Cancer Risk Associated with Inhalation Exposure to PM₁₀-Bound PAHs and PM₁₀-Bound Heavy Metals in Polish Agglomerations

Abstract

Particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and heavy metals (HMs) present in polluted air are strongly associated with an increased risk of respiratory diseases. In our study, we grouped cities based on their pollution levels using a method called Ward’s cluster analysis and looked at the increased cancer risk from PM₁₀-bound harmful substances for adult men and women living in Polish cities. The analysis was based on data from 8 monitoring stations where concentrations of PM₁₀, PAHs, and HMs were measured simultaneously between 2018 and 2022. The cluster analysis made it possible to distinguish three separate agglomeration clusters: cluster I (Upper Silesia, Wroclaw) with the highest concentrations of heavy metals and PAHs, with mean levels of lead 14.97 ± 7.27 ng·m⁻³, arsenic 1.73 ± 0.60 ng·m⁻³, nickel 1.77 ± 0.95 ng·m⁻³, cadmium 0.49 ± 0.28 ng·m⁻³, and ∑PAHs 15.53 ± 6.44 ng·m⁻³, cluster II (Warsaw, Łódź, Lublin, Cracow) with dominant road traffic emissions and low emissions, with average levels of lead 8.00 ± 3.14 ng·m⁻³, arsenic 0.70 ± 0.17 ng·m⁻³, nickel 1.64 ± 0.96 ng·m⁻³, and cadmium 0.49 ± 0.28 ng·m⁻³, and cluster III (Szczecin, Tricity) with the lowest concentration levels with favourable ventilation conditions. All calculated ILCR values were in the range of 1.20 × 10⁻⁶ to 1.11 × 10⁻⁵, indicating a potential cancer risk associated with long-term exposure. The highest ILCR values were reached in Upper Silesia and Wroclaw (cluster I), and the lowest in Tricity, which was classified in cluster III. Our findings suggest that there are continued preventive actions and stricter air quality control. The results confirm that PM₁₀ is a significant carrier of airborne carcinogens and should remain a priority in both environmental and public health policy.

1. Introduction

The World Health Organization (WHO) has identified climate change as one of the greatest threats to health in the 21st century. Air pollution is also one of the greatest environmental threats to public health and economic progress in the modern society [1].

Air pollution contributes to the development of various diseases and premature death, particularly cardiovascular and respiratory diseases (including lung disease and lung cancer), as well as nervous and endocrine disorders, fertility issues and the acceleration of neurodegenerative diseases [2,3,4,5,6]. The combined impact of outdoor and household air pollution is responsible for around 6.7 million premature deaths each year, affecting people in countries with low, middle and high incomes [1].

Significant deterioration in air quality is observed in urbanized, densely populated urban areas. These regions are typically associated with intense industrial activity, heavy vehicular traffic, and high levels of economic activity. In many urban centres, the supporting infrastructure remains underdeveloped [7,8,9,10]. Contributing factors include the absence of bypass roads, industrial facilities being in close proximity to residential zones, and the widespread use of low-quality fuels [11,12,13]. Furthermore, limited air circulation exacerbates the accumulation of pollutants such as particulate matter (PM), volatile organic compounds (VOCs), nitrogen oxides (NOx), carbon monoxide (CO), heavy metals, and persistent organic pollutants [14]. Elevated noise levels also pose a concern, negatively impacting human well-being and potentially contributing to mental health disorders. Consequently, urban areas typically exhibit higher concentrations of air pollutants than non-urban regions [15,16,17].

Global epidemiological studies indicate that residents of large urban centres with high concentrations of particulate matter (PM₁₀ and PM₂.₅) are more susceptible to cancer and a range of other diseases such as ischaemic heart disease, cardiovascular conditions and lung cancer [18,19,20]. An increase in PM₂.₅ concentrations of 10 μg·m⁻³ is associated with a 6–8% increase in lung cancer-related mortality [18,21,22]. These studies also reveal a correlation between daily fluctuations in PM concentrations and short-term mortality rates. Some of the most extreme air pollution levels are recorded in India, where air quality frequently reaches hazardous levels. Bhiwadi and New Delhi are among the world’s most polluted cities [23].

Although overall pollution levels in the United States are generally lower than in many Asian nations, cities such as Los Angeles, Chicago, and Washington still report high concentrations of PM₂.₅ and polycyclic aromatic hydrocarbons (PAHs) [24]. Elevated levels of heavy metals, including cadmium (Cd), nickel (Ni), lead (Pb), and arsenic (As), are particularly prevalent in regions characterised by intensive industrial activity and heavy road traffic [25,26]. In the European Union, it is estimated that inhaling air containing fine particulates caused approximately 240,000 premature deaths in 2020, including around 39,300 in Poland [27,28].

In the context of public health, particulate matter poses a significant threat to humans. It has been classified as carcinogenic to humans (Group 1) by both the World Health Organization (WHO) and the International Agency for Research on Cancer (IARC) [29,30,31,32]. Depending on its origin, particulate matter primarily consists of organic carbon (OC), elemental carbon (EC), water-soluble ions, and potentially toxic elements, including heavy metals and persistent organic pollutants (POPs) such as polycyclic aromatic hydrocarbons and their derivatives [33]. The chemical composition and particle size of PM significantly impact human health risks [34,35]. Epidemiological studies have revealed links between ambient PM₁₀ levels and higher rates of total, cardiovascular, and respiratory mortality, as well as hospital admissions [36,37]. The absorption of particulate matter by living organisms poses a serious threat due to the variety of toxic, carcinogenic, and mutagenic chemicals it often contains [26,38]. Additionally, certain components of particulate matter can trigger allergic reactions. Particularly hazardous are toxic metals and their compounds, persistent organic pollutants, sulphates, and others.

PM-bound PAHs and PM-bound heavy metals, particularly fine particles, can re-enter the air or enter the human body via ingestion, inhalation or skin contact [39,40]. Heavy metals pose a significant health threat due to their tendency to be absorbed, retained and biomagnified within the body, potentially leading to various diseases [41]. The specific health effects depend on the type of metal involved. For example, the International Agency for Research on Cancer [30] has classified arsenic, cadmium, and nickel as carcinogenic to humans (Group 1), and they are linked to fatal cancers of the lungs, trachea and bronchi. Lead, categorised as possibly carcinogenic (Group 2A), can cause neurological damage and impair kidney function [35]. In children, long-term lead exposure has been associated with developmental delays and learning difficulties [42]. Overall, heavy metals have the potential to disrupt the nervous system, hinder kidney function, interfere with bone formation and negatively affect various other organs [17,43,44].

