Pollution Prevention

Our strategy is to apply IEMB's expertise in indoor air quality (i.e., source characterization, ventilation, filtration, modeling, biocontaminants, and sustainable buildings) to work cooperatively with industry, trade associations, consumers, and other affected parties to identify and prevent emissions from indoor sources. This can be accomplished by:

encouraging the development of low-emitting materials, products, and equipment;
evaluating existing data to identify low-emitting materials; and
developing appropriate test methods for use by industry to promote pollution prevention (e.g., test method to measure emissions from office equipment).

We are currently working, together with many industries, trade associations, and academia, to apply pollution prevention to improve indoor air quality. Specific pollution prevention research areas (current and completed) include office equipment, aerosol consumer products, engineered wood products, conversion varnishes used on wood products, and water-based cleaners.

Office Equipment - Current Work
As part of the prior measurement of photocopier emissions, limited testing was conducted to assess VOC concentrations in the head spaces above multiple samples of nominally identical toners, when these toners were heated to the temperatures they see in the fusers of copiers. With some of these "identical" toner samples, the concentrations of certain Hazardous Air Pollutants (HAPs) — styrene, ethylbenzene, and the xylene isomers — were 50 to 80% lower than the concentrations above other samples. It was postulated that perhaps the lower emissions from some samples resulted because they had been manufactured by a different process.

This observation suggests that perhaps significant reductions in indoor VOC emissions from copiers might be achieved through judicious selection of the manufacturing process, or perhaps of the purity of the polymer feedstocks used in the manufacturing process. The purpose of the currently ongoing work is to evaluate this potential pollution prevention opportunity.

If such a pollution prevention opportunity exists, its impact could be widespread. Modeling has recently been completed based on available emissions data from photocopiers and copied paper. Recent computer modeling results show that indoor concentrations of styrene, ethylbenzene, and the xylene isomers can exceed a total of 200 µg/m³ in the copier room, and 20 µg/m³ in the adjoining office space. The office levels caused by the photocopier are about twice the concentration that exists in the outdoor air, based upon the national and California ambient VOC data bases; the copier room levels are 20 times ambient. Given the widespread exposure to photocopier emissions in office buildings, a 50 to 80% reduction in the emissions of these HAPs from copiers could have a significant national impact.

To explore this pollution prevention (P2) opportunity, two toners — manufactured for one specific copier — were obtained from different sources. One toner — produced using a non-vented extrusion process — was obtained directly from a manufacturer who is independent of the vendor of the copier. The second toner was purchased from local retailers, and was sold under the brand name of the copier. These two toners had different VOC emission characteristics.

Two types of experiments were conducted on these two toners. The first type of experiment involved a laboratory thermal desorption test protocol, wherein samples were heated ballistically to the temperature of the fuser (185 °C) for the particular copier for which this toner is made. The off-gases from this procedure were collected on Tenax sorbent for analysis. The relative masses of VOCs emitted from the two toners during this screening protocol were compared, to estimate the extent to which one toner might be "cleaner" than the other during actual use in a copier.

The second type of experiment involved generation of copied paper using each of these two toners, and measuring the emissions of VOCs from the freshly copied sheets for 500- to 800-h periods in 53-L dynamic test chambers. The objective was to develop emission models which, together with an indoor air mass balance model, could be used to predict whether indoor VOC concentrations resulting from copied paper in a typical office might be significantly reduced by use of a low-emitting toner for a given copier.

Thermal Desorption Testing
The results of the thermal desorption testing have been published (Henschel, D.B., R.C. Fortmann, N.F. Roache, and X. Liu. Variations in the emissions of volatile organic compounds from the toner for a specific copier. Journal of the Air & Waste Management Association, 51:708-717, 2001.

