Semi-volatile organic compounds (SVOCs) are an important class of indoor pollutants that are of great health concern. However, they have not received much attention within the ASHRAE community. This column provides an overview of the sources, sinks, transport mechanisms, and potential health effects, and discusses how HVAC systems may affect occupants' exposure to SVOCs.Mechanical Engineerin

Xu, Ying

Zhang, Jianshun

English

Texas ScholarWorks

Syracuse UniversitySURFACEMechanical and Aerospace Engineering College of Engineering and Computer Science12-2011Understanding SVOCsYing XuJianshun ZhangSyracuse University, jszhang@syr.eduFollow this and additional works at: http://surface.syr.edu/maePart of the Mechanical Engineering CommonsThis Article is brought to you for free and open access by the College of Engineering and Computer Science at SURFACE. It has been accepted forinclusion in Mechanical and Aerospace Engineering by an authorized administrator of SURFACE. For more information, please contactsurface@syr.edu.Recommended CitationXu, Y. and J.S. Zhang. 2011. "Understanding SVOCs." ASHRAE Journal 53(12):121-125.Dec ember  2011  ASHRAE Jou rna l  121IAQ APPLICATIONS Understanding SVOCsSemi-volatile organic compounds (SVOCs) are an important class of indoor pollutants that are of great health concern. However, they have not received much attention within the ASHRAE community. This column provides an overview of the sources, sinks, transport mechanisms, and potential health effects, and discusses how HVAC systems may affect occupants’ exposure to SVOCs. By Ying Xu, Ph.D., Member ASHRAE; and Jensen Zhang, Ph.D., Fellow ASHRAEOccurrence and sources of SVOCs. Building materials, consumer products and furnishings contain a vast array of chemicals that are emitted to indoor en-vironments. Among the chemicals found indoors, SVOCs constitute an important class1 that includes phthalate esters, brominated flame-retardants, polychlo-rinated biphenyls, nonionic surfactants and pesticides (Table 1). Many SVOCs are high production volume chemicals used in plastics, detergents, furniture, building material components such as insulation and caulking, and other house-hold and consumer products, making them ubiquitous in indoor environments.2 Additionally, SVOCs persist for long periods of time, even after the primary source is removed.1 Potential health effects. SVOCs have been linked to serious adverse health effects (Table 1). Many SVOCs are endocrine-disrupting chemicals, which mean they interfere with, mimic or block endogenous hormones. For example, recent studies show that exposure to some phthalates results in profound and irreversible changes in the development of the reproductive tract in males;3 expo-sure to polybrominated diphenyl ethers (PBDEs) causes impairment of brain and nerve tissues.4 Concentrations of SVOC’s metabolites, measured in the general population us-ing biomonitoring methods (blood and urine), provide direct evidence of wide-spread human exposure.3 Biomonitoring data suggest that more than 95% of the U.S. population is exposed to phthalates.5 For PBDEs, the body burden in North Americans is 10 to 100 times higher than in Europeans, due to the much higher indoor exposure experienced by the U.S. population.6 Therefore, we need to ad-vance strategies to control and reduce ex-posure to SVOCs in indoor environments.Indoor transport and exposure pathways. As shown in Figure 1, SVOCs enter indoor environments along several pathways, including infiltra-tion of outdoor air, indoor combustion, spray products, and material additives. Because the vapor pressures of SVOCs at 25°C (77°F) (10–9 to 10 Pa) are low compared to volatile organic compounds (VOCs) (10 to 104 Pa), they are com-monly found in gas and condensed phases, redistributing from their original source to indoor air and interior surfaces including airborne particles, dust, and skin.3 Therefore, indoor exposure (via inhalation of air and airborne particles, dermal absorption from air and depos-ited particles, and non-dietary ingestion of dust) occurs following emission from sources into air and subsequent migra-tion to different media, and reemission/Figure 1: Representation showing the fate, transport and exposures of SVOCs in indoor environments.Supply AirAHUOutdoor AirReturn AirExhaustWallFilterIngestion of DustInhalationDermalApplication of PesticidesOutdoor AirIndoor CombustionEmmission of Material AdditivesParticle Deposition/ResuspensionFurnitureParticleCeilingWallGlass WindowFlooringDesorptionfromFilterThis article was published in ASHRAE Journal, December 2011. Copyright 2011 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Posted