CONCENTRATIONS OF PARTICULATE MATTERS(TSP, PM 10, PM 2.5, AND PM 1 ) AND BIOAEROSOL IN THE ABOVE- AND UNDER-GROUND SUBWAY OFFICES IN SEOUL HJ Lim, HW Kim *, and SC Lee Dept. of Prevention medicine, College of Medicine, The Catholic university of Korea ABSTRACT This study investigated the indoor and outdoor air qualities of the offices located in the subway stations. Indoor and outdoor air samples were collected and analyzed for particulate matters(pm) including TSP, PM 10, PM 2.5 and PM 1, bioaerosol, CO 2, RH(%) and temperature. The levels of PM 10 in subway offices ranged from 27.5 to 267.9(85.3± 61.8) μg /m 3. Although PM concentrations in the under-ground offices (UO) were higher than those in the above-ground offices(ao), no statistically significant difference was found by the location of offices. Since the I/O levels of TSP, PM 10, PM 2,5 and PM 1 in the offices were higher, especially for smaller particle sizes, it is believed that human activities in the offices may be a contributing factor. In addition, it was found that PM concentrations in indoor air were seriously affected by smoking in the offices. Bioaerosol concentrations, ranged 10 to 540 CFU/m 3, showed no statistical difference between UO and AO. INDEX TERM; particulate matters, bioaerosol, indoor air, offices, I/O ratio INTRODUCTION In Korea, the Ministry of Environment promulgated a law to control indoor air quality (IAQ) of public places such as hospital, terminal, library and concert hall, etc. in 2004. In the law, specific numerical limits were set for 5 important indoor air pollutants and while guidelines were established for 5 other indoor air pollutants. However, such public places as school classrooms and offices were excluded because these places were regulated by the different guidelines and laws. Nonspecific building-related symptoms(brs) have been known as occupational and environmental health issues since 1980s (Burge 1987). Related environmental factors of BRS were investigated including temperature, humidity, VOCs, particulate matters, and bioaerosols. BRS and relevant IAQ environmental factors were known to be important factors that adversely affect workers productivity in the office (Wyon 2004). For outdoor air particulate matters, relationship between exposure to fine particle(<2.5 μm (PM 2.5 ) and changes in morbidity and mortality rates were reported. Outdoor fine particles can penetrate indoors, subsequently resulting increase of indoor level of PM 2.5 being affected by outdoor levels (Brauer 1989). Mucosal complaints of upper airway from offices workers in modern buildings were reported. It is speculated that these symptoms may, at least in part, be due to inhalation of particles suspended in the indoor air (Skyberg 2001). Therefore, characterization of particulate concentrations indoors may be critical to assess total exposure to particulate matter for indoor workers. This study is designed to evaluate the level of particulate matters(pm) in the under- and above-ground offices in subway stations in Seoul. The results can be used to assess impacts of environmental influence to health outcomes of the subway employees. RESEARCH METHODS In Seoul, there are eight(8) subway lines currently in operation. Each subway line has a number of offices that were located either above- or under-ground. Offices can be classified as management and station offices. Management offices are equipped with general office supplies including fax, computers, printers and copy machines. Station offices have not only office equipment but also other larger size equipment including monitors, communication systems, ticketing machine, and gate controller, etc. Although most of station offices have independent rooms for these larger size equipments, due to space limitation, some of them have no independent rooms and office workers have to share their workspaces with the equipments in the office. Working conditions of subway employees * Corresponding author email: hwkim@catholic.ac.kr 1596
including work time, shift type, number of employees at a given shift, space, HVAC, and office furniture, etc., and the indoor environments in the offices are very similar to each office. For this survey, total 25 offices, 17 under- and 8 above-ground offices, were chosen by random selection from the subway lines of 1 to 4. The survey was conducted from July 2004 to December 2004. In this study, PM was monitored by a light scattering device(dustmate, USA). The monitor measured particle sizes from 0.4 μm to 20 μm and detection range of mass is 0~ >60,000 μg /m 3. While indoor samplers were collected at the breathing zone (1.2~1.5m) of employees in the represented areas in offices, the corresponding outdoor samples were taken near the fresh air intake of the sampled subway station. For UO offices, intake air inlet is located on the pavement, which is very close to the adjacent road. The surface of the