Journal Archive

The study investigates fine dusts (PM_2.5) and distribution features of gaseous and particle PAHs from 6 spots in each 8 facilities (underground subway stations, child-care facilities, elderly care facilities, super market, indoor parking lot, terminal waiting room, internet café, movie theater). The descriptions of public facilities are shown in Table 1. The site survey of the study covered a total of 32 facilities in 4-5 groups for 4 months from July to November, 2012. In addition, the outdoor air is measured from 18 places. The cities under the survey include 3 large cities (Pusan, Incheon, Daegu) and 5 medium and small cities (Suncheon, Gwangyang, Yeosu, Jinju, Changwon).

Indoor and outdoor sampling was performed in agreement with the usual recommended practices (US EPA, 1990). Sample were collected approximately in the centre of the public facilities, for collecting particulate phase simultaneously at a human breathing height (1.5-1.8 m), distant from corners and as fas as possible, from obstruction (Masih et al., 2010). The outdoor level samples were collected at 4-5m above the road to protect samplers against vandalism (Menichini et al., 2007). 24-h samples were simultaneously collected, respectively.

The method of sampling indoor and outdoor air, pretreatment and analysis is based on the US EPA Compendium Method TO-13A (U.S. EPA, 1999) and the prior study (Kim et al., 2013; Wang et al., 2013) performed the PAHs evaluation through the sampling with the diameter <2.5 μm(PM_2.5).

The preliminary study was performed to check the indoor PAH detection rate. The survey shows that the PAHs detection rate (higher than 80%) is proper within the flow range of 4-5 L/min and the sampling time is configured at least 24 hours to minimize the error in the weight concentration of the PM_2.5 considering the PAHs features in high loss rates during the pre-treatment process. In addition, the PAHs surveyed in the study are analyzed by the PAHs standard (Quebec Ministry of Env. PAHs 24 Mix) provided by AccuStandard (AccuStandard Inc., U.S.A). The PAHs standard materials used in the preliminary survey uses the product of Supelco (EPA 610 mix, U.S.A).

The PM_2.5 and PAHs samples are taken by the Minivol portable sampler (PAS-201, Air Metrics, U.S.A) by connecting the PTFE filter (Teflon 47 mm, 1.0 μm, PALL Life sciences., U.S.A) and the PUF glass cartridge (polyurethane foam installed) to the small-sized sampler for 24 hours with the amount of 5 L/min. The PTFE filter to take samples of the PM_2.5 and particle PAHs is used after depositing into the acetone : methanol (7 : 3, v/v) solution, cleaning with the microwave for 2 hours and drying with the high purity nitrogen (N₂) to remove organic impurities before use. The pretreated filter weighs after measuring the moisture for 24 hours in the desiccator to measure the mass concentration of the PM_2.5. The filter is sealed into the petri dish (50Φ) made with the polystyrene for storage and carriage. The PTFE filter for sampling is stored in the thermo-hygrostat for 24 hours before and after the sampling, weighed by the analysis scale with more than 0.001 mg of sensitivity (AT261, Mettler toledo, Switzerland) for 3 times and the arithmetic average is taken. The weight is measured by the same method with the filter taken by the control filter before and after the sampling to minimize the error in the weight measurement due to temperature and humidity to calculate the weight concentration of the PM_2.5 and the weight difference before and after the measurement is applied to each sampling filter. The absorbent to sample the gaseous PAHs (polyurethane foam, PUF) is rinsed in the soxhlet extractor for 16 hours (6 cycles/ hour) with the order of methylene chloride-acetone, dried, wrapped in the aluminium foil and sealed in a glass jar before sampling. The PAHs analysis uses the Agilent GC/MS (HP-6890/HP-5973N) and applies the analysis procedure for the EPA TO-13A Method and the local air pollution process test standard (ES 01552.1) as mentioned before. The GC column is the HP-5 with the dimensions of 30 m length, 0.32 mm external diameter and 0.25 μm internal diameter and the sample is analyzed by injecting 1-2 μL each.

This study investigated 20 PAH substances selected out of 32 substances known to be carcinogenic or potentially carcinogenic by the International Agency for Research on Cancer (IARC) and the US EPA(Table 1). Table 1 shows the average RPFs based on tumor bioassay data with their associated range and relative confidence ratings, and an overview of the tumor bioassay database for this compound. Risk assessments and potency assessments of various individual PAHs and complex mixtures of PAHs have been attempted. BaP is the only PAH for which a database is available, allowing a quantitative risk assessment.