Abstract) The conclusions of this study are as follows:

From comparison of Toners A and B from the two manufacturer runs, it is apparent that toners from different production runs — produced for the same copier by the same manufacturer using the same process — can have modestly different emissions of certain individual VOCs, by up to 18%. In this study, the observed emission differences more likely are due to differences in extruder operation rather than in feedstock characteristics.
The tests on the manufacturer toners and feedstocks demonstrated that all major compounds observed in the toner emissions result, at least in part, from impurities that are present in the feedstocks to begin with. The tests also demonstrated that the concentrations of some species can be increased during the extrusion process, presumably by oxidative degradation of the polymer. No major new compounds appear to be created during extrusion.
From comparison of the manufacturer and retailer toners tested here, it is clear that toners from different suppliers — manufactured to meet the fuser specifications for a single photocopier, but using different feedstocks and, potentially, different manufacturing processes or different process operating conditions — can have significantly different emissions of individual VOCs when heated in the laboratory. Emissions of a given compound can vary by a factor of 2 or more between toners.
Even when there are significant differences in emissions of individual VOCs between toners, it might not be possible to recommend one as a clearly preferable low-emitting product. Comparison of the manufacturer and retailer toners indicates that — while the retailer toners had much lower emissions of some compounds (ethylbenzene, xylenes, styrene, acetophenone) — they had higher emissions of other compounds (such as benzaldehyde and phenol). All of these compounds, except benzaldehyde, are Hazardous Air Pollutants. Moreover, the difference in total VOC emissions between the two toner sets is modest, and sometimes not statistically significant.

Chamber Tests on Copied Paper
Emissions of more than 25 individual VOCs were measured during the tests on copied paper with the two ("manufacturer" and "retailer") toners in the 53-L dynamic chambers. Data analysis to date has been completed for one of these compounds — styrene — a VOC that was consistently present in significant quantities from all the toners tested.

The analysis shows that the styrene emissions were best represented by either a third-order decay model, or by a power law model having an exponent between 0.3 and 0.5 (R² = 0.94 to 0.99). The two toners resulted in copied paper having significantly different styrene emissions (p<0.01). Predicted unit mass emissions of styrene from the paper (µg/m²) over 1,000 h were 9 times greater with the higher-emitting toner. But even copied paper produced using a still higher-emitting toner reported in the literature — having "typical maximum" toner coverage (15%) — is predicted to produce peak indoor styrene concentrations in a typical office less than 0.3% of the estimated minimum concentration of concern to susceptible sub-populations. Thus, for the toners considered here, indoor styrene exposures from copied paper appear too limited to provide incentive for switching to the lower-emitting toner.

Office Equipment - Completed Work
In a recently completed project, EPA, Research Triangle Institute, and Underwriters Laboratories worked together with industry to identify and evaluate pollution prevention opportunities to reduce indoor air emissions from office equipment. The project included:

conducting a literature review on indoor air emissions from office equipment,
developing standard test guidance to characterize indoor air emissions from office equipment,
measuring indoor air emissions from selected types of office equipment, and
identifying and evaluating pollution prevention approaches for reducing indoor air emissions from office equipment.

Literature Review
The literature review "Office Equipment: Design, Indoor Air Emissions, and Pollution Prevention Opportunities," (EPA-600/R-95-045, NTIS PB95-191375, March 1995) summarizes information on office equipment design; indoor air emissions of organics, ozone, and particles from office equipment; and potential pollution prevention approaches for reducing these emissions.

The report covers 1) dry and wet process photoimaging machines (copiers, printers, and faxes), 2) spirit duplicators, 3) mimeograph machines, 4) digital duplicators, 5) diazo (blueprint) machines, 6) computers, 7) impact matrix printers, and 8) other equipment types. Photoimaging machines are emphasized in the report because of their prevalence and potential opportunities for pollution prevention.

Development of Standard Test Guidance, and Measurement of Photocopier Emissions
A significant effort has been completed to provide standardized guidance for testing emissions from photocopiers. In the process, emissions from four dry-process copiers were measured. The results of this effort have been published in an EPA report entitled "Indoor Air Emissions from Office Equipment: Test Method Development and Pollution Prevention Opportunities" (EPA-600/R-98-080, NTIS PB98-165137, July 1998). (Abstract)

Evaluation of VOC Emissions from Printed Circuit Boards
VOC off-gassing from printed circuit boards has also been studied. The results of this effort have been published in an EPA report entitled "Personal Computer Monitors: A Screening Evaluation of Volatile Organic Emissions from Existing Printed Circuit Board Laminates and Potential Pollution Prevention Alternatives" (EPA-600/R-98-034, NTIS PB98-137102, April 1998). (Abstract)

Aerosol Consumer Products - Completed
Because aerosol consumer products, such as those used for personal care, pest control, and cleaning, are commonly used in the indoor environment, APPCD has supported research to 1) better understand personal exposures to aerosol consumer products and 2) to develop pollution prevention techniques to reduce exposures. A group of Industry Partners was actively involved in the research to ensure that the results will be practical for industry.

