Developing a Reference Material for Diffusion-Controlled Formaldehyde Emissions Testing Zhe Liu, † Xiaoyu Liu, ‡ Xiaomin Zhao, † Steven S. Cox, † and John C. Little §, * † Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States ‡ National Risk Management Research Laboratory, Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States § School of Civil Engineering, University of Sydney, Sydney, New South Wales 2006, Australia * S Supporting Information ABSTRACT: Formaldehyde, a known human carcinogen and mucous membrane irritant, is emitted from a variety of building materials and indoor furnishings. The drive to improve building energy efficiency by decreasing ventilation rates increases the need to better understand emissions from indoor products and to identify and develop lower emitting materials. To help meet this need, formaldehyde emissions from indoor materials are typically measured using environmental chambers. However, chamber testing results are frequently inconsistent and provide little insight into the mechanisms governing emissions. This research addresses these problems by (1) developing a reference formaldehyde emissions source that can be used to validate chamber testing methods for characterization of dynamic sources of form- aldehyde emissions and (2) demonstrating that emissions from finite formaldehyde sources can be predicted using a fundamental mass-transfer model. Formaldehyde mass-transfer mechanisms are elucidated, providing practical approaches for developing diffusion-controlled reference materials that mimic actual sources. The fundamental understanding of emissions mechanisms can be used to improve emissions testing and guide future risk reduction actions. ■ INTRODUCTION Formaldehyde (H 2 CO) is a flammable colorless gas with a pungent odor at room temperature and is classified by the U.S. Department of Health and Human Services National Toxicology Program as a known human carcinogen and mucous membrane irritant. One of the primary uses of formaldehyde is for the production of synthetic resins (including urea-formaldehyde, phenol-formaldehyde, mela- mine-formaldehyde, and polyacetal resins), which are used as adhesives, impregnating resins, and curable molding products in the wood, textile, leather, rubber, and cement industries. 1 These products and many other indoor materials, including natural wood, can emit formaldehyde during the use phase, although emission rates vary greatly. 2-4 Concentrations of formaldehyde in indoor air typically range from 10 to 4000 μg/m 3 . 1,5,6 While exposure to formaldehyde can occur through multiple pathways, indoor air is the largest source of formaldehyde exposure for the general population, although occupational exposures are important for specific populations such as employees in formaldehyde-related industries. 7 Due to the potential health risks associated with indoor formaldehyde exposure, various guidelines, standards, and recommendations have been established. 5 In the United States, the Formaldehyde Standards for Composite Wood Products Act, enacted as Title VI of the Toxic Substances Control Act (TSCA), was signed into law in July 2010. TSCA Title VI requires formaldehyde emissions testing in chambers to demonstrate compliance with these standards. Emissions testing performance is often evaluated through interlaboratory studies, but these are costly and time- consuming and may lead to inconclusive results. A well- characterized reference formaldehyde emissions source would be a valuable tool for verifying and validating emissions testing procedures. A recently published study describes a semi-infinite, steady-state formaldehyde emissions source that would be useful for validating single-point or steady-state chamber testing procedures such as those described in ASTM E1333-10, ASTM D6007-02, and EN 717-1. 8-11 The subject of this research is a dynamic formaldehyde emissions reference material with an emissions profile similar to the emissions profile of finite sources of formaldehyde. A dynamic reference emissions source would be useful for validating full emissions profile character- ization tests such as those described in ASTM D5116-10. 12 In collaboration with the National Institute of Standards and Technology (NIST), researchers at Virginia Tech (VT) previously developed a reference material for volatile organic Received: July 3, 2013 Revised: October 3, 2013 Accepted: October 8, 2013 Published: October 8, 2013 Article pubs.acs.org/est © 2013 American Chemical Society 12946 dx.doi.org/10.1021/es402911e | Environ. Sci. Technol. 2013, 47, 12946-12951