Phthalates, non-phthalates, polychlorinated biphenyls, and phenyl phosphates in atmospheric suspended particulate matter of Dhahran City, Saudi Arabia: levels and seasonal variation

This is the first report to describe the seasonal variations, levels, and possible health effects of groups of persistent organic pollutants (POPs) as phthalates (Ps), non-phthalates (NPs), polychlorinated biphenyls (PCBs), and phenyl phosphates (PhePhs) in ambient total suspended particles (TSP) from the city of Dhahran, Saudi Arabia. The mass concentrations of TSP ranged from 88 ± 32 μg m−3 in winter to 350 ± 320 μg m−3 in summer. The total concentrations of these compounds varied from 337 ± 266 ng m−3 in summer to 469 ± 403 ng m−3 in winter. The major compounds were Ps (235 ± 199 ng m−3 in summer to 389 ± 335 ng m−3 in winter), PCBs (30.7 ± 19.3 ng m−3 in autumn to 65.6 ± 61.2 ng m−3 in summer), NPs (4.9 ± 2.3 ng m−3 in summer to 11.9 ± 12.5 ng m−3 in winter), and PhePhs (4.1 ± 4.0 ng m−3 in spring to 13.3 ± 3.2 ng m−3 in summer). The proportional fractions of these POPs relative to natural biogenic sources and petroleum-related emissions were extremely high ranging from 17% in winter to 47% in autumn. Significant correlations were found among these different POP groups and total concentrations, suggesting that they were from local sources. Principal component analysis indicated that Ps and NPs were from the same initial sources, and the PhePhs as well as PCBs were from different regional sources, where the latter were dependent on the TSP levels. In the long term, the elevated levels of these POPs in the TSP of these urban areas will affect human health by eventually developing a range of illnesses.


Introduction
Different additives of organic compounds are mixed with basic plastic polymers, such as polyvinyl chloride (PVC), to improve the functional properties and flexibility of the final products. These additives include plasticizers, antioxidants, and flame retardants (Zweifel et al. 2001), which are commonly comprised of branched and linear phthalates, adipates, phosphate esters, mellitates, and polymeric esters (Graham 1973;Liepins and Pearce 1976). More than 3 million metric tons per year of phthalates are used in the plastic industry (Bizzari et al. 2000), making them susceptible to be released into the environment as persistent organic pollutants (POPs). Also, they are not chemically bonded to the plastic polymers and can easily leak to the environment during manufacturing, littering, and waste burning (Simoneit et al. 2005;Peréz-Feás et al. 2011;Bagel et al. 2011;Chiellini et al. 2011;Kastner et al. 2012).

Regional relevance
There has been an increase in industrial activities and development related to oil production in the eastern province of the Kingdom of Saudi Arabia. There the metropolitan area of Dammam is the largest industrial region of the country, where different petroleum and petrochemical manufacturing corporations and companies have been established in the cities of Dammam, Al-Hasa, and Al-Jubail (El-Sharkawy and Zaki 2012). Plastic manufacturing is one of the main industrial activities in the Dammam area and Al-Jubail in the north as the largest regional industrial complex. The air quality of the region is ultimately affected by these industries and related activities in the area (Salama et al. 2015;Rushdi et al. 2017;El-Sharkawy and Dahlawi 2019). There is a lack of information regarding the compositions, levels, and seasonal variation of POP and petrochemical additives in atmospheric particulate matter of the major cities of the Kingdom and specifically the eastern province of Saudi Arabia.
The main purpose of this study is to determine the occurrence, concentration, and seasonal variation of the dominant plastic-related POPs in atmospheric suspended particulate matter in the City of Dhahran, one of the major urban areas in the Dammam metropolitan region, where the largest petrochemical manufacturers, producers, and distributors are active.

Study area
This study was conducted in Dhahran (population 99,540), located in the eastern province of Saudi Arabia (Fig. 1). It is the base of the largest oil company in the Middle Eastthe Saudi ARAMCO (Arabian American Oil Company) adjoining the Dammam metropolitan area. The weather is mainly a desert climate, characterized by very hot weather (may reach > 50 °C) during summertime, cold (may fall to > − 2 °C) in winter, and high humidity (34-73%). The rain precipitation generally takes place between November and May of the year and ranges between 55 to 73 mm. The major winds during the months of summer are mainly dust storms from the north, known as the Shamal winds, which can continue for about six months. Al-Jubail Industrial City, which is located about 98 km north of Dammam city, is the largest industrialized complex in the region and an important commercial hub for different manufacturers, especially for petrochemical production. were collected on QMA quartz fiber filters (20.3-25.4 cm) with a standard high-volume sampler. The sampler was set up on the roof (~ 10 m above the ground) of the Center of Water and Environmental Studies of KFUPM. Prior to sampling, the quartz filters were heated at ~ 600 °C to reduce their organic background content and then placed in clean aluminum containers. The filters were tared before and weighed after TSP acquisition. The sampler was operated at a flow rate of 1.2 m 3 min −1 for 24 h.

