SVOCs in the Indoor Environment: Mechanistic Insights to Support Sustainable Product Design, Safe Use and Improved Public Health



John Little [] and Elaine Cohen Hubal []


Steering Committee

William Fisk, Hal Levin, Tom McKone, William Nazaroff, Charles Weschler




Thousands of chemicals are currently in commercial use and hundreds more are introduced each year.  Of these, only a small fraction has been assessed adequately for potential risks.  REACH in Europe and the current emphasis on chemical screening and prioritizing in the United States (Cohen Hubal et al., 2008, 2010; Judson et al., 2010) highlight the critical need for improved tools to characterize and predict potential exposures associated with the indoor use of building materials and consumer products.  These tools are urgently required to characterize and classify thousands of environmental chemicals in a rapid and efficient manner to prioritize testing and assess potential for risk to human health.  Rapid risk assessment requires prioritization based on both hazard and exposure.  In addition, the framework for design, manufacture and management of chemicals is transforming in response to society’s need for safe and effective chemicals.  Prediction of potential exposures across the product lifecycle for all chemical classes and use scenarios is required under green engineering principles to minimize potential health risks to all vulnerable groups.  Principles of green chemistry and sustainable chemical use require comprehensive consideration of integrated environmental, economic, and social factors.


The importance of exposures to manufactured chemicals and products in the indoor environment is broadly recognized as an important health issue in the developed world.  For example:

•                The Swedish government has shifted policies and reallocated resources to achieve sixteen long-term environmental goals, among them “a non-toxic environment,” and “a good built environment” (see; and

•                The U.S. Department of Housing and Urban Development (HUD) announced HUD’s Healthy Homes Strategic Plan in June 2009.  The HUD Deputy Secretary joined the Acting Surgeon General in launching a coordinated national effort to produce healthier housing, as they issued a national “call to action” to confront the prevalence of home-related preventable diseases.


Consideration of the indoor uses and sources of chemicals is critical to achieving the objectives of green chemistry.  Of special interest are semi-volatile organic compounds (SVOCs) including plasticizers, flame retardants, and pesticides.  SVOCs have been associated with adverse health outcomes including endocrine disruption in laboratory animals and in early-stage environmental epidemiology studies (Birnbaum, 2010; Rudel et al., 2009; Rudel and Perovich, 2009; Howdeshell et al., 2008; Jaakkola and Knight, 2008; Bornehag et al., 2004).  SVOCs are released from a vast range of building materials and consumer products, and are found in essentially all environmental media including food, saliva, air, dust, water, and blood (Weschler and Nazaroff, 2008; Rudel and Perovich, 2009). Important considerations required to evaluate and manage the health risks of indoor SVOCs include:

1.              Approaches for incorporating information on indoor sources and fate of SVOCs for rapid prioritization;

2.              Exposure information for SVOCs in the indoor environment required to inform toxicity testing design and interpretation of real-world health risks;

3.              Exposure considerations across the lifecycle, but with a particular focus on the indoor residential environment to inform chemical and product design.


Workshop Objectives


A “Pilot” Workshop on SVOCs in the Residential Environment (SVOC Workshop 1) was held at EPA in Research Triangle Park in August 2009.  Using one class of SVOCs (phthalates) as an example, a strategy was proposed for linking information on exposure potential for SVOCs in the indoor environment with information on hazard for rapid chemical prioritization and risk characterization.  This strategy provided a tiered approach for rapid exposure-based screening followed by targeted modeling and measurement to develop a mechanistic understanding of important physical-chemical-biological processes required to predict exposure and risk associated with SVOCs used or emitted in the residential environment.   In this workshop (SVOC Workshop 2) our specific objectives are to:

•                Interrogate and generalize the framework proposed in SVOC Workshop 1 by considering a broad range of SVOCs to demonstrate the extent to which mechanisms along the source-to-dose continuum are controlled by physical/chemical properties of the SVOCs or their metabolites;

•                Consider extension of framework for a holistic systems-based approach that enables relevant processes to be linked across the source-to-dose continuum, adjusting the scales of the various mechanistic processes so that these can be appropriately integrated;

•                Consider extension of framework to evaluate potential exposures across the product lifecycle for all chemical classes and for all use scenarios to inform design, evaluation and risk management;

•                Propose screening-level, rapid exposure assessment approaches based on simplified forms of mechanistic exposure models.


Organizational Sponsor

Indoor Air Institute (William Fisk, Hal Levin, William Nazaroff)


Financial Sponsors

American Chemistry Council (ACC) (Tina Bahadori)

EPA ORD (Linda Sheldon and Roy Fortmann)

EPA NCCT (David Dix)

EPA Indoor Environment (Laureen Burton)

ExpoCast™ Semi-Volatile Organic Compounds Indoor Environment Workshop

Results of the Workshop

1. JC Little, CJ Weschler, W Nazaroff, Z Liu, EA Cohen Hubal, Rapid methods to estimate potential exposure to semivolatile organic compounds in the indoor environment, Environmental Science & Technology, doi: 10.1021/es301088a.  Download here

2. WW Nazaroff, CJ Weschler, JC Little, EA Cohen Hubal, Intake to production ratio: A measure of exposure intimacy for manufactured chemicals, Environmental Health Perspectives, Download here