at www.ashrae.org. This article may not be copied and/or distributed electronically or in paper form without permission of ASHRAE. For more information about ASHRAE Journal, visit www.ashrae.org.122  A SHRA E Jou rna l  ash rae .o rg   D e c e m b e r  2 0 1 1IAQ APPLICATIONS desorption from these media as air conditions (temperature and concentration) change.Effect of the air change rate on indoor SVOC concentra-tions and exposures. Based on experimental chamber data,7,8 Xu and Little9 developed and validated a model to predict the emission rate of SVOCs from polymer materials. We extended this chamber-based model to examine the effect of the air change rate on SVOC concentrations and human exposures in SVOC Compounds Uses Sources Potential Health EffectsAlkylphenolsExample:  4-nonylphenol, 4-octylphenolNonionic Surfactants Detergents, Disinfectants, Surface CleanersMay Interfere With, Mimic or Block HormonesOrganochlorinesExample:  DDT, ChlordanePesticides, Termiticide, Bactericide(Some Have Been Banned or Restricted in the 1980s)Outdoor and Indoor Air, Tracked-In Dust, Disinfecting ProductsNeurotoxicity, Effects on Developing Reproductive Systems And on Lactation, CancerOrganophosphorus CompoundsExample:Tris(2-chloroethy)phosphate (TCEP),Tris(chloropropyl)phosphate (TCPP)Plasticizers, Antifoaming Agents, Flame Retardants, PesticidesPolymeric Materials, Fabrics, Polyurethane Foams, Electronics (Cable Sheathing and Casings), Outdoor and Indoor Air, DustEffects on Neurodevelopment and Growth in Developing Tissue, Relate To Respiratory Disease in Children Through Dysregulation of the Autonomic Nervous SystemPhthalatesExample:Di(2-ethylhexyl)-phthalate (DEHP),Di-iso-nonyl-phthalate (DINP)Plasticizers, Solvents, Fixing Fragrances (Use of DEHP And BBP Reduced Due to the Concern on Health Effects)Flexible PVC, PVC Flooring, Wall Covering, Electrical Cable and Casings, Personal Care ProductsEffects on the Development of Male Reproductive Tract, Prenatal Mortality, Reduced Growth and Birth Weight, May Relate to Asthma and Allergies in ChildrenPolybrominated Diphenyl Ethers (PBDEs)Example:Hexabromodiphenyl ether (BDE-153),Tetrabromodiphenyl ether (BDE-47)Flame Retardants (Use of  Penta- and Octa-BDEs Have Been Restricted)Carpet Padding, Wall Coverings, Electronics (Casings), Furniture (Foam Cushioning and Mattress)Effects on the Development of Brain And Nerve Tissues, Permanent Learning and Memory Impairment, Behavioral Changes, Delayed Puberty Onset, Fetal Malformations, Thyroid Hormone DisruptionPolychlorinatedBiphenyls (PCBs)Example:2,2’,5,5’-tetrachloro-1,1’-biphenyl (PCB 52),2,2’,4,4’,5,5’-hexachloro-1,1’-biphenyl (PCB 153)Heat Transfer Fluids, Stabilizers, Flame Retardants,(Have Been Banned or Restricted in the 1970s)Floor Finishes, Foam Cushioning and Mattresses, Oil-Filled Transformers, CapacitorsDevelopmental Neurotoxicants, Effects on Immune, Reproductive, Nervous, and Endocrine Systems, Cancer (Including Breast Cancer)Polycyclic Aromatic Hydrocar-bons (PAHs)Example:Benzo(a)pyrene, PyreneCombustion ByproductsOutdoor Air, Cooking, SmokingCataracts, Kidney and Liver Damage, Jaundice, Increased Risk Of Skin, Lung, Bladder, and Gastrointestinal CancersPyrethroidsExample:Cyfluthrin, PermethrinInsecticides Outdoor and Indoor Air, Tracked-In Dust, Cleaning ProductsWeak Anti-Androgenic, Anti-Estrogenic, or Estrogenic EffectParabensExample:Butyl paraben, Methyl parabenBactericides, Antimicrobial Agents, PreservativesPersonal Care Products, Canned Food, FabricsWeak Environmental EstrogensTable 1: SVOCs in indoor environments: sources and potential health effects.Dec ember  2011  ASHRAE Jou rna l  123IAQ APPLICATIONS a realistic indoor environment, and compared it with the results for VOCs. Vinyl material covering the floor area is the only contamination source in the modeled room (5 m × 4 m × 3 m [16 ft × 13 ft × 10 ft]), while the walls and ceiling are the only sink surfaces. We selected a range of contaminating materials to investigate: VOCs (phenol and pentadecane) and SVOCs (di-butyl-phthalate [DBP], butyl-benzyl-phthalate [BBP], and di-iso-decyl-phthalate [DIDP]). Two primary differences exist between the emissions of targeted VOCs and the SVOCs. First, the vapor pressures of the SVOCs are orders-of-magnitude lower than those of the VOCs. The much lower vapor pressures mean that the SVOC tend to be in the adsorbed phase, as opposed to the gas phase. The second primary difference is that the material-phase con-centrations of SVOCs are several orders-of-magnitude higher than those of VOCs. The high material-phase concentration and low emission rate mean that the material-phase concentration will be relatively