The study performs the degree management using PAHs standard, proxy standard and internal standard materials to raise the reliability for the analyzed materials. The degree management performs the linearity and dwelling times reproduction assessment of the calibration curves, detection limit, recovery factor assessment of pre-treated samples, recovery factor assessment of pre-treatment devices using standard materials and blank test assessment. The linearity assessment of the calibration curve shows proper linearity with higher than 0.98 of the correlation efficient (R²) for most materials and the reproduction of the dwelling time (RSD %) is less than 0.1%. The reproduction assessment of the instrument detection limit (IDL) shows that the reproduction based on the benzo (a)pyrene is proper with 2.06% of the RSD and the method detection limit (MDL) is 0.02 ng/μL based on the benzo(a)pyrene. In addition, the detection limit after conversion to the air concentration by applying the sampling flow (7,200 L) is 0.003 ng/m³ and the data below the figure are treated as N.D (Not Detected).

The PAHs extraction recovery rate (%) is assessed by injecting 80-100 μL of the substitute standard (SS: 10 μg/mL) and 30-50 μL of the internal standard (IS: 10 μg/mL) to calibrate the losses during the pre-treatment process for the all samples (particles and gases). The study uses 5 SS (Naphthalene-d8, Acenaphthened10, Phenanthrene-d10, Chrysene-d12 and Perylened12) and 2 IS (Benzo(a)pyrene-D12, Pyrene-D10) materials to assess the recovery and the average recovery of the gaseous collection material (PUF) satisfy the recovery rate (60-120%) recommended by the US EPA Method 8100 for 4 materials except the Acenaphthene-d10 including 65.4% for Naphthalene-d8, 127.2% for Acenaphthene-d10, 112.5% for Phenanthrene- d10, 78.1% for Chrysene-d12 and 60.7% for Perylene-d12.

In addition, the average recovery of the particle sampling media (filter) satisfies the recovery rates (60-120%) recommended by the US EPA Method 8100 for Naphthalene-d8 and Chrysene-d12 including 77.6% for Naphthalene-d8, 132.5% for Acenaphthene-d10, 127.6% for Phenanthrene-d10, 73.1% for Chrysened-12 and 57.7% for Perylene-d12. The average recovery through the extraction and concentration without the filter or the PUF using the PAH standard material (24 mix, 10 μg/mL) to understand the PAHs extraction recovery (%) for the pre-treated equipment (soxhlet extractor) is 88.8%. The recoveries of each PAH from the PUF and filters ranged between 60.7% to 127.2% and 57.7% to 127.6% respectively and its relative standard deviation (RSD) ranged from 0% to 11.1%.

The risk assessment in the study estimates the excess cancer risk (ECR) by applying various toxic equivalency factor (TEF) like the prior study of Kim et al. (2013). Therefore, the study first performs the Surrogate method of the PAHs, the assessment by applying the relative potency factors (RPF) method calculated by the concentration and the carcinogenic potency as the benzo(a)pyrene indicator and second, the assessment by applying the EPA(1993) TEF for 7 of 24 carcinogenic PAHs. Third, the Malcolm and Dobson (1994) method providing the TEF values for 24 types and last, the TEF values of the EPA(2010) are used to calculate the final PAHs risk degrees with 4 categories.

The study configures average users for each facility depending on the features of the public facilities, ages and gender features of the average users and determines the representing exposure factors (weight, breathing rate, dwelling time, visiting times, etc.) which form the WIES and the MIES. The survey covers the average number of visitors, ages, gender and dwelling time for the facilities. The number of subjects is 144 users (visitors) and workers and the exposure factors are finally figured based on the survey results. The body exposure may be calculated by considering the contamination concentration, inhalation rate, body weight, exposure frequency, exposure duration and lifetime. Here, the daily inhalation rate is applied by assuming the average exposure time and the exposure for 24 hours in the facilities based on the survey. The inhalation rate is 13.3 m³/day, daily average inhalation rate by referring to the recommended value of the US EPA. The body weight is 60 kg, average weight of Korean adults proposed by the Ministry of Health and Welfare, selected and applied as the representing value. The average life is 70 years, the life expectancy of Koreans surveyed by the National Statistics Office. The study finds out the medical facilities for the senior people is the highest (24 hours/day), followed by Childcare facilities (9.0 hours/day), internet cafe (3.6 hours/day), movie theater (3.5 hours/day), super market (1.4 hours/day), underground subway station and terminal waiting room (1.0 hour/day) and indoor parking lot (0.5 hour/day). The medical facilities for the senior shows the highest visiting frequency (360 times/month), followed by daycare centers (252 times/month), underground subway station (125 times/month), Internet cafe (103 times/month), super market (29 times/month), indoor parking lot (27 times/month), movie theaters (18 times/month) and terminal waiting room (15 times/month) (Table 3).

