RISK ASSESSMENT OF EXPOSURE TO BENZENE, TOLUENE AND FORMALDEHYDE IN RESIDENTIAL ENVIRONMENT IN CHINA

RISK ASSESSMENT OF EXPOSURE TO BENZENE, TOLUENE AND FORMALDEHYDE IN RESIDENTIAL ENVIRONMENT IN CHINA C Zheng 1, GQ Zhang 1,*, J.H Hao 2, J.P Lin 2, YH Liu 2 1 College of Civil Engineering, Hunan University, Changsha 410082, China 2 China Architecture Design & Research Group, Beijing 100044, China ABSTRACT In this study, a wide field study of VOCs pollution was made in five cities in different regions in China. The survey results of three target VOCs pollutants (benzene, toluene and formaldehyde) indicated that toluene and formaldehyde exceeded the national action levels. Based on these survey results, both chronic non-cancer risks and potential carcinogenic individual risks assessment on three different groups of people, office workers, housewives and schoolchildren, for lifetime exposure to the VOCs were estimated. The results showed that all of the estimated Lifetime Cancer Probabilities (LCPs) of benzene are not acceptable in five cities; the LCPs were one or two orders of magnitude larger than the benchmark. According to USEPA, toluene has no carcinogenic effect on human beings, also the chronic health effects results were affirmative, the Hazard Indices (HI) of toluene in selected cities were all less than 1, except in Beijing. The most serious indoor pollutant was formaldehyde, whose highest LCP was up to 3.410E-3, more than 3000 times over the acceptable benchmark. Meanwhile, the chronic health effect caused by formaldehyde cannot be ignored, for whose HI ranged from 20.00 to 136.94. INDEX TERMS VOCs, Risk assessment, Carcinogenic, Chronic, China INTRODUCTION Health risks, put simply, are a measure of the chance that people will experience health problems can increase their health risks. For example, breathing air toxics could increase people s risk of non-cancer effects such as emphysema or reproductive disorders. Risk assessment is one tool used in risk management which contains a 4-step process (Figure 1). It is the process that scientists and government officials use to estimate the increased risk of health problems in people who are exposed to different amounts of toxic substances (USEPA 2002). With economic and living standard improving consistently in China, the decoration of residential apartments became more and more common and more luxurious in urban cities since the mid-1990s., but indoor air pollution problem, mainly VOCs pollution problem, also came to us. So, this study aimed to measure the exposure of people in different cities in China to airborne VOCs in residential environment. The lifetime carcinogenic and chronic health risks on office workers (male), housewives and children associated with the VOCs exposures were evaluated. SURVEY AND CALCULATION METHOD Field survey This paper made a wide field study of indoor air quality in five cities in different regions in China from July. 2003 to Aug. 2004 (Zheng C. et al. 2004). Three most important indoor air contaminations (Zhang G.Q. and Yu L.K. 2003), benzene, toluene and formaldehyde, were selected as estimating indices. A total of 43 apartments were selected from five cities, including Harbin (8), Beijing (7), Shanghai (6), Changsha (10), and Shenzhen (12), and there were four sampling points in each residential home, including living-room, master bedroom, kitchen and outdoor. The field measurement methods used in this study confirmed to the Indoor Air Quality Standard of China (AQSIQ et al. 2002). The mean, maximum and minimum pollutant levels in five cities are presented in Table 1. Table 1 shows that the pollution level of benzene is the lowest among these three contaminations. The average benzene concentrations in all five cities were lower than national action level. This may relate to that benzene is characterized as a known human carcinogen and is classified as Category A by USEPA (1998), and, consequently, the use of benzene in * Corresponding author email: gqzhang@vip.sina.com 898