constant, and that under these conditions, the in-material diffusion may not be an important mechanism. Instead, the mass transfer resistance across the boundary layer or “air film” over the surface becomes the factor that controls the rate.The total airborne concentrations of SVOC and VOC follow-ing the installation of vinyl flooring were simulated under two air change rates (0.5 h–1 and1.5 h–1). After some period of time, emissions from vinyl flooring result in a steady-state SVOC airborne concentration (Figure 2a), but VOC concentrations decrease quickly (Figure 2b). Suspended particles account for the major portion of the total airborne SVOC concentration, while 100% of the VOCs appear in the gas phase. An increase of the air change rate reduces the total airborne concentrations; the dilution ratio was similar for the SVOCs and VOCs we inves-tigated. For some SVOCs with different emission mechanisms, ventilation rate may not be as important as in the simulations.The model results also indicate the need to evaluate exposure to vapor-phase SVOCs in the air, particle-bound SVOCs in the air, and SVOCs in settled dust. The exposure pathways of inter-est are inhalation of vapor- and particle-bound SVOCs, dermal absorption of SVOCs, and non-dietary ingestion via household dust. As shown in Figure 3, the amount of SVOCs taken up via dermal absorption or dust ingestion is greater than the amount taken up through inhalation. Although inhalation is not the primary exposure pathway for SVOCs, dermal exposure and oral ingestion depend strongly on concentration of gas-phase SVOCs, so the air change rate still has a strong influence on total exposure for relatively light SVOCs (DBP, BBP and DIDP in Figure 3). In addition, particle resuspension due to occupant activity could increase particle inhalation exposure as high as 30%.10 This further increases the exposure to light and heavy particle-bound SVOCs. The previous are results of preliminary studies, and more work, especially experimental, will be neces-sary to validate the results.Figure 2: The influence of air change rate on total airborne SVOC (A) and VOC (B) concentrations. Total Airborne SVOC Concentration (µg/m3 )1010.1ACH = 0.5ACH = 1.5ACH = 0.5ACH = 1.5ACH = 0.5ACH = 1.50 10 20 30 40 50 60 70 80DBPGas Phase: 97%Particle Phase: 3%BBPGas Phase: 44%Particle Phase: 56%DIDPGas Phase: 1%Particle Phase: 99%Time (Days)Total Airborne VOC Concentration (µg/m3 )4035302520151050ACH = 0.5ACH = 1.5ACH = 0.5ACH = 1.50 10 20 30 40 50 60 70 80PhenolGas Phase: 100%Particle Phase: 0%PentadecaneGas Phase: 100%Particle Phase: 0%Time (Days)A BFigure 3: The influence of air change rate on total exposures to SVOCs for adults.Total SVOC Exposure (µg/kg/d)120100806040200ACH = 0.5ACH = 1.5ACH = 0.5ACH = 1.50 10 20 30 40 50 60 70 80DBPInhalation: 5%Dermal: 64%Dust Ingestion: 31%BBPInhalation: 2%Dermal: 5%Dust Ingestion: 93%DIDPInhalation: 1%Dermal: 0%Dust Ingestion: 99%Time (Days)ACH = 0.5ACH = 1.5Get the free app for your phone athttp://gettag.mobiSNAPITeLearning_2010414125648.pdf   1   4/19/2010   2:52:24 PM*Requirements vary by organization and state. For multiple user license information, contact elearningsales@ashrae.org. Each 12 month subscription gives you access 24/7 to training  complete with reading assignments, interactive exercises, and  examinations for analysis of content comprehension.Select from hundreds of training options, including an assortment  of economical eLibraries and great courses, including:• Advanced Energy Design – Small Office/ Retail Buildings• Sustainable Buildings & High Performance Systems Design• ASHRAE Standards 62.1 and 90.1• Data Centers: Equipment Load Trends and Planning for the Future• Fundamentals of RefrigerationASHRAE eLearning: Anytime, Anywhere, OnlineWithout the Hassle and Expense of Travel To subscribe, visit www.ashrae-elearning.orgReduce Costs,  Get Training You Can Trust, and Earn PDHs/CEUs* in the ProcesseLearning Tramp.indd   1 10/12/2010   3:27:54 PMwww.info.hotims.com/37993-92IAQ APPLICATIONS 124  A SHRA E Jou rna l    D e c e m b e r  2 0 1 1The potential role of HVAC systems in controlling expo-sure to SVOCs. The contamination of indoor environments has been recognized as a significant uptake pathway for SVOCs.2 Ventilation is used to remove pollutants and improve indoor air quality, and the effect of ventilation has been studied extensively for VOCs. However, no experimental data in the literature sup-port ventilation strategies to control indoor contamination by SVOCs. The previous analysis under two different air change rates indicates that adjusting the ventilation rate may reduce total indoor airborne SVOCs levels