OTS0524661
FORMALDEHYDE EXPOSURE IN RESIDENTIAL
SETTINGS: SOURCES, LEVELS AND
EFFECTIVENESS OF CONTROL OPTIONS (INTERIM
FINAL REPORT) (EPA CONTRACT #68-02-3968)
19 JUL 1985
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CODING FORM FOR SRC INDEXING
REVISED 10/15/86
M.cretich« NP.
Submitting Organization
WERSftR INC
Document THte I
FORMALDEHYDE EXPOSURE IN RESIDENTIAL SETTINGS: SOURCES
U.'VELS flND EFFECTIVENESS OF CONTROL OPTIONS (INTERIM FINflL
REPORT) (EPO CONTRftCT #68-05-3968)
FORMPLDEHYDE
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Interim Final Report
Formaldehyde Exposure In Residential Settings:
Sources, Levels, and Effectiveness of Control Options
EPA Contract No. 68-02-3968
Task No. 14
Prepared by:
Versar Inc.
6850 Versar Center
Springfield. Virginia 2?151
Prepared for:
U.S. Environmental Protection Agency
Exposure Evaluation Division
Office of Toxic Substance
401 M Street. S.W.
Washington, D.C. 20460
Revised July 19. 19Br»
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Disclaimer
This 1s an Interim final report and should not at this time be
construed to represent Agency policy. It 1s being circulated for
comments on Us technical merit and policy Implications. Mention of
trade names or commercial products does not constitute endorsement or
recommendation for use by the U.S. Environmental Protection Agency.
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Acknowledgements
This project was funded by the U.S. Environmental Protection Agency,
Office of Toxic Substances (OTS), Exposure Evaluation Division. This
report was prepared by Versar. Inc. of Springfield. Virginia, 1n response
to EPA Work Order 14 of Contract No. 68-02-3968.
This EPA Project Officer for this contract Is Michael Callahan.
Greg Schweer, the CPA Task Manager, deserves special thanks for his
active participation and expert guidance 1n all phases of the project.
Ne are also Indebted to Harold Podall of the Economics and Technology
Division of OTS for his Input on the chemistry of formaldehyde resins. A
number of Versar personnel have contributed to this task over a period of
performance:
Program Management - Gayaneh Contos
Task Management - G1na D1xon
Technical Staff - Tom Chambers
Pat Mood
Ray Glvonettl
Dede Gamgoum
Alan Glelt
Sh1v Krlshnan
Secretarial Staff - Shirley Harrison
Franklin Clay
Donna Barnard
Sue Elhusseln
Kathy Zavada
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TABLE OF CONTENTS
Page No.
EXECUTIVE SUMMARY 1
1.0 INTRODUCTION 16
1.1 Background 16
1.2 Report Organizet*an 16
2.0 PRESSEO-UOOO PRODUCTS CONTAINING UF RESINS 18
2.1 Product Descriptions 18
2.1.1 Partleleboard 18
2.1.2 Medium-Density Floorboard (MOF) 22
2.1.3 Hardwood Plywood 23
2.2 Sources and Mechanisms of Formaldehyde Formation
and Release 25
2.2.1 Chemical Species Capable of Producing
Formaldehyde 25
2.2.2 Relative Importance of Chemical Species
as Sources of Formaldehyde 26
2.3 factors Affecting Formaldehyde Release from
Pressed Wood Products 30
2.3.1 Product-Specific Factors 30
2.3.2 Environmental and Architectural Factors 39
2.4 Formaldehyde Emission Rate Testing Methods 44
2.4.1 Background 44
2.4.2 Methods 45
?.4.3 Inter-Method Correlations 55
2.5 Formaldehyde Emission from Conventional Pressed-
Wood Products SB
2.5.1 1980 and 1982 NPA Surveys (NPA 1984) 65
2.5.2 CPSC Pressed-Mood Product Survey 67
3.0 OTHER RESIDENTIAL SOURCES 77
3.1 Urea Formaldehyde Foam Insulation (UFFI) 77
3.2 Construction Products Containing Phenol-
Formaldehyde (PF) Resins 80
3.3 Consumer Products Potentially Containing
Formaldehyde Resins 83
3.4 Combustion 85
3.5 Outdoor Air 90
3.6 Relative Significance of Sources on Air
Levels Indoors 94
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TABLE OF CONTENTS (continued)
Page Ho.