household products has decreased significantly in recent years. Many manufacturers select toluene to take place of benzene, which leads to the serious toluene pollution. Among the surveyed cities, the most seriously polluted cities by toluene are Harbin and Beijing, with the over limit rate of 81% and 60% respectively; and the average concentration in Beijing is 0.941mg/m 3, four times over the action level. The formaldehyde pollution levels in Harbin, Beijing and Shenzhen are basically the same, and lower than 0.10mg/m 3 (GB/T 18883-2002). The cities in which average formaldehyde concentrations exceeded the standard are Changsha and Shanghai. Hazard Identification What health problems are caused by the pollutant? Exposure Assessment How much of the pollutant do people inhale during a specific time period? How many people are Dose-Response Assessment What are the health Figure 1. The 4-Step Risk Assessment Process Risk calculation For cancer health risks, the individual lifetime cancer probability (LCP) is defined as the increase in the probability of cancer occurring against a background of continuous exposure to the cancerogenic air pollutants. LCP is simply expressed by the product of the chronic daily intake (CDI) and a potency factor (PF) of a specific cancer substance: LCP = CDI PF. CDI in mg/kg/day can be computed according to the following equation (Gurjar B.R. et al. 1996, USEPA 1989): CC IR ET EF ED AF CDI = (1) BW LT Where CDI = chronic daily intake (mg/kg/day). CC = concentration of contaminant in air, IR = inhalation rate (m 3 /h), ET = exposure time (h/day), EF = exposure frequency (days/year), ED = exposure duration (years), AF = absorption factor, BW = body weight (kg), and LT = the average life span (age) over which exposure is averaged (days). Benzene Table 1. Survey data in five cities and standard of benzene, toluene and formaldehyde (Unit: mg/m 3 ) Changsha Harbin Beijing Shanghai Shenzhen GB/T 18883-2002 Mean 0.061 0.041 0.038 0.011 0.017 Toluene Formalde Hyde Risk Characterization What is the extra risk of health problems in the exposed population? Min 0.000 0.000 0.000 0.000 0.000 Max 0.295 0.209 0.090 0.030 0.060 Outdoor 0.009 0.037 0.000 0.000 0.001 Mean 0.065 0.396 0.941 0.176 0.094 Min 0.000 0.000 0.020 0.020 0.000 Max 0.220 1.521 3.820 0.360 1.000 Outdoor 0.007 0.457 0.165 0.050 0.011 Mean 0.113 0.078 0.086 0.493 0.072 Min 0.031 0.027 0.027 0.090 0.013 Max 0.197 0.174 0.241 0.817 0.121 Outdoor 0.045 0.065 0.107 0.074 0.032 Certain assumptions are made for average body weight and the amount of air breathed. The USEPA has suggested standard values, such as average body weight and amount of air breathed per day, for adults and children (Guo et al. 0.11 0.2 0.1 899

2004, USEPA 1994). For adults, the exposures were converted to a daily dose by assuming 20m 3 inspired air per day and average body weights of 70kg for men and 60kg for women. The average body weight of a child was assumed to be 20kg and an average of 5m 3 of air per day was used for the daily intake calculations for children. An entire lifetime of 70 years was applied to all individuals. The absorption factor of the VOCs for humans was assumed to be 90%. This study made risk assessment on male office workers, housewives and children (pupils). In order to ease the process of exposure and risk assessment, several assumptions regarding individual exposure were made. In China, office workers spend, on average, 13h at home per workday and 18h per holiday (Guo et al. 2004). They work 5 days a week and normally have 3 weeks special holidays (Lunar new year, May 1 st Golden Week, National day), that s to say there are 49 workweeks each year. The work lifetime is assumed to be 40 years. A housewife may spend the most time at home compared to office workers. It is assumed that a housewife spends her lifetime on her family (19 hours per day; 7 days per week; 52 weeks per year; and a total of 45 years as being a housewife). On average, many Chinese pupils attend 5 school days per week, and stay at home for 13 hours. They may have about 165 school holidays, and during holidays children generally stay at home for 17 hours. Also, schoolchildren generally attend school for 6 years during primary school. For chronic non-cancer health risks, the hazard index (HI) is a measure of the relative significance of the exposure to a chemical, and is estimated by dividing the exposure level by a reference concentration (RfC). The RfC for chronic non-cancer effects is defined as the long-term exposure to toxic compounds in mg/m 3, without any adverse effects (Dourson M. and Stara J. 1983, Wu et al. 2003). The HI of chronic non-carcinogenic effects is calculated from HI=CC/RfC. Where HI = health index, CC = concentration of contaminant in air, and RfC is the inhalation reference exposure level for chronic non-cancer health effects. All of the potency factors and reference concentrations for selected contaminations are listed in Table 2. Table 2. Potency factors and RfCs for selected VOCs Contaminations RfC Reference PF (mg/kg/day) -1 Reference Benzene 0.03 USEPA 0.029 USEPA Toluene 0.4 NTP N/A. (Not available) Formaldehyde 0.0036 CAPCOA, California EPA 0.0455 USEPA RESULTS AND DISCUSSIONS The calculated cancer probability and non-cancer health risks of exposure to these three VOCs in five cities are listed in Table 3. For toluene is classified as Category D which means it has no carcinogenic effect on human being (USEPA 2004), there s no LCP data of toluene. Table 3. Lifetime cancer probability and non-cancer health risks of exposure to selected three VOCs in five cites in China Cities Changsha Harbin Beijing Shanghai Shenzhen 0.061 0.041 0.038 0.011 0.017 LCP (housewives) 2.689E-4 1.807E-4 1.675E-4 4.849E-5 7.494E-5 HI 2.03 1.37 1.27 0.37 0.57 Benzene Toluene 0.065 0.396 0.941 0.176 0.094 HI 0.16 0.99 2.35 0.44 0.24 0.113 0.078 0.086 0.493 0.072 LCP (housewives) 7.815E-4 5.394E-4 5.948E-4 3.410E-3 4.980E-4 HI 31.39 21.67 23.89 136.94 20.00 Note: LCP (office workers) = 0.618 LCP (housewives); LCP (children) = 0.079 LCP (housewives); HI (office workers) = HI (children) = HI (housewives). Formald ehyde 900