effectively, reducing hu-man exposures. Our recent computational fluid dynamics simulation11 showed that not only ventilation rate, but also ventilation mode (and thus room air distribution) could also play an important role in controlling the occupants’ exposure to indoor SVOCs. Although the gas-phase concentration of SVOCs in indoor air is normally lower than the concentra-tion of VOCs, a relatively small change in the gas-phase concentration, such as 0.1 ppb, is sufficient for meaningful vapor transport of SVOCs and its consequent partitioning between the gas phase and surfaces of airborne particles and human skin, and has significant influences on indoor SVOC exposures.12 Therefore, the ventilation system can play important roles in controlling the occupants’ exposure to SVOCs.Furthermore, because SVOCs are expected to sorb on par-ticles and dust, particle filtration in an HVAC system may be used to mitigate indoor SVOC exposures in combination with ventilation. With the increase of particles collected on a filter, SVOCs accumulate on the filter as well. As long as there is equilibrium between the adsorbed SVOC species and those in the ventilation airstream, no adverse effects are discern-ible. However, equilibrium can be perturbed by changes in climatic conditions, e.g., temperature and relative humidity. If the equilibrium is perturbed in a fashion that redistributes SVOCs from the filter into the airstream (e.g., an increase in temperature), the resulting release of SVOCs from a ‘‘loaded’’ filter may take place. Further investigation is needed to exam-ine the degree to which this could happen, and how to prevent it from occurring.The occurrence of SVOCs in indoor environments is emerging as an important research topic, but SVOCs have not been studied as widely as other classes of indoor pollutants, due in part to the analytical challenges in measuring SVOCs.1 Theoretically, HVAC systems can play an important role in controlling the occupants’ exposure to SVOCs. Research is needed to evaluate how HVAC www.info.hotims.com/37993-34Dec ember  2011  ASHRAE Jou rna l  125IAQ APPLICATIONS systems affect SVOC emission and distribution to provide solid scientific evidence for potential guidelines to reduce harmful SVOCs exposure in indoor environments.References1. Weschler, C.J., W.W. Nazaroff. 2008. “Semivolatile organic com-pounds in indoor environments.” Atmos. Environ. 42(40):9018–9040.2. Rudel, R.A., L.J. Perovich. 2009. “Endocrine disrupting chemicals in indoor and outdoor air.” Atmos. Environ. 43(1): 170 – 181.3. Heudorf, U., et al. 2007. “Phthalates: Toxicology and exposure.” International Journal of Hygiene and Environmental Health 210(5): 623 – 634.4. Vonderheide, A.P., et al. 2008. “Polybrominated diphenyl ethers: Causes for concern and knowledge gaps regarding environmental distribution, fate and toxicity.” Science of the Total Environment 400(1-3):425 – 436.5. Kato, K., et al. 2004. “Mono(2-ethyl-5-hydroxyhexyl) phthalate and mono-(2-ethyl-5-oxohexyl) phthalate as biomarkers for human exposure assessment to di-(2-ethylhexyl) phthalate.” Environmental Health Perspectives 112(3):327 – 330.6. Sjodin, A., et al. 2008. “Concentration of polybrominated di-phenyl ethers (PBDEs) in household dust from various countries,” Chemosphere 73(1):S131 – S136.7. Clausen, P., et al. 2004. “Emission of Di-2-ethylhexyl phthalate from PVC flooring into air and uptake in dust: Emission and sorption experiments in FLEC and CLIMPAQ.” Environmental Science and Technology 38(9):2531 – 2537.8. Xu, Y., et al. 2011. “Emissions of phthalate plasticizer from vinyl flooring (I): study in a specially-designed emission chamber.” Submit-ted to: Environmental Science and Technology.9. Xu, Y., J.C. Little. “Predicting emissions of SVOCs from poly-meric materials and their interaction with airborne particles.” Environ. Sci. Technol. 40(2):456 – 461.10. Kopperud, R., et al. 2004. “Outdoor versus indoor contributions to indoor particulate matter (pm) determined by mass balance methods.” Journal of Air and Waste Management 54:1188 – 1196.11. Wang, X., et al. 2011. “A study of phthalate concentration distri-bution in indoor environment.” Proc. Indoor Air 2011.12. Weschler, C.J. 2003. “Indoor/outdoor connections exemplified by processes that depend on an organic compound’s saturation vapor pressure.” Atmos. Environ. 37(39 – 40):5455 – 5465.Ying Xu, Ph.D., Member ASHRAE, is an assistant professor at the Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, Texas; and Jensen Zhang, Ph.D., Fellow ASHRAE, is a professor and director at Building Energy and Environmental Systems Labora-tory, Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, N.Y.