4.0 RESIDENTIAL HONIIORING DATA 99
4.1 Major Studies of Residential Levels 99
4.2 Studies Examining Factors Affecting Air Levels ... 126
4.3 Ongoing Monitoring Studies 140
4.4 European Studies 148
4.5 Summary of Monitoring Data 157
5.0 SHORT. AND LONG-TERM EFFECTIVENESS OF FORMALDEHYDE
CONTROL OPTIONS 162
5.1 Changes In UP Resin Formulation 162
5.1.1 Reduction In the F:U Ratio 168
5.1.2 Formulation of Scavengers Into the
UF ResIn/Hood System 173
5.2 Post-Cure Board Treatments 181
5.2.1 Ammonia Fumigation 181
5.2.2 Post-Cure Board Treatments with Other
Scavengers 193
5.2.3 Non-Scavenger Emission Barriers 195
5.3 Substitute Resins 198
5.3.1 Phenol Formaldehyde Resin as a Substitute
for Urea Formaldehyde Resin 198
5.3.2 Isocyanate Resins 202
5.4 Substitute Wood Products 208
5.4.1 Hardboard 206
5.4.2 Gypsum Board 209
5.4.3 Other Substitutes 209
5.5 Increased Room Ventilation 209
5.6 Presale Storage (Board Aging) 211
5.7 Approaches to Reducing Formaldehyde Emissions
From UF Bonded Ucod Products Based on Resin
Chemistry 213
6.0 FORMALDEHYDE STANDARDS FOR WOOD PRODUCTS
AND INDOOR AIR 215
6.1 Denmark 215
6.2 Finland 218
6.3 west Germany 218
6.4 Netherlands 218
6.5 Sweden 219
6.6 united States 219
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TABLE OF CONTENTS (continued)
Page Ho.
7.0 MODELING FORMALDEHYDE RELEASE FROM PRESSED-WOOO
PRODUCTS AND EXPOSURE IN RESIDENTIAL SETTINGS 220
7.1 CPSC Indoor A1r Quality Model 221
7.2 Matthews et al. Simple Steady-State Model fo'
Indoor Formaldehyde Concentrations 22S
7.3 Derivation of a Best-Fit Decay Curve to Predict
Long-Tern levels of Formaldehyde 1n Homes 228
7.3.1 Description of Data Sets 229
7.3.2 Results of Statistical Analysis of the
Decay Function 233
7.3.3 Statistical Analysis of Separate and
Combined Data Sets 233
7.3.4 Conclusion 245
8.0 REFERENCES 246
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LIST OF TABLES
Page Ho.
Table 1 Use of Pressed-Uood Products In Home
Construction 20
Table 2 A Rough Estimate of the Relative Amounts of the
Various Formaldehyde Derived Species In a Cured
Board with 1.3:1 F/U Hole Ratio Resin 27
Table 3 Relative Rates of Formation of Formaldehyde and
Duration of Release from a Cured UF Board .... 29
Table 4 Potential Effects of Temperature and Relative
Humidity Changes on Formaldehyde A1r
Concentration: (ppm) 43
Table 5 Summary of Plant Participation 1n NPA's 1980 and
1982 Surveys 66
Table 6 NPA 1980 and 1982 Survey Summary Results 68
Table 7 CPSC Pressed-Uood Product Survey Emission Rate
Summary Results 71
Table 8 Comparison of 1980 CPSC and 1980. 1982 NPA
Test Results 76
Table 9 Average Formaldehyde Measurement 1n UFFI Homes by
Age 79
Table 10 Release of Formaldehyde from Specific Consumer
Products 84
Table 11 Summary of Formaldehyde Emission Rates from
Unvented Combustion Appliances 87
Table 12 Ambient Air Measurements of Formaldehyde at
Urban Sites In the United States 91
Table 13 Potential Impact of PF Resin-Containing Products.
Consumer Products and Combustion on Indoor
Formaldehyde Concentrations 96
Table 14 Potential Impact of UF Resin-Containing Mood
Products and Insulation on Indoor Formaldehyde
Concentrations 97
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LIST OF TABLES (continued)
Page No.