The IARC classifies PAH congeners according to their carcinogenicity: as carcinogenic to humans (Group 1), probably carcinogenic to humans (Group 2A), or possibly carcinogenic to humans (Group 2B) [30]. For example, benzo[a]pyrene is categorized as a Group 1 carcinogen, whereas benzo[a]anthracene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, dibenzo[a,h]anthracene, and indeno[1,2,3-cd]pyrene are classified as Group 2B compounds.

PAHs can be inhaled as vapours or adsorbed onto airborne particulate matter. The site at which they are deposited within the respiratory tract is influenced by the particles’ aerodynamic diameter [45]. Ultrafine particles can penetrate deep into the alveolar region and subsequently enter the bloodstream, spreading throughout the body. In contrast, larger particles are usually deposited in the bronchiolar regions [35]. Due to their lipophilic nature, PAHs accumulate in adipose tissue [46]. Studies demonstrate that benzo[a]pyrene accumulates in pulmonary tissue, as well as in the heart, liver, spleen, kidneys and skeletal muscle [47,48]. During biotransformation in the human body, PAHs are metabolised into reactive intermediates that can form covalent adducts with DNA, RNA and proteins [49,50]. This mechanism is widely recognised as a critical contributor to carcinogenesis [51,52]. However, it has yet to be definitively established whether carcinogenic outcomes are attributable to individual PAH congeners or the combined effect of multiple compounds [53].

Despite ongoing reductions in emissions, most of the European urban population continued to be exposed to hazardous air pollutants in 2022. In particular, they were exposed to concentrations of PM_2.5 above the WHO’s 2021 annual guideline level of 5 µg·m⁻³ [54]. In Poland, high concentrations of PM, PAHs, and heavy metals pose a particular risk in urban areas such as Cracow, Upper Silesia, and Wroclaw, where normative values are consistently exceeded. In 2023, the average annual concentration of B[a]P, a key indicator of human exposure to priority PAHs [55,56], in Poland was 1.53 ng·m⁻³ This level exceeds both the European Union’s target value of 1.0 ng·m⁻³ [57,58] and the WHO’s recommended guideline of 0.12 ng·m⁻³ [59].

The report’s authors [60] indicate that the number of deaths in Poland attributable to exposure to suspended particulate matter is twice the European Union average. The report also emphasises the significant role of air pollution as a lung cancer risk factor, a factor that has previously been underestimated. The primary challenge in this area is accurately assessing the health risks associated with exposure to particulate matter. Firstly, particulate matter contains various pollutants, including known carcinogens such as polycyclic aromatic hydrocarbons and heavy metals, and its chemical composition varies depending on the emission source. Secondly, public health is influenced by numerous additional factors, including tobacco use (both traditional cigarettes and e-cigarettes), lifestyle choices, dietary habits, genetic predispositions, and other variables. Furthermore, we employ various methodological approaches to assess health risks. In our study, we estimated the total lifetime incremental cancer risk from inhaling carcinogens associated with PM₁₀ among adult men and women living in Polish urban areas with populations exceeding 250,000. To achieve this, we selected monitoring stations in Poland that measured air quality, including PM₁₀, PAHs, and heavy metals, for the specified time period.

2. Materials and Methods

2.1. Study Area and Sample Collection

In this study, we used daily measurements of PM₁₀, PM₁₀-bound PAHs, and PM₁₀-bound heavy metals (Ni, Cd, Pb, and metalloid As) collected from 2018 to 2022. The data was retrieved from the Chief Inspectorate of Environmental Protection (CIEP) website [61] in Poland. The air monitoring data were officially validated data. We selected those monitoring stations located in urban agglomerations that met the criterion of simultaneous measurement of PM₁₀ and PAHs such as benzo[a]anthracene B[a]A, benzo[a]pyrene B[a]P, benzo[b]fluoranthene B[b]F, benzo[j]fluoranthene B[j]F, benzo[k]fluoranthene B[k]F, dibenzo[a,h]anthracene DBA, indeno[1,2,3-cd]pyrene IP, and Ni, Cd, Pb, and As concentrations in the period 2018–2022.

The selected sites include Tricity (Gdańsk, PL0052A); Upper Silesia (Katowice- PL0008A); Cracow (PL0501A); Lublin (PL0085A); Łódź (PL0100A); Szczecin (PL0248A); Warsaw (PL0214A); and Wroclaw (PL0194A). The locations of the individual stations represent diverse environmental settings, including highly urbanised and industrialised areas (Upper Silesia, Wroclaw, and Łódź); agglomerations with dominant administrative and service functions (Warsaw, Cracow); coastal regions (Tricity, Szczecin); and cities with moderate levels of traffic and industrial activity (Lublin). The individual agglomerations also differ in terms of meteorological conditions. Tricity and Szczecin have a maritime climate characterised by high air humidity, frequent winds, and relatively mild winters that favour the dispersal of pollutants. However, frequent temperature inversions, especially during the heating season, expose Upper Silesia and Cracow, fostering the accumulation of pollutants near the ground. In addition, due to its location in a valley with limited air ventilation, Cracow has unfavourable conditions for the dispersal of pollutants. Warsaw, Łódź, and Wroclaw have transitional conditions between maritime and continental climates, with periodic stagnant air and varying wind speeds. Lublin, which lies in the valley of the Bystrzyca River, has numerous depressions of land and hills and is characterised by moderate circulation conditions and relatively few inversions. This arrangement of stations allows us to evaluate how risk patterns change in different environmental and human-made situations (Figure 1).

Detailed information on the location of air quality monitoring stations and the number of inhabitants in individual agglomerations is shown in Table S1.

At the air quality monitoring stations, particulate matter was manually collected over continuous 24 h periods using high-volume samplers operating at an airflow rate of 30 m³·h⁻¹. Each sampler was fitted with a PM₁₀ inlet and a system for automatically placing quartz fibre filters into the sampling channel. The amount of PM₁₀ was measured using a standard method that involves weighing, following the PN-EN 12341:2014−07 standard [62], and it can detect levels as low as 1 μg·m⁻³.

