Exposure and Risk Assessment to Airborne dl-PCBs and Dioxins in the Population Living in the Neighborhood of a Cement Plant: A Pilot Study in the Valencian Region of Spain

Emissions from cement manufacturing facilities may increase health risks in nearby populations. For this reason, dioxin-like PCB (dl-PCB), polychlorinated dibenzo-p-dioxin (PCDD), and polychlorinated dibenzofuran (PCDF) concentrations in PM10 samples were assessed in the vicinity of a cement manufacturing plant located in the Valencian Region (eastern Spain). The total concentrations of the sum of dl-PCBs, PCDDs, and PCDFs ranged between 1.85 and 42.53 fg TEQ/m3 at the assessed stations. The average daily inhalation dose (DID) for the sum in adults ranged from 8.93 · 10−4 to 3.75 · 10−3 pg WHO TEQ kg−1 b.w. d−1, and, for children, the DID ranged from 2.01 · 10−3 to 8.44 · 10−3 pg WHO TEQ kg−1 b.w. d−1. Risk assessment for adults and children was performed using both daily and chronic exposure. The hazard quotient (HQ) was calculated considering 0.025 pg WHO TEQ kg−1 b.w. d−1 to be the acceptable maximum permitted inhalation exposure. The HQ obtained was slightly higher than 1 for PCDD/Fs at one of the stations (Chiva), indicating a possible health risk for the population under study due to inhalation exposure. In the case of chronic exposure, cancer risk (>10−6) was observed for some samples in one of the assessed sampling sites (Chiva).


Introduction
Cement production has increased around the world as a consequence of the growth of population and urbanization ratio [1]. Dioxins, furans (PCDD/Fs), and dioxin-like PCBs (dl-PCBs) can be produced in the cement plant due to the fuel or to its synthesis in the gas treatment system [2]. Combustible material introduced in the precalcination zone can react with the chlorine not retained by the alkaline matrix of the clinker producing dl-PCB and dioxin emissions [3].
Dl-PCBs and PCDD/Fs are regulated and are part of the "dirty dozen" (the 12 persistent organic pollutants regulated by the Stockholm Convention) [4]. Their prolonged exposure can cause reproductive, endocrine, and immunological disorders [5][6][7]. The impact and exposure of dl-PCBs and dioxins is a concerning matter because people are exposed to these contaminants for large periods of their lives.
Although many studies have focused on knowing the emissions of PCDD/Fs and PCBs from cement industries by sampling directly inside the stack gas [8,9], there is little written about the exposure of populations close to the cement industry. Breathing dl-PCBs and dioxins airborne in polluted ambient air around locations close to hotspots such as cement plants could be a relevant exposure source in nearby populations. According to the World Health Organization, the daily inhalation exposure can be considered to be 10% of the tolerable daily intake (TDI) by ingestion exposure if we consider the worst-case Toxics 2023, 11, 389 2 of 12 scenario [10]. Ingestion exposure is considered the main source of dioxin and dl-PCB exposure in non-hotspot areas [11].
Previous risk assessment studies have studied PCDD/Fs in the ambient air of populations living close to cement plants [12][13][14][15]. Nevertheless, no study has investigated the exposure to dl-PCBs in the population located close to cement plants.
Previous studies have shown the population exposure to dl-PCBs and PCDD/Fs in the Valencian Region (Spain). Quijano et al., 2018 [16] observed that the average adult's daily intake through diet was 1.58 pg TEQ (toxic equivalent) kg −1 b.w. day −1 , and the average for children was 2.76 pg TEQ kg −1 b.w. day −1 . Daily inhalation exposure to dl-PCBs and PCDD/Fs has been assessed by López et al., 2021 [17], observing a maximum average inhalation exposure of 1.08 · 10 −2 pg TEQ kg −1 b.w. day −1 in adults and 2.42 · 10 −2 pg TEQ kg −1 b.w. day −1 in children.
The exposure of lactating mothers and breastfed infants to PCDD/Fs and dl-PCBs was below the reference level reported by the EFSA (5.9 pg TEQ g −1 ) [18], but this value was exceeded when the 95th percentile or the maximum level was considered in a study carried out in the same region in breast milk samples [19]. Consequently, exposure of these compounds in infants, children, and adults is relevant. It is important to highlight that these substances can produce endocrine, reproductive, neurological, and immunological diseases and, finally, decrease life expectancy [20].
Due to the scarce international information about the influence of cement manufacturing emissions on inhalation risk assessment for dl-PCBs, the present work is a pilot study that has focused on measuring dl-PCB, PCDD, and PCDF profile congeners close to a cement plant located in the Valencian Region (Spain) and assessing the potential human health risks in nearby populations.