Table 15 Summary of Formaldehyde Concentrations 1n Indoor
Environments Studies by the Lawrence Berkeley
Laboratory 100
Table 16 Summary of Observed Aldehyde Concentrations In
U.S. Homes Monitored by Geomet, Inc 102
Table 17 Number of Samples 1n Formaldehyde Concentration
Ranges Found by University of Washington 104
Table 18 Number of Samples 1n Formaldehyde Concentration
Ranges Found by Private Washington Laboratories . . 105
Table 19 HHI Mobile Home Stude Test Results and
Test Details 107
Table 20 Summary of Results of Canadian National
Testing Survey 109
Table 21 Comparison of Two Canadian Hone Populations
by Average Formaldehyde Concentration 110
Table 22 Number of Observations Found In Concentration
Intervals by Clayton Environmental Consultants ... 112
Table 23 Number of Observations Found In Concentration
Intervals by Wisconsin Division of Health 114
Table 24 ORLN/CPSC Mean Formaldehyde Concentrations (ppm)
as a Function of Age and Season (Outdoor Heans
Are Less Than 25 ppb Detection Limit) 116
Table 25 ORNL/CPSC Formaldehyde Levels Observed 1n Houses
with and without UFFI 117
Table 26 Summary of Formaldehyde Monitoring Data from
Complaint Homes Collected by the Minnesota State
Health Department 119
Table 27 Summary of Formaldehyde Concentrations Measured
in Complaint Mobile Homes 1n Tennessee from
March 1982 through September 1983 120
Table 28 Summary of Formaldehyde Concentrations Measured
1n Complaint Mobile Hones In Kentucky from
September 1979 through December 1980 122
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LIST OF TABLES (continued)
Page No.
Table 29 Highest Measured Formaldehyde Concentrations In
Dutch Houses 128
Table 30 Formaldehyde Levels 1n Dutch Houses Before and
After Panel Coatings 129
Table 31 Formaldehyde Concentrations Found In Conventional
Homes Monitored by the University of Iowa 131
Table 32 Formaldehyde Levels Found in Indiana Study 133
Table 33 Summary of One-Week Average Indoor Formaldehyde
Data Observed In Fleming and the Associates Study . 13B
Table 34 Indoor Mean Formaldehyde Concentrations Measured
In 164 Mobile Homes by the Texas Indoor Air
Quality Study {Preliminary Results) 144
Table 35 Mean Formaldehyde Concentration and Temperature '
Measurements For Texas Indoor Air One Meek
Study I and II 147
Table 36 Formaldehyde Measurements 1n Swiss Houses Over
Four Seasonal Periods (ppm) ">-'•'
Table 37 Average. Median. 10th and 90th Percentlles
and Highest and Lowest Values Found 1n Haarlem
District Study (The Netherlands) 151
Table 38 Formaldehyde Concentrations 1n German Homes (ppm) . 153
Table 39 Frequency Distribution of Formaldehyde
Concentrations of Swedish Homes 154
Table 40 Formaldehyde Concentration in Danish Homes 155
Table 41 Summary of U.K. Study and Comparison with
Canadian UFFI/ICC Data 158
Table 42 Summary of Residential Formaldehyde Monitoring ... 159
Table 43 Summary of Data on Formaldehyde Emission
Control Options 163
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LIST OF TABLES (continued)
Page No.
Table 44 Comparison of Formaldehyde Emission from
Partlcleboard Prepared with UF Resins of
Different Molar Ratios 171
Table 45 Comparison of Formaldehyde Emission from MOF
Prepared with UF Resins of Different Molar Ratios . 172
Table 46 Combined Effect of Aging and Varying Molar
Ratios In Adhesive* on Formaldehyde Emissions
from Partlcleboard 174
Table 47 Combined Effect of Press Tempeature/T1ne and
Varying Holar Ratios 1n Adhesive; on Formaldehyde
Emissions from Partlcleboard 175
Table 48 Formaldehyde Emissions from Boards Formulated with
Scavengers 178
Table 49 Effect on Several Pre-Press Scavengers on
Formaldehyde Emissions from Plywood 180
Table 50 Effectiveness of RVAB and Suedspan Ammonia
Fumigation of Boards 187
Table 51 Effectiveness of Swedspan Method of Formaldehyde
Emission Reduction 189
Table 52 Results of Ammonia Fumigations of 12 Mobile
Homes 191
Table 53 Summary of Formaldehyde Test Data from Various
Phenolic-Bonded Panel Products Measured by
Or. M.F. Lehmann of 'Weyerhaeuser Co 203
Table 54 Results of Large-Scale Dynamic Chamber Tests and
Two-Hour Desiccator Tests on Various Types of
Phenolic Panel Products 204
Table 55 International Indoor Air Standards for
Formaldehyde- Standards and for Formaldehyde
Emission from Pressed-Hood Products 216
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LIST OF TABLES (continued)
Page Ho.