Understanding Svocs

Semi-volatile organic compounds (SVOCs) are an important class of indoor pollutants that are of great health concern. However, they have not received much attention within the ASHRAE community. This column provides an overview of the sources, sinks, transport mechanisms, and potential health effects, and discusses how HVAC systems may affect occupants’ exposure to SVOCs

Syracuse University Research Facility and Collaborative Environment

Syracuse University SURFACE Mechanical and Aerospace Engineering College of Engineering and Computer Science 12-2011 Understanding SVOCs Ying Xu Jianshun Zhang Syracuse University, jszhang@syr.edu Follow this and additional works at: https://surface.syr.edu/mae  Part of the Mechanical Engineering Commons Recommended Citation Xu, Y. and J.S. Zhang. 2011. "Understanding SVOCs." ASHRAE Journal 53(12):121-125. This Article is brought to you for free and open access by the College of Engineering and Computer Science at SURFACE. It has been accepted for inclusion in Mechanical and Aerospace Engineering by an authorized administrator of SURFACE. For more information, please contact surface@syr.edu. Dec ember  2011  ASHRAE Jou rna l  121IAQ APPLICATIONS Understanding SVOCsSemi-volatile organic compounds (SVOCs) are an important class of indoor pollutants that are of great health concern. However, they have not received much attention within the ASHRAE community. This column provides an overview of the sources, sinks, transport mechanisms, and potential health effects, and discusses how HVAC systems may affect occupants’ exposure to SVOCs. By Ying Xu, Ph.D., Member ASHRAE; and Jensen Zhang, Ph.D., Fellow ASHRAEOccurrence and sources of SVOCs. Building materials, consumer products and furnishings contain a vast array of chemicals that are emitted to indoor en-vironments. Among the chemicals found indoors, SVOCs constitute an important class1 that includes phthalate esters, brominated flame-retardants, polychlo-rinated biphenyls, nonionic surfactants and pesticides (Table 1). Many SVOCs are high production volume chemicals used in plastics, detergents, furniture, building material components such as insulation and caulking, and other house-hold and consumer products, making them ubiquitous in indoor environments.2 Additionally, SVOCs persist for long periods of time, even after the primary source is removed.1 Potential health effects. SVOCs have been linked to serious adverse health effects (Table 1). Many SVOCs are endocrine-disrupting chemicals, which mean they interfere with, mimic or block endogenous hormones. For example, recent studies show that exposure to some phthalates results in profound and irreversible changes in the development of the reproductive tract in males;3 expo-sure to polybrominated diphenyl ethers (PBDEs) causes impairment of brain and nerve tissues.4 Concentrations of SVOC’s metabolites, measured in the general population us-ing biomonitoring methods (blood and urine), provide direct evidence of wide-spread human exposure.3 Biomonitoring data suggest that more than 95% of the U.S. population is exposed to phthalates.5 For PBDEs, the body burden in North Americans is 10 to 100 times higher than in Europeans, due to the much higher indoor exposure experienced by the U.S. population.6 Therefore, we need to ad-vance strategies to control and reduce ex-posure to SVOCs in indoor environments.Indoor transport and exposure pathways. As shown in Figure 1, SVOCs enter indoor environments along several pathways, including infiltra-tion of outdoor air, indoor combustion, spray products, and material additives. Because the vapor pressures of SVOCs at 25°C (77°F) (10–9 to 10 Pa) are low compared to volatile organic compounds (VOCs) (10 to 104 Pa), they are com-monly found in gas and condensed phases, redistributing from their original source to indoor air and interior surfaces including airborne particles, dust, and skin.3 Therefore, indoor exposure (via inhalation of air and airborne particles, dermal absorption from air and depos-ited particles, and non-dietary ingestion of dust) occurs following emission from sources into air and subsequent migra-tion to different media, and reemission/Figure 1: Representation showing the fate, transport and exposures of SVOCs in indoor environments.Supply AirAHUOutdoor AirReturn AirExhaustWallFilterIngestion of DustInhalationDermalApplication of PesticidesOutdoor AirIndoor CombustionEmmission of Material AdditivesParticle Deposition/ResuspensionFurnitureParticleCeilingWallGlass WindowFlooringDesorptionfromFilterThis article was published in ASHRAE Journal, December 2011. Copyright 2011 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Posted at