November 9, 2017
By Hans Schleibinger, PhD, and Doyun Won, PhD
What could be more fundamental than the air we breathe? As it is invisible and a part of everyday life, people can sometimes take the quality of air for granted. Indoor air in Canadian buildings may contain hundreds of volatile organic compounds (VOCs)—a diverse group of chemicals emitted as a gas at room temperature that often reach higher concentrations than outdoors.
The known or suspected health effects of VOCs vary from one chemical to another, with adverse effects potentially including eye, nose, and throat irritation and respiratory symptoms. At higher concentrations, another potential long-term effect for certain VOCs may be cancer. Considering Canadians spend approximately 90 per cent of their time indoors, indoor air quality (IAQ) may significantly affect human health and well-being, according to the World Health Organization (WHO). (For more, check out 2010’s WHO Guidelines for Indoor Air Quality: Selected Pollutants, available at www.euro.who.int/__data/assets/pdf_file/0009/128169/e94535.pdf.)
To control the level of exposure in buildings to VOCs like formaldehyde, which was declared toxic under the 1999 Canadian Environmental Protection Act (CEPA) (more information is available through Health Canada’s 2006 publication, Residential Indoor Air Quality Guideline: Formaldehyde) and has been identified as a known human carcinogen by the U.S. National Toxicology Program (NTP) (this information was derived from National Toxicological Program’s 2016 Report on Carcinogens, Fourteenth Edition: Formaldehyde, from Research Triangle Park, NC, U.S. Department of Health and Human Services, and Public Health Service, available at ntp.niehs.nih.gov/go/roc14), there are two approaches: selecting low-emitting materials such as low-VOC paints, and diluting the concentration by increasing fresh air ventilation.
For a long time, source control has been recognized worldwide as a more effective and energy-efficient strategy for improving IAQ. (Read P.M. Bluyssen, E. De Oliviera Fernandes, L. Groes, G. Clausen, P.O. Fanger, O. Valbjørn, C.A. Bernhard, and C.A. Roulet’s 1996 report, “European Indoor Air Quality Audit Project in 56 Office Buildings,” in Indoor Air for more.) Since off-gassing from building materials and consumer products is considered the main contributor of most VOCs, labelling construction materials and products as ‘low-VOC-emitting’ is a very promising approach to this issue. A U.S. publication on indoor air quality requirements for green building certifications showed selecting low-emitting materials was already recommended in the majority of cases. (In this 2015 publication, Building and Environment, W. Wei, O. Ramalho, and C. Mandin discuss the topic of “Indoor Air Quality Requirements in Green Building Certifications.”) Material labels on VOC emissions will enable builders, retrofitters, facility managers, and homeowners to actively select low-emitting products and materials.
Development of a Canadian emissions standard for building materials
There are currently a number of international labelling schemes to limit VOC emissions from building materials. (For more on these labelling schemes, consult V.M. Brown, D.R. Crump, and P.T.C. Harrison’s 2013 article, “Assessing and Controlling Risks from the Emission of Organic Chemicals from Construction Products into Indoor Environments,” in Environmental Sciences: Processes and Impacts.) In Canada, the first health-based emissions standard was released in 2016 through the Canadian Standards Association (CSA) with financial support from Health Canada (HC). CSA O160-16, Formaldehyde Emissions Standard for Composite Wood Products, sets limits for the allowable levels of formaldehyde emissions from composite wood panels. The need for this standard was supported by observations that the eight-hour average indoor guideline for formaldehyde (50 mg/m3 [40 ppb]) was frequently exceeded in Canadian homes. (The observations are discussed in greater detail in P. Lajoie, D. Aubin, V. Gingras, P. Daigneault, F. Ducharme, D. Gauvin, D. Fugler, J.M. Leclerc, D. Won, M. Courteau, S. Gingras, M.È. Héroux, W. Yang, and H. Schleibinger’s “The IVAIRE Project – A Randomized Controlled Study of the Impact of Ventilation on Indoor Air Quality and the Respiratory Symptoms of Asthmatic Children in Single-family Homes” in a 2015 edition of Indoor Air.)
In collaboration with Health Canada’s Water and Air Quality Bureau, the National Research Council of Canada (NRC) did extensive work to identify the most relevant sources of formaldehyde indoors. For instance, the evaluation of 82 building materials for volatile organic compound emissions showed composite wood products are often the main sources of formaldehyde. This can be observed in Figure 1, which shows the amount in mg of formaldehyde emitted per surface area (m2) per time (h) for subsets of tested materials, including 15 composite wood materials, 11 paints, and 12 insulations.