Sampling site and collection
Bimonthly samples were obtained from the sampling site ( Fig. 1) for the determination of the organic composition of TSP. A total of 22 samples were collected to cover the different seasons (i.e., 6 samples in summer, 7 samples in autumn, 4 samples in winter, and 5 samples in spring). The TSP contents for the samples varied seasonally, where the maximum was observed during the dust storm season in late spring to the begin of summer (Table 1). After sampling, each filter was covered with pre-cleaned aluminum foil, stored in a pre-cleaned polyethylene container, and transferred to the laboratory in the same building. The filters were weighed after transferring into desiccators and then stored at -20 °C until analysis. Procedure sample blanks were also taken for analyses.

Extraction
The extraction method was the same as described by Rushdi et al. (2017). A mixture of dichloromethane and methanol (v/v = 2:1) was used to extract the organic matter of the filters using stainless steel ASE (Accelerated Solvent Extractor) cells (Dionex, Sunnyvale CA, USA). Prior to extraction, a pre-weighed sample filter was placed in each ASE cell, which had been pre-cleaned by organic solvents; then, the cell was filled with diatomaceous earth and capped. Extraction was performed at 100 °C, 1500 psi, 2 times of 5 min cycles, and a flush volume of 150%. The extract was concentrated in a TurboVap II (Zymark, Hopkinton, MA) to 500 µL with nitrogen gas.

Instrumental analysis
The analysis was carried out by gas chromatography-mass spectrometry (GC-MS) using an Agilent 6890 gas chromatograph coupled to a 5975C Mass Selective Detector (Agilent). The capillary column was an Agilent DB-5MS fused silica capillary column (30 m long, 0.25 mm internal diameter, and 0.25 µm film thickness), and the carrier gas was helium. The GC oven temperature was programmed after an initial hold of 2 min from 65 °C to 310 °C at 6 °C/min and isothermal final hold for 20 min. The electron impact mode at 70 eV was selected as ion source energy for the MS. The GC-MS ChemStation data system was used to acquire and process the mass spectrometric data.

Quality control
The technical accuracy of the methods has been applied in this study and it included the sampling collection, analytical chemistry, treatment, and interpretation of the data of this research. Background and cross-contamination as a result of laboratory procedures have been tested and corrected from procedural blanks for quality and quantity control. Blank extracts were also carried out throughout the procedures after batches of three samples. Five different standards (dibutyl phthalate, di-n-octyl phthalate, bis(2-ethyhexyl) phthalate, bis-(2-ethylhexyl) adipate, and diphenyl phosphate, all from Sigma-Aldrich) were prepared as stock solutions and a standard of seven polychlorinated biphenyl (Sigma-Aldrich) was used to quantify phthalates, non-phthalates, phenyl phosphates, and polychlorinated biphenyls with the GC-MS. We prepared and evaluated the limit of detection (LoD) and limit of quantification (LoQ) the same way with the samples. Also, we used the least square method to test the linearity of the calibration curve and to fit the concentrations of the different standards versus their relative responses. The correlations between the concentrations and the relative responses were significant with correlation coefficients, R 2 , of 0.94-0.98 for phthalates and non-phthalates, 0.91-0.95 for phenyl phosphates, and 0.92-0.96 for polychlorinated biphenyls. The software SPSS 6.0 (IBM-Statistical Package for Social Science, version 16.0) was used to treat the data.