3. H-M Shin, TE McKone and DH Bennett, Intake fraction for the indoor environment: a tool for prioritizing indoor chemical sources, environmental science and technology Download here


Workshop Location and Dates

EPA, Research Triangle Park, North Carolina

January 5—7, 2011


Download the draft agenda here

Download the draft paper here

Download the workshop summary here

The agenda and most of the presentations are available at




Adibi, J. J., Whyatt, R. M., Williams, P. L., Calafat, A. M., Camann, D., Herrick, R., et al. “Characterization of Phthalate Exposure among Pregnant Women Assessed by Repeat Air and Urine Samples,” Environmental Health Perspectives, Vol. 116, 2008, pp. 467-473.

Birnbaum, L. S., “Green Chemistry and Environmental Health,” Presentation on 3 Feb, 2010.

Bornehag, C. G., Sundell, J., Weschler, C. J., et al. “The Association between Asthma and Allergic Symptoms in Children and Phthalates in House Dust: A Nested Case–Control Study,” Environmental Health Perspectives, Vol. 112, 2004, pp. 1393-1397.

Clewell, H. J. et al. “Quantitative Interpretation of Human Biomonitoring Data,” Toxicology and Applied Pharmacology, Vol. 231, 2008, pp. 122–133.

Cohen Hubal, EA, A Richard, L Aylward, S Edwards, J Gallagher, M-R Goldsmith, S Isukapalli, R Tornero-Velez, E Weber, R Kavlock. Advancing Exposure Characterization for Chemical Evaluation and Risk Assessment.  J Toxicol Environ Health, In Press.

Cohen Hubal EA, Richard AM, Imran S, Gallagher J, Kavlock R, Blancato J, Edwards S.  (2010) Exposure science and the US EPA National Center for Computational Toxicology.  Journal Expo Sci Environ Epidemiol. 2010 May;20(3):231-6. Epub 2008 Nov 5.

Howdeshell, K. L., Wilson, V. S., et al. “A Mixture of Five Phthalate Esters Inhibits Fetal TesticularTestosterone Production in the Sprague-Dawley Rat in a Cumulative, Dose-Additive Manner,” Toxicological Sciences, Vol. 105, No. 1, 2008, pp. 153–165.

Jaakkola, J. J. K. and Knight, T. L. “The Role of Exposure to Phthalates from Polyvinyl Chloride Products in the Development of Asthma and Allergies: A Systematic Review and Meta-analysis,” Environmental Health Perspectives, Vol. 116, 2008, pp. 845-853.

Jackson, LP. (2009) Administrator Lisa P. Jackson, Remarks to the Commonwealth Club of San Francisco, As Prepared 09/29/2009.

Judson, R. S. et al., In Vitro Screening of Environmental Chemicals for Targeted Testing Prioritization: The ToxCast Project, Environmental Health Perspectives, Vol. 118, 2010, pp. 485-492.

Rudel, R. A. and Perovich, L. J. “Endocrine Disrupting Chemicals in Indoor and Outdoor Air,” Atmospheric Environment, Vol. 43, 2009, pp. 170-181.

Rudel, R. A. et al. “Phthalates, Alkylphenols, Pesticides, Polybrominated Diphenyl Ethers, and Other Endocrine-Disrupting Compounds in Indoor Air and Dust,” Environmental Science & Technology, Vol. 37, 2003, pp. 4543-4553.

Rudén, C. and Hansson, S. O. “REACH is but the First Step – How Far Will it Take Us? Six Further Steps to Improve the European Chemicals Legislation,” Environmental Health Perspectives, Vol. 118, No. 1, 2010, pp. 6-10.

Schettler, T. “Human exposure to phthalates via consumer products,” International Journal of Andrology, 29, 2006, pp. 134-139.

Weschler C. J. and Nazaroff W W. “Semivolatile Organic Compounds in Indoor Environments, Atmospheric Environment, Vol. 42, 2008, pp. 9018-9040.

Wormuth, M., Scheringer, M., Vollenweider, M. and Hungerbuhler, K. “What are the sources of exposure to eight frequently used phthalic acid esters in Europeans?” Risk Analysis, Vol. 26, 2006, pp. 803-824.

Xu, Y., Cohen Hubal, E. A., Clausen, P. A. and Little, J. C. “Predicting Residential Exposure to Phthalate Plasticizer Emitted from Vinyl Flooring – A Mechanistic Analysis,” Environmental Science & Technology, Vol. 43, 2009, pp. 7512-7520.

Xu, Y., Cohen Hubal, E. A. and Little, J. C. “Predicting Residential Exposure to Phthalate Plasticizer Emitted from Vinyl Flooring – Sensitivity, Uncertainty, and Implications for Biomonitoring,” Environmental Health Perspectives, Vol. 118, No. 2, 2010, pp. 253-258.

Zhang, X., Diamond, M. L., Ibarra, C., and Harrad, S. “Multimedia Modeling of Polybrominated Diphenyl Ether Emissions and Fate Indoors,” Environmental Science & Technology, Vol. 43, 2009, pp. 2845-2850.