Developing Measurement Methods and Models
Georgia Tech and the University of Illinois worked together to develop measurement methods and models for manufacturers to use to develop a better understanding of aerosol behavior. This improved understanding may be used by manufacturers to develop and produce more efficacious and less toxic aerosol consumer products. Georgia Tech developed a Mass Spectrometer (MS) system for the chemical characterization of representative aerosol products. They also measured particle sizes for various spray patterns using a Malvern Analyzer and are developing an electron mobility analyzer for future work on particle sizing in conjunction with the MS system. The MS system eliminates the need for collection and concentration techniques and chromatographic separations, and is particularly sensitive to polar compounds. As a result, the system is well suited for real-time, direct analysis of aerosol consumer products. The University of Illinois developed techniques and instrumentation capabilities to measure aerosol transport and distribution in rooms. A model was developed to predict aerosol behavior in rooms. Researchers at the University of Illinois analyzed the spray patterns of representative aerosol products using particle image velocimetry (PIV) techniques. The ultimate outputs from this project include 1) indoor air characterization data on emissions from representative aerosol consumer products as a function of time; 2) methods, technology, and models to measure and predict emissions and personal exposures from use of aerosol products indoors; and 3) pollution prevention techniques and guidelines for the manufacture and use of these products. The EPA report describing this work is in preparation.

Innovative Spray Nozzle Design
Purdue University has developed and demonstrated an innovative spray nozzle design for use with precharged aerosol containers. This design is similar to one previously developed and demonstrated at Purdue for pump-and-trigger-dispensed aerosol products. The new dispenser design allows manufacturers to reformulate selected aerosol consumer products (e.g., personal care, hair care, degreasers, and hard surface cleaners) using water and air in place of VOC solvents and hydrocarbon propellants in precharged systems, while still maintaining acceptable product delivery characteristics. Laser diffraction measurements made at Purdue indicate that the new dispenser design produces product droplets in the desired size range. Data demonstrate that Sauter Mean Diameters (SMDs) are within experimental error of 70 µm for air-to-liquid ratios (ALRs) as low as 0.75%. Reducing the ALR below 0.75% results in a rapid increase in the mean drop size. The data also indicate little sensitivity of mean drop size to viscosity over the range considered in this study (0.020 to 0.080 kg/m-s, or 20 to 80 cP). Data also show that air consumption is below target values and supply pressures are acceptable. Dispenser performance is relatively insensitive to product formulation, as described by its viscosity and surface tension. This simplifies manufacturing since a single dispenser design can be used with a wide array of products. Research at Purdue addressed three questions necessary to provide rational design guidelines to industry. First, when the product exits the dispenser, how does it break up into ligaments and drops? Second, to what extent does the spray entrain surrounding air? Third, what challenges must be met during intermittent nozzle operation? Pulsed holography and PIV were used to acquire the necessary data to answer these questions.

The results of the Purdue effort are described in an EPA report entitled "Development of an Innovative Spray Dispenser to Reduce Indoor Air Emissions from Aerosol Consumer Products" (EPA-600/R-98-089, NTIS PB98-172471, July 1998).

Composite Wood Products - Completed
The objective of this project was to characterize indoor air emissions from composite wood products and to identify and evaluate pollution prevention approaches for their manufacture that may reduce indoor emissions.

The first step in the study of composite wood products was to complete a literature survey, and to evaluate existing data and methodologies. Two EPA reports have been published based on this initial effort. The first is entitled "Characterization of Manufacturing Processes and Emissions and Pollution Prevention Options for the Composite Wood Industry" (EPA-600/R-96-066, NTIS PB96-183892, June 1996). The second report is "Sources and Factors Affecting Indoor Emissions from Engineered Wood Products: Summary and Evaluation of Current Literature" (EPA-600/R-96-067, NTIS PB96-183876, June 1996).