www.ashrae.org. This article may not be copied and/or distributed electronically or in paper form without permission of ASHRAE. For more information about ASHRAE Journal, visit www.ashrae.org.122  AS HRAE Jou rna l  ash rae .o rg   D e c e m b e r  2 0 1 1IAQ APPLICATIONS desorption from these media as air conditions (temperature and concentration) change.Effect of the air change rate on indoor SVOC concentra-tions and exposures. Based on experimental chamber data,7,8 Xu and Little9 developed and validated a model to predict the emission rate of SVOCs from polymer materials. We extended this chamber-based model to examine the effect of the air change rate on SVOC concentrations and human exposures in SVOC Compounds Uses Sources Potential Health EffectsAlkylphenolsExample:  4-nonylphenol, 4-octylphenolNonionic Surfactants Detergents, Disinfectants, Surface CleanersMay Interfere With, Mimic or Block HormonesOrganochlorinesExample:  DDT, ChlordanePesticides, Termiticide, Bactericide(Some Have Been Banned or Restricted in the 1980s)Outdoor and Indoor Air, Tracked-In Dust, Disinfecting ProductsNeurotoxicity, Effects on Developing Reproductive Systems And on Lactation, CancerOrganophosphorus CompoundsExample:Tris(2-chloroethy)phosphate (TCEP),Tris(chloropropyl)phosphate (TCPP)Plasticizers, Antifoaming Agents, Flame Retardants, PesticidesPolymeric Materials, Fabrics, Polyurethane Foams, Electronics (Cable Sheathing and Casings), Outdoor and Indoor Air, DustEffects on Neurodevelopment and Growth in Developing Tissue, Relate To Respiratory Disease in Children Through Dysregulation of the Autonomic Nervous SystemPhthalatesExample:Di(2-ethylhexyl)-phthalate (DEHP),Di-iso-nonyl-phthalate (DINP)Plasticizers, Solvents, Fixing Fragrances (Use of DEHP And BBP Reduced Due to the Concern on Health Effects)Flexible PVC, PVC Flooring, Wall Covering, Electrical Cable and Casings, Personal Care ProductsEffects on the Development of Male Reproductive Tract, Prenatal Mortality, Reduced Growth and Birth Weight, May Relate to Asthma and Allergies in ChildrenPolybrominated Diphenyl Ethers (PBDEs)Example:Hexabromodiphenyl ether (BDE-153),Tetrabromodiphenyl ether (BDE-47)Flame Retardants (Use of  Penta- and Octa-BDEs Have Been Restricted)Carpet Padding, Wall Coverings, Electronics (Casings), Furniture (Foam Cushioning and Mattress)Effects on the Development of Brain And Nerve Tissues, Permanent Learning and Memory Impairment, Behavioral Changes, Delayed Puberty Onset, Fetal Malformations, Thyroid Hormone DisruptionPolychlorinatedBiphenyls (PCBs)Example:2,2’,5,5’-tetrachloro-1,1’-biphenyl (PCB 52),2,2’,4,4’,5,5’-hexachloro-1,1’-biphenyl (PCB 153)Heat Transfer Fluids, Stabilizers, Flame Retardants,(Have Been Banned or Restricted in the 1970s)Floor Finishes, Foam Cushioning and Mattresses, Oil-Filled Transformers, CapacitorsDevelopmental Neurotoxicants, Effects on Immune, Reproductive, Nervous, and Endocrine Systems, Cancer (Including Breast Cancer)Polycyclic Aromatic Hydrocar-bons (PAHs)Example:Benzo(a)pyrene, PyreneCombustion ByproductsOutdoor Air, Cooking, SmokingCataracts, Kidney and Liver Damage, Jaundice, Increased Risk Of Skin, Lung, Bladder, and Gastrointestinal CancersPyrethroidsExample:Cyfluthrin, PermethrinInsecticides Outdoor and Indoor Air, Tracked-In Dust, Cleaning ProductsWeak Anti-Androgenic, Anti-Estrogenic, or Estrogenic EffectParabensExample:Butyl paraben, Methyl parabenBactericides, Antimicrobial Agents, PreservativesPersonal Care Products, Canned Food, FabricsWeak Environmental EstrogensTable 1: SVOCs in indoor environments: sources and potential health effects.Dec ember  2011  ASHRAE Jou rna l  123IAQ APPLICATIONS a realistic indoor environment, and compared it with the results for VOCs. Vinyl material covering the floor area is the only contamination source in the modeled room (5 m × 4 m × 3 m [16 ft × 13 ft × 10 ft]), while the walls and ceiling are the only sink surfaces. We selected a range of contaminating materials to investigate: VOCs (phenol and pentadecane) and SVOCs (di-butyl-phthalate [DBP], butyl-benzyl-phthalate [BBP], and di-iso-decyl-phthalate [DIDP]). Two primary differences exist between the emissions of targeted VOCs and the SVOCs. First, the vapor pressures of the SVOCs are orders-of-magnitude lower than those of the VOCs. The much lower vapor pressures mean that the SVOC tend to be in the adsorbed phase, as opposed to the gas phase. The second primary difference is that the material-phase con-centrations of SVOCs are several orders-of-magnitude higher than those of VOCs. The high material-phase concentration and low emission rate mean that the material-phase concentration will be relatively constant, and that under these conditions, the in-material