CSA O160 was developed through a committee formed with representatives from Canadian stakeholders Health Canada, the Canada Housing Builders Association (CHBA), FPInnovations, the Composite Panel Association (CPA), the Canadian Wood Council (CWC), the Canadian Lung Association, numerous wood product manufacturers, NRC, and APA−the Engineered Wood Association. The standard is intended to harmonize with the existing, mandatory California Air Resources Board (CARB) Airborne Toxic Control Measure (ACTM) 93120, which will take effect as the U.S. Environmental Protection Agency’s (EPA’s) regulation on formaldehyde emission for composite wood products in 2018. (This information comes from the U.S. Environmental Protection Agency [EPA]. For more, visit www.epa.gov/formaldehyde/formaldehyde-emission-standards-composite-wood-products.)
The scope of CSA O160 and the U.S. standard is limited to hardwood plywood (HWPW), particleboard (PB), medium-density fibreboard (MDF), and thin MDF. Figure 2 lists maximum allowable chamber concentrations of formaldehyde for these material categories. (For more, consult Canadian Standards Association [CAN/CSA] O160-16, Formaldehyde Emissions Standard for Composite Wood Products.) How these chamber concentrations are typically measured will be described later in this article.
While CSA O160 is a voluntary standard, it is expected to serve as the basis for Canadian manufacturers to certify their low-emitting products. Since the development of CSA O160, a Notice of Intent (NOI) to develop a regulation targeting formaldehyde was published in Canada Gazette, Part I, on March 18, 2017. The NOI states that Health Canada and Environment and Climate Change Canada are initiating the development of proposed regulations to be made under CEPA seeking to reduce emissions of formaldehyde in composite wood products by regulating the manufacturing, use, processing, sale, offer for sale, and importation of these products into Canada.
Creating effective and targeted IAQ standards requires the consideration of two main elements: the use of widely accepted standardized testing methods and the availability of health-based reference values for acceptable emissions and exposure levels. To be fair and consistent to all manufacturers, emission results need to reproducible from lab to lab. This is only possible through standardized testing and test protocols, requiring specific quality assurance provisions.
Test conditions also need to resemble, as much as possible, an actual indoor environment, which means describing and standardizing test methods close to the conditions found in indoor environments, such as the amount of building material present, typical ventilation rate, temperature, and relative humidity. The comprehensively described test method must also be comprehensible to a multitude of stakeholders to ensure the test’s broad acceptance.
Equally important, the health-based reference values for chemicals of concern must be established by credible health organizations, which are responsible for the jurisdictions in question and operate in a transparent fashion. Formaldehyde was declared toxic under CEPA, as its continued and increasing use was “entering the Canadian environment in a quantity or concentration that constitutes or may constitute a danger for the environment on which life depends and a danger in Canada to human life or health.” (This information was obtained from Environment Canada and Health Canada’s 2001 Priority Substance List Assessment Report: Formaldehyde.)
Health Canada has developed Residential Indoor Air Quality Guidelines (RIAQG) for some of the VOCs most commonly found in indoor air, which can guide setting the maximum allowable concentrations indoors. For example, HC established a RIAQG for formaldehyde in 2006 based on eye irritation and respiratory symptoms. For formaldehyde, a one-hour average exposure limit is established at 123 µg/m3 or 100 parts per billion, based on eye irritation in a study performed in the United States.
An eight-hour average exposure limit has been established at 50 µg/m3 (40 ppb) that was the lower end of the exposure level associated with no significant increase of asthma hospitalization in a 2002 study. (The study in question, “Domestic Exposure to Formaldehyde Significantly Increases the Risk of Asthma in Young Children,” was published in Eur. Respir. J. by K.B. Rumchev, J.T. Spickett, M.K. Bulsara, M.R. Phillips, and S.M. Stick in 2002.) This eight-hour average exposure limit was used to assess whether the maximum allowable chamber concentrations specified in CSA O160 would ensure an indoor air concentration below the exposure limit.
Material emissions testing for VOCs
Chemical emissions from building materials are typically determined in an enclosure that is climatically controlled
to mimic typical indoor environmental conditions. The most frequently used enclosures are ‘small-scale’ chambers with volumes of 1000 L (35 cubic ft) or below. NRC used 50-L (1.76 cubic ft) chambers (Figure 3) to characterize the emissions from composite wood products. The results were used to develop pertinent sections of CSA O160. Small-scale chambers at NRC meet the specifications given in ASTM D6007, Standard Test Method for Determining Formaldehyde Concentrations in Air from Wood Products Using a Small-scale Chamber, which is the small-scale emission test method referenced in CSA O160 and CARB ACTM 93120. The test conditions given in ASTM D6007, including temperature, humidity, air change rate, and material loading ratio, are summarized in Figure 4.