In general, the risk of cancer in the general population is higher than 1E-6 LCP and workplace risks greater than 1E-4 LCP (Gratt 1996), the corresponding exposure levels warrant further investigation and remediation. While all of the estimated cancer risks of benzene and formaldehyde are larger than 1E-6 LCP and imply a significant concern for carcinogenic effects in residential environment. For benzene, although it s an identified carcinogenic pollutant, although the dose of benzene in binder has been reduced, although the average pollution levels in five cities are below the action level of 0.11mg/m 3, the LCPs are still one or two orders of magnitude larger than the acceptable level of 1E-6, which range from 3.828E-6 to 2.689E-4. Only the risks of pupils in Shanghai and Shenzhen are acceptable. The carcinogenic effect of formaldehyde is about 3.410E-3 to 7.815E-4, which implies a significant concern for carcinogenic effects in the surveyed residential environment. And Table 3 shows the estimated cancer risk for housewives is the highest, as they spend most of their time at home. The second highest lifetime cancer risks from benzene and formaldehyde exposure are for the group of office workers. These two groups of people are in the same orders of magnitude, for the exposure time, inhalation rate of these two groups are almost the same. The schoolchildren have the lowest lifetime risks of VOCs exposure, because of the less inhalation rate (5m 3 /day) and the less exposure duration (6 years). They are one order of magnitude lower than the other two groups of people. As far as non-cancer health risks are concerned, this index is usually compared with 1, exposure or dose below the benchmark (HI<1) are not likely to be associated with adverse health effects, and the higher index means the more serious effect on human health. Considering the results presented in Table 3, the toluene s contribution to chronic individual risks may be the lowest, for HI values in most cities are less than 1, except in Beijing. And the HI values of benzene are around 1: the risk conditions are better in Shanghai and Shenzhen, while the risk in Changsha may be the highest (HI=2.03). Compared to the former results, the risk of chronic health effects of formaldehyde exposure is most serious, with the HI values ranging from 20.00 to 136.94. This is mainly due to the high hazard of formaldehyde, so the benchmark of RfC of formaldehyde is much less than the other two. The results of risk assessment may be something different compared with the conclusion of field survey: firstly, according to national standard, the benzene pollution are acceptable in these five cities, while the carcinogenic risk levels are much higher than the benchmark recommended by Gratt (1996). Also the concentrations of formaldehyde are around the action level, but because of its high hazard, under such pollution condition, the possibility of people getting cancer or other chronic health problem are very high. Oppositely, the survey data shows the most serious pollution is caused by toluene, but the risk assessment indicates it may cause little hazard on people. This conflict indicates while estimating the environmental impact, only comparing the pollutant s concentrations with the standards is not enough, some further studies should also be carried out. CONCLUSIONS By carcinogenic risk assessment, all of the estimated LCP of benzene are not acceptable in five cities. This means even the pollutant whose concentration below the standard also may have carcinogenic effect to human beings; the LCPs are still one or two orders of magnitude larger than the acceptable level of 1E-6. And the Health Index (HI) of chronic non-cancer effects caused by benzene are around 1. According to the USEPA (2004), toluene has no carcinogenic effect on human being, there s no carcinogenic risk data of exposure to toluene. Also the chronic health effects indices are affirmative, which are all less than 1, except in Beijing. From the estimation, the most important pollutant indoor is formaldehyde, whose highest LCP is up to 3.410E-3, more than 3000 times over the acceptable benchmark. Meanwhile, the chronic health effect caused by formaldehyde cannot be ignored. The risks of carcinogenic and non-cancer chronic effects estimated from this study show that identifying the sources of formaldehyde and performing mitigatory actions are necessary. Among the three estimated groups of people, the highest carcinogenic risk appeared in housewives, and the lowest group is pupils, which is mainly caused by different body weight, endure time, inhalation rate etc. Further more, the conflict between results of risk assessment and field survey via national standards shows while estimating the environmental empact, only comparing the pollutant s concentrations with the standards is not enough; some further studies such as human health risk assessment are necessary. ACKNOWLEDGEMENTS The work of this paper is financially supported by the National Natural Science Foundation of China (No.50078020), the 10th Five Year National Key Project of China (No.2002 BA 806 B02) and the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of MOE, PR China. 901

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