AIVC 11693 PERGAMON Building and Environment 34 (1999) 213-220 A territory wide survey on indoor particulate level in Hong Kong Thomas C. W. Tunga·*, Christopher Y. H. Chaob, John Burnetta, S. W. Pant, Raymond Y. M. Leec "Departmenr of Building Serrices Engineering The Hong Kong Polytechnic Unit-ersity, Hung Hom, Kowloon, Hong Kang b Depar1men1 of lv/echanicalEngineering The Hong Kong Unirersity of Science and Technology 'The Hong Kong Enrironmental Protection Deparrment Abstract Airborne particulates are a major air pollution problem in Hong Kong. Very high outdoor airborne particulate levels have been recorded in the outdoor monitoring stations managed by the Hong Kong Environmental Protection Department (HKEPD). However, information on the concentrations of indoor total suspended particulate (TSP) and particulate matters of aerodynamic size less than I 0 µm {PM 10) ha been scarce. In view of this. a territory-wide survey was conducted from September 1996 to January 1997 to investigate the indoor airborne particulate levels in SO residential apartments in Hong Kong. In this study, 50 residential premises were selected in 18 districts of Hong Kong covering both public housing and private housing. Two Mini-Vol sampling pumps were located al each site to collect both 24 h TSP ilnd PM 10 samples in filters which were analyzed by gravimetric method using a precision mas balance. The living habit . ventilation characteristics and other indoor activities were recorded in a survey form. The TSP level varied from 37.5 pg m-3 to 227.1 11g m-3 and the PMio level varied from 35. l µg m-3 to 161.6 µg m-3, which were much higher than the levels measured in western countries. PMio/TSP percentages varied from 49.7 to 100% (average 85.0%) which were also higher than the data obtained in other overseas studies. A high proportion of respirable content in the indoor environment indicated that there is a significant contribution from indoor activities on the residential premises, e.g. smoking, incense burning and cooking, etc. The findings have been useful for evaluating long term policy regarding environmental protection in the domestic environment. © 1998 Elsevier Science Ltd. All rights reserved. Key1rnrds: Indoor and outdoor; Particulate; PM,0; TSP 1. Introduction al. [3] the indoor to outdoor PM10 ratio was found to be about 0.46. Studies of indoor particulate level on residential prem­ Measurements have also been conducted in similar ises have been conducted by many researchers in different Asian cities such as Taipei. Li [4] reported mean indoor parts of the world. Early work conducted by Spengler et PM10 level of 83 pg m-3 and outdoor level of 107 µg m-3 al. [I] in the US showed that mean PM10 level in 35 homes in 15 homes in the Taipei urban area. Correlation of with non-smokers was 24.4 µg m -3, in 15 homes with one indoor PM1 0 to TSP has been studied by Kamens et al. smoker 36.5 µg m-1 and in 5 homes with two smokers as [5]. In their report the average PM10/TSP ratio at three high as 70.4 pg m-3• The corre ponding outdoor level US homes was 63%. PMIO/TSP ratio as high as 86% has was 21.1 11g m-3• An investigation was conducted by also been reported in the study conducted by Raiyani et Colome et al. [2] at 10 homes in Southern California on al. [6] for houses in India where the influence of cooking both indoor and outdoor PM10• The mean 24 h indoor activities was investigated. In Hong Kong, outdoor particulate levels are moni­ PMio concentration measured was 42.5 µm -3 while the correlated outdoor level was 60.8 µg m-3• Over 50% of tored on a daily basis but not much information has been the outdoor measurement and nearly 30% of the indoor reported for particulate level in the indoor environment measurements exceeded the 24 h California State Stan­ [7]. A pilot study on indoor particulate level wa con­ dard (50 µg m-3). In another similar report by Kado et ducted from September 1996 to January 1997 on 50 resi­ dential premi e located all over Hong Kong. Both total su pended particulate (TSP) and particulate matters with size le s than IO 11m (PM 10) were measured on a 24 h *Corresponding author. basis. Mean TSP and PMio levels at different districts 0360-1323/99/$-see front matter © 1998 Elsevier Science Ltd. All rights reserved l Pl!: S0360-l 323(98)00013-4 214 T.C. W. Tung/Building and £11L"iro11111en1 34 ( 1999) 213-220 were evaluated and correlation was also drawn between suggested that at least one cleaning