Since emission rates tend to change over time, it is important to select an optimal test period in order to reach a balance between correctly characterizing long-term emissions and keeping the test costs reasonable. The European Committee for Standardization (CEN) recommends air samples should be taken after three to four days to characterize short-term emission behaviour, and after 28 days to understand long-term emission behaviour. (These recommendations can be found in European Committee for Standardization Technical Specification [CEN/TS] 16516:2013, Construction Products–Assessment of Release of Dangerous Substances–Determination of Emissions into Indoor Air.) In North America, a conditioning period is recommended for a short-term test. For example, ASTM D6007 and ASTM E1333, Standard Test Method for Determining Formaldehyde Concentrations in Air and Emission Rates from Wood Products Using a Large Chamber, require seven-day conditioning before one-day testsfor formaldehyde emissions from wood products, while a 10-day conditioning period is required before four-day tests for VOC emissions from indoor sources. (This requirement is stated under California Department of Public Health’s [CDPH’s] Standard Method for the Testing and Evaluation of Volatile Organic Chemical Emissions from Indoor Sources Using Environmental Chambers–Version 2.1 [Emission Testing Method for California Specification 01350].)
At NRC, temperature control is achieved using an environmental enclosure that can hold the temperature at a desired level (e.g. 23 C [73 F]). The humidity in the chamber is maintained by blending dry and humidified airstreams, typically with mass flow controllers, and continuously monitoring the exhaust air for relative humidity.
In order to limit the emissions to the material surface, NRC developed and custom-fabricated a specimen holder, mimicking the emissions in real environments, minimizing emissions from specimen edges and back, and therefore precisely meeting the material loading ratio requirements. Meeting the requirement of a material loading ratio (i.e. the ratio of the area of exposed surface of the test specimen to the chamber volume) is particularly important, as it can affect the chamber concentration and emission rate. This practically means that emissions are fairly characterized, like in a real indoor environment.
VOCs and formaldehyde emitted from the building material into the chamber are then drawn out of the chamber onto a sampling medium (i.e. sorbent) at a designated time, and subsequently analyzed with a gas chromatography/mass spectrometry (GC/MS) and high-performance liquid chromatography (HPLC). Since materials can emit hundreds of chemicals, which cannot all be caught by the same sorbent, it is sometimes necessary to sample onto several sorbents in parallel and analyze them with different apparatus.
While small-scale testing is one very useful approach, in some cases it is more appropriate to do large-scale experiments for room-size building materials, material assemblies, and furnishings. It may also be helpful to think of your office and all that is in it. The 31,000- to 55,000-L (31 to 55m3) full-scale test chamber at NRC (Figure 5) was developed to assess exactly this type of scenario. The room-sized chamber has a dedicated HVAC system, which also includes charcoal and high-efficiency particulate air (HEPA) filters to clean the supply air, which is identical to the small-scale chamber in principle. This chamber meets the specifications stated in ASTM E1333, which is adopted as the full-scale testing method by CSA O160 and CARB ACTM 93120.
Screening of SVOC emissions
In addition to formaldehyde and VOCs, building materials may contain so-called semivolatile organic compounds (SVOCs). The main difference between VOCs and SVOCs is the latter have higher boiling points, which means only a smaller portion is released from the building materials as compared to volatile organic compounds, with the majority of the released SVOCs then ‘sticking’ to indoor surfaces or airborne particulates. While this can mean lower levels of chemicals in air as compared to VOCs, the chemicals that are present in building materials will be emitted over much longer time periods. Many different chemical classes fall under the category of SVOCs, such as flame retardants (including polybrominated diphenyl ethers [PBDEs]), plasticizers (including phthalates), and biocides, to name a few.
Health effects of SVOCs or classes of SVOC vary widely, and are dependent on chemical classes and their individual chemical properties. Health effects potentially associated with exposure to some classes of SVOC include allergic symptoms in children, effects on the reproductive system and birth weight, and endocrine disruption. (For more, see C.J. Weschler and W.W. Nazaroff’s “Semivolatile Organic Compounds in Indoor Environments,” in Atmospheric Environment 42, 9018−9040.)
Some SVOCs found in building materials are on the List of Toxic Substances under CEPA. Examples are diethylhexyl phthalate (DEHP) used as a plasticizer, PBDEs used as a flame retardant, and hexabromocyclododecane, 90 per cent of which is used in polystyrene insulation. (For more information, consult the Government of Canada’s Toxic Substances List–Schedule 1, from April of this year, at www.ec.gc.ca/lcpe-cepa/default.asp?lang=En&n=0DA2924D-1&wsdoc=4ABEFFC8-5BEC-B57A-F4BF-11069545E434. More on hexabromocyclododecane is available at www.ec.gc.ca/toxiques-toxics/default.asp?lang=En&n=58F1CC80-1.) When investigating SVOC emissions from building materials, test conditions should be modified to consider SVOCs’ high boiling point and low volatility relative to VOCs, which would lead to high absorption rates on the test chamber surfaces. Therefore, it might take up to several months to achieve a steady state between surface and chamber air concentrations. Steady-state conditions are desirable to reproducibly assess emission rates. Furthermore, sampling before steady state could lead to chamber concentrations that are too low to be reliably detected.