The PM₁₀-bound polycyclic aromatic hydrocarbons (PAHs) were isolated using an organic solvent extraction method. Analysis was then carried out using high-performance liquid chromatography (HPLC) with fluorescence detection, in accordance with the PN-EN 15549:2011 standard [63]. This analytical technique enables the quantification of benzo[a]pyrene and its congeners within a concentration range of approximately 0.05 to 20 ng·m⁻³.

The PM₁₀-bound heavy metals (Ni, Cd, Pb, and As) were mineralised using microwaves and analysed using a graphite furnace and atomic absorption spectrometry, according to PN-EN 14902:2010 [64]. We apply this method across the following concentration ranges: Ni: 2–100 ng·m⁻³, Cd: 0.1–50 ng·m⁻³, Pb: 1–4000 ng·m⁻³, As: 0.5–350 ng·m⁻³. Where the measured concentration was below the method detection limit (MDL), this value was treated as a non-detect and substituted with half the MDL.

2.2. Statistical Analysis

To provide a comprehensive yet concise characterisation of the analysed concentrations, fundamental descriptive statistical parameters were computed for each monitoring station. These included the mean, median, standard deviation, maximum and minimum values, as well as the first and third quartiles. To find similarities between individual agglomerations, cluster analysis was used to distinguish groups/clusters (in this case, agglomerations). A single input vector was created for each city, covering the average daily concentrations of all the analysed pollutants (PM₁₀, PM₁₀-bound metals, and PM₁₀-bound PAHs) from 2018 to 2022. The full-time period was analysed, and the data were not aggregated. Finally, each agglomeration was represented by a set of values corresponding to the daily concentrations of all pollutants, enabling their levels and structures to be considered simultaneously.

The Ward method employed the variance analysis approach to estimate distances between groups and calculate the distances between individual clusters. Before starting the cluster analysis, the input data was standardised so that when calculating the distance between objects, the variables had comparable values. The outcome of the cluster analysis was recorded as a dendrogram. All statistical analyses were conducted using Statistica 13 software from StatSoft, with a significance threshold set at α = 0.05.

2.3. Cancer Risks Assessment

According to the United States Environmental Protection Agency (USEPA) [65,66], probabilistic methods can be used to estimate the health risks associated with exposure to polycyclic aromatic hydrocarbons and heavy metals in particulate matter (PM₁₀). As a result, the Incremental Lifetime Cancer Risk (ILCR) method was used to assess the possible cancer risk from seven PAHs and four heavy metals found in PM₁₀. A gender-specific analysis was conducted for both males and females. The assessment focused on inhalation as the primary exposure pathway.

The ILCR is defined as the increased probability of an individual developing cancer over their lifetime due to cumulative exposure to selected carcinogens. It was calculated for lifetime exposure. The ILCR quantifies the probability of developing cancer as a result of exposure to PM₁₀-bound metals and PAHs. For example, an ILCR of 1 × 10⁻⁵ indicates that an additional case of cancer could occur among 100,000 individuals exposed to these substances.

We assessed exposure via inhalation using the formula in Equation (1) to estimate the lifetime average daily inhaled dose (LADD_inh) [67,68,69,70]:

$${LADD}_{inh}={\displaystyle \frac{C_{air}\times {IR}_{inh}\times EF\times ED\times cf}{BW\times AT}},$$

(1)

where C_air—concentration PAHs/heavy metals in air (ng·m⁻³); for the PAHs was used the B[a]P equivalent concentration (TEQ) calculated according to: TEQ = ∑C_iPAH × TEF_iPAH, toxic equivalent factor (TEF) values for B[a]A, B[a]P, B[b]F, B[j]F, B[k]F, DBA, IP were adopted as 0.005, 1, 0.1, 0.05, 0.05, 1.1, 0.1, respectively as per Larsen and Larsen [71]. IR_inh—air inhalation rate 20.9 for males and 16.2 for females (m³·d⁻¹) [72], EF—exposure frequency 350 (d·yr⁻¹) [73], ED—exposure duration (18 to average life expectancy of males/females—Table S2) (yr), cf—conversion factor 10⁻⁶, BW—body weight 86 for males and 73 for females (kg), AT—averaging time for carcinogens 365 d·yr⁻¹ × ED (d).

The health risks associated with carcinogenic pollutants and the incremental lifetime cancer risk (ILCR_inh) due to inhalation were calculated as the additional probability of developing cancer throughout a person’s lifetime due to prolonged exposure to these pollutants. The formula for calculating ILCR_inh is as follows [68,74]:

$${ILCR}_{inh}={LADD}_{inh}\times ({CSF}_{inh}\times \sqrt[3]{{\displaystyle \frac{BW}{70}})},$$

(2)

where CSF_inh cancer slope factor for As, Pb, Cd, Ni, TEQ is 1.2 × 10¹, 4.2 × 10⁻², 1.5 × 10¹, 9.1 × 10⁻¹, and 3.9, respectively (mg·kg⁻¹·d⁻¹)⁻¹ [75].

In Equation (2), we corrected the cancer slope factors for non-standard populations using the correction term $\sqrt[3]{BW/70}$, in accordance with USEPA guidelines [76]. This is because our calculations used gender-specific body weights that differed from the standard reference weight of 70 kg. This adjustment is often omitted in studies because its effect on the calculated ILCR_inh values is generally negligible, and researchers typically assume a default adult reference weight of 70 kg [68,77].

The incremental lifetime cancer risk associated with inhalation was calculated as the sum of ILCR_PAHₛ and ILCR_HM.

3. Results and Discussion

Poland has experienced excessive air pollution for decades. According to the Institute of Environmental Protection—National Research Institute (IEP-PIB), a downward trend in the concentrations of PM₁₀ and other pollutants has been observed since 2010, affecting both annual and daily averages [78]. However, current concentrations of PM₁₀, PM₁₀-bound PAHs, and PM₁₀-bound metals (Pb, Cd, Ni, and As) remain significantly elevated, particularly in urban areas such as Upper Silesia, Cracow, Łódź, and Wroclaw [61].