diffusion may not be an important mechanism. Instead, the mass transfer resistance across the boundary layer or “air film” over the surface becomes the factor that controls the rate.The total airborne concentrations of SVOC and VOC follow-ing the installation of vinyl flooring were simulated under two air change rates (0.5 h–1 and1.5 h–1). After some period of time, emissions from vinyl flooring result in a steady-state SVOC airborne concentration (Figure 2a), but VOC concentrations decrease quickly (Figure 2b). Suspended particles account for the major portion of the total airborne SVOC concentration, while 100% of the VOCs appear in the gas phase. An increase of the air change rate reduces the total airborne concentrations; the dilution ratio was similar for the SVOCs and VOCs we inves-tigated. For some SVOCs with different emission mechanisms, ventilation rate may not be as important as in the simulations.The model results also indicate the need to evaluate exposure to vapor-phase SVOCs in the air, particle-bound SVOCs in the air, and SVOCs in settled dust. The exposure pathways of inter-est are inhalation of vapor- and particle-bound SVOCs, dermal absorption of SVOCs, and non-dietary ingestion via household dust. As shown in Figure 3, the amount of SVOCs taken up via dermal absorption or dust ingestion is greater than the amount taken up through inhalation. Although inhalation is not the primary exposure pathway for SVOCs, dermal exposure and oral ingestion depend strongly on concentration of gas-phase SVOCs, so the air change rate still has a strong influence on total exposure for relatively light SVOCs (DBP, BBP and DIDP in Figure 3). In addition, particle resuspension due to occupant activity could increase particle inhalation exposure as high as 30%.10 This further increases the exposure to light and heavy particle-bound SVOCs. The previous are results of preliminary studies, and more work, especially experimental, will be neces-sary to validate the results.Figure 2: The influence of air change rate on total airborne SVOC (A) and VOC (B) concentrations. Total Airborne SVOC Concentration (µg/m3 )1010.1ACH = 0.5ACH = 1.5ACH = 0.5ACH = 1.5ACH = 0.5ACH = 1.50 10 20 30 40 50 60 70 80DBPGas Phase: 97%Particle Phase: 3%BBPGas Phase: 44%Particle Phase: 56%DIDPGas Phase: 1%Particle Phase: 99%Time (Days)Total Airborne VOC Concentration (µg/m3 )4035302520151050ACH = 0.5ACH = 1.5ACH = 0.5ACH = 1.50 10 20 30 40 50 60 70 80PhenolGas Phase: 100%Particle Phase: 0%PentadecaneGas Phase: 100%Particle Phase: 0%Time (Days)A BFigure 3: The influence of air change rate on total exposures to SVOCs for adults.Total SVOC Exposure (µg/kg/d)120100806040200ACH = 0.5ACH = 1.5ACH = 0.5ACH = 1.50 10 20 30 40 50 60 70 80DBPInhalation: 5%Dermal: 64%Dust Ingestion: 31%BBPInhalation: 2%Dermal: 5%Dust Ingestion: 93%DIDPInhalation: 1%Dermal: 0%Dust Ingestion: 99%Time (Days)ACH = 0.5ACH = 1.5Get the free app for your phone athttp://gettag.mobiSNAPITeLearning_2010414125648.pdf   1   4/19/2010   2:52:24 PM*Requirements vary by organization and state. For multiple user license information, contact elearningsales@ashrae.org. Each 12 month subscription gives you access 24/7 to training  complete with reading assignments, interactive exercises, and  examinations for analysis of content comprehension.Select from hundreds of training options, including an assortment  of economical eLibraries and great courses, including:• Advanced Energy Design – Small Office/ Retail Buildings• Sustainable Buildings & High Performance Systems Design• ASHRAE Standards 62.1 and 90.1• Data Centers: Equipment Load Trends and Planning for the Future• Fundamentals of RefrigerationASHRAE eLearning: Anytime, Anywhere, OnlineWithout the Hassle and Expense of Travel To subscribe, visit www.ashrae-elearning.orgReduce Costs,  Get Training You Can Trust, and Earn PDHs/CEUs* in the ProcesseLearning Tramp.indd   1 10/12/2010   3:27:54 PMwww.info.hotims.com/37993-92IAQ APPLICATIONS 124  AS HRAE Jou rna l    D e c e m b e r  2 0 1 1The potential role of HVAC systems in controlling expo-sure to SVOCs. The contamination of indoor environments has been recognized as a significant uptake pathway for SVOCs.2 Ventilation is used to remove pollutants and improve indoor air quality, and the effect of ventilation has been studied extensively for VOCs. However, no experimental data in the literature sup-port ventilation strategies to control indoor contamination by SVOCs. The previous analysis under two different air change rates indicates that adjusting the ventilation rate may reduce total indoor airborne SVOCs levels effectively, reducing hu-man exposures. Our recent computational fluid dynamics simulation11 showed that not