Results and discussion
The major industrial organic compounds in the TSP extracts were phthalates (Ps), non-phthalates (NPs), phenyl phosphates (PhePhs), and polychlorinated biphenyls (PCBs) as illustrated in Fig. 2. The dominant compounds identified are listed in Table 1. The synthetic compound groups are discussed in detail below.
The air temperatures and mass concentrations of the TSP from Dhahran city are summarized in Fig. 3. The air temperatures in the city were usually hot in summer and cooler in winter. The range was wide with a summer high median  Table 1 and structures are illustrated in Figure (Fig. 3a). The seasonal concentrations of TSP also had a wide range with median values of 220.5 µg m −3 , 152.8 µg m −3 , 87.5 µg m −3 , and 272.3 µg m −3 in summer, autumn, winter, and spring, respectively (Fig. 3b). The data showed that there was a positive relationship between the mass concentrations of TSP and air temperature as indicated by their median values. The elevated temperatures enhanced the volatilization of the individual compound emissions.  Fig. 4a).
Twenty-three phthalate compounds (structures are shown in the Supplemental Materials section) were identified in the TSP with high mean concentrations for example 253.2 ng m −3 during summer and 388.7 ng m −3 in winter (Table 1) Table 1.
The high concentrations of total Ps in the TSP samples confirmed that the ambient air of Dhahran city is contaminated by plastic additives. Generally, the presence of Ps in the environment is related to plastic manufacturers and markets (Sun et al. 2013;Gao and Wen 2016;Kim et al. 2020) as well as littering and plastic waste burning (Simoneit et al. 2005;Fu and Kawamura 2010;Rushdi et al. 2010;Kumar et al. 2015;Zhen et al. 2019). The major worldwide phthalate product used in PVC plastic is DEHP, representing 37.1% of the total plastic additives (ECPI 2016), and recently, DNP and DUP have regularly been utilized as additives instead of DEHP (ECPI 2016). The presence of high levels of DEHP and relatively low concentrations of DNP and DUP in these TPS samples presumably indicated that DEHP was still produced as a major plasticizer additive in the region and DNP, or DUP has not completely replaced DEHP in production by the manufacturers.
The concentrations of Ps in the TSP samples were relatively similar to the concentrations reported for other major cities in the world. The DEP concentrations were much lower than the levels reported for other cities in the world (Table SM-1) such as Paris-France, Stockholm-Sweden, Berlin-Germany, and Tokyo-Japan (Otake et al. 2001;Fromme et al. 2004;Teil et al. 2006;Bergh et al. 2011), probably due to lower retention on filters based on its greater volatility. The DBP concentrations (Table SM-1) were similar as measured in Nanjing-China, and Portland-Oregon-USA (Ligocki and Pankow 1989;Wang et al. 2008), lower as in Stockholm (Otake et al. 2001;Fromme et al. 2004;Bergh et al. 2011), and higher than for Paris, Yamato-Japan, Barcelona-Spain, Austin and Waco-Texas-USA, and Murry-Kentucky-USA (Toda et al. The DEHP concentrations were similar as in Yamato (Toda et al., 2004), higher than Paris and Nanjing (Teil et al. 2006;Wang et al. 2015), but lower than Stockholm, Santiago-Chile, Beijing-China, Guangzhou-China, and major USA cities such as Portland, Austin, Waco, and Murry (Ligocki and Pankow 1989;Simoneit et al. 2005;Bi et al. 2008Bi et al. , 2018Zhou et al. 2009;Bergh et al. 2011;Subedi et al. 2017;Ma et al. 2020;Li et al. 2018) (Table SM-

Non-phthalates (NPs)
The relative seasonal concentrations of non-phthalates (NPs) in the TSP were comparatively low comprising 1.7 ± 0.6 to 2.0 ± 0.4% of the total concentrations (Table 1), with low levels and medians of 5.6 ng m −3 in summer and 9.5 ng m −3 in winter (Fig. 4b). Only di(2-ethylhexyl) adipate (DEHA = 4.7-10 ng m −3 ) and tri(2-ethylhexyl) mellitate (TEHM = 0.6-1.6 ng m −3 ) were detected in these samples. The presence of NPs in these TSP samples suggested that alternative plasticizers were a minor component in the Dhahran atmosphere but also used as additives for plastic production in the region. The concentrations of DEHA in the TSP of Dhahran were lower than that reported in the cities of Waco-Texas and Murry-Kentucky (Subedi et al. 2017) (Table SM-1).