Table 56 Results of Statistical Analyses of Clayton Data ... 237
Table 57 Results of Statistical Analyses of Wisconsin Data . . 239
Table 58 Results of Statistical Analyses on the
Aggregated Data Set 241
Table 59 Analysis of Data Grouped Into Intervals 244
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LIST OF FIGURES (continued)
Page No.
Figure 15. Profile of the Formaldehyde Emission Rates of the
Partlcleboard and Hardwood Plywood Paneling Boards
Tested In the CPSC Survey 72
Figure 16. Profile of the Formaldehyde Emission Rates of
the HOP, Partlcleboard and Hardwood Plywood
Paneling Tested 1n the CPSC Survey 73
Figure 17. Inter-Board Variation In the CPSC Survey 75
Figure 18. Calculated Tine-Weighted Average Formaldehyde
Levels In a Mobile Home 135
Figure 19. Formaldehyde Levels 1n a New. Unoccupied Mobile
Home as a Function of Time of Day and
Temperature 136
Figure 20. The Verkor FO-EX Chamber 183
Figure 21. Effectiveness of FD/EX Treatment 184
Figure 22. RYAB's Casing Equipment 186
Figure 23. The Swedspan Ammonia Treatment Method 188
Figure 24. UKI Method Test Results for Cured Resin/Wood
Composites and Dried Wood Products 206
Figure 25. Plot of the Clayton Data 231
Figure 26. Plot of Combined Data Set 232
Figure 27. Plot of Combined Data Set 234
Figure 28. Regression Analysis of Clayton Data -
Exponential Model 238
Figure 29. Regression Analysis of Wisconsin Data -
Exponential Model 240
Figure 30. Regression Analysis of Combined Data Set -
Exponential Model 242
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EXECUTIVE SUMMARY
The U.S. Environmental Protection Agency (EPA) 1s reexamlnlng
existing Information on residential exposure to formaldehyde released
from pressed-wood products containing urea-formaldehyde (UF) resins.
This report addresses two general topic areas:
Current levels of exposure to formaldehyde In housing, the source of
that exposure, and factors that affect these levels.
Reduction In exposure levels that could result from Implementation of
measures to control formaldehyde emissions from pressed wood products.
Pressed Mood Products Containing UF Resins
Formaldehyde 1s released from all pressed-wood products containing UF
resin. The three types of pressed-wood products formulated with UF resin
are particleboard, medium density flberboard (MDF), and hardwood plywood.
Partlcleboard 1s composition board comprised of 6 to 10 percent resin
(by weight), and small wood particles; additives are also a small
fraction of the board. UF 1s the resin used for the vast majority of
partlcleboard. though producers accounting for 10 percent of total
production In 1983 used other resins (phenol-formaldehyde, 6 percent;
Isocyanate, 4 percent). Manufacture entails mixing these components and
pressing the mixture at elevated temperatures. The 1983 production of
partlcleboard was over 3 billion square feet, of which 70 percent was
used 1n furniture, fixtures, cabinets, and slnllar products. The
remaining 30 percent was used for construction purposes. Including mobile
home manufacture (common uses are as decking or flooring underlayment).
Partlcleboard Is used Increasingly as a substitute for whole-wood
products. Partlcleboard Is commonly used In mobile home construction at
a loading rate of 0.5 square meters per 1 cubic meter of Indoor air
volume. The results of a recent survey of homebullders Indicate that
partlcleboard. when used in new conventional home construction. 1s used
at an average loading rate of 0.17 m /m .
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Medium-density, fiber-board (HDF) 1s currently made only with UF
resin. The resin accounts for 7 to 9 percent of the board weight. Ten
companies with 11 plants produced over 600 million square feet 1n 1983.
Approximately 95 percent of that total was turned Into doors, furniture,
fixtures, and cabinetry; the other 5 percent went Into miscellaneous
products. HDF differs from partlcleboard mainly 1n the character of Its
wood particles (known as "furnish"). As the name Implies, the wood Is
separated by cooking or shredding Into fibers smaller than 1 mm. The
resulting pressed-wood product Is more homogeneous In texture, appears
more like wood, and can be machined. The extent to which HDF 1s used In
housing 1s uncertain and Is probably highly variable.