3.1. The Concentration of PM₁₀ and PM₁₀-Bound PAHs, and PM₁₀-Bound Metals

In major Polish urban agglomerations between 2018 and 2022, the annual mean PM₁₀ concentrations ranged from 17.42 to 43.20 µg m⁻³, depending on location and year (Table S3). Despite the observed downward trend recently, these values considerably exceed those reported in most other European countries [79,80]. The results of other detailed studies conducted in various Polish cities confirm similar trends, indicating a decrease in air pollutant concentrations [81,82]. In 2022, Poland’s annual average PM₁₀ concentration reached 23.99 μg m⁻³, whereas in Slovakia, Lithuania, the Czech Republic, and Latvia—where these pollutants are also prevalent—the values were 20.91, 19.75, 19.00 and 18.09 μg m⁻³, respectively [54]. The highest multi-year mean PM₁₀ concentration (average of annual values for the period 2018–2022) was recorded in the Łódź (35.04 μg·m⁻³), Cracow (33.75 μg·m⁻³) and Upper Silesia (32.31 μg·m⁻³) agglomerations. The lowest levels were recorded in the Szczecin (19.73 μg × m⁻³) and Tricity (21.13 μg × m⁻³) agglomerations. In 2018, the average annual concentrations in the agglomerations of Cracow, Łódź and Upper Silesia exceeded the national limit value of 40 µg·m⁻³ [83]. Compared to the WHO guideline of 15 µg × m⁻³, exceedances occurred at all monitoring stations in all years (Figure 2). Additionally, the regulatory threshold of 50 µg/m³ is exceeded on more days per year than is permitted [83]. The maximum average daily concentration recorded in Cracow was 190.2 μg × m⁻³, which is almost four times higher than the permissible limit. This highlights the seriousness of acute pollution episodes. Cracow’s specific location in the Vistula River valley naturally weakens the influx of westerly winds, which are dominated by hills to the west. Consequently, wind speeds in the city tend to be much lower than in the surrounding areas, which limits the city’s natural ventilation [84,85]. In addition, a temperature inversion often forms over Cracow, leading to higher concentrations of PM₁₀, particularly on windless, cold days, mainly during the autumn and winter. While the presence of the Vistula River has a positive effect on local aeration, it is unable to completely negate the effects of the inversion and restricted air circulation.

Poland has consistently recorded the highest average annual concentrations of B[a]P of all European countries. In 2022, the concentration of this representative compound from the PAH group reached 2.41 ng·m⁻³, whereas in Slovakia, the Czech Republic, and Croatia, where B[a]P levels are also elevated, the values were 1.51, 1.19, and 0.87 ng·m⁻³, respectively [54]. The presented study found that all major urban areas in Poland experienced peak B[a]P concentrations in 2018, ranging from 1.50 ng·m⁻³ in Warsaw to 4.89 ng·m⁻³ in Cracow, with similarly high levels observed in Upper Silesia (4.73 ng·m⁻³). It is notable that the results of the studies conducted by Kaleta and Kozielska [86] in the Silesian Voivodeship confirm the persistence of high B[a]P concentrations in this region, with annual averages ranging from 6.2 to 7.1 ng·m⁻³ between 2018 and 2021. Significantly, average B[a]P concentrations can exceed 28 ng·m⁻³ during the heating season (from October to the end of March). These concentrations significantly exceed the regulatory limits established by the EU (1 ng·m⁻³) and the WHO (0.12 ng·m⁻³).

Table 1. Annual average (min–max) concentrations of PM-bound the sum of PAHs in the period 2018–2022 in Polish Agglomerations, ng·m⁻³.

Agglomeration	2018	2019	2020	2021	2022
Tricity	9.49 (0.37–42.90)	5.17 (0.31–26.05)	5.59 (0.34–25.62)	7.50 (0.38–42.40)	4.47 (0.35–26.39)
Upper Silesia	25.59 (1.27–89.95)	21.96 (0.96–74.67)	19.78 (1.43–69.09)	21.75 (1.18–83.61)	14.18 (1.38–45.62)
Cracow	21.15 (1.20–101.58)	16.96 (0.70–77.63)	16.36(0.72–80.06)	16.27 (0.88–72.37)	9.90 (0.66–40.55)
Lublin	9.35 (0.10–47.53)	6.30 (0.08–21.60)	8.56 (0.31–31.42)	10.64 (0.24–40.35)	7.27 (0.35–30.61)
Łódź	16.47 (0.26–64.08)	12.83 (0.36–49.02)	11.60 (0.47–41.27)	12.47 (0.32–41.32)	10.83 (0.44–38.72)
Szczecin	18.50 (0.77–68.97)	6.85 (0.47–40.55)	5.21 (0.54–27.26)	5.61 (0.25–21.54)	6.11 (0.45–30.12)
Warsaw	10.23 (0.29–39.24)	8.17 (0.38–31.77)	6.56 (0.18–25.74)	8.05 (0.35–47.85)	5.46 (0.35–16.83)
Wroclaw	14.04 (0.41–87.93)	9.34 (0.35–50.72)	12.14 (0.35–55.92)	10.97 (0.35–45.99)	5.55 (0.43–36.88)

shows the annual average concentrations of PM-bound ∑7 PAHs. The highest concentrations were consistently recorded in Upper Silesia, Cracow, and Łódź. Although levels decreased over the study period, they remained very high. In 2018, the maximum concentration of PAHs was observed in Cracow, reaching 101.58 ng·m⁻³. Szczecin also exhibited a high annual average concentration of total PAHs in the same year, at 18.50 ng·m⁻³, which was 2.7 to 3.5 times higher than in subsequent years. Benzo[a]pyrene constitutes between 12% and 25% of the total ∑7 PAH concentration. The high concentrations of PAHs in urban areas of Poland, including less urbanised regions, are primarily attributed to communal and household emission sources. In 2021, total PAH emissions amounted to 260.51 Mg, 206.53 Mg (79.28%) of which originated from household fuel combustion [87]. Exceedances of permissible levels of B[a]P and its congeners are mainly caused by the combustion of solid fuels in household boilers, particularly coal and wood [86,88,89,90,91].

Of the analysed metals, Pb and Ni were the most abundant in PM₁₀ at the monitored stations. Their annual mean concentrations in the eight agglomerations between 2018 and 2022 ranged from 3.19 to 27.85 ng·m⁻³ for Pb and from 0.61 to 4.27 ng·m⁻³ for Ni. Lower concentrations were recorded for As (0.45 ÷ 2.66 ng·m⁻³) while Cd was the least abundant metal in PM₁₀, with concentrations ranging from 0.10 to 1.00 ng·m⁻³ (Table S3). To better understand these differences, it is important to consider national emission inventories.