Sampling and Site Characterization
Samples were collected, as a pilot study, in two towns (Chiva and Buñol) located close to a cement plant in different periods during the year 2020. The S1 sampler was placed in the town of Chiva (14,941 inhabitants) located to the east of the cement plant and 289 m above sea level. Thirteen PM 10 samples were collected at this station from February to June 2020.
The S2 sampler was placed in the town of Buñol (9517 inhabitants), located to the west of the cement plant. Ten PM 10 samples were collected from August to October 2020 at this station (see Figure 1).
Air samples were taken as described in López et al. (2021) [17], using a high-volume sampling device (HVS) from Digitel (DPA-80, Volketswill, Germany). Total sampling volumes were around 1500 m 3 (see Supplementary Table S1) with a sampling flow of 30 m 3 h −1 for 48 h. For this, 150 mm diameter quartz fiber filters (QFF) were employed, which were supplied by Munktell Filter AB (Falun, Sweden). Samplers belong to the monitoring network of the Regional Valencia Government (Generalitat Valenciana). were supplied by Munktell Filter AB (Falun, Sweden). Samplers belong to the monitoring network of the Regional Valencia Government (Generalitat Valenciana). Figure 1. Location of the evaluated stations (S1 and S2) and cement plant.

Analytical Methodology and Identification Criteria
Sample preparation and GC-HRMS system were previously described by López et al., (2021) [17].
For the calculation of the LOQ (quantification limit), the "Guidance Document on the Estimation of LOD (detection limit) and LOQ (quantification limit) for Measurements in the Field of Contaminants in Feed and Food" [23] was employed. The quantification limit for each sample in PM10 was calculated using TargetQuan software, and the average for the ∑PCDD/Fs and ∑dl-PCBs were 0.43 fg TEQ/m 3 and 0.03 fg TEQ/m 3 , respectively.

Quality Control Protocol
Each batch of samples included a blank field that was treated in the same way as the air samples. In addition, quality control was carried out using a spiked blank every two analytical sets, and surrogates were evaluated in each sample. Filter analysis was performed after sampling or after the storage period at −20 °C.

Gaseous-Particle Partitioning Model
To estimate the total air concentrations from the obtained results for PM10, the model validated previously by López et al., (2021) [17] was used, in which the fraction of the compound in the particle phase (ø) and gas phase (1−Ø) was calculated using the Harner-Bidleman absorption model [24]: where CTSP is the concentration of total suspended particles in the air. According to Yusà et al., (2014) [24], its value is 55 µg m −3 in the assessed region, and Kp (m 3 µg −1 ) is the gas-particle partition coefficient; its value can be calculated using the Equation (2): where log fOM is the fraction of organic matter that was calculated assuming a fOM of 0.2 as representative values in the studied region (Yusà et al., 2014) [25]. Log Koa is the octanolair partition coefficient, which is different for PCDD/Fs and dl-PCBs. For PCDD/Fs, Koa is a function of the retention time indices (RTI) and temperature (T). The employed formula is different for tetra-to hexa-chlorinated PCDD/Fs (3) and for other PCDD/Fs (4) [24]: Figure 1. Location of the evaluated stations (S1 and S2) and cement plant.

