Developing an indoor air quality index system based on the health risk assessment

Transcription

1 Indoor Air 2008, August 2008, Copenhagen, Denmark - Paper ID: 749 Developing an indoor air quality index system based on the health risk assessment H. Wang *, C. Tseng and T. Hsieh Institute of Environmental Engineering and Management, National Taipei University of Technology, Taiwan, Taipei * Corresponding t @ntut.edu.tw SUMMARY Many countries have set up indoor air quality standards or guidelines to protect human health in recent years. In Taiwan, however, current studies of the indoor environment index are based on the design of building and air conditioning, with the focus on comfort and energy saving. Therefore, the indoor air quality index (IAQI) system is developed in this research based on the results of risk assessment, epidemiology studies, and current regulations and standards. Eleven major indoor air pollutants are discussed: PM 10, PM 2.5, O 3, CO, CO 2, HCHO, TVOC, bacteria, fungi, SO 2, and NO 2. The developed IAQI system, based on the two classes of Taiwan indoor air quality guideline (IAQG), uses the similar scale of the U.S. ambient air quality index (AQI) system. The above pollution concentrations are defined as the IAQI ratings of 100 (IAQG-class I) and 150 (IAQG-class II) to develop a local index system for the human health protection in Taiwan. The investigation of IAQI for various building types is presented in this paper as well. KEYWORDS Air quality index (AQI), Air quality guideline (AQG), Risk assessment, Cancer risk assessment, Hazard quotient (HQ) INTRODUCTION The purpose of the Air pollution control act is to protect people health. However, people stay indoor environment higher than 90% of their total time every day in the present day, and this shows an importance of the indoor air quality in human health effects. Numerous kinds of air pollutants and sources indoors could damage health (such as: human activities, decoration materials, furniture, air-conditioning system, and outdoor air pollutants etc) (Spengler and Sexton, 1983), and different types of indoor air pollutants cause different health effects, which makes the evaluation of indoor air quality more complex. In addition, although the partial indoor air pollutants can only cause discomfort health effect slightly to human body without threat of life, the possibility of chronic illnesses or cancer could be increased if people expose under the polluted air with lower concentration of emission in long term. (Jones, 1999) Therefore, the research adopts the methodology of air quality index (AQI) developed by U.S. Environmental protection agency (U.S. EPA), and it is based on the viewpoint of health risk to set up an indoor air quality index (IAQI) system that can be applicable and simply estimates in Taiwan local area. Air quality index (AQI) In 1999, U.S. Environmental protection agency (EPA) issued a standard air quality index (AQI) for ambient air quality. The AQI provide an index report for daily air quality. The real time information from AQI will indicate people how clean or polluted in breathing air and the

2 possible health effects in both short term and long term. The AQI is calculated by U.S. EPA including five major air pollutants (i.e. O 3, PM, CO, SO 2, and NO 2 ) for human health protection. The range of AQI value is from 0 to 500, including 0, 50, 100, 150, 200, 300, and 500. The higher AQI level shows higher level in air pollution and health damage at the same time. The feature of this index system is to add statements to unhealthy groups (people from sensitive groups). For example, the value of 50 represents a good air quality while the AQI value of 100 represents the air quality to meet the National ambient air quality standard (NAAQS). The AQI value of over 100 indicates the unhealthy group. The purpose of AQI value is established for human health protection. Indoor air quality guideline (IAQG) The current ambient air quality index in Taiwan, Pollution standards index (PSI), is mostly set up to consider with the general public, but not focus on the sensitive population who spend more time indoor. The indoor air quality for sensitive population (such: children and elderly who require higher indoor air quality) has gained more attentions in Taiwan. Therefore, Taiwan EPA announced Indoor Air Quality Guideline (IAQG) in Dec Nine major air pollutants are included: PM 10, PM 2.5, CO 2, CO, O 3, HCHO, TVOC, bacteria, and fungi. For providing better indoor air quality for sensitive population, the values of guideline are divided into two classes, the class I guideline with high IAQ requirement is applied for buildings with sensitive population (IAQG-I), and the class II guideline is applied for buildings with general public (IAQG-II). (EPA R.O.C, 2005) Due to the lack of development of indoor air quality index in many countries, people usually consult with U.S. EPA AQI system for air quality. For this reason, this study based on the AQI system develops an IAQI system for local area. The developed indoor air quality index is based on the Taiwan IAQG and health risk assessment mainly. It can provide the public with a meaningful measure of real time indoor air quality and promote the management of indoor air quality. METHODS Nine indoor air pollutants are included in Taiwan IAQG: PM 10, PM 2.5, O 3, CO, CO 2, HCHO, TVOC, bacteria, and fungi. However, we consider other air pollutants (NO 2 and SO 2 ) as major indoor air pollutants in this research because their health impact is not less than other IAQG pollutants. Therefore, eleven major indoor air pollutants were discussed here. Moreover, the IAQI system is developed based on the results of risk assessment, epidemiology studies, and current regulations and standards, etc. The following pollution concentrations are defined as the IAQI values of upper limit to develop a local index system for the human health protection in Taiwan. Health risk analysis EPA is to develop the human health risk assessment. The risk assessment process can be divided into four major sections including: hazard identification, dose response assessment, exposure assessment, and risk characterization. Firstly, hazardous situations can be identified. The more likelihood of human exposures in air pollution affects human health that is quantified in the second and third steps. In the final step, the exposure assessment is integrated to characterize the whole risk of a hazard. Through the performance of risk assessment, we can understand the processes of human health problems that are caused by indoor pollutants in the indoor environment. The damages of indoor air pollutants are included two substances: carcinogenicity and non-carcinogenicity. In this research, we have to divide the IAQI values with their correspondence concentration between cancer risk