Following the completion of this initial work, an experimental program was conducted. The results of this experimental effort have been published in a report entitled "The Application of Pollution Prevention Techniques to Reduce Indoor Air Emissions from Engineered Wood Products" (EPA-600/R-98-146, NTIS PB99-118309, November 1998). (Abstract)

Indoor Emissions from Acid-Catalyzed Varnishes
Practically all furnishings sold in the United States have a coating on the surface to provide water and stain protection and to enhance appearance. One type of coating used extensively in the furniture industry is the alkyd/urea-formaldehyde topcoat. These are thermosetting resins and are frequently called conversion varnishes or catalyzed finishes. Conversion varnishes are clear varnishes commonly used as coatings on wooden cabinets and, less frequently, on furniture. They do not cure by drying, as do many coatings, but rather by a chemical reaction, creating a durable water- and chemical-resistant coating that protects the wood during its use.

Conversion varnishes are of interest for ambient air quality because of emissions during manufacturing. From an indoor air perspective, these varnishes are of interest because volatile organic compounds (VOCs), including formaldehyde, may be emitted during use. EPA has conducted analyses to gain an understanding of the magnitude of emissions from conversion varnishes and to develop methods and protocols for testing and analysis of these emissions.

Three conventional conversion varnish systems, coded A, B, and C, were obtained from three different manufacturers. Several tests were run: EPA Method 24 - Determination of Volatile Matter Content, Water Content, Density, Volume Solids, and Weight Solids of Surface Coatings; proposed EPA Method 311 - Analysis of Hazardous Air Pollutant Compounds by Direct Injection into a Gas Chromatograph; a determination of free formaldehyde content in amino resin; and small chamber testing to determine emission rate profiles.

The free formaldehyde content of the amino resins was determined using a method based on the quantitative liberation of sodium hydroxide when formaldehyde reacts with sodium sulfite:

HCHO + Na₂SO₃ + H₂O → NaOH + HOCH₂SO₃Na.

The small chamber tests were conducted according to the procedures in ASTM D5116-90, except that alterations were necessary to accommodate the required high-temperature drying period specified by the manufacturer for two of the varnishes. Stainless steel 53-L chambers were used. One chamber was outfitted with heating jackets. Three thermocouples were strategically placed inside the chamber to monitor the temperature of the chamber air and the substrate surface, and the internal temperature of the substrate. The chamber air temperature was monitored in the center of the chamber directly below the mixing fan. Each test was performed with a temperature protocol developed using the manufacturer's recommendations for curing temperatures and times.

The organic solvents used in these varnishes are fairly volatile. The majority of the VOCs from these solvents are released into the air within several hours of application. A comparison of emissions measurements on three different substrates (glass, oak board, oak veneered hardboard) showed no effect of substrate on emissions.

The free formaldehyde contents of the three conversion varnish systems ranged from 1.46 to 5.35 mg/g varnish. Results of small chamber tests confirmed that the amount of free formaldehyde initially applied to the surface represents only a fraction of the total formaldehyde emitted. Formaldehyde is generated during cure and ageing. For the three conversion varnishes tested, the total formaldehyde emissions are 2 to 8 times the amount of free formaldehyde applied. As shown in Figure 1, varnish B has the highest short-term emission rate and varnish C the lowest. Two factors may have contributed to this result: (1) Varnish B has the highest free formaldehyde content, and (2) The higher curing temperatures specified by the manufacturer may accelerate the emissions.

The long-term emission data show a very different picture. The decay of the formaldehyde emission rate is a slow process. Varnish C has the highest rate, but the three varnishes follow a very similar pattern (Figure 2). Even 3000 hours (125 days) after application, the formaldehyde emission rate is greater than 0.1 mg/m²/hr. For comparison purposes, the standard set by the U.S. Department of Housing and Urban Development for plywood is also shown in Figure 2.

The long-lasting formaldehyde emissions can cause elevated concentrations in indoor environments. To assess the impact, we assume that a set of kitchen cabinets is installed in a typical house (300 m³ volume) with a formaldehyde emission rate of 0.5 mg/m²/hr, which is about the rate at 42 days (1000 hours) after varnish application. The predicted indoor concentrations with different source areas and air exchange rates are shown in Figure 3. At 0.5 air exchanges per hour, the indoor formaldehyde concentration due to cabinets alone could be 16 µg/m³ (12 ppb) if the source area is 5 m², and 67 µg/m³ (50 ppb) if the source area is 20 m². The irritancy threshold for formaldehyde is 100 ppb.

(EPA contact: Betsy Howard, 919-541-7915, howard.betsy@epa.gov)

Office of Research & Development | National Risk Management Research Laboratory

Pollution Prevention

Local Navigation