should be done for the indoor and outdoor particulate levels obtained from every even sample . The amplin11: pumps were tested outdoor database developed by the Hong Kong Environ­ in the laboratory after ten amplings were taken to ment Protection Department. en ure that the flow rate \ a correct and no air leakage exi reel. or quality control purpo e, five of the sites were elec­ 2. Measurement ted for duplicate 'tests and the election wa made ·o that premi es in different di trict were included. Four Fifty re idential premi ·e were elected for thi tlldy. ampling pumps were u ed in each duplicate te l. Two The premises formed a r ugh representation of the popu­ were for TSP measurement and two were for Pi 1111 lation living in private and pllblic hou ing among the J 8 mea urement. Blank te ·t were performed on fi e filter . di tricL in Hong Kong. In the urvey. 29 pri ate pre111i es and 21 pllblic premises were elect d. Public prcmi es refer lo tho e hou ing estates managed by the H ng Kong 3. Results and discussion Government for familie u. ually with lower income. A questionnaire was designed for collection of site infor­ The number of occupants on each premises varied from mation. The information included di ·trict. building type. one to ix. Among the e 50 premi es, I 0% had smokers, building age group, elevation of premi e (number of 24% carried out incen e burning and 56% had cooking floors from ground level), room ·ize. room height, room activitie . The percentage of these sites that had cleaning v·olume and indoor fini hing materials. The area of the activitie during the ampling period was 56, 24% were premises varied from 5 m1 (a very small room) to 140 1n! located near construction sites and 42% near automobile (classified as a luxurious apartment in Hong Kong). The sources (main roads). Premises located near industrial elevation of the premises varied from the ground floor 10 areas amounted to 8%. Since the study was conducted the 35th floor. The que·tionnaire al o included infor­ from September to January, rain did not occur very fre­ mation on the indoor activities and ventilation charac­ quently. Only 6% of the measurements were done while teristics, date of measurement, window opening it was raining outside. Air conditioning was used in 12% frequency, ventilation and fan operation characteristics, of the sites during the measurement period and 4% of house keeping details, adjacent environment and the sites had their windows closed all the time. meteorological conditions during measurement. Table l shows the PM10 and TSP levels at each site, as Measurement started in late September 1996 and ended well as the ratio of PM 10 to TSP (%). Mean temperature in mid January 1997. Two Airmetric Mini-Vol Samplers and relative humidity of the indoor environment during were used in each test. One was for TSP and the other the sampling period were also recorded. The indoor tem­ one was for PM 10• Each was drawn at an air sampling perature varied from 16.7 to 29.0 C and the relative 1 flow rate of 5 I per min. (1 min- ) and the duration of humidity varied from 32.8 10 81.0%. PM 10 level aried each te t was 24 h. The particulates were collected by the from as low as 35.1 pg m-3 to a high a l6 l .6 11g m-3. filters in the sampling pumps. The samplers were located TSP level varied from 37.5 to 227. l pg/m '. PM 10/TSP at the site for 24 h and the tests were completed on the ratio varied from 49. 7 to 100%. Based on the re ults at following day. The sampling flow rates of the amplers these 50 sites, mean and standard deviation of PM 10 level ·were calibrated by a Primary Flow Calibrator (Trade­ on Hong Kong residential premises have been found to mark Gilibrator), manufactured by Gili<tn Instrument be 78.8 and 25.911g m-3 respectively. Mean and standard Corp. It was a bubble type flow calibrator with three deviation of TSP level were 93.9 and 33.2 pg m-3 respec­ interchangeable flow cell assembles: low range, standard tively. The mean indoor PM10/TSP ratio was 85.0%. and range and high range. The standard range was used for the tandard deviation was 9.7%. Tho ·e ites bowing the flow calibration in this study. Flow calibration was very high indoor particulate levels. e.g. Site 9, 12, 20. 28. conducted once every three tests. Whatman Grade QM­ 29 and 46, were found to be either very clo e to (\ ithin A Quartz Filters were used in collecting the particulate 200 m measured at ground level) con truction ·ites.