Phenyl phosphates (PhePhs)
The phenyl phosphates (PhePhs) in the TSP were also low, ranging from 1.1 ± 1.2 to 3.4 ± 1.7% of the total concentrations (Table 1), with similar levels for all seasons (Fig. 4c). The major compound was triphenyl phosphate (TPhePh) with concentrations ranging from 3.9 ng m −3 in spring to 6.5 ng m −3 in winter (Table 1). Diphenyl p-and m-tolyl phosphates (DPhepTPh and DPhemTPh) were relatively significant at 0.7 ng m −3 in spring to 4.5 ng m −3 in autumn.   Phenyl di(p-and m-tolyl) phosphates (PheDpTPh and PheDmTPh) were low ranging from 0.3 ng m −3 in spring to 2.5 ng m −3 in summer, with traces of tri(p-and m-cresyl) phosphates (TpCPh and TmCPh) ( Table 1). The concentration of TPhePh was similar as in Islamabad, Pakistan (Faiz et al. 2018) and higher than in Nanjing-China (Wang et al. 2008;Faiz et al. 2018) (Table SM-1). TPhePH was the dominant compound of the phenyl phosphates emitted in TSP from an e-waste recycling facility in South China (Bi et al. 2010).

Correlation and source comparison
Pearson's correlation statistical analysis was used to assess the association and relationship between these POP groups detected in the TSP samples. The outcome of Pearson's correlation (Table 2) showed that the correlations between the TSP and these groups were insignificant (r < 0.439), except for phthalate, which showed a significant correlation at p-value of 0.05 and insignificant at the p-value of 0.01. Also, insignificant correlations were found between air temperatures and different groups (r < 0.377). The correlations between total concentrations and different groups were found to be significant (r = 0.537 to 0.985). The insignificant correlation among TSP, air temperature, and these POP groups demonstrated that these were not important factors in controlling the concentrations and distribution of POPs in the atmosphere of Dhahran. On the other hand, the significant correlations between total compounds and their different groups indicated that they apparently were from similar local sources. The data were analyzed by principal component analysis (PCA), using varimax rotation to examine the similarities and distinctions between the levels and sources of the plasticizer groups in the TSP of Dhahran. The PCA output identified three significant components (C1, C2, and C3) elucidating 90.69% of the variance at an eigen value of > 1 (Table 3, Fig. 5). We have interpreted the data using factor loadings of > 0.65 for each component. The C1 revealed a variance of 54.39% with phthalates and non-phthalates as dominant, indicating that they were from the same sources. The C2 showed a variance of 25.06% with TSP and PCBs, specifying that the concentration of TSP had an effect on the levels of PCBs in the atmosphere of the city. The C3 revealed a variance of 11.32% with only phenyl phosphates, confirming that these plasticizers were from different sources. Therefore, phthalates and non-phthalates were likely released mainly from the plastic manufacturers around the city (Rushdi et al. 2017;Saini et al. 2019) or as a result of the combustion of plastic waste in the region (Simoneit et al. 2005). The similarity and correlation between TSP and PCBs were probably due to spills, leaks, or disposal of PCBs from paint and metallurgical industries (Zhao et al. 2019) into local topsoil and resuspension of soil particles into the atmosphere. The sources of phenyl phosphates were likely emissions from residential sources (Saini et al. 2019).