The study determines various toxic indicators of the PAHs carcinogens (carcinogenic potency, unit risk, exposure reference, POD) and applies safety coefficients from collected toxic data to evaluate the noncarcinogenic PAHs and to calculate the RfC. The carcinogenic potency evaluation or inhalation unit risk is calculated from the collected human carcinogenic data to evaluate the non-carcinogenic features of the PAHs.

As assessed by Kim et al. (2013), the study finally calculates the risk degree with (1) the method which expresses the relative cancer potency for individual PAH for the Benzo(a)pyrene (Yang et al., 2007) and (2) the method which applies the toxic equivalent quotient (TEQ) of the PAHs mixture using the TEFs of individual PAH(Chen and Liao, 2006).

The PM_2.5 concentrations measured from 32 facilities in 8 groups show that the internet cafe marks the highest value, followed by underground subway station, medical and child-care facilities, elderly care facilities, waiting room, indoor parking lot, super market and movie theater.

In particular, it is the internet café (PC-room) that marks the highest PM_2.5 concentration and the average concentration of 10 spots (2 spots for each cafe) is 73.3 μg/m³ (range: 6.8-185.2 μg/m³) (p<0.01) (Table 4). Castro et al. (2011) has investigated the indoor PM_2.5 ranged, from 37 to 82 μg/m³ (mean of 57.2 μg/m³) at the home influenced by tobacco smoke. The non-smoking home exhibited lower PM_2.5 revels, 8.3 to 22.5 μg/m³ (mean of 14.5 μg/m³). The prior study of Kim et al. (2013) shows that the PM_2.5 concentration of the internet cafe reaches 110.0 μg/m³ on average, much higher than that of the study (range: 83.5-138.5 μg/m³). Comparing such values to the PM_2.5 guideline of the WHO (average 25 μg/m³ for 24 hours, 10 μg/m³ on the annual average), the Internet cafe and the underground subway station are far beyond the standards and the concentrations in the elderly care facilities, terminal waiting room and indoor parking lots are similar to the standard values.

The indoor/outdoor concentration ratio (I/O ratio) of the PM_2.5 for 8 facilities in the study shows that the internet cafe is the highest (9.7), followed by the indoor parking lot (2.0), underground subway station (1.6), super market (1.5), child-care facilities (1,4), elderly care facilities (1.1), movie theater (1.0) and terminal waiting room (0.8), meaning that the indoor values are higher than those of the outdoor except the terminal waiting room. The internet cafe shows the lowest outdoor concentration (7.5 μg/m³) but the highest indoor concentration of 73.3 μg/m³.

As surveyed by Kim et al. (2013), most internet cafes are placed underground and not equipped with indoor ventilation and the sampling process seems to be affected by some smokers (Castro et al., 2011; Mitra and Ray, 1995). In addition, the indoor parking lot is a facility mostly with large malls and features insufficient ventilation, as well as shows high concentration due to the emission by cars with frequently visit and scattering dusts on the floor. In contrast, the terminal waiting room shows that the outdoor PM_2.5 is observed higher than the indoor environment and it is because the outdoor air is highly polluted due to vehicles and other transportation, as well as the emitted gas due to idling in the terminal. It is judged that the cinema shows low concentration because it is located in a large-sized multiplex building with mechanical ventilation compared to the internet cafe. The highest PM_2.5 pollution was found at site internet cafes (PC-rooms) area which might be influenced by human activity, such as smoking and cooking. Dust particles could be resuspened via human activities, recontributing to the indoor PM_2.5 (Wang et al., 2013). Exposure to PM and associated PAHs are of particular concern for both children and adults (Ohura et al., 2005).

