollution parameters, and metrological parameters.
The designed SMC realizes an expert approach to the tasks of risk assessment for public health, corresponding with the current legislation in Ukraine, taking into account regulations of the US Environmental Protection Agency, and grounded by the results of the analysis and appropriate interpretation of ecological monitoring data. 11,12 The Popov et al  The framework of the given approach uses the US Environmental Protection Agency classification of human health risks and reduces uncertainties during the assessment of total noncarcinogenic risk of substances of unidirectional action ( Table 3). 11

Results
According to the air pollution index, air pollution in the summer months of 2017 was generally characterized as very high. It differed across regions: at POS 7 it was characterized as very high (greater than 14); at POS 5 as high (7)(8)(9)(10)(11)(12)(13)(14); at POS 2 as elevated (5)(6)(7); and at POS 1 as low (less than 5). In general, the average monthly concentrations of four pollutants in the city exceeded the maximum permissible daily average concentration: formaldehyde by 4.3

Figure 3 -Risk of chronic intoxication (а) and risk of immediate toxic effects (b) as a result of air pollution in Kyiv in January-December 2017
Research times, nitrogen dioxide by 4 times, nitrogen oxide by 1.7 times, phenol by 1.1 times, and suspended substances by 1.3 times. The contents of other substances in the air did not exceed health-based exposure limits.
Since 2007, significant seasonal changes in formaldehyde concentrations have been observed.
Thus, in the winter months, this figure does not exceed the MPC, and in the summer the concentration increases sharply and exceeds the MPC by 5-7 times, which is quite dangerous for the most sensitive categories of the city population. These fluctuations may be caused by the intensification of construction and repair work, which is common in the city within each district. However, further investigation is needed to identify all the causes of this situation.  The risk values for the population of Kyiv proved to be very high. The worst environmental conditions were identified in the northwest where the RCI exceeded 0.2, indicating that more than 20% of the population of the given districts are at risk for chronic diseases. The RITE is also highest for the population in the northwestern part of the city.

Figure 4a -Risk of chronic intoxication in Kyiv territory according to averaged risk values from 2011-2017
Research The designed SMC makes it possible to obtain the dynamics of risk values for the region under investigation (Table  4).
According to the data, the risk values differ across districts of the city, indicating unstable ecological conditions of atmospheric air in Kyiv. Thus, the lowest risk values were found at the territory of the Hydropark (from 0.025 to 0.137) which is a park complex with minimum impact from traffic and industry.  Figure 4a shows the distribution of Kyiv's territory with the risk levels of chronic intoxication according to the avaraged risk data that were obtained from 2011 to 2017. Each bar of Figure 4a represents the percentage of Kyiv's territory (Y axis), which is characterised by the correspondent risk levels (X axis). Figure 4b shows the distribution of Kyiv`s territory with the risk of immediate toxic effects according to the averaged risk values for the same period of time (each bar represents part of Kyiv`s territory in percentage with the defined risk levels).
In order to obtain a more precise environmental risk assessment, it is necessary to modernize the existing monitoring system, increase the number of observation stations and measurements of harmful pollutants. Risk value deviations depend on high concentrations of formaldehyde, which is not measured at some observation stations. The absence of values for some pollutants and the lack of statistical data affect the accuracy of the obtained results and limit the possibilities of their current interpretation.

Discussion
There have been many studies of the impact of air pollution on population health. Min    The largest enterprises in Kyiv that influence the atmospheric air quality are given in Table 6 and their location is shown on the map (Figure 1).

Conclusions
Analysis of the results of atmospheric air monitoring data demonstrate an unfavorable environmental health situation in Kyiv from 2016-2017. Significant excesses are noted for formaldehyde, nitrogen dioxide, nitrogen oxide, phenol and suspended substances, which significantly raise the risk of toxicity and associated chronic diseases.
Risk assessments, grounded on the basis of monitoring data, reveal that the majority of the city's population is exposed to pollution levels significantly surpassing acceptable limits.