Plasticizer and flame retardant levels relative to other urban organic compounds
The total extractable organic matter of the atmospheric TSP from Dhahran city also contained compounds from different natural and anthropogenic sources. These compounds included n-alkanes, hopane biomarkers, PAHs, unresolved complex mixture (UCM), methyl n-alkanoates, and n-alkanones (Table 1).
The dominant n-alkanes ranged from C 16 to C 40 with maximum (C max ) concentrations of tetracosane or nonacosane (C max = 24 or 29) and total concentrations varying from 216.5 ng m −3 in winter to 382.9 ng m −3 in summer ( Table 1). The C max of the n-alkanes indicated that the major sources were from terrestrial plants (C max = 29) and petroleum residues (C max = 24) (Scalan and Smith 1970;Simoneit 1989). The carbon preference index (CPI (o/e) = ΣC i(o) /ΣC i(e) , Mazurek and Simoneit 1984) values for the entire n-alkane range were 1.5 ± 0.3 in autumn to 2.1 ± 0.4 in spring, also confirming a mixture of natural and petroleum sources. The concentrations of terrestrial plant wax n-alkanes were calculated according to Simoneit et al. (1991) and estimated to range from 42.0 ng m −3 in winter to 111.6 ng m −3 in summer. n-Alkanes from fossil fuel emission sources ranged from 105.2 ng m −3 in spring and 239.3 ng m −3 in summer (Table 1) indicating that their major sources in the Dhahran TSP are crude oil and petroleum products (the latter from both production and utilization in transport traffic).
The methyl n-alkanoate (e.g., fatty acid methyl ester) concentrations in the atmospheric TSP samples were 80.6 ng m −3 in spring to 134.8 ng m −3 in summer (Table 1). They ranged from C 10 to C 32 with C max at 16 (as acids), and their even-to-odd carbon preference indices (CPI (e/o) = TC even /TC odd ) varied from 7.9 ± 3.9 in summer to 10.1 ± 5.8 in spring (Table 1). Methyl n-alkanoates may be formed by transesterification in the extraction solvent from fatty acids or wax esters present. Their sources are Plasticizers and Flame Retardants similar to n-alkanoic acids from biogenic sources, including terrestrial vegetation, marine plants, microbial mats, and bacteria (Simoneit 1978;Perry et al. 1979;Volkman et al. 1980;Kharlamenko et al. 1995;Budge and Parrish 1998). The total concentrations of n-alkanones in the TSP varied from 8.1 ng m −3 in spring to 16.8 ng m −3 in summer with a C max at 18 (Table 1), indicating that they also were mainly from biogenic sources.
Hopane biomarkers were detectable in the TSP samples ranging from C 27 to C 35 (no C 28 ) with C max at 29 or 30 and concentrations varying from 2.36 ng m −3 in spring to 47.90 ng m −3 in winter. The C 31 and C 32 S/(S + R) ratios of the extended hopanes were ~ 0.6 for all seasons (Table 1). This confirmed that petroleum was the source of the hopanes in the TSP samples because they are typical for mature crude oils and petroleum-derived hydrocarbons (Peters and Moldowan 1993;Rushdi and Simoneit 2002a, b).
PAHs were detected in these TSP samples at total concentrations from 5.6 ng m −3 in spring to 42.7 ng m −3 in winter. The major PAH compounds included fluoranthene, pyrene, benzo [g,h,i] [g,h,i]perylene. The parent and alkyl phenanthrenes were at low concentrations (0.2 ng m −3 ) only in winter. The absence of such volatile low molecular weight PAHs was likely due to their state in the vapor phase not as TSP under the ambient high temperature of the region. The seasonal variation of the PAHs in the region was noticeably impacted by the air temperature and dilution effects of the TSP concentrations; for example, the minimum concentrations of the PAHs were observed in the summer and spring times where high levels of TSP and low temperatures were observed.
The unresolved complex mixture (UCM) of branched and cyclic hydrocarbons had concentrations from 209 ng m −3 in spring to 1231 ng m −3 in summer. The major sources of the UCM (Fig. 2) were generally due to emissions from utilization of fossil fuels and lubricant oils (Simoneit 1984(Simoneit , 1985Tolosa et al. 2004;Harji et al. 2008).
The total concentrations of POPs in the TSP of Dhahran were very high compared to the compound levels from natural and urban anthropogenic sources. The relative concentrations of POPs ranged from 17% in winter to 47% in autumn, whereas the natural inputs were 9% in summer to 21% in spring, and petroleum-related products varied from 39% in autumn to 67% in winter (Fig. 6). Therefore, the dominant sources of organic matter in atmospheric TSP of Dhahran city were inputs from fossil fuel emissions and synthetic industrial organic chemicals.