3 assessment and non-cancer hazard index assessment. Therefore, the health risk assessment can be explained as follows: Cancer risk assessment HCHO is only one that contains carcinogenicity substance in Taiwan IAQG. Therefore, a level of 1 in 1,000,000 was used as the acceptable level of cancer risk for the cancer risk assessment standard of HCHO. The cancer risk is calculated from Eq. (1), Cancer risk=contaminant Concentration (mg/m 3 ) Unit risk factor (URF)(mg/m 3 ) -1 (1) The URF is the unit risk factor of cancer substance for HCHO, the URF is 1.3*10-8 (mg/m 3 ) -1, provided by U.S. EPA IRIS database. Non-cancer hazard quotient (HQ) assessment Non-cancer risk assessment is to calculate hazard quotient (HQ) ratio. The HQ values calculated from Eq. (2) are for unitary contaminant. If the calculated HQ is less than 1.0, there is no adverse on health effect at present exposure contaminant concentration. If the calculated HQ is greater than 1.0, it is expected that damages occur on health at present exposure contaminant. The HQ ratio can indicate the level of damage on human health. When value of HQ is larger, at the same time, the adverse on health effects will be larger simultaneously. HQ = Non - cancer intake dose (mg/kg - day) Non - cancer ID (mg/kg - day) = Permission exposure dose of lifetime (mg/kg - day) PEDL (mg/kg - day) (2) The Non-cancer ID is the intake dose of human (mg/kg-day), and the PEDL is the permission exposure dose of human lifetime (mg/kg-day) Permission exposure dose of lifetime (PEDL) According to the level of risk degree and estimated evaluation of various conditions, the permission exposure dose of lifetime (PEDL) is calculated to estimate the lifetime intake dose of each human body exposed in air pollution in order to exam the safety dose that allow people to expose for long-term or lifetime without serious health damages. For health risk assessment, human factors of various groups (including sensitive population) needs to be considered for calculating the lifetime risk value of exposure level for human health. For this research, the Taiwan IAQG-I does, adopted as a permissible level of indoor environmental priority, can calculate the level of the PEDL base on the sensitive population worst case (stern condition), such as: maximum breathing, and longest time and longest term. The reason is to provide a good design to protect general human health including the sensitive population. In the non-cancer risk estimation, the definition of the PEDL is similar with RfD (Reference dose). The RfD is calculated by No-observable-adverse-effect-level (NOAEL) or Lowestobserved-adverse-effect-level (LOAEL) division factor of safety (FS) (the level is 10) generally. The parameters of interrelated with safety coefficient multiple, referral conditions, and safety coefficient are used to assess for every air pollutants of indoor air from Table. 1. The permission exposure dose of lifetime (PEDL) is calculated by Eq. (3), PEDL (mg/kg-day)= C IAQG 3 3 (mg/m ) IR (m /h) ET(h/event) EF(events/yr) ED(yr) BW(kg) AT(days) Factor of Safety (FS) = ID IAQG (mg/kg day) FS (3) The ID IAQG is the permissible intake dose, is calculated by IAQG-I (except the ID IAQG of the

