SEMI-VOLATILE ORGANIC POLLUTANTS IN INDOOR AIR AND INDOOR DUST IN OTTAWA RESIDENCES AND IMPLICATIONS FOR HUMAN EXPOSURE

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1 SEMI-VOLATILE ORGANIC POLLUTANTS IN INDOOR AIR AND INDOOR DUST IN OTTAWA RESIDENCES AND IMPLICATIONS FOR HUMAN EXPOSURE Jiping Zhu 1, Tom Harner 2, Cariton Kubwabo 1, Paul White 3, Mahiba Shoeib 2, Bryony.H. Wilford 2, and Yong.-Lai Feng 1 1 Chemistry Research Division, Safe Environments Programme, Health Canada, AL: 0800C, Tunney s Pasture, Ottawa, Ontario, Canada, K1A 0L2. 2 Science and Technology Branch, Air Quality Research Division, Environment Canada 3 Environmental and Occupational Toxicology Division, Safe Environments Programme, Health Canada ABSTRACT Potentially-harmful chemicals could be released from many indoor materials, including consumer products and building materials, into indoor environments. Semi-volatile chemicals (SVOCs) due to their lower vapor pressure, are often present, either primarily in indoor dust or in both indoor air and indoor dust. Several types of SVOCs have been measured in indoor air and indoor dust of Ottawa residential homes. This paper reports the summary results with focuses on the relative levels among the several types of SVOCs, their concentration ratios in air and dust, and the potential for human exposure through inhalation of indoor air and ingestion of indoor dust for different age groups. The integrated data of indoor air and indoor dust provides a more complete picture of human non-dietary exposure to these SVOCs. The results showed several orders of magnitude difference in indoor levels among SVOCs with phthalates being the most predominant ones, and also showed correlation between the octanol-air partition coefficient and the distribution of contaminants in air and dust. The estimated daily intake of SVOCs also indicated the greater exposure of children to SVOCs in dust on per body weight basis. KEYWORDS Semi-VOCs, Indoor Environments Quality, Human Exposure, Residential Homes INTRODUCTION Surveys of volatile organic compounds (VOCs) in indoor air (residence, offices and schools) have been conducted since the 1970s and were largely driven by concerns of poor indoor air quality. This was partly attributed to a tightening of the building envelope for the purpose of energy conservation that resulted in reduced ventilation. More recently, there has been an emphasis on less volatile chemicals, commonly referred to as semi-volatile organic compounds (SVOCs), especially those derived from use of indoor materials that are treated with these chemicals. Unlike VOCs, SVOCs are present in both indoor air and indoor dusts and often primarily in the latter depending on the vapour pressures of the compounds (Rudel et al., 2003). As people in modern societies spend the majority of their times indoors - homes, offices, schools and during transportation - there is a need to assess human exposure to these chemicals and measure their concentrations in both indoor air and indoor dust (Wilford et al., 2005a). It is a natural evolution in our understanding of indoor contaminants that settled house dust has become an important indicator of the quality of indoor environments quality especially in the context of SVOCs, along with indoor air (Butte and Heinzow, 2002). A number of SVOCs including polybrominated diphenyl ether fire retardants (PBDEs), fluorinated chemicals such as polyfluoroalkyl sulfonate/acid (PFOS/PFOA), polyfluorinated telomer alcohols Corresponding Author: Tel: , Fax: address: jiping_zhu@hc-sc.gc.ca

2 Table 1 Concentration of individual SVOCs in indoor air and indoor dust and their ratios Compound Indoor Air (pg/m 3 ) Indoor Dust (ng/g) Air/dust Ratio n= Range Mean Median n= Range Mean Median Mean Median PFOA E E E E+01 PFOS E E E E+01 PFHS E E E E+01 6:2FTOH 52 < dl - < dl < dl < dl E E E E+01 8:2FTOH E E E E E E E E :2FTOH E E E E E E E E Et FOSA E E E E < dl - < dl < dl < dl MeFOSE E E E E E E E E EtFOSE E E E E E E E E Total fluorinated compounds 9.5E E E E+02 BDE <dl - 1.6E E E < dl - 1.5E E E BDE <dl - 3.1E E E < dl - 5.5E E E BDE <dl - 2.4E E E BDE <dl - 1.6E E E E E E E BDE <dl - 9.8E E+00 <dl 64 < dl - 1.8E E E BDE <dl - 1.6E E E E E E E BDE <dl - 8.9E E E E E E E BDE <dl - 3.2E E-01 <dl 64 < dl - 9.7E E E BDE <dl - 5.7E E+00 <dl E