inlet is slightly higher than that of the pavement surface. To measure bioaerosols in indoor and outdoor air of under and above ground offices, one stage impactor(skc co.) was used with a 9cm petri dish contained MEA media in this study. Flow rate used was from 28.3 to 30.0L/min, and sampling time was from 5min to 10min. After sampling, sampling dishes were incubated at 30 for seven days. RESULTS Levels of particulate matters and bioaerosol The indoor concentrations of TSP, PM 10, PM 2,5 and PM 1 in the offices were shown in Table 1. PM 10 concentrations were under the Korean standard of 150 μg / m3 set by the Ministry of Labor and the Ministry of Environment, except three(3) under ground offices. Six offices located above-ground had no HVAC system installed. For two of these buildings, windows were installed but cannot be opened by workers. The concentrations of fungal spores in the underground offices, ranged 10 to 540 CFU/ m3, were relatively higher than that of above-ground offices. The I/O ratios of fungal spore in both offices were 0.9 to 3.1. Table 1. The concentrations of particulate matters and bioaerosol in offices range(mean±s.d.) Position Above Under TSP ( μgm3 / ) PM 10 ( μgm3 / ) PM 2.5 ( μgm3 / ) PM 1 ( μgm3 / ) Fungi I-45.5~156.0 (85.8±34.3) I-27.5~93.9(54.0±19.6) I-12.8~31.1 (20.8±6.2) I-5.6~13.4 (8.5±2.8) I-20-226 (104±72) O-131.4-245.1(192.3±44.7) O-87.0~166.1(112.4±23.1) O-15.1~39.6(26.6±7.3) O-4.8~12.9(9.7±2.5) O-10~240 (108±73) I-64.1~377.8(150.7±105.7) I-39.6~267.9(102.0±70.3) I-19.5~122.2(43.3±27.9) I-7.1~40.4 (15.3±8.8) I-23~540 (191±182) O-151.7~383.3(227.5±72.5) O-84.4~196.9(127.1±35.5) O-15.1~77.5 (18.5±39.8) O-4.8~33.0 (15.0±8.4) O-67~400 (164±114) Although no statistical significant difference was found in terms of concentrations of PM regardless of location of the offices, higher outdoor PM levels were measured at the UO compared with that of at the AO. These trends were noticed at the offices located at outskirt of the city. It could have been attributed to the volume of traffic nearby the offices located. I/O ratio of PM in air Since the I/O ratio has been used to evaluate the level of pollution between indoor and outdoor air, this study also utilize the ratio to express indirect indicator of pollution and to imply a source relationship. Table 2 showed the range and mean±s.d. of the I/O ratios of TSP, PM 10, PM 2,5 and PM 1 for the above- and under-ground offices. Despite higher PM levels of outdoor air for UO than those for AO, the I/O ratios of UO were higher than those of AO. It implies that either there may be a particulate generation source in the indoor or fine particulates can be migrated from other sources in the indoor. It was also found that the smaller the particle sizes, the larger the I/O ratios of the indoor and outdoor air. 1597
1.4 I/O ratios of TSP, PM 10, PM 2.5 and PM 1 1.2 1.0 0.8 0.6 0.4 0.2 above-ground offices Under-ground Offices Total 0.0 TSP-I/0 PM10-I/O PM2.5-I/O PM1-I/O Figure 1. I/O ratios of TSP, PM 10, PM 2,5 and PM 1 for above and under-ground offices* Table 2. I/O ratios of TSP, PM 10, PM 2,5 and PM 1 for above and under-ground offices Offices TSP- I/O PM 10-I/O PM 2.5-I/O PM 1-I/O Above-ground 0.78~0.28 (0.45±0.17) 0.86~0.27 (0.49±0.20) 1.12~0.58 (0.79±0.16) * 1.20~0.51 (0.91±0.25) Under-ground 2.04~0.22 (0.45±0.17) 2.15~0.31 (0.81±0.52) 2.18~0.47 (1.15±0.25) * 2.12~0.48 (1.13±0.50) *p<0.05 Relationship of particulate matters in indoor and outdoor air of subway offices The contribution of PM 10 to TSP, PM 2,5 and PM 1 to PM 10, and PM 1 to PM 2,5 for indoor and outdoor air in subway offices were presented in table 3. Compared with outdoor air, PM 10 of indoor air both in the under and above offices were well correlated with TSP. On the other hand, the ratio of PM 2,5 and PM 1 to PM 10 in indoor air of AO was not well correlated than that of UO. Table 3. Relationship of TSP, PM 10, PM 2,5 and PM 1 at subway offices Offices PM 10/TSP (R 2 ) PM 2,5 / PM 10 (R 2 ) PM 1/ PM 10 (R 2 ) PM 1/ PM 2,5 (R 2 ) Above-ground Under-ground I-0.64±0.04(0.9825) O-0.59±0.09(0.6196) I-0.68±0.05(0.9776) O-0.57±0.09(0.7569) I-0.40±0.10(0.4209) O- 0.24±0.05(0.5989) I-0.45±0.09(0.9034) O-0.31±0.15(0.4348) I-0.17±0.05(0.3031) O-0.09±0.03(0.1887) I-0.17±0.05(0.8365) O-0.12±0.05(0.3340) I-0.41±0.03(0.9589) O-0.37±0.04(0.7334) I-0.36±0.04(0.9134) O-0.36±0.04(0.9645) The R 2 of PM 10 /TSP, PM 2,5 /PM 10, PM 1 /PM 10 and PM 1 /PM 2,5 in indoor air was higher than that of outdoor air. On the other hand, when taking the location into consideration, the R 2 of PM 2,5 /PM 10, and PM 1 /PM 10 of indoor air for the AO were lower than those for the UO. Effect of smoking to indoor air pm in office 600 The level of TSP, PM 10, PM 2.5 and PM 1 in indoor 500 400 300 200 100 smoking in office TSP PM10 PM2.5 PM1 Guideline(PM10) 0 0 20 40 60 80 100 Time(min) Figure 2. Concentration of particulate mattes by time due to smoking in indoor air. 1598