Analytical Methodology and Identification Criteria
Sample preparation and GC-HRMS system were previously described by López et al. (2021) [17].
For the calculation of the LOQ (quantification limit), the "Guidance Document on the Estimation of LOD (detection limit) and LOQ (quantification limit) for Measurements in the Field of Contaminants in Feed and Food" [23] was employed. The quantification limit for each sample in PM 10 was calculated using TargetQuan software, and the average for the ∑PCDD/Fs and ∑dl-PCBs were 0.43 fg TEQ/m 3 and 0.03 fg TEQ/m 3 , respectively.

Quality Control Protocol
Each batch of samples included a blank field that was treated in the same way as the air samples. In addition, quality control was carried out using a spiked blank every two analytical sets, and surrogates were evaluated in each sample. Filter analysis was performed after sampling or after the storage period at −20 • C.

Gaseous-Particle Partitioning Model
To estimate the total air concentrations from the obtained results for PM 10 , the model validated previously by López et al. (2021) [17] was used, in which the fraction of the compound in the particle phase (ø) and gas phase (1−Ø) was calculated using the Harner-Bidleman absorption model [24]: where C TSP is the concentration of total suspended particles in the air. According to Yusà et al. (2014) [24], its value is 55 µg m −3 in the assessed region, and K p (m 3 µg −1 ) is the gas-particle partition coefficient; its value can be calculated using the Equation (2): where log f OM is the fraction of organic matter that was calculated assuming a f OM of 0.2 as representative values in the studied region (Yusà et al., 2014) [25]. Log K oa is the octanol-air partition coefficient, which is different for PCDD/Fs and dl-PCBs. For PCDD/Fs, K oa is a function of the retention time indices (RTI) and temperature (T). The employed formula is different for tetra-to hexa-chlorinated PCDD/Fs (3) and for other PCDD/Fs (4) [24]: Dl-PCBs K oa was calculated using the following Equation (5) [26]: where K OW is the octanol-water coefficient for each analyte, T is the temperature (295 K), R is the gas constant (8.21 · 10 −5 atm m 3 mol −1 K −1 ), and H is the Henry coefficient (atm m 3 mol −1 ).

Exposure and Risk Assessment
Based on the risk assessment protocol for human health [27], both (a) daily inhalation exposure and (b) lifetime exposure to PCDD/Fs and dl-PCBs were considered: (a) In order to calculate the daily intakes, the daily inhalation dose (DID) was estimated for both adults and children (<6 years): where C is the total ambient air concentration of PPCDD/F and dl-PCB using upper limit concentrations in pg TEQ/m 3 ; IR is the inhalation rate per hour (0.83 m 3 h −1 for adults and 0.4 m 3 h −1 for children); ET is the exposure time (24 h); and BW is the mean body weight (70 kg for adults and 15 kg for children) [28].
To estimate the risk, the recommended tolerable daily intake (TDI) (0.25 pg TEQ kg −1 day −1 for PCDD/Fs plus dl-PCBs) was taken as reference, according to the EFSA [18].
In order to put this exposure (DID) in a risk assessment context, a hazard quotient (HQ) was also calculated, considering: (1) The DID value in each station as p95.
(2) Considering that daily inhalation exposure accounts for around 10%, this percentage of TDI as a reference health-based value was employed (Equation (7)) [29].
(b) To calculate the risk of cancer due to lifetime exposure, the product of chronic exposure (CE) and the slope factors (SF) was used [30].
Cancer risk= CE·SF (8) Cancer exposure was estimated by multiplying the total concentration of each compound analyzed in mg m −3 (C air ) and the inhalation factor (IF) (Equation (9)), obtained from Equation (10): where IR inh is the inhalation rate per day (20 m 3 day −1 ); EF is the exposure frequency (365 days) per year; ED is the exposure duration (70 years); ET is the exposure time (24 h day −1 ); BW is the body weight of the subject (70 kg); and AT is average length of time of carcinogenic exposure over a lifetime (25,500 days = 70 years × 365 days per year) [29]. Using these parameters and the Inhalation Risk Units (IUR) of each contaminant, which represent the cancer potency factor for inhalation exposure [30], the SF was calculated according to Equation (11). The IUR values used are shown in Table S2.
The cancer risk values were compared to the carcinogenic benchmark level, considering values higher than 10 −6 as concerned cancer risk and values higher than 10 −4 as unacceptable [27]. Figure 2 and Table S3 show the results obtained in the S1 (Chiva) and S2 (Buñol) sampling sites for the total concentration (particulate phase plus gas phase) of the ∑dl-PCBs, ∑PCDD/Fs, and the sum of both, in fg TEQ/m 3 . Overall results are shown in Table 1.