E E E BDE <dl - 7.4E E+00 <dl E E E E BDE < dl - 2.0E E E+00 BDE < dl - 6.5E E E+01 BDE < dl - 4.8E E-01 < dl BDE E E E E+02 Total brominated Compounds 2.6E E E E+03 Acenaphthylene 51 <dl - 1.7E E E+00 Fluorene 51 <dl - 1.4E E E+01 Phenanthrene E E E E+03 Anthracene 51 <dl - 6.6E E E+02 Pyrene E E E E+03 Benz[a]anthracene E E E E+02 Chrysene E E E E+03 Benzo[b]fluoranthene E E E E+03 Benzo[k]fluoranthene E E E E+02 Benzo[a]pyrene E E E E+02 Indeno[1,2,3-c,d]pyrene E E E E+02 Dibenz[a,h]anthracene E E E E+02 Benzo[g,h,i]perylene E E E E+02 Total PAHs 3.3E E E+04 DMP 73 <dl - <dl <dl <dl 56 <dl - 1.9E E+02 <dl DEP E E E E <dl - 3.4E E E DiBP E E E E+03 DBP E E E E E E E E BBP 73 <dl - <dl <dl <dl E E E E+04 DEHA <dl - 9.2E E E+03 DEHP E E E E E E E E DOP like <dl - 1.5E E E+04 DOP 73 <dl - <dl <dl <dl 56 <dl - 3.1E E+04 <dl DDcP <dl - 4.1E E E+04 Total phthalates 9.3E E E E+05 dl = detection limit (FTOHs) and perfluorooctane sulfonamides (FOSAs), polycyclic aromatic hydrocarbons (PAHs) and phthalates have been measured in indoor air and indoor dust in Ottawa, Canada. The samples were collected in the winter of as part of the residential air survey in the city (Zhu et al., 2005), in randomly-selected residential homes. Although the results of individual groups of contaminants have been published elsewhere (Kubwabo et al., 2005; Shoeib et al., 2005a, 2005b, 2007; Wilford et al., 2004, 2005; Zhu et al., 2003, 2006), it is the objective of this paper to provide an integrated picture of

3 SVOCs as a complex mixture in the indoor environments, and to estimate human exposure to these contaminants. METHODS Study design and sample collections The strategy of selecting representative residential homes, where indoor air and indoor dust samples were collected, has been described elsewhere (Zhu et al., 2005). Air samples (100 liters) for the analysis of phthalates were collected in an XAD tube using a pump over 100 minutes. Air samples for all other contaminants were collected using PUF-disk passive air samplers deployed for 3-week periods. For indoor dust, the whole vacuum cleaner bag was removed from the family vacuum cleaner and placed in a clean polyethylene zip-seal plastic bag. In case of central vacuum system, dust in the collection bin was emptied directly into the polyethylene plastic bag. The dust samples were sieved using an all stainless steel sieve with a 150 µm size cut-off and placed in clean glass jars and stored frozen at 20ºC until analysis. Sample preparation and analysis For the anaylsis of phthalates (dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DiBP), dibutyl phthalate (DBP), benzylbutyl phthalate (BBP), di-(2-ethylhexyl) adipate (DEHA), di-(2-ethylhexyl) phthalate (DEHP), dioctyl phthalate (DOP), unknown isomer of DOP (DOP like), didecyl phthalate (DDcP)), XAD tubes were eluted with dichloromethane (DCM) followed by GC/MS analysis (Zhu et al., 2003). PUF disk passive air samples for PBDEs and fluorinated chemicals (6:2 FTOH, 8:2 FTOH, 10:2 FTOH, N-methylperfluorooctane sulfonamidoethanol (MeFOSE), N-ethylperfluorooctane sulfonamidoethanol (EtFOSE), N- ethylperfluorooctane sulfonamide (EtFOSA)) were extracted with petroleum ether by Soxhlet and extracts analyzed by GC/MS (Wilford et al., 2004; Shoeib et al., 2005). Dust samples for phthalates and PAHs were extracted with hexane/dcm (1:1) using Accelerated Solvent Extraction equipment followed by sample clean up on a preparative GPC column and analysed by GC/MS (Zhu et al., 2006). For perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHS), dust was extracted with acetonitrile, cleaned-up on a C18 SPE cartridge (eluting with acetonitrile) and analyzed by LC/MS/MS (Kubwabo et al., 2005). For other fluorinated compounds and PBDEs, dust was extracted with DCM using a Soxhlet device and analysed by GC/MS (Wilford et al., 2005, Shoeib et al., 2005a, 2005b). Phthalates Phthalates Median PAHs Br-compds Mean Br-compds Median Mean F-Compds F-Compds Concentration (pg/m 3 ) Concentration (ng/g) Figure 1. Relative mean and median concentrations of four groups of SVOCs in indoor air (left picture) and indoor dust (right). Notice that the concentrations are on a log scale. (Br- brominated; F-fluorinated) RESULTS AND DISCUSSION SVOC levels in indoor air and indoor dust The concentration range, mean and median values of individual compounds in indoor air and indoor dust are summarized in Table 1. PFOS/PFOA and PAHs were not measured in indoor air. For indoor air,