4 PM 10 is calculated by Class II), and FS is the factor of safety is determined from Table 1. Table 1. The determination of safety coefficients with consider factors. Coefficient The meanings of consider factor Symbol number 10 The variability of sensitive for human A 10 Animal to human extrapolations B 10 The highest dose administered that fails to elicit an adverse effect, NOAEL. (No-observed-adverse-effect-level, NOAEL) C In this study, the PEDL parameter of risk assessment is an important factor, so PEDL must be calculated base on the Taiwan IAQG-I, the parameters of human factors (Table 2) from the sensitive population including breathing rate of maximum, and exposure parameters which means the longest exposure time (A.P. Jones, 1999). The purpose of PEDL is to provide a good design in order to protect general human health including the sensitive population. The results of the PEDL in this research show as Table 3. Table 2. Parameters of human factors and exposure factors. Human factor Adult Child (9~12 Year of age) Average Worst case Average Worst case Inhalation rate IR (m 3 /h) Exposure time ET (h/event) Exposure frequency EF (events/yr) Exposure duration ED (yr) carcinogenic non-carcinogenic Body weight BW (kg) Average time AT (days) carcinogenic non-carcinogenic Table 3. Evaluation of permission exposure dose of lifetime (PEDL). IAQ guideline ClassⅠ ClassⅡ C IAQG-Ⅰ (mg/m 3 ) Factor of safety Consider symbol PEDL (mg/kg-day) Unit risk (mg/m 3 ) -1 HCHO (ppm) E-8 TVOC (ppm) C PM 10 (mg/m 3 ) ( IAQG Ⅱ ) 10 C PM 2.5 (mg/m 3 ) C CO (ppm) C CO 2 (ppm) C O 3 (ppm) A*C Bacteria (CFU/m 3 ) Fungi (CFU/m 3 ) SO 2 (ppm) (2 ppm-osha) 100 A*C NO 2 (ppm) (3 ppm-osha) 100 A*C INDOOR AIR QUALITY INDEX (IAQI) SYSTEM This research firstly adopts the methodology of AQI to set up the range of IAQI value from 0 to 500, including 50, 100, 150, 200, 300, and 500. The IAQI value of 100 and 150 corresponded with the concentration in the Taiwan IAQG standard. Other IAQI values of 50,

5 200, 300, and 500 corresponded with the concentration ranks by several reference resources as follows: U.S. EPA AQI system, PSI system of Taiwan, and the NIOSH (National institute for occupational safety and health) defined limits concentration included the TWA (Time weighted average), STEL (Short term exposure limit), and IDLH (Immediately dangerous to life and health). Detail descriptions are listed at Table 4: 1. TLV-TWA: is the amount of chemical in the air that most workers can be exposed. It is based on working an 8-hour work every day and 40-hour work every week. 2. TLV-STEL: is the amount of chemical in the air averaged over 15 minutes that should not be exceeded during the work shift without irritation, chronic illness, and un-renewal harm. 3. IDLH: that poses a threat of exposure to airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment. Workers should not be in an IDLH environment for any length of time unless they are equipped and protected to be in that environment. Table 4. IAQI values are evaluation for IAQI system. IAQI value Color Significance instruction Method of evaluation Applies 0~50 ( Good) 51~ 100 ( Moderate) 101~ 150 (Unhealthy for sensitive groups) 151~ 200 (Unhealthy) 201~ 300 (Very Unhealthy) 301~ 500 (Hazardous) Green little or no risk Yellow acceptable air quality poses, and sensitive population or respiratory symptoms are concerned Orange sensitive population have health effects with the exposure of this air quality Red each individual could have health effects for long-term exposure Purple everyone has more serious health effects for short-term exposure Maroon everyone has health warning of emergency conditions Highest exposure factor of sensitive subpopulations to calculate upper limit for permissible health risk 1. IAQG-Ⅰ 2. Base on the highest exposure factor of the sensitive population 1. IAQG-Ⅱ 2. Base on the average exposure factor of adults The IAQI value is set up by the ranks of reference resource, to wit: U.S. EPA AQI; Taiwan PSI; IDLH The IAQI value is set up by the ranks of reference resource, to wit: U.S. EPA AQI; Taiwan PSI; IDLH The IAQI value is set up by the ranks of reference resource, to wit: U.S. EPA AQI; Taiwan PSI; IDLH All types of building are allowable For IAQG -Ⅰ For IAQG -Ⅱ short-term exposure (15 min) for public location All types of building are unallowable All types of building are unallowable Calculating Indoor Air Quality Index (IAQI) Value All on-site concentration of indoor air pollutants to combine with IAQI system (Table 5). IAQI values are calculated by interpolation method for each air pollutants. The IAQI value Q is calculated by Eq. (4): Q = ( Pi ( Q i - Po ) ( C - Qo ) + Po - Q ) o (4) where Q is the IAQI value of indoor air pollutant, C is the on-site concentration of indoor air pollutanti is greater than or equal to the on-site boundary value of air pollutant concentration corresponded with IAQI value, and Qo is smaller than or equal to on-site boundary value of air pollutant concentration corresponded with IAQI value, and Pi is greater than or equal to boundary value of IAQI value corresponded with on-site air pollutant concentration, Po is smaller than or equal to boundary value of IAQI value corresponded with on-site air pollutant concentration.