Total Concentrations
The cancer risk values were compared to the carcinogenic benchmark level, considering values higher than 10 −6 as concerned cancer risk and values higher than 10 −4 as unacceptable [27]. Figure 2 and Table S3 show the results obtained in the S1 (Chiva) and S2 (Buñol) sampling sites for the total concentration (particulate phase plus gas phase) of the ∑dl-PCBs, ∑PCDD/Fs, and the sum of both, in fg TEQ/m 3 . Overall results are shown in Table 1.  Concentrations of dl-PCBs in Chiva (S1) ranged from 0.59 to 3.03 fg TEQ/m 3 , obtaining an average mean of 1.43 fg TEQ/m 3 . Obtained concentrations in Chiva for dl-PCBs were similar to other metallurgical and ceramic areas assessed in the Valencian Region in 2019 (López et al., 2021) [17] and lower than the obtained levels in two different urban areas (more than 2 fg TEQ/m 3 ) of the city of Valencia (the big city close to the assessed sites, around 30 km). Moreover, levels of dl-PCBs in Chiva were lower than other industrial areas in Asia [31][32][33].

Total Concentrations
Concentrations of dl-PCBs in Buñol (S2) oscillated from 0.51 fg TEQ/m 3 to 2.36 fg TEQ/m 3 , with an average mean of 1.31 fg TEQ/m 3 . The obtained average mean of dl-PCBs in this area was lower than the obtained levels in a previous study carried out by our research group in the surroundings of four industrial and two urban areas in the Valencian Region [17]. Furthermore, the obtained levels were around three to five times lower than other industrial areas in China [31], Vietnam [32], and Kuwait [33].
The fg TEQ/m 3 profile obtained for the dl-PCBs in Chiva and Buñol (see Figure S1) shows that PCB-126 is clearly the most present congener. These results are similar to those obtained in other industrial and urban areas of the Valencian Region [17] and other studies around the world [32,36,37]. According to Luthardt et al. (2002) [38], in industrial sources, the contributions of PCB-126 are more than 90% of PCB-TEQ. Moreover, the presence of PCB-169 is characteristic of industrial areas [39]. On the other hand, PCB-118 and PCB-156 are more characteristic of samples close to a cement kiln. Martínez et al. (2010) [39] showed that the concentration profiles taken at a cement plant stack present PCB-118 as the main PCB and PCB-105 as the second one.
For the profile concentrations (fg/m 3 ) of PCDD/Fs in Chiva (see Figure S2) (fg/m 3 ), the congeners with the highest concentrations were 1,2,3,4,7,8,9-HpCDF, OCDF, and OCDD. This profile is similar to those obtained by Abad et al. (2004) [40]. In contrast, at the Buñol station, the congeners with the highest concentrations were OCDD, 1,2,3,4,6,7, 8 Table 4 shows the AM and percentile 95 (p95) values related to the inhalation exposure to dl-PCBs, PCDD/Fs, and the sum of dioxins, furans, and dl-PCBs in adults and children. To our knowledge, this is the first study to assess dl-PCB inhalation in the surroundings of cement plants. Table 4. Daily inhalation exposure in adults (>12 years) and children (1.5-6 years) at each station in pg WHO TEQ kg −1 b.w. d −1 .