Enter the micro-chamber
To overcome the challenges of measuring SVOCs, micro-chambers (Figure 6) are often used as the more appropriate test environment, as opposed to small- or full-scale chambers. These micro-chambers are well-suited for measuring SVOCs because of their relatively high SVOC concentration levels, as a result of relatively large specimen surface area compared to the micro-chamber surface area. Emissions can also be accelerated with high chamber flow rates, making the chamber concentrations level off quickly. Testing speed benefits further from high operating temperatures and, since all the ‘exhaust air’ from the chamber goes through the sampling tube, this method leads to high analytical sensitivity—all while ensuring shorter testing times and lower costs.
In 2012, NRC developed a fast screening method using micro-scale chambers to determine phthalate emissions from building materials. (More on this method can be found in D. Won, E. Lustztyk, G. Nong, and H. Schleibinger’s 2012 Client Report: Materials Emissions Testing for Phthalates.) A total of 101 household materials, including 75 building materials and 26 consumer products, were tested using the method to identify the sources of 23 phthalates. Of these 23 sources, 19 have been prioritized for risk assessment in the second phase of the Chemicals Management Plan (CMP) by Health Canada. DEHP was one of the most frequently detected phthalates in these materials. The highest emission factors, though, were associated with diisononyl phthalate (DINP) in household products such as vinyl flooring, wallcoverings, and wires. The results also showed DEHP, which is on the List of Toxic Substances under CEPA, is in the process of being substituted by DINP in certain product categories. The results demonstrate the usefulness of the micro-scale chamber method for identifying the main sources of health-relevant phthalates, which are otherwise not easily detected or measured reliably with small- and full-scale chambers.
With the development of new building technologies and the movement toward the conception of greener buildings including all aspects from design through to the construction phase, it is important to have testing methods, facilities, and experts that can evolve with the times. There is a growing global demand for materials and products with low VOC emissions. For instance, Leadership in Energy and Environmental Design (LEED) certification takes into account air quality and has provisions for formaldehyde and various VOCs.
Canada is certainly no exception to this trend, as a recent release of the voluntary standard CSA O160 and an NOI by Health Canada to develop a regulation to reduce emissions of formaldehyde from composite wood products seem to be pushing the industry more actively in the low-VOC direction. While the health-based requirements for low-emitting materials in Canada are mainly focused on formaldehyde, more indoor chemicals in the VOC and SVOC categories may be expected to be the subject of Canadian labelling systems as more information on their toxicity to humans becomes available, and their exposure limits are more commonly considered.
NRC continues to put its resources and efforts toward developing test methods and solutions to support stakeholders with identifying and minimizing harmful chemicals at their sources, and to benefit manufacturers in developing low-emission products, as well as aiding building authorities in establishing feasible and meaningful criteria for material emissions guidelines and standards. There is always more work to be done, and NRC will continue working with partners in ensuring we are ready for tomorrow’s buildings. (The authors wish to acknowledge contributions in the areas of the health relevance of volatile organic compounds [VOC]) and semi-volatile organic compounds [SVOCs], as well as guidelines and regulations, from members of Health Canada’s Water and Air Quality Bureau and its Healthy Environments and Consumer Safety Branch—specifically, Patrick Goegan, Michelle Deveau, Katherine Guindon-Kezis, Lynn Bernd-Weiss, and Lara Kouri.)
Hans Schleibinger, PhD, is an environmental engineer who worked in the areas of air and water pollution control, prevention of mould growth, hospital hygiene, toxicology, and environmental analysis in Germany. He has headed the Ventilation and Indoor Air Quality Group of the National Research Council (NRC) since 2005, evaluating products and technological solutions and creating evidence-based knowledge for Canadian stakeholders. Schleibinger was one of the founders of the Canadian Committee on Indoor Air Quality and Buildings (CCIAQB). He can be reached at firstname.lastname@example.org.
Doyun Won, PhD, is a senior research officer at NRC, working on indoor air quality (IAQ) and ventilation. She has 19 years of experience in testing building materials and consumer products for chemical emissions, predicting their impacts on IAQ, and developing IAQ mitigation strategies. A member of the technical committee for Canadian Standards Association (CSA) O160-16, she currently serves as an associate editor for Indoor and Built Environment journal. She can be reached via e-mail at email@example.com.
The authors would like to acknowledge the important contributions by Wenping Yang, Gang Nong and Stephanie So in NRC’s laboratories.
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