Unlike the two composition boards discussed above, hardwood plywood
1s a laminated product; the resin 1s used as a glue to hold thin layers
of wood and veneers together. It contains only 2.5 percent resin (by
weight). Nearly 2 billion square feet were produced In 1983; consumption
1s estimated as 55 percent to Indoor paneling. 30 percent to furniture
and cabinets, and 15 percent to doors and laminated flooring. A large
part of the hardwood plywood used In the U.S. Is Imported lauan plywood,
which Is preflnlshed In the U.S. by a variety of decorative processes.
Causes of Formaldehyde Release from Pressed Wood Products
An understanding of the exposure to formaldehyde releases from
pressed-wood products must be based on at least a rudimentary
understanding of the chemistry of UF resins. Urea-formaldehyde resins
are prepolymers that result from the reaction of excess formaldehyde with
urea; additives such as catalysts and waxes can be added to the resin
mixture. The product 1s adjusted to suit Its specific end-use (resins
used 1n different products can vary 1n formaldehyde:urea ratio, among
other variables). UF resin 1s a thermosettlng resin. Implying that the
resin undergoes crosslInking and other changes when subjected to heat
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during product manufacture. The heating Is called curing 1n the
pressed-wood product business, and curing does change the nature of the
resin. It 1s speculated that ten major types of organic compounds and
organocellulose complexes are formed, and each 1s a potential source of
formaldehyde release to the atmosphere.
There are two basic sources of formaldehyde that can be released from
pressed-wood products:
(1) Free (unreacted) formaldehyde present as a result of Incomplete
crossllnking during resin cure.
(2) Decomposition of unstable UF resin or resin-wood chemical
species as a result of their Intrinsic Instability and/or due to
hydrolysis.
Free formaldehyde, which Is present In cured resin at low levels (<1
percent) Is the most significant source of formaldehyde release from
pressed-wood products In the Initial period after they are manufactured.
The specific time period In which free formaldehyde dominates releases Is
not known.
The second source, decomposition and hydrolysis, pertains to the
large proportion of formaldehyde-bearing species like methylene ureas,
urea methylene ethers, and cellulose-crossllnked species that may release
formaldehyde for a much longer period of time. These species differ In
their susceptibility to hydrolytu attack and decomposition, and their
relative rates and durations of release can only be hypothesized at this
time.
Factors Affecting Formaldehyde Release from Pressed Wood Products
A variety of factors affect the amount of each formaldehyde-releasing
species present 1n the finished product. The resin formulation has a
direct effect on release; resins with a low formaldehyde:urea ratio have,
when cured, a lower level of free formaldehyde but nay be less stable and
more susceptible to hydrolysis. Other additives to the resin, such as
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add catalysts, change the resin chemistry and Influence the release
profile. The conditions under which the resin 1s cured affect bond
strength, determining to some extent the stability of the resin
components. The character of the wood Itself also affects formaldehyde
release; the more acidic the wood, the greater the tendency for add
hydrolysis and formaldehyde release.
Many other product-specific factors Influence release. The more
porous composition boards (partlcleboard and medium-density flberboard)
generally release more formaldehyde than laminated plywood. Emissions
are a function of the surface roughness of the product as well, and a
diffusion-theory approach that links boundary layer thickness and surface
velocity has been experimentally validated. Formaldehyde emission rates
are controlled by an equilibrium process that lowers the emission rate as
the formaldehyde level 1n the air rises; that effect 1s more pronounced
In smooth-surfaced products like flberboard and plain plywood.
Environmental and architectural conditions also affect releases.
Numerous Investigators have evaluated the effect of temperature and, to a
lesser extent, humidity on formaldehyde emission from pressed-wood
products. These studies Indicate that formaldehyde emission depends
strongly on temperature and moderately on humidity. Experimentally-
determined correction factors are generally used to correct monitoring
data to a standard temperature and relative humidity. The temperature
effect 1s exponential and 1s better understood than the humidity factor.
Pressed-wood products respond to humidity changes by taking up some of
the atmospheric moisture. Depending on the chen.1cal moieties present In
the resin and their susceptibility to hydrolysis, varying levels of
formaldehyde may then be released.