In 2021, the annual emissions of Pb, Ni, As, and Cd in Poland amounted to 279.90 Mg, 77.41 Mg, 14.95 Mg, and 10.96 Mg, respectively. While industrial processes were the main source of Pb, Cd and As emissions-accounting for 55%, 39% and 36% of total emissions, respectively—the dominant source of nickel was fuel combustion in the energy sector, accounting for 43% of national Ni emissions [87].

The diverse emission sources, meteorological conditions, and urban characteristics of the individual agglomerations contribute to the observed regional differences in heavy metal concentration levels. The highest average annual concentrations of Pb, Cd, and Ni were recorded in the Upper Silesia Agglomeration (Pb: 27.85 ng·m⁻³; Cd: 1.00 ng·m⁻³; Ni: 4.27 ng·m⁻³). This is a consequence of the large number of industrial facilities in the area, including coal-fired power stations, steel mills, coking plants, and other industrial plants. Numerous studies confirm that emissions from the combustion of fossil fuels, metallurgy, and metal ore processing are the main sources of these elements in PM₁₀ in this region [92,93,94]. However, of particular significance is the fact that the highest maximum daily average lead concentration in the period 2018–2022 was not recorded in the Upper Silesia Agglomeration but in Wroclaw in 2021, at 106.02 ng·m⁻³. This is over 26% higher than the maximum lead concentration recorded in Upper Silesia in the same year (83.80 ng·m⁻³). Despite the area’s lack of heavy industries, such high concentrations may be the result of local episodes of low emissions, increased road traffic, and specific meteorological conditions favouring the accumulation of pollutants.

The studies by Kalbarczyk and Kalbarczyk [95], as well as Czernecki et al. [96], showed a strong link between high Pb levels and weather conditions like temperature and rainfall. They also highlighted how seasonal air inversions and stagnant air are important. Rogula-Kozłowska et al. [97] noted that road transport is a significant source of heavy metals, including Pb, in PM₁₀ in cities that don’t have heavy industry, particularly in places with poor air circulation. They also emphasised the importance of seasonal air inversion and stagnation. Furthermore, the highest annual mean As concentrations, ranging from 1.71 to 2.66 ng·m⁻³, were recorded in Wroclaw each year. Such high As concentrations can be linked to local emission sources, primarily the individual heating of buildings and emissions from road transport, especially during the heating season. Additionally, the meteorological conditions typical of Wroclaw—frequent temperature inversions and episodes of poor air ventilation—favour the accumulation of As near the ground surface, thereby increasing its concentration in the air [98]. In Lublin, abnormally high annual mean nickel values (up to 3.79 ng·m⁻³) were observed between 2018 and 2020. Such high values may be due to local emissions, including the combustion of fuel oil and low-quality fuels in the municipal sector, as well as the activities of small workshops and metalworking businesses. The presence of Ni was also confirmed in Lublin street dust, indicating the role of road transport and dust resuspension [99]. Unfavourable dispersion conditions during the heating season, such as temperature inversion, may have further favoured Ni accumulation at ground level [100].

However, in Szczecin, researchers observed an unusually high annual mean nickel concentration of 2.01 ng·m⁻³ in 2022, despite generally lower concentrations of other metals being present. This variation may be partly attributed to the limited availability of measurement data in earlier years (approximately 50% of days monitored), as well as to specific local emission sources. Contributors are likely to include emissions from port operations, waterborne transport, and transshipment terminals, all of which are characteristic of this coastal region. Furthermore, frequent shifts in wind direction and high air humidity, which are common meteorological features in Szczecin, may influence the dispersion and deposition patterns of pollutants [101]. In comparison, other areas with a lot of road traffic and common use of solid fuels for home heating showed more consistent metal levels that followed clearer seasonal and weather patterns, like thermal inversions and low air movement.

It should also be noted that the concentration of the analysed pollutants—Pb, Ni, Cd, As, and ∑PAHs—can reach 1.69 mg per gram of PM₁₀ (Figure 3). An extreme case was recorded in Upper Silesia in 2022, where the Pb content alone reached 0.97 mg per gram of PM₁₀. Unfortunately, PM₁₀ in Upper Silesia is rich in heavy metals and PAHs, with total pollutant concentrations ranging from 1.26 to 1.69 mg per gram. Similar pollutant levels, exceeding 1000 ppm, were observed in Wroclaw (2018–2021) and Szczecin (2018–2019). In the case of Szczecin, the elevated concentration levels observed during this period can be attributed to the fact that measurements covered less than 80% of the annual total. In general, across Poland, lead and polycyclic aromatic hydrocarbons constitute the largest share of pollutants in PM₁₀.

Based on cluster analysis using Ward’s method, the agglomerations were grouped according to the similarity of the PM₁₀ and PM₁₀-bound Pb, Ni, Cd, As and PM₁₀-bound PAH concentrations for the period 2018–2022. The application of this method made it possible to distinguish three statistically distinct groups of agglomerations: cluster I—Upper Silesia, Wroclaw; cluster II—Warsaw, Łódź, Lublin, Cracow; cluster III—Tricity, Szczecin (Figure 4). To deepen the analysis within each cluster, the mean concentration values of each pollutant analysed were compared along with the standard deviation (Figure 5).

This procedure made it possible not only to confirm cluster differences but also to determine the degree of variability, the level of environmental pressure, and potential emission sources. The first cluster includes agglomerations: Wroclaw and Upper Silesia which have much higher pollution levels, especially for lead (14.97 ± 7.27 ng·m⁻³), arsenic (1.73 ± 0.60 ng·m⁻³), cadmium (0.49 ± 0.28 ng·m⁻³) and ∑PAHs (15.53 ± 6.44 ng·m⁻³) with average concentrations of these metals being 2–3 times greater than in clusters II and III. These agglomerations are characterised by the highest pollution levels and high daily and seasonal variability. This situation may be due to the strong industrialisation of these regions, the high proportion of low emissions, and the significant impact of traffic emissions. Similar results have been obtained in studies conducted in Romania, Malaysia, and China, where urban agglomerations with a dominant share of industrial and road emissions showed high levels of metals in PM₁₀ [102,103,104]. The second cluster is formed by agglomerations: Warsaw, Cracow, Łódź, and Lublin. Although the average PM₁₀ concentrations (29.36 ± 6.57 μg·m⁻³) are comparable to group I, the levels of metals and ∑PAHs are noticeably lower.