Health effects
Continuous exposure and uptake of these POP compounds through inhalation and dermal absorption will ultimately accumulate considerable quantities of these chemicals in the human body leading to potential health issues (WHO 1998(WHO , 2000Ghisari and Bonefeld-Jorgensen 2009;Aneck-Hahn et al. 2018;Doherty et al. 2019). The health effects of POPs may include skin lesions, respiratory dysfunctions, heart diseases, neuropsychological disorders, reproductive system diseases, and infant development (Foster et al. 2001;Latini 2005;Hauser and Calafat 2005;Kim and Park 2014). Phthalates are toxicants to humans and animals and can affect reproductive systems as endocrine disruptors in humans (Foster et al. 2001;Latini 2005;Heudorf et al. 2007;Kay et al. 2013). They may produce skin irritation with extended exposure to the chemicals (David and Gans 2003;Hauser and Calafat 2005), respiratory disease, childhood obesity, and neuropsychological disorders (Kim and Park 2014;Katsikantami et al. 2016). There is a relationship between phthalate exposure, mainly inhalation, and asthma (Jaakkola and Knight 2008;Bornehag and Nanberg 2010;Ventrice et al. 2013). Inhalation of phthalate aerosols increases the levels of inflammatory cells in the lung and bronchoalveolar lavage fluid (Kimber and Dearman 2010).
Phenyl phosphates are generally related to their contents of o-phenolic residues (Craig and Barth 1999;Mackerer et al. 1999). For instance, tricresyl phosphates are reported as neurotoxicants to humans and animals (Craig and Barth 1999;Patisaul et al. 2013). Recent studies have shown that there were significant correlations between neurodevelopment impairments in the exposure of children to phenyl phosphates (Castorina et al. 2017;Alzualde et al. 2018). These plasticizer and flame retardant compounds have been detected in tissue, milk, and urine samples (Sundkvist et al. 2010;Ding et al. 2016;Zhao et al. 2019). On the other hand, polychlorinated biphenyls were reported to have different toxic effects such as acne and pigmentation in various parts of the body (Kuratsune et al. 1972), skin rashes and irritation (Fischbein et al. 1979(Fischbein et al. , 1982Smith et al. 1982), cardiovascular disease and blood pressure increase (Kreiss et al. 1981;Smith et al. 1982), pulmonary dysfunction (Lawton et al. 1986), pregnancy loss and infant development (Allen et al. 1979;Fein et al. 1984;Gladen et al. 1988), and memory and cognitive function impairments (Kilburn et al. 1989;Nicholson and Landrigan 1994).
Recent studies have shown that BBP can cause a change in hormone availability in children and the increase body mass index in adults at 0.1-0.7 μg g -1 range, DIBP can cause behavioral changes in children at 0.1-0.5 μg g -1 , DBP can lower thyroid hormones in women at 0.2-2.8 μg g -1 , and DEHP can impact female fertility at 10-243 μg g -1 (Eales et al. 2022;Maffini et al. 2021). Accordingly, the European Union and the United States have implemented regulations for the uses of the exposure to phthalates, where the regulatory safe level of exposure (FfDs) have been defined at 35 μg g -1 for DEHP, 6.7 μg g -1 for DBP, 500 μg g -1 for BBP, and 0.08 μg g -1 for DIBP (Muafini et al. 2021). Our measured values were higher than the RfDs for DEHP (237-1794 ug g -1 ), DBP (138-984 μg g -1 ), and DIBP (43-302 μg g -1 ), but lower for BBP (3-9 μg g -1 ). The levels of these phthalate compounds potentially affect human health in the region and they should be regulated by the metropolitan authorities.
Further studies are crucial to access the toxicity of these plasticizers on humans due to inhalation by investigating the levels of these substances in smaller sized TSP such as PM 2.5 and PM 10 .

Conclusion
This is the first report on the occurrence and levels of POPs (Ps, NPs, and PhePhs) and PCBs in ambient TSP from Saudi Arabia. They were detected in all samples collected from Dhahran in the different seasons. High concentrations of Ps were from 253 ± 199 ng m −3 (74.0% of total plasticizers) in summer to 389 ± 335 ng m −3 (87.6%) in winter, with the major compounds in the order of DPPP, DBP, DEHP, and DIBP, respectively. The total concentrations of NPs were relatively low, ranging from 4.9 ± 2.3 ng m −3 (1.5%) in summer to 11.9 ± 12.5 ng m −3 (2.0%) in winter and comprising only DEHA and TEHM. The total PhePh concentrations were also low ranging from 4.1 ± 4.0 ng m −3 (1.1%) in spring to 13.3 ± 3.2 ng m −3 (3.4%) in summer, with TPhePh and DPhePhs as the major compounds. Total PCB concentrations ranged from 30.7 ± 19.3 ng m −3 (9.1%) in autumn to 65.6 ± 61.2 ng m −3 (21.6%) in summer, with the TCB congeners as dominant compounds.
The seasonal distribution of these POPs indicated that Ps and NPs had high levels during spring and low in summer, whereas PCBs and PhePhs showed the opposite trend as high during summer and low in spring. Significant correlations were found among the different plasticizer groups and their totals suggesting comparable local sources. Principal component analysis indicated that Ps and NPs were from the same sources, and PCBs and PhePhs were from different sources where the concentrations of PCBs were controlled by the levels of TSP in the atmosphere. The presence of the total plasticizers and PCBs in atmospheric TSP of Dhahran city was extremely high relative to the concentrations of the other typical urban organic compounds.
The presence of these POPs in the atmosphere and their human uptake via dermal exposure or inhalation will eventually affect public health by developing different types of illnesses such as skin irritation, pulmonary diseases, neurological disorders, carcinogenicity, and reproductive system diseases. Therefore, more studies are needed to measure the concentrations of such POPs in different ambient environments to identify their levels, major sources, and health effects.