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As mentioned earlier, formaldehyde emission 1s an Inverse function of
the background concentration of formaldehyde In the air surrounding the
board. Unlike other chemicals that are removed with ventilation air 1n a
home, the formaldehyde concentration 1s not a direct function of
ventilation r air exchange rate. Though an Increase In ventilation does
reduce levels by dilution of formaldehyde with clean air, any
concentration reduction 1s followed by an Increase in the emission rate.
Doubling the ventilation rate nay achieve only a one-third reduction or
less 1n atmospheric formaldehyde levels. If the outside air has elevated
levels, air exchange can become a source In hones.
Measures to Control Formaldehyde Emissions from Pressed Mood Products
Each control option under consideration by EPA Is based on
controlling one or more of the above-mentioned factors affecting
emissions. As there are essentially two types of emissions — long-term
hydrolysis and decomposition and short-term release of free formaldehyde
— a control may reduce one type while either not affecting or, 1n some
cases, actually Increasing the other.
Reduction In the formaldehyde-urea ratio Is a control already
practiced by much of Industry. In recent years, partlcleboard
manufacturers have been using resins with a ratio of 1.2 or 1.3 parts
formaldehyde per part urea, down from the resins with ratios of 1.6 or
higher used prior to 1982. Resins with ratios of less than 1.2 have been
developed and are being evaluated further. The use of lower mole ratio
resins has been attributed with the demonstrated decline 1n emissions
over recent years. All testing to date has, however, focused on the
short-term emissions of free formaldehyde that are measured by the
commonly-used emissions test methods (described In this report). It has
been shown that the free formaldehyde emissions are lowered by the switch
to low mole ratio resins In a proportion approximately equal to the
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degree of ratio reduction. As measured by the two-hour desiccator test.
emissions from partkleboard with a ratio of <1.1 are In the range of 0.4
to 0.8 ug/ral. while conventional resins with ratios of -1.3 have
emissions of 1.2 to 2.0 ug/ml. Reducing the ratio In resins made for
medium-density flberboard 1s more difficult because a loss 1n essential
properties Is highly possible, but a reduction from l.b (current) to 1.2
can reduce emissions from 3.8 ug/ml to 0.6 to 1.4 ug/ml. It has been
postulated, however, that lower mole ratio resins are less stable and
more likely to hydrolyze; only repeated emissions testing, designed to
detect hydrolyrlng moieties, can resolve this question.
Formulation of scavengers Into UF resin/wood systems also provides
short-term reductions 1n emissions by adding reactive chemicals that bind
the free formaldehyde 1n the resin, forming more stable complexes.
Reactive scavengers added to the resIn/wood system are designed to
control formaldehyde that Is unreacted or 1s released during the curing
process; If scavengers are present 1n excess, they may affect emissions
of decomposing or hydrolyzlng products as well. The additives are
generally ammonium compounds, urea, or sulfUes. The long-term stability
of these complexes has not been demonstrated; It 1s unlikely that they
would be totally Inert over years of product use 1n various environmental
conditions. Short-term measurements Indicate that various scavengers can
reduce emissions by 50 to 75 percent.
Post-cure treatments with formaldehyde scavengers may be accomplished
by placing finished products 1n the presence of a reactive gas (ammonia)
ui painting or spraying the board surface with the scavenger. The
treatments control free formaldehyde In the short term, and can control
long term releases If an excess of the scavenging agent Is maintained 1n
place.
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There are a number of ammonia treatment processes that have been
patented for formaldehyde control -- the Verkor FD-EX. the RYAB, the
Swedspan. the BASF, and the Heyerhauser processes. The process
variations that make these different are largely the actual method of
ammonia application and whether the application takes place under
pressure. In a test of the effectiveness of the Verkor method, performed
three months after treatment, the process had reduced a partlcleboard's
emission rate from 174 rag/1OOg wood to 5.5 mg/lOOg (perforator method).
It Is similarly effective on plywood paneling. The RYAB and Swedspan
methods have been shown to be slightly less effective. Some of these
treatment methods, Including Verkor, Involve removing excess ammonia as a
final step; only the presence of excess, unreacted ammonia would ensure
the long-term ability of these processes to reduce formaldehyde
emissions. Another ammonia treatment method Is an In-home fumigation,
which could be used to reduce formaldehyde emissions. The long-term
effectiveness of that method has not been well documented.