This variation indicates a different structure of the pollution profile—the dominant role is most likely played by traffic-related emissions, low emissions during the winter season, and dense urban development. Despite geographic differences, the similarity of urban layout and local emission sources leads to similar pollution levels and structure. Other researchers [82,105,106,107] found similar trends, showing that the PM₁₀ levels were mainly influenced by local factors like building designs and transportation intensity, leading to a consistent pattern in urban areas where road emissions are the main source. The third cluster is formed by the Szczecin and Tricity agglomerations, which show substantial similarity among themselves, as well as significant distinctiveness in relation to the other cities. Lower levels of PM₁₀ (20.43 ± 3.09 μg·m⁻³) and associated compounds may be related to more favourable ventilation conditions (e.g., proximity to the sea, coastal winds, open development), less frequent inversion, and thus better dispersion of pollutants, as well as lower saturation of heavy industry and a greater share of natural emission sources. A similar observation was described in an article [108] concerning port regions in Italy, where cluster analysis revealed the distinctiveness of zones exposed to lower industrial loads and better dispersal conditions.

3.2. Health Risk Assessment

The incremental lifetime cancer risk (ILCR) associated with inhalation exposure was estimated based on the concentrations of PM₁₀-bound PAHs and PM₁₀-bound metals in the atmospheric air. The analysis covered eight Polish agglomerations, with risk estimates calculated separately for adult men and women over a five-year period (2018–2022). The results are presented in

Table 2. Incremental lifetime cancer risk from inhalation exposure in Polish Agglomerations (2018–2022) by sex.

Agglomeration	2018	2019	2020	2021	2022
MALES
Tricity	5.46 × 10−6	3.09 × 10−6	3.08 × 10−6	3.53 × 10−6	3.05 × 10−6
Upper Silesia	1.11 × 10−5	9.47 × 10−6	9.47 × 10−6	7.42 × 10−6	8.41 × 10−6
Cracow	8.48 × 10−6	7.26 × 10−6	6.64 × 10−6	6.36 × 10−6	4.70 × 10−6
Lublin	4.41 × 10−6	3.95 × 10−6	4.35 × 10−6	4.71 × 10−6	2.69 × 10−6
Łódź	8.30 × 10−6	6.18 × 10−6	5.43 × 10−6	6.36 × 10−6	5.84 × 10−6
Szczecin	8.80 × 10−6	4.75 × 10−6	4.59 × 10−6	3.88 × 10−6	4.41 × 10−6
Warsaw	3.91 × 10−6	3.14 × 10−6	2.73 × 10−6	3.30 × 10−6	2.72 × 10−6
Wroclaw	1.02 × 10−5	8.14 × 10−6	8.98 × 10−6	8.33 × 10−6	6.44 × 10−6
FEMALES
Tricity	2.41 × 10−6	1.735 × 10−6	1.33 × 10−6	1.50 × 10−6	1.32 × 10−6
Upper Silesia	4.87 × 10−6	4.12 × 10−6	4.08 × 10−6	3.14 × 10−6	3.61 × 10−6
Cracow	3.82 × 10−6	3.25 × 10−6	2.94 × 10−6	2.79 × 10−6	2.10 × 10−6
Lublin	1.98 × 10−6	1.77 × 10−6	1.91 × 10−6	2.02 × 10−6	1.20 × 10−6
Łódź	3.63 × 10−6	2.70 × 10−6	2.69 × 10−6	2.69 × 10−6	2.51 × 10−6
Szczecin	3.89 × 10−6	2.10 × 10−6	2.01 × 10−6	1.68 × 10−6	1.93 × 10−6
Warsaw	1.75 × 10−6	1.40 × 10−6	1.20 × 10−6	1.43 × 10−6	1.22 × 10−6
Wroclaw	4.54 × 10−6	3.61 × 10−6	3.95 × 10−6	3.59 × 10−6	2.82 × 10−6

.

The calculations considered a number of parameters, including the average life expectancy of males and females (Table S2). On average, women live longer than men, with the difference in Poland amounting to around seven years. Between 2018 and 2022, average life expectancy ranged from 70.4 to 75.9 years for men and from 78.7 to 83 years for women. During this period, particularly in 2020 and 2021, life expectancy decreased for both sexes (Table S2), primarily due to the impact of the COVID-19 pandemic. In 2021 alone, the pandemic accounted for an additional 48,805 male and 42,389 female deaths in Poland, with nearly 18% of all deaths that year being attributed to the virus [109].

Cancer remains the second leading cause of death in Poland, after cardiovascular diseases, accounting for around a quarter of all fatalities [60,110]. Historically, cancer incidence has been higher in men; however, since 2021, the number of newly diagnosed cases of cancer in women has surpassed that in men [111]. Lung cancer remains the leading cause of cancer-related death, accounting for 22% of fatalities. In 2021, it caused 20,841 deaths nationwide [110,111]. Air pollution, both outdoor and indoor, is estimated to contribute to around 2% of all cancer-related deaths in Europe. For lung cancer specifically, the proportion is considerably higher, with conservative estimates at 9%, and more comprehensive assessments suggesting up to 17% [112,113].

In our study, people living in Upper Silesia, Cracow, and Wroclaw were the groups most affected by air pollutants that can cause cancer or might cause cancer (such as PM₁₀-bound PAHs and PM₁₀-bound HM) through breathing, among Polish urban agglomerations. As shown in Table 2, the highest ILCR values for adult men in 2018 were recorded in Upper Silesia (1.11 × 10⁻⁵) and Wroclaw (1.02 × 10⁻⁵). The ILCR values for women were slightly lower but comparable overall. Although some studies suggest that women may be at a higher risk of carcinogenesis due to their lower body weight, our results consistently show higher inhalation rate coefficients (IRC) for men across all investigated agglomerations. The difference is primarily due to the higher inhalation rates assumed for men (20.9 m³·day⁻¹) than for women (16.2 m³·day⁻¹), based on exposure factors commonly used in environmental risk assessments. When normalised by body weight, the inhaled air volume per kilogram of body weight is slightly higher for men (0.24 m³·kg⁻¹·day⁻¹) than for women (0.22 m³·kg⁻¹·day⁻¹). This means that, despite men’s higher body weight, the greater air intake rate is the dominant factor influencing the ILCR. Other studies have observed similar relationships, with differences in inhalation rate outweighing the effect of body weight in ILCR calculations [114]. The finding indicates that factors such as inhalation rate can greatly affect risk estimates and should be considered when examining differences in ILCR between sexes.