4 three of the six measured phthalates were detected. Among them, DEP had the highest level, followed by DBP and DEHP. Among fluorinated compounds, FTOHs and FOSAs are considered precursors of PFOS /PFOA (Shoeib et al., 2005a, 2005b) and have vapour pressure high enough to be detected in indoor air. The highest level was observed for 8:2 FTOH and MeFOSE in indoor air and dust samples. Among the PBDEs, 10 Conc Ratio (Air/Dust) y = 1E+27x R 2 = Mean Median y = 2E+26x R 2 = Log(Koa) Figure 2. Correlation of octanol-air partition coefficient and concentration ratio in air and dust among PBDE congeners. BDE47 had the highest level in indoor air, followed by BDE99, BDE28 and BDE17. Among the three groups of contaminants measured in indoor air, the levels of phthalates (10 6 pg/m 3 ) were several orders of magnitude higher than the fluorinated (10 4 pg/m 3 ) and brominated (10 2 pg/m 3 ) target compounds (Figure 1, left). For the SVOCs measured in indoor dust, similar distribution patterns among different groups of contaminants can be observed. Again, levels of phthalates dominate with the median and median values of DEHP close 10 6 ng/g. The next dominant SVOCs in dust were PAHs with the value around 10 4 ng/g. The mean and median values of brominated and fluorinated compounds were further lower at between 10 2 and 10 4 ng/g (Figure 1, right). Another interesting observation is that the concentration ratio of indoor air to indoor dust decreased remarkably with the increase in molecular size within each chemical class. For PBDEs, the concentration pattern among congeners in indoor dust differed from that in indoor air with a higher proportion on dust for the heavier congeners. For example, BDE99 had the highest median value, and other heavy congeners such as BDE153 and BDE154 were enriched on dust. This pattern was also observed for the phthalate congeners. DEHP, a high molecular weight phthalate, was enriched on dust and the lighter DEP was a minor contributor to dust levels of phthalates. The partitioning of a given SVOC in indoor air and indoor dust is probably governed by its vapour pressure or octanol-air partition coefficient (Koa) (Lei et al., 2004). The correlation of selected SVOCs, for example BDE-47 and BDE-99 in indoor air and indoor dust in individual homes have been reported (Wilford et al., 2005). In this study, among the PBDE congeners for example, a good correlation between the Koa value and median (r 2 = ) or mean (r 2 =0.9996) air/dust concentration ratio values was observed (Figure 2). Human exposure to SVOCs in indoor environment The estimation of human exposure to the measured SVOCs through inhalation and dust ingestion was based on their mean and median concentration levels, respectively, in indoor air and indoor dust for both adults and small children aged 6 to 24 months (Table 2). The daily exposure to SVOCs (DI) can be

5 calculated by multiplying the concentration in the matrix (levels in air or dust) with the amount of intake of the given matrix (volume of air or mass of dust) per day. The breathing rate of 20 m 3 /day and 3.8 m 3 /day were assumed for adults and children respectively (Health Canada, 1994). For the dust intake, we provided the estimates of both the average (MN) and incident (Max) ingestion rates for this two population groups based on information from US EPA (US EPA, 1997). Since people spend most of their time indoors, we further assumed 100% indoor time for both air and dust intake. Table 2 Estimation of daily intake (ng/day) of selected SVOCs from indoor air and indoor dust based on median values found in these two media and intake ratio between the two Adult Children (6-24 months) Compound Air Dust Air/Dust Ratio Air Dust Air/Dust Ratio Mean High Mean High Mean High Mean High 20 m 3 /d 4.16 mg/d 100 mg/d 3.8 m 3 /d 55 mg/d 200 mg/d 8:2FTOH :2FTOH MeFOSE EtFOSE BDE BDE BDE BDE BDE DEP DBP DEHP The daily exposure to SVOCs indoors can then be calculated for all measured individual SVOCs from the concentrations provided in Table 1. For this paper, we selected only those with measured levels in both indoor air and indoor dust (Table 2) to illustrate the proportion