Fig 2 showed changes in concentration level of particulate matters by time in an under-ground office when an employee smoked. These results showed clearly that the concentrations of particulate matters were significantly affected by smoking. The mean concentration level of PM 10 was 240.1±73.7 μg / m3 (118.1 to 404.6 μg / m3 ) which was over the PM 10 guideline of 150 μg / m3. It took about an hour for PM 10 concentration to decrease under the guideline. The decrease in PM concentration was achieved with a wall-mounted small fan. Though the company to improve indoor air quality provided HVAC system and supplemental air cleaner, these systems were not functioning properly. The results suggest that strong enforcement of smoking ban in the office is needed and improvement and proper maintenance of HVAC system is required. DISCUSSION In this study, only PM concentrations were measured and no chemical and physical properties of the particulates were analyzed. Further studies are needed to know exact nature of the PM compositions. Kruse(2002) reported that particulates in indoor air of offices were composed of concrete, gypsum, other mineral particulates, iron oxide, other inorganic particulates, skin scales, organic fibers, other organic particulate and aggregates of small particulates. Kim(1994) identified cements, iron and soil in the PM samples collected at the subway platform. These studies indirectly suggest the characteristics of PMs that may be expected within the offices. Liu (2004), using a similar light-scattering measurement equipment, reported the I/O ratios of PM in different indoor environments, including computer rooms, offices, classrooms, libraries, supermarkets, copy rooms, laboratory, and underground. The average I/O ratios of PM in offices were 0.484(TSP), 0.534(PM 10 ), 0.705(PM 2.5 ), and 0.692(PM 1 ). The I/O ratios of PM showed an increasing tendency with decreasing particulate sizes. In addition, Liu (2004) reported that the ratios of PM 10 /TSP, PM 2,5 /PM 10, and PM 1 /PM 10 in offices were 0.561, 0.452 and 0.232, respectively. A similar trend was also found in this study. These results may indicate the ratios of the smaller particulate sizes can be used as an indicator of status of particulate matters in indoor air quality Previous studies showed that smoking indoor would be the most important source for PM among many sources. The ranges of PM 2.5 were 32 to 50 μg / m3 (Lindai 2003) and 20 to 100 μg / m3 (Brauer 2000). The PM 2.5 level of this study was higher than these studies. No direct comparison, however, is advisable because the devices used, size of offices, and number and location of smokers in the offices in these studies were different. CONCLUSION AND IMPLICATION In this study, we evaluated levels of particulate matter in the offices that were located under- and above-ground subway stations. All PM levels in the offices surveyed except three offices were within the current governmental guidelines. Although no serious indoor air quality problems were found, it is strongly recommended to maintain PM levels within guidelines. Since I/O ratios of UO were higher than those of AO, more efforts should be directed to improve indoor air quality in UO. Further studies are needed to evaluate the relationship of indoor and outdoor level of PM, particularly for smaller particle sizes, outdoor and indoor PM sources, and the HVAC system and PM. REFFERENS Brauer M., Koutrakis P. and Spengler JD. 1989 Personal exposure to acidic aerosols and gases. Environmental Science and Technology Vol 23, pp1408-1412. Brauer M., Hirtle R., Lang B. and Ott W..2000 Assessment of indoor fine aerosol contributions from environmental tobacco smoke and cooking with a portable nephelometer. J. Exposure analysis and Environmental Epidemiology. Vol10, pp 136-144. Burge S., Hedge A., Willson S., Bass JH. and Rorberston A.1987 Sick building syndrome: a study 4973 offices workers, Ann Occup Hyg Vol 31, pp493-504. Kim DS., Kim SD., Kim YS., Shin EB. and Lee TJ.. 1994 Quantitative determination of Aerosol contribution in Seoul metropolitan subway stations. J. of KSEE, Vol 16(3), pp309-319. Kurse K., MadsØ L., Skogstad A., Eduard W., Levy F., Skulberg K. and Skyberg K.. 2000 Characterization of particle types in modern offices. Proceedings of the 9 th International Conference on Indoor Air Quality and Climate Indoor Air 02, Montersy, Clifornia. : Indoor Air 02, Vol 1,pp 880-884. Liu Y., Chen R., Shen X. and Mao X.. 2004 Winter indoor air levels of PM 10, PM 2.5 and PM 1 at public places and their contributions to TSP Environment International Vol30, pp 189-197. Lidia M., Congrong H., Jane H., Kerrie M. and Dale G. 2003 Characteristics of particle number and mass concentrations in residential houses in Brisbane, Australia. Atmospheric Envrionment. Vol. 37, pp. 4195-4203. 1599
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