Furthermore, Wu et al. demonstrated that exposure levels were significantly higher in the winter than in the summer [114]. Studies by Kaleta and Kozielska [86] and Agudo-Castaeda et al. [115] also observed this dependency.

According to standard ILCR risk assessment guidelines, values below 1 × 10⁻⁶ are considered negligible. Values between 1 × 10⁻⁶ (1 in 1,000,000) and 1 × 10⁻⁴ (1 in 10,000) indicate a potential cancer risk, whereas values exceeding 1 × 10⁻⁴ are associated with a high potential risk and may necessitate corrective action [116]. In Polish agglomerations, based on the methodology applied in our study, no ILCR values below 1 × 10⁻⁶ were recorded at any monitoring site. At all locations, ILCR values fell within the 1 × 10⁻⁶ to 1 × 10⁻⁴ range. For males, the values ranged from 2.69 × 10⁻⁶ (Lublin) to 1.11 × 10⁻⁵ (Upper Silesia), and for females, from 1.20 × 10⁻⁶ (Warsaw, Lublin) to 4.87 × 10⁻⁶ (Upper Silesia). Upper Silesia is known as one of the most polluted regions in Poland [85,117].

In our study, we found that the levels of PAHs have the biggest effect on the ILCR value, followed by As, Cd, Ni, and Pb, making up 43.2%, 36.3%, 14.3%, 5.0%, and 1.2% of the total, respectively (Table S4). Interestingly, arsenic accounts for the largest share of the ILCR value in Wroclaw (60%), corresponding to values of 5.04 × 10⁻⁶ and 2.21 × 10⁻⁶ for men and women, respectively. A similar pattern was observed for Warsaw and the Tricity area, although in these cases, the impact of As on the ILCR value is only slightly greater than that of PAHs. The ILCR value in Upper Silesia during the studied time period is the highest in Poland for both men and women. Each year, the content of the analysed components exceeds 1200 ppm. The total amount of PAH concentrations is about 18 to 32 times greater than the amounts of As and Cd, but their impact on the ILCR is ranked as follows: PAHs make up 42.3%, As 30.1%, Cd 22.2%, Ni 3.7%, and Pb 1.7%.

The inhalation carcinogenic risk reported by other researchers (

Table 3. Selected studies on health risk assessments via inhalation of PAHs and heavy metals reported in the literature.

Country, City		Compounds		Estimated Carcinogenic Risk	Reference
China, Bengbu	Male	PM10	16 EPA priority PAHs	1.61 × 10−4 ÷ 8.11 × 10−4	[114]
	Female			1.51 × 10−4 ÷ 7.59 × 10−4
	Children			3.98 × 10−5 ÷ 6.09 × 10−4
USA, Los Angeles	Worst case	PM2.5	PAHs and Ni, Cd, Pb, As Cr(VI)	3.36 × 10−6	[118]
	Best case			2.07 × 10−6
Greece Thessaloniki	Worst case			6.51 × 10−6
	Best case			4.02 × 10−6
Italy, Milan	Worst case			14.92 × 10−6
	Best case			12.11 × 10−6
Cyprus, Nicosia	Lifetime	PM2.5	PAHs	2.55 × 10−7	[119]
			As, Cd, Co, Ni, Pb	5.29 × 10−5
Iran, Zabol	Children	TSP	Ni, Cr, Cd, Co, Pb and As	8.4 × 10−5	[70]
	Adult			4.5 × 10−4
	Children	PM2.5		5.0 × 10−5
	Adult			2.7 × 10−4
Belgrade, Serbia	Lifetime	PM2.5	PAHs	5.77 × 10−5 ÷ 2.27 × 10−4	[120]
Poland	Smog episodes	PM10	B(a)P and As, Cd, Pb, and Ni	1.13 × 10−5	[121]
	No smog episodes			1.04 × 10−5
Poland, Silesian Voivodeship	Heating season	PM10	B[a]P	6.72 × 10−6÷9.74 × 10−5	[86]
	Non-heating season			0.6 × 10−6 ÷ 8.7 × 10−6
Poland, Agglomerations	Male	PM10	PAHs and Ni, Cd, Pb, As	2.69 × 10−6 ÷ 1.02 × 10−5	[This study]
	Female			1.20 × 10−6 ÷ 4.87 × 10−6

) varies significantly depending on location, age group, pollution level, and season. The highest risks were observed in Zabol, Iran, where the ILCR for adults was 4.5 × 10⁻⁴, and in Bengbu, China, where the values for adults ranged from 1.51 × 10⁻⁴ to 8.11 × 10⁻⁴. Seasonal and scenario-based differences, as observed in Poland, Los Angeles, and Milan, demonstrate the significant impact of heating periods, smog episodes, and local air quality on exposure levels. For instance, in Poland’s Silesian Voivodeship, ILCR values ranged from 6.72 × 10⁻⁶ to 9.74 × 10⁻⁵ during the heating season, dropping to 0.6 × 10⁻⁶ to 8.7 × 10⁻⁶ outside of it. In Los Angeles, the ILCR varied from 2.07 × 10⁻⁶ to 3.36 × 10⁻⁶ between the best- and worst-case scenarios. Although the ILCR values in Polish cities in this study are lower than those in the most polluted areas, they are still important for public health, showing that we need to keep managing air quality.

Toxicological studies by Majewski et al. [122] have demonstrated a higher risk of heavy metal exposure among the Zabrze population compared to the Warsaw population. These findings are consistent with the results of our study. Furthermore, numerous researchers have observed that adults may be slightly more susceptible to developing cancer due to exposure to heavy metals and PAHs than children [114,122,123,124]. However, it should be noted that children are more vulnerable to the adverse effects of environmental pollution and even lower ILCR values in children than in adults may pose a significant risk to their health.