Analyte
Chiva Buñol The inhalation exposure to dl-PCBs for adults at the Chiva station was 4.08 · 10 −4 pg WHO TEQ kg −1 b.w. d −1 , and 9.18 · 10 −4 pg WHO TEQ kg −1 b.w. d −1 for children. Hazard quotients for dl-PCBs calculated for both populations were 2 times lower than 1 (see Figure 3), so no risk by inhalation pathway was observed. At the Buñol station, inhalation exposure to dl-PCBs in adults was 3.72 · 10 −4 pg WHO TEQ kg −1 b.w. d −1 , and 2.01 · 10 −3 pg WHO TEQ kg −1 b.w. d −1 for children. The calculated HQ was lower than 1 (see Figure 3) in both populations, so no inhalation risk was noted. The studies carried out in the literature on the risk of dioxins and furans in the vicinity of cement plants did not estimate the risk of dl-PCBs, so it is not possible to compare the results obtained for dl-PCBs with other similar studies. exposure to dl-PCBs in adults was 3.72 · 10 −4 pg WHO TEQ kg −1 b.w. d −1 , and 2.01 · 10 −3 pg WHO TEQ kg −1 b.w. d −1 for children. The calculated HQ was lower than 1 (see Figure 3) in both populations, so no inhalation risk was noted. The studies carried out in the literature on the risk of dioxins and furans in the vicinity of cement plants did not estimate the risk of dl-PCBs, so it is not possible to compare the results obtained for dl-PCBs with other similar studies. The inhalation exposure to adults of PCDD/Fs in Chiva was 3.34 · 10 −3 pg WHO TEQ kg −1 b.w. d −1 , and 7.52 · 10 −3 pg WHO TEQ kg −1 b.w. d −1 for children. The calculated hazard quotient for children was slightly higher than 1 (1.02) at the Chiva station, considering p95 of daily inhalation exposure, so possible risk was observed due to inhalation. The obtained average value for inhalation exposure in adults is similar to other studies in the vicinity of cement plants, which range between 2.1 · 10 −3 and 1.2 · 10 −2 pg WHO TEQ kg −1 b.w. d −1 (see Table S4). The inhalation exposure to PCDD/Fs observed in Buñol (5.22 · 10 −4 pg WHO TEQ kg −1 b.w. d −1 for adults and 1.17 · 10 −3 pg WHO TEQ kg −1 b.w. d −1 for children) was a magnitude order lower than the studies carried out in Catalonia in the vicinity of cement plants (see Table 2). The calculated HQ for PCDD/Fs was lower than 1 in adults and children at the Buñol station. The inhalation exposure to adults of PCDD/Fs in Chiva was 3.34 · 10 −3 pg WHO TEQ kg −1 b.w. d −1 , and 7.52 · 10 −3 pg WHO TEQ kg −1 b.w. d −1 for children. The calculated hazard quotient for children was slightly higher than 1 (1.02) at the Chiva station, considering p95 of daily inhalation exposure, so possible risk was observed due to inhalation. The obtained average value for inhalation exposure in adults is similar to other studies in the vicinity of cement plants, which range between 2.1 · 10 −3 and 1.2 · 10 −2 pg WHO TEQ kg −1 b.w. d −1 (see Table S4). The inhalation exposure to PCDD/Fs observed in Buñol (5.22 · 10 −4 pg WHO TEQ kg −1 b.w. d −1 for adults and 1.17 · 10 −3 pg WHO TEQ kg −1 b.w. d −1 for children) was a magnitude order lower than the studies carried out in Catalonia in the vicinity of cement plants (see Table 2). The calculated HQ for PCDD/Fs was lower than 1 in adults and children at the Buñol station.