of importance of the two media for different chemicals and for different age groups. Several interesting observations can be extracted from Table 2. First, the exposure ratio of air to dust depends on the volatility of the SVOCs, and second, the ratio was much smaller for children compared to adults indicating the importance of exposure through dust among children. For example, the exposure ratio ranged from 281 to 0.10 for adult, which reduced to 4.0 to for children using the mean ingestion rate of both populations. This means that for some measured SVOCs, such as BDE99 and BDE100, exposure through dust ingestion is several hundred times higher than the inhalation exposure. The importance of exposure through dust ingestion is further augmented when the high dust ingestion rate is considered. CONCLUSIONS This paper has summarized and integrated information on the content and partitioning behaviour of SVOCs in both indoor air and indoor dust. While the volatile organic compounds (VOCs) are still thought to be responsible for various indoor air quality problems, the contribution of SVOCs to indoor air quality and potential sick building syndrome related effects has yet to be investigated. Based on our results, we recommend that indoor work and residential environments be designed with strategies to minimize exposure to SVOCs, particularly through dust, in order to provide people with healthier living environments. ACKNOWLEDGEMENTS

6 Contributions of Ron Newhook and Leonora Marro of Health Canada in house selection and questionnaire design, and technical assistance of many laboratory technicians from all research groups are acknowledged. REFERENCES 1. W. Butte and B. Heinzow (2002) Pollutants in house dust as indicators of indoor contaminants, Rev Environ Contam Toxicol, Vol. 175, Y. D. Lei, F. Wania, D. Mathers and S. A. Mabury (2004) Determination of vapour pressure, octanol-air, and water-air partition coefficients for polyfluorinated sulphonamide, sulfonaminoethanols, and telomere alcohols, J. Chem. Eng. Data, Vol. 49, R. A. Rudel, D. E. Camann, J. D. Spengler, L. R. Korn and J. G. Brody (2003) phthalates, alkylphenols, pesticides, polybrominated diphenyl ethers, and other endocrine-disrupting compounds in indoor air and dust, Environ Sci & Technol, Vol. 37, B. H. Wilford, T. Harner, J. Zhu, M. Shoeib and K. C. Jones (2004) Passive sampling survey of polybrominated diphenyl ether flame retardants in indoor and outdoor air in Ottawa, Canada: implications for sources and exposure, Environ Sci. Tech. Vol. 38, J. P. Zhu, R. Newhook, L. Marro, L. and C. C. Chan (2005) Selected Volatile Organic Compounds in Residential Air in the city of Ottawa, Canada, Environ. Sci. Technol., Vol. 39, B. H. Wilford, M. Shoeib, T. Harner, J. Zhu and K. C. Jones (2005) Polybrominated diphenyl ethers in indoor dust in Ottawa, Canada: implications for sources and exposure, Environ. Sci. Technol., Vol. 39, M. Shoeib, T. Harner, B. H. Wilford, K. V. Jones and J. Zhu (2005b) Perfluorinated sulfonamides in indoor and outdoor air and indoor dust: occurrence, partitioning and human exposure, Environ. Sci. Technol., Vol. 39, C. Kubwabo, B. Stewart, J. Zhu and L. Marro (2005) Occurrence of perfluorosulfonates and other perfluorochemicals in dust from selected homes in the city of ottawa, canada, J. Environ. Moniot., Vol. 7, M. Shoeib, T. Harner, B. H. Wilford and J. Zhu (2005a) Polyfluorinated telomer alcohols (FTOHs) in indoor dust, Proceedings of 25th International Symposium on Halogenated Environmental Organic Pollutants and POPs, Vol. 67, US Environmental Protection Agency (1997) Exposure Factors Handbook, EPA/600/P-95/002Fa, National Center for Environmental Assessment: Washington, DC, Vol. 1, Chapter J. Zhu, J., and X. Yang (2006) Semi-volatile organic compounds in residential house dust potential human exposure to phthalates, Proceedings of 8 th ISIAQ International Conference, Vol. 1, J. Zhu, Y.-L. Feng, S. MacDonald, R. Newhook, L. Marro (2003) Phthalates in indoor air of Canadian residences, Proceedings of 7 th ISIAQ International Conference, Vol. 1, M. Shoeib, T. Harner, J. Zhu (2007) Indoor air & dust concentrations of fluorotelomer alcohols, Proceedings of 27 th International Symposium on Halogenated Environmental Organic Pollutants and POPs, Japan, Sept. 2-7, 2007, submitted.