Coatings that contain reactive scavengers are also considered viable
control options. All tests to date have demonstrated short-term
effectiveness but the option would appear to have longer term
possibilities because the coating would Inhibit diffusion of water vapor
and formaldehyde across the wood-air boundary layer. Tests on
partlcleboard coatings Include vinyl-toluene, which resulted In a 1.5 to
3-fold reduction 1n room air levels; a melamlne coating that was 90 to 98
percent effective; and Fallma-F, the active Ingredient of which is
unknown, which reduced emissions to <0.1 ug/m2/hr. A urea-containing
coating, Valspar, was applied to plywood and found to be 90 percent
effective 1n short-term dynamic chamber tests, reducing chamber levels
from 3 to 0.3 ppm.
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Non-scavenger emission barriers perform two functions: they Inhibit
the ability of a pressed-wood product to absorb water vapor from the air,
which speeds hydrolytlc formaldehyde production and release; and they
present a barrier to the formaldehyde diffusing out of the product.
Paints, coatings, vinyl veneers, and other decorative overlays Inhibit
formaldehyde release; the effectiveness of the barrier Is a function of
the degree to which It Inhibits permeability and porosity. Effectiveness
ranges from over 30 percent for wallpapers on plywood paneling to 98
percent for partlcleboard coated on all Its edges with
nitrocellulose-based paint. Nonscavenger emission barriers would be
expected to be less efficient than scavenger coatings because of the lack
of reactive chemicals to actually bind formaldehyde to prevent Us
release.
Resin substitution. Involving use of either Isocyanate binders or
phenol-formaldehyde resins In place of urea-formaldehyde resin, would
virtually eliminate release of formaldehyde from pressed-wood products.
Isocyanate resin products contain no formaldehyde per si, though some
Incidental release as a result of decomposition of cellulose might
occur. Phenol-formaldehyde (PF) resins do contain formaldehyde, but are
so stable that they emit relatively low levels of formaldehyde. The
disadvantages to these resins, besides Increased costs, are that they
cannot be universally substituted. PF can be used 1n partlcleboard and
In hardwood plywoods except those with light-colored veneers (the resin
Is dark and can discolor light wood); Its ability to be used In HOF 1s
not known. Isocyanate may not be suitable for plywood but Is currently
used successfully 1n partlcleboard and HDF manufacture.
Substitute wood products are available for all pressed-wood products
that currently contain UF resins. Formaldehyde release from products
like hardboard and softwood plywood does occur, but at very low levels.
Gypsum board Is another possible substitute, and 1t contains no
formaldehyde, so only Inddentlal release would be expected.
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Increased ventilation does lower formaldehyde levels, though not In
direct proportion to the Increase 1n air exchange rate. It 1s the only
option listed here that 1s not an emission control; It Is, rather, an
exposure control measure. As mentioned earlier, a reduction Is Followed
closely by an Increase In emission'rate from a pressed-wood product.
Increasing ventilation 1s effective both In the short term and 1n the
long term, and this control will be effective for other pollutants In the
Indoor air environment. Increased ventilation, unlike the other controls
listed, 1s effective on all residential sources of formaldehyde, not only
pressed-wood products.
Other Residential Sources of Formaldehyde
There are numerous other sources of formaldehyde 1n homes:
construction products containing PF resins (e.g., fibrous glass celling
tiles and softwood plywood); appliances that Incompletely burn
hydrocarbon fuels, releasing formaldehyde and other aldehydes; smoke from
cigarettes and other tobacco products; upholstered furniture and
draperies with OF resin permanent press finishes; urea-formaldehyde foam
Insulation; and outdoor air used 1n ventilation. The significance of
these other sources relative to pressed-wood products with UF resins
varies widely with the occurrence of the sources In homes.
Though no residential sources of formaldehyde have been as
well-studied as urea-formaldehyde foam Insulation (UFFI) and pressed-wood
products made from UF resins, there are enough data on man" of these
other sources to enable estimates to be made of their probable Impacts on
residential air levels of formaldehyde.
Emission rate Information for fibrous glass Insulation and celling
tile containing PF resins Indicates that these products are not likely to
cause Increases In Indoor formaldehyde levels greater than 0.02 ppm even
when subjected to elevated temperatures and relative humidities.
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Similarly, emission rate testing of pressed wood products manufactured
with PF resins Indicates that these products will contribute less than
0.1 ppm to Indoor air even when used at high loadings; monitoring
conducted 1n three new mobile homes constructed with only PF resin wood
products showed formaldehyde levels ranging from 0.02 to 0.07 ppm.