Chronic Exposure
The study assessed the chronic exposure to dioxins, furans, and dl-PCBs by calculating the cancer risk from inhalation at each station over a period of 70 years. The results indicate that certain samples from the Chiva sampling site ( Figure 4A) show values higher than 10 −6 , especially those collected at the beginning of the summer. However, according to the EPA [27], cancer risk levels must be above 10 −4 to be considered unacceptable, and chronic exposure levels in the area are lower than those detected in other industrial areas of the Valencian Region. On the other hand, chronic exposure levels at the Buñol station ( Figure 4B) were below 10 −6 in all samples evaluated, suggesting that the detected concentrations do not pose a long-term risk to the assessed population.

Chronic Exposure
The study assessed the chronic exposure to dioxins, furans, and dl-PCB calculating the cancer risk from inhalation at each station over a period of 70 years results indicate that certain samples from the Chiva sampling site ( Figure 4A) values higher than 10 −6 , especially those collected at the beginning of the sum However, according to the EPA [27], cancer risk levels must be above 10 −4 considered unacceptable, and chronic exposure levels in the area are lower than detected in other industrial areas of the Valencian Region. On the other hand, ch exposure levels at the Buñol station ( Figure 4B) were below 10 −6 in all samples evalu suggesting that the detected concentrations do not pose a long-term risk to the ass population.

Study Limitations
Only the particle phase (PM10) has been collected and analyzed in the present study Total concentrations including the gaseous phase have been calculated using a mathematical model previously validated by López et al., 2021 [17].

Conclusions
The concentrations of airborne dl-PCBs measured in the present study were found to be similar to those obtained in other industrial and urban areas in the assessed region Regarding the obtained profiles for the analyzed compounds, dl-PCB profiles are identical at all studied sampling stations.

Study Limitations
Only the particle phase (PM 10 ) has been collected and analyzed in the present study. Total concentrations including the gaseous phase have been calculated using a mathematical model previously validated by López et al., 2021 [17].

Conclusions
The concentrations of airborne dl-PCBs measured in the present study were found to be similar to those obtained in other industrial and urban areas in the assessed region. Regarding the obtained profiles for the analyzed compounds, dl-PCB profiles are identical at all studied sampling stations.
The estimated HQ for daily exposure in adults and children at the assessed sampling sites was less than 1 for dl-PCBs but slightly higher than 1 for PCDD/Fs in one of the investigated areas, indicating possible risk and the need of more-in-depth studies. For chronic exposure, some results at one sampling site have concerning levels. However, none of the obtained results showed exposure levels higher than 1.0 · 10 −4 ; consequently, the adoption of immediate corrective measures is not required.
To our knowledge, this study is the first to assess inhalation risk in the population for dl-PCBs together with PCDDs and PCDFs in the vicinity of cement plants.
Taking into account our results, implementation of future monitoring programs in order to control industrial airborne pollution could be interesting for protecting the public health of the population living in the neighborhood of hotspot locations such as cement plants.
Supplementary Materials: The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/toxics11040389/s1, Section S1: Analytical performance parameters and identification criteria; Table S1: Sampling dates of the analyzed filters and total sample volume (m 3 );  Table S3: Concentrations of ΣPCDD/Fs + dl-PCBs, ∑ dl-PCBs, and ∑ PCDD/Fs obtained at Chiva (C) and Buñol (B) stations in fg TEQ/m 3 ; Table S4: Exposure of dioxins and furans in adults in the vicinity of cement plants; Figure S1: Profile of concentrations of dl-PCBs detected at Chiva and Buñol stations using concentrations (fg/m 3 ) and toxic equivalents (TEQ) (fg TEQ/m 3 ); Figure S2: Profile of concentrations of PCDD/Fs detected at Chiva and Buñol stations using concentrations (fg/m 3 ) and toxic equivalents (TEQ) (fg TEQ/m 3 ).
Funding: These studies have been performed using analytical instruments financed by the European Commission through the European Regional Development Funds (ERDF) Operational Programme of the Valencia Region (2014-2020).
Institutional Review Board Statement: Not applicable.

Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.