6 According to the Q value for each air pollutants calculated, then the maximum IAQI value can be considered as the indoor IAQI value, shown as Eq. (5): IAQI = Max Q Q HCHO CO2 O3 TVOC PM10 Bacteria PM 2.5 Fungi CO SO2, NO2 (5) Table 5. Indoor air quality index (IAQI) system. HCHO TVOC PM 10 IAQI PM 2.5 CO value (ppm) (ppm) (μg/m 3 ) (μg/m 3 ) (ppm) CO 2 (ppm) O 3 (ppm) Bacteria (CFU/m 3 ) Fungi (CFU/m 3 ) SO 2 (ppm) NO 2 (ppm) 1hr 1hr 24hr 24hr 8hr 8hr 8hr Maximum Maximum 24hr 1hr (10) * 0.3* 15* 10* 0.2* 350* 0.01* 200* 600* 0.02* 0.03* 100 IAQG -Ⅰ 0.04* 0.9* 60 (7) 45* 2.0 (7) 600 (7) 0.03 (7) 500 (7) 800 (8) 0.06* 0.10* 150 IAQG -Ⅱ 0.10 (7) 3.0 (7) 150 (7) 100 (7) 9.0 (7) 1000 (7) 0.05 (7) 1000 (7) 1000 (7) 0.15* 0.25* (6) 4.6 (9) 350 (11) 135 (12) 15.4 (4) 5000 (6) 0.12 (4) 1500* 2000* 0.30 (4) 0.60 (11) (5) 21.4 (9) 420 (11) 250 (4) 30.4 (4) (5) 0.37 (4) 3500* 4000* 0.60 (4) 1.24 (4) (2) 38.0 (9) 600 (11) 500 (4) 50.4 (4) (2) 0.60 (4) 9000* 10000* 1.00 (4) 2.04 (4) * calculate value RESULTS The test results of IAQI for various building types Finally, thirty IAQI results for various building types in Taipei Metropolitan Area were studied, including: hospitals (H), kindergartens (S), office buildings (O), libraries (L), exhibitions (E), shopping malls (M), and hotels (HT). Furthermore, the IAQI results of all building types must be analyzed and discussed with human health in this research. The test results should let everyone understand real time IAQ easily and the major source of indoor air pollutant for improving the IAQ. The results of IAQI analysis for various building types are summarized at Figure 1 and studied below Class I Class II IAQI average 160 IAQI guideline: 150 IAQI leve IAQI guideline: H S O L E M HT Type of building Figure 1. The IAQI values for various building types. Five hospitals (H1~H5) were examined with the IAQI values of 136 (116~155); all were higher than IAQG (100). Seven kindergartens (S1~S7) were examined with the IAQI values of 140 (95~157). The IAQI values of six examined kindergartens were higher than IAQG (100) among most examined kindergartens; the percentage of unqualified buildings was