only ventilation rate, but also ventilation mode (and thus room air distribution) could also play an important role in controlling the occupants’ exposure to indoor SVOCs. Although the gas-phase concentration of SVOCs in indoor air is normally lower than the concentra-tion of VOCs, a relatively small change in the gas-phase concentration, such as 0.1 ppb, is sufficient for meaningful vapor transport of SVOCs and its consequent partitioning between the gas phase and surfaces of airborne particles and human skin, and has significant influences on indoor SVOC exposures.12 Therefore, the ventilation system can play important roles in controlling the occupants’ exposure to SVOCs.Furthermore, because SVOCs are expected to sorb on par-ticles and dust, particle filtration in an HVAC system may be used to mitigate indoor SVOC exposures in combination with ventilation. With the increase of particles collected on a filter, SVOCs accumulate on the filter as well. As long as there is equilibrium between the adsorbed SVOC species and those in the ventilation airstream, no adverse effects are discern-ible. However, equilibrium can be perturbed by changes in climatic conditions, e.g., temperature and relative humidity. If the equilibrium is perturbed in a fashion that redistributes SVOCs from the filter into the airstream (e.g., an increase in temperature), the resulting release of SVOCs from a ‘‘loaded’’ filter may take place. Further investigation is needed to exam-ine the degree to which this could happen, and how to prevent it from occurring.The occurrence of SVOCs in indoor environments is emerging as an important research topic, but SVOCs have not been studied as widely as other classes of indoor pollutants, due in part to the analytical challenges in measuring SVOCs.1 Theoretically, HVAC systems can play an important role in controlling the occupants’ exposure to SVOCs. Research is needed to evaluate how HVAC www.info.hotims.com/37993-34Dec ember  2011  ASHRAE Jou rna l  125IAQ APPLICATIONS systems affect SVOC emission and distribution to provide solid scientific evidence for potential guidelines to reduce harmful SVOCs exposure in indoor environments.References1. Weschler, C.J., W.W. Nazaroff. 2008. “Semivolatile organic com-pounds in indoor environments.” Atmos. Environ. 42(40):9018–9040.2. Rudel, R.A., L.J. Perovich. 2009. “Endocrine disrupting chemicals in indoor and outdoor air.” Atmos. Environ. 43(1): 170 – 181.3. Heudorf, U., et al. 2007. “Phthalates: Toxicology and exposure.” International Journal of Hygiene and Environmental Health 210(5): 623 – 634.4. Vonderheide, A.P., et al. 2008. “Polybrominated diphenyl ethers: Causes for concern and knowledge gaps regarding environmental distribution, fate and toxicity.” Science of the Total Environment 400(1-3):425 – 436.5. Kato, K., et al. 2004. “Mono(2-ethyl-5-hydroxyhexyl) phthalate and mono-(2-ethyl-5-oxohexyl) phthalate as biomarkers for human exposure assessment to di-(2-ethylhexyl) phthalate.” Environmental Health Perspectives 112(3):327 – 330.6. Sjodin, A., et al. 2008. “Concentration of polybrominated di-phenyl ethers (PBDEs) in household dust from various countries,” Chemosphere 73(1):S131 – S136.7. Clausen, P., et al. 2004. “Emission of Di-2-ethylhexyl phthalate from PVC flooring into air and uptake in dust: Emission and sorption experiments in FLEC and CLIMPAQ.” Environmental Science and Technology 38(9):2531 – 2537.8. Xu, Y., et al. 2011. “Emissions of phthalate plasticizer from vinyl flooring (I): study in a specially-designed emission chamber.” Submit-ted to: Environmental Science and Technology.9. Xu, Y., J.C. Little. “Predicting emissions of SVOCs from poly-meric materials and their interaction with airborne particles.” Environ. Sci. Technol. 40(2):456 – 461.10. Kopperud, R., et al. 2004. “Outdoor versus indoor contributions to indoor particulate matter (pm) determined by mass balance methods.” Journal of Air and Waste Management 54:1188 – 1196.11. Wang, X., et al. 2011. “A study of phthalate concentration distri-bution in indoor environment.” Proc. Indoor Air 2011.12. Weschler, C.J. 2003. “Indoor/outdoor connections exemplified by processes that depend on an organic compound’s saturation vapor pressure.” Atmos. Environ. 37(39 – 40):5455 – 5465.Ying Xu, Ph.D., Member ASHRAE, is an assistant professor at the Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, Texas; and Jensen Zhang, Ph.D., Fellow ASHRAE, is a professor and director at Building Energy and Environmental Systems Labora-tory, Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, N.Y.

Understanding SVOCs

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Understanding Svocs

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