The PM_2.5 exposure is related to deteriorating lung functions, increasing lung infection, respiratory system symptoms, deteriorating the cardiovascular system and causing chronic obstructive pulmonary diseases. Even worse, it may be a cause of oxidation stress in the human DNA, the important phase of forming certain cancers (Novotna et al., 2007).

The materials with 2-4 rings show high detection frequency in the gaseous phase out of 24 PAHs from the facilities and 7 materials like naphthalene, acenaphthylene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene show 100% detection rates and benzo(a)pyrene marks 68% detection rate. The study finds out that 13 of 24 materials show the detection rates higher than 80% and 5 materials are not detected, meaning that the materials with 5-6 rings show low detection rates. The PAHs are categorized into 3 groups including 2-3 rings, 4 rings and 5-6 rings (Schauer et al., 2003).

The acenaphthene shows the highest concentration of 30.87 ng/m³, followed by the phenanthrene of 18.93 ng/m³, naphthalene of 19.08 ng/m³ and these materials show relatively high concentrations (Table 5). Therefore, it may be said that the PAHs with 2-3 rings show high concentrations as a whole.

The PAHs with 2-3 rings are detected in the gaseous phase much and known that they mark relatively high concentrations and their emission sources are placed indoor (Castro et al., 2011; Slezakova et al., 2010; Lizhong Zhu, 2009; Fanf et al., 2004). The study also shows that the acenaphthene, phenanthrene, naphthalene and fluorene, PAHs with 2-3 benzene rings, mark high concentrations. The prior study of Kim et al. (2013) indicates that the internet cafe and the underground subway station show the high concentrations and both facilities commonly show high concentrations of the acenaphthene (38.37 and 28.17 ng/m³) and naphthalene (15.72 and 5.17 ng/m³). The prior study of Wang (2013) shows that the PAHs with 2-4 rings (Phe>Nap>Flu and Pyr) show high concentrations and reports that it is mainly due to the coal and wood combustion. The research facilities covered by the study do not perform the direct coal and wood combustion and it is judged that the internal and external sources of pollution from gas utilities, cooking (frying and oil combustion), smoking and incense burning (Masih et al., 2010) jointly contribute to the pollution.

The survey result of the materials detected with the highest concentration from all the studied facilities based on the particle PAHs concentration shows that the acenaphthene marks the highest concentration of 7.83 ng/m³ (Table 5). As the same with the study of Kim et al. (2013), the study shows that the acenaphthene marks the highest concentration among gaseous and particle PAHs. It is reported that the particle PAHs are detected from materials with 5-7 rings (Slezakova et al., 2010; Lizhong Zhu, 2009; Li et al., 2006) and the heavy-weight PAHs are mainly related to the particle materials (Pan et al., 2012). The study shows that the concentration distribution of the particle materials with more than 5 rings increases compared to the gaseous ones and the acenaphthene with 3 rings shows the highest concentration from all the facilities. The acenaphthene shows the highest concentration of 7.83 ng/m³ in the internet cafe and other substances show the concentrations with less than 1 ng/m³.

In conclusion, the study of Kim et al. (2013) and the annual study show that the naphthalene, acenaphthene and phenanthrene are the most crucial PAHs and in particular, Kim et al. (2013) shows that the acenaphthene records the high concentration among the particle PAHs, meaning that the gaseous PAH concentration distribution ranges 34.5-55.9%, lower gaseous concentration distribution compared to the study. As shown in the previous study, the study demonstrates that the particle materials take higher proportion due to much affected by physical environment like the temperature and humidity (Lu et al., 2008; Tsapakis and Stephanou, 2005).

Kim et al. (2013) shows that remaining 7 facilities other than the underground subway station exceed the benzo(a)pyrene concentration recommended by the WHO, 1.0 ng/m³ but the study evaluates it as an improved environment because the facility shows the level below the recommended value. It is expected to implement local situations and regulation on nonsmoking movement in the indoor environment including the internet cafe or large restaurants. It is reported that the tobacco smoking is the most important source of pollution of the PAHs and recently shows that 549 individual PAHs are caused by the tobacco smoking (Thielen et al., 2008).