The calculated lifetime lung cancer risk values are based solely on exposure via inhalation to the PAHs and four heavy metals contained in PM₁₀. It is important to note that this study did not include certain hazardous substances, such as chromium (particularly Cr(VI)), which are known carcinogens associated with PM exposure [30]. Therefore, the calculated ILCR values should be considered conservative estimates, as they are based on a limited set of monitored substances. Including additional carcinogens, such as Cr(VI), could lead to higher ILCR values. The study by Dahmardeh Behrooz et al. [70] demonstrated that the calculated ILCR value of 4.5 × 10⁻⁴ for metals contained in TSP for adults is primarily influenced by Cr(VI) (approximately 55%) and As (43%). The ILCR value for this metalloid was found to be 1.9 × 10⁻⁴. The contributions from the other components (Pb, Ni, Co, and Cd) were found to be 3.8 × 10⁻⁷, 1.9 × 10⁻⁸, 5.2 × 10⁻⁶, and 9.6 × 10⁻⁸, respectively. Nevertheless, other factors can also influence and increase the risk of lung cancer, such as smoking, indoor emissions from burning solid fuels (coal and wood) in stoves, occupational exposure, or genetic factors of individuals [60]. Goudarzi et al. [125] suggest that the risk of developing cancer associated with inhaling PAHs via particulate matter through the oral and nasal pathways is negligible. However, Iakovides et al. [119] demonstrated that the lifetime cumulative cancer risk is influenced almost equally by inhalation (33%), ingestion (31%), and dermal contact (37%). Further studies support the substantial contribution of oral and dermal exposure routes to cancer risk in both children and adults [125]. Therefore, neglecting these additional exposure pathways could lead to an underestimation of the overall health risk in this study.

Conversely, exposure assessments are subject to inherent uncertainty because they rely on several assumptions. These include the exposure duration and frequency, inhalation rate, average body weight, and annual mean air pollutant concentrations. These parameters can vary considerably depending on individual characteristics, such as physical activity and lifestyle [72]. In particular, the inhalation rate can vary considerably. In the present study, however, these variables were not explicitly incorporated. Furthermore, the cancer slope factors applied in the risk assessment also entail a degree of uncertainty.

Using annual average pollutant concentrations fails to capture temporal exposure variability, which is particularly relevant in Poland. Here, both particulate matter levels and composition undergo significant seasonal fluctuations, with the most pronounced changes observed during the winter months [16,86,126]. In addition to this long-term variability, short-term smog episodes, especially in winter, can lead to acute spikes in pollutant concentrations that often exceed daily limit values several times over. Immediate health impacts are associated with these peaks, especially for vulnerable groups like children, the elderly, and individuals with pre-existing respiratory or cardiovascular conditions. Even brief exposure to such episodes has been associated with hospital admissions, asthma exacerbations, and elevated cardiovascular stress [127,128]. Given these fluctuations, the ILCR values estimated in this study should be interpreted as approximate indicators of potential carcinogenic risk. To better account for uncertainties and individual variability, probabilistic approaches such as Monte Carlo simulations should be employed [118,129]. Furthermore, incorporating a wider range of environmental variables and demographic characteristics would enhance the robustness and credibility of health risk assessments.

4. Conclusions

Air pollution from PM₁₀ and other harmful substances, especially polycyclic aromatic hydrocarbons (PAHs) and heavy metals such as lead (Pb), cadmium (Cd), arsenic (As), and nickel (Ni), remains a significant environmental issue in Poland, particularly in densely populated urban areas. Although recent data show a downward trend in emissions and atmospheric concentrations of these pollutants, levels in many Polish agglomerations, such as Upper Silesia, Wroclaw, Cracow, and Łódź, still exceed EU and WHO standards. Of particular concern are the concentrations of benzo[a]pyrene (B[a]P), which exceed permissible levels several times over during winter. In Cracow, the average annual concentration of B[a]P was as high as 4.89 ng·m⁻³, which is well above the EU’s recommended value of 1 ng·m⁻³ and the WHO’s guideline of 0.12 ng·m⁻³.

Cluster analysis revealed three groups of agglomerations that differed in terms of pollutant concentration levels and structure. These groups reflect the influence of regional emission sources, urbanisation, and meteorological conditions. The first group (Upper Silesia and Wroclaw) exhibited the highest concentrations of heavy metals and PAHs, with an average lead level of 14.97 ± 7.27 ng·m⁻³ and ∑PAHs of 15.53 ± 6.44 ng·m⁻³. The second group (Cracow, Łódź, Warsaw, and Lublin) showed medium pollution levels dominated by traffic emissions, while the third group (Szczecin and Tricity) had the lowest concentrations and favourable airing conditions.

The study also included a cancer risk assessment using the Incremental Lifetime Cancer Risk (ILCR) method, with a focus on inhalation as the primary exposure pathway. This procedure enabled the actual impact of the hazardous substances contained in PM₁₀ (and PM₁₀ itself) on public health to be estimated. The highest average ILCR values were recorded in Upper Silesia (9.18 × 10⁻⁶ for males and 3.96 × 10⁻⁶ for females), and the lowest in the Warsaw area (3.16 × 10⁻⁶ for males and 1.40 × 10⁻⁶ for females). The calculated ILCR values for both sexes ranged from 1.20 × 10⁻⁶ to 1.11 × 10⁻⁵, indicating a level of health risk that cannot be considered negligible.

It is important to emphasise that this study focused on only a few pollutants. However, particulate matter is a chemically complex mixture containing many other toxic components, such as additional organic compounds, elemental carbon, and potentially carcinogenic metals (e.g., Cr(VI)), which were not included in our analysis. Furthermore, the risk assessment is based on several assumptions, including toxic equivalency factors (TEFs) for polycyclic aromatic hydrocarbons (PAHs), standardised average body weights, inhalation rates, and other exposure parameters. While inhaling ambient air is the main way in which the general population is exposed to PAHs and heavy metals, other pathways, such as dermal contact, ingestion, and combined exposure, can also contribute to the total absorbed dose. Consequently, the actual health risk associated with PM₁₀ exposure may be underestimated. Another limitation relates to the frequency and continuity of data collection at certain monitoring stations, particularly in cities such as Szczecin. Insufficient data coverage may have affected the accuracy of the calculated annual average concentrations and, consequently, the ILCR estimates. Although we used all available measurements to provide the most reliable exposure assessment possible, the limited temporal coverage could have resulted in an under- or overestimation of actual exposure levels. To obtain a more comprehensive picture of the health risks associated with air pollution, future studies should consider a broader range of pollutants and their temporal variability. This would enhance our understanding of the various factors affecting ambient air quality and support the development of more effective public health policies.

Despite some limitations, the findings of this study clearly highlight the urgent need to continue anti-smog efforts and to implement effective local environmental protection policies, particularly in areas of significant industrial activity and high traffic density where residential emissions also play a significant role. It is also essential to establish effective public information systems to minimise the population’s exposure to carcinogenic air pollutants in urban areas. Further research is necessary to better understand the impact of toxic and carcinogenic air pollutants on human health, particularly among vulnerable groups such as children and the elderly.