7 85.7%. The IAQI values of 144 (125~163) were in eight office buildings (O1~O8), including four Office buildings were unqualified with IAQG (150), the percentage of unqualified buildings was 50%. The IAQI values were 130 (106~153) in two libraries. IAQI value of only one examined library was higher than IAQG (150), the percentage of unqualified buildings was 50%. Three exhibition halls (E1~E3) were examined, the IAQI values of 155(133~179). IAQI values of two exhibition halls were higher than IAQG. The percentage of unqualified buildings was 66.7%. The IAQI values were 137 (117~152) in three shopping malls (M1~M3). Only one mall was unqualified with IAQG (150). The percentage of unqualified buildings was 33.3%. Two hotels (HT1 and HT2) were examined, the IAQI values of 157 (152~162), both were higher than IAQI guideline (150). Test results indicate that indoor HCHO in hotels should be controlled firstly because it is carcinogenic and dangerous to human health. For most class I buildings (hospitals and kindergartens), IAQI values were higher than IAQI guideline (100-Moderate). The IAQI values of Exhibitions and Hotels were averagely higher than IAQI guideline (150-Unhealthy for sensitive population). In addition, although the IAQI values of office buildings, libraries, and shopping malls of 144 (125~163), 130 (106~153), and 137 (117~152) individually were compliance with IAQI guideline (150), but the IAQI values were still higher than IAQI guideline value in any single building. CONCLUSIONS AND SUGGESTIONS An indoor air quality index (IAQI) system is developed based on the results of risk assessment, epidemiology studies, and current regulations and standards. According to the investigation of IAQI for various building types, the following conclusions may be made: 1. For hospitals, the major source of indoor air pollutant was CO 2, followed by O 3, and bacteria. The results can be explained that the characteristics of indoor air pollution for hospital include: numerous people and patients, and air pollutants from traffic emission near by hospital were lead to high air pollution indoor. 2. For kindergartens, the major source of indoor air pollutant was CO 2, followed by O 3, and HCHO. The characteristics of indoor air pollution in kindergartens were indicated including: numerous children, general use of air cleaner (with anion or ozone), the use of wooden furniture or floor, and other decoration in the indoor environment. 3. For office buildings, the major source of indoor air pollutants was CO 2, followed by HCHO, and O 3. The results can show that the characteristics of indoor air pollution for offices buildings, including: numerous people with poor ventilation, a large portion of wooden material for decoration, the general use of copy machine and printer in the indoor environment. 4. For libraries, the major source of indoor air pollutant was CO 2. The main characteristic of indoor air pollution for library includes: numerous people with poor ventilation. 5. In exhibition halls, the major source of indoor air pollutants was HCHO, followed by CO 2. The characteristics of indoor air pollution for Exhibitions include: decoration material for woods mostly, numerous people with poor ventilation. 6. For shopping malls, the major source of indoor air pollutants was HCHO, followed by CO 2. The results can be to show that the characteristics of indoor air pollution for shopping mall, including: the use of wooden material for decoration and adhesive, and numerous people with poor ventilation in the indoor environment. 7. For hotels, the major source of indoor air pollutant was HCHO. The results can be explained that the characteristics of indoor air pollution for hotel include: the use of wooden material for decoration and adhesive, and people smoking.

8 8. The average IAQI values of class I buildings (hospitals and kindergartens) were higher than IAQI guideline (100-Moderate). The average IAQI values of exhibitions and hotels were higher than IAQI class-ii guideline (150-Unhealthy for sensitive population). Although the average IAQI values of office buildings, libraries, and shopping malls were compliance with IAQI guideline, some IAQI values were higher than IAQI guideline in the single building. The IAQI values and health risk of class I buildings are relatively higher than class II buildings. SUGGESTIONS 1. The IAQI value of 150 should be set up for the health protection of the sensitive population (children, elderly, or people with respiratory illness) who have higher risks of unhealthy or respiratory system illness when the boundary value of IAQI was greater than 150. Furthermore, according to test results, IAQI values for building types of class I buildings are relatively higher than class II buildings. Therefore, the air pollutants of indoor air should be reduced in order to improve human health protection for the sensitive population (for class-i) especially in children, elderly, or people with respiratory illness firstly. 2. All indoor air pollutants are quantified to explain the level of damage, response the real time level of indoor air pollution, and understand the current level of damage in human health. These results support the building users and administrator, policy administrator, experts, or scholars to provide a good indoor air quality for human health protection. ACKNOWLEDGEMENT This study was supported by the Indoor Environmental Quality Research Center (IEQ-RC) by the National Taipei University of Technology (NTUT). REFERENCES (1) Spengler J.D, and Sexton, K Indoor air pollution: a public health perspective. Science, 221 (4605). (2) National Institute for Occupational Safety and Health (NIOSH) Documentation for Immediately Dangerous to Life or Health Concentrations (IDLH): NIOSH Chemical Listing and Documentation of Revised IDLH Values. (3) Jones A.P Indoor air quality and health. Atmospheric Environment, 33, (4) U.S. Environmental Protection Agency (U.S. EPA) Quality of Air Means Quality of Life - Air Quality Index A Guide to Air Quality and Your Health, EPA-454/K (5) Occupational Safety and Health Administration (OSHA). STEL (short term exposure limit). (6) Occupational Safety and Health Administration (OSHA). TWA (8-hr time weighted average exposure limit). (7) Environmental Protection Administration, Taiwan (R.O.C) Indoor Air Quality Guideline. (8) Ministry of Environment Republic of Korea. Indoor Air Quality Management - Indoor Air Quality Standards. (9) Che-Ming. Chiang et al A Study on the Indoor Environment Index (IEI) for labelling Green Buildings in Taiwan. architectural institute of the republic of China. (10) Godish Thad Environmental science and technology: Air quality/thad Godish-4 th ed. Lewis publishers. (11) Environmental Protection Administration, Taiwan (R.O.C). Air Pollution Index. (12) Geneva Guideline for Air Quality.