The comparison of the indoor and outdoor ratio (I/O ratio) of the average naphthalene for 7 facilities shows that the child-care facilities marks the highest level, followed by the underground subway station and the internet cafe and the phenanthrene shows high level in the cinema and the underground subway station (Fig. 1). The annual prior study of Kim et al. (2013) shows the tendency in exceeding 1 in the underground subway station, followed by the child-care facilities and the internet cafe, demonstrating the clear existence of the indoor source of pollution. As similar to the study, Kim et al. (2013) contains the measurement for once (24 hours) per facility not in winter, but from June to October and the result does not measure the outdoor air quality. Therefore, it is estimated that the indoor sources of pollution and indoor in the public facilities affect more than the seasonal effect (Zhang and Tao, 2008) (Menichini et al., 2007). The distribution of PAHs between both phases predominantly depends on the physical characteristics of the compounds and physical conditions such as temperature and humidity (Lu et al., 2008). The seasonal variation of energy consumption in the residential sector that are mainly generated from combustion sources (Zhang and Tao, 2008).

Fig. 1. 
I/O (indoor/outdoor) Ratio of PAHs concentrations in various public facilities.

The comparison of Kim et al. (2013) and the study on the distributions of gaseous and particles PAHs for the facilities shows that the gaseous PAHs accounts for 69.8% of the total PAHs concentration and the distribution in other 5 facilities ranges from 84.1 to 92.8%. The reason why the gaseous concentration distribution in the internet cafe is low compared to other facility groups is that the PM_2.5 concentration is high, as well as the particle PAHs.

The result of the risk assessment based on the exposure scenario in the public facilities due to the PAHs proposed by the 4 TEF-adjusted methods is in Table 6.

The risk estimate shows that the excessive carcinogenic risk of the surrogate approach ranges 10^-8-10^-6 for each facility within the safe category and the internet cafe shows higher than 10^-6. Assuming the worst exposure of 24 hours/lifetime estimates that the surrogate approach shows the range of 10^-6-10^-4 for each facility. The excessive carcinogenic risk of the 7 carcinogens in the RPFs assessment ranges 10^-8-10^-6 and the internet cafe and the health and welfare centers for the senior show higher than 10^-6. Assuming the exposure of 24 hours/lifetime estimates the range of 10^-6-10^-4 for each facility.

The excessive carcinogenic risk of the Malcolm and Dobson (1994) RPFs assessment shows the range of 10^-8-10^-6 for each facility and the internet cafe (smoking/ non-smoking) and elderly care facilities show higher than 10^-6. Assuming the exposure of 24 hours/ lifetime estimates the range of 10^-5-10^-4 for each facility. The excessive carcinogenic risk of the EPA(2010) RPFs assessment shows higher than 10^-6 for each facility except the terminal waiting room and the super market. Assuming the exposure of 24 hours/lifetime estimates the level of 10^-5-10^-4 for each facility. The RPFs of 11 PAHs proposed by the US EPA (2010) shows 1 for the benzo(a)pyrene, 10 for the dibenzo(a,h) anthracene and 30 for the dibenzo(a,l)pyrene, meaning that the risk assessment is different depending on the concentration of each material. Kim et al. (2013) substitutes the TEFs values of the US EPA and estimates 1.78E-04 assuming the exposure in the basic scenario and in the worst case scenario (24 hours), the internet cafe and the indoor parking lot show the risk level of 10^-3 and other facilities mark the level of 10^-4.

The recent study of Castro et al. (2011) reports that the lifetime lung cancer risk exceeds the risk of 4.1×10^-3 for a smoking family, 1.7×10^-3 for a non-smoking family and 8.7×10^-5 (ng/m³)-1 (Ohura et al., 2004), the health-based guideline level and Wang et al. (2013) states that the general household has the risk of 10^-6-10^-5 due to the PAHs exposure of the PM_2.5. Therefore, the risk level shows difference depending on the features in the studies including the characteristics of the source of pollution in the indoor environment, smoking and external air(Wang et al., 2013; Zhou and Zhao, 2012; Zhang et al., 2009; Menichini et al., 2007; Ohura et al., 2004; Zhu et al., 2002). The limitation in the study is that the number of total samples is not enough and the risk assessment assumes the exposure for 24 hours in the facilities. The important uncertainties in our exposure scenario of potential exposures and health risks remain (Kim et al., 2012). In addition, we investigated 32 public facilities, the selected facilities and could not be to represent.