The data on combustion appliances show that formaldehyde release 1s a
function of whether the appliance Is tuned and functioning properly. Gas
ovens and ranges may emit less than 2 to nearly 30 mg formaldehyde per
hour of use; gas space heaters can emit less than a to over 60 mg/hour.
depending on the efficiency of burning; and new kerosene space heaters
emit up to 6 mg/hr of formaldehyde.
The emissions data on sldestream cigarette smoke range from 20 ug per
cigarette to nearly 1.5 mg/clgarette. Several studies, however, concur
on an emission rate of 1.0 to 1.2 mg/clgarette. The Importance of this
source 1s obviously related to use patterns. Studies where numerous
persons chain-smoked In a poorly ventilated room did Indeed show that
Formaldehyde levels were elevated after a short period of time, but other
studies In the homes of smokers Indicated that, at a smoking rate of 10
cigarettes per day. formaldehyde levels were not elevated over controls
with similar loading rates of other sources.
Available data on drapery and upholstery fabrics indicate that, with
emission rates only as high as 15 ug/m /hr, these could cause Indoor
air levels to Increase by greater than 0.01 ppm only under very high
loading situations. Although emission rates for new unwashed apparel
have been reported a high as 31 ug/m2/hr. the Impact of apparel on
Indoor air levels Is expected to be negligible because laundering will
significantly decrease the emission rate. A modeling exercise discussed
1n Section 3.6 of this report was Intentionally designed to estimate the
relative Importance of numerous sources of residential Formaldehyde In a
10
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model mobile home and model conventional home. Reasonable estimates of
the loadings of the sources were made and It was conservatively assumed
that the emission rate from each source was Independent of emissions from
other sources. A simplified ranking follows; setting the most Important
sources as 1 and scaling the other appropriately:
Model Mobile Home Model Conventional Home
Hardwood paneling = 1.0 Industrial partlcleboard = 1.0
Partlcleboard flooring o 0.55 Gas space heater » 0.84
Industrial partlcleboard ° 0.22 MDF = 0.76
Gas space heater = 0.19 Partlcleboard flooring = 0.73
MDF = 0.17 Hardwood paneling = 0.56
Other combustion sources = 0.12 Other combustion sources => 0.56
All other sources =<0.10 All other sources «<0.40
The "all others' category Includes textiles, carpeting, fiberglass
Insulation and celling tiles with PF resins, and other sources.
Current Levels of Exposure
Because of the changing nature of pressed-wood products with UF
resins and the constant evolution and Improvement In monitoring
techniques, the universe of residential monitoring data Is not the most
appropriate data base for describing formaldehyde exposure 1n homes.
Many data sets are based on Investigation of hones from which complaints
of formaldehyde symptoms have been filed; these data sets may not be
representative of average exposure because of bias toward high
concentrations. Homes studied before 1980 were built with products made
of high F:U ratio resins that are no longer on the market; they cannot be
considered as baseline exposures for that reason. The most appropriate
data for describing current exposures In mobile and conventional homes
are therefore those generated by random sampling oF noncomplalnt homes
after 1980. preferably after 1982 (when manufacturers began using resins
with mole ratios of 1.5 or less). These restrictions on the
"appropriate" data base still leaves a considerable volume of monitoring
data on levels 1n homes.
11
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Numerous studies on conventional homes are discussed 1n this report.
Studies performed by the Lawrence Berkeley Laboratories, the Consumer
Product Safety Commission, the government of Canada, and state and
academic officials 1n Washington, Iowa, and Indiana are the most recent
and representative of average exposure 1n conventional homes, per the
criteria discussed above. These studies Indicate that the average level
of formaldehyde In conventional homes Is approximately 0.05 ppm. and that
the age and construction of the home are the major determinants of the
concentration. Newer homes and energy-efficient homes with low air
exchange rates tend to have higher formaldehyde levels (around 0.1 to 0.2
ppm) than older (over five year old) homes, with average levels of 0.005
to 0.08 ppm. Comparison of these data with data collected prior to 1980
Indicates that there has been little change in conventional home levels
since 1978, the data of the earliest comprehensive survey of home levels.
The average level 1n mobile homes appears, however, to have declined
In recent years. Average levels 1n the existing stock of mobile homes
are now around 0.2 to 0.5 ppm, with mean levels 1n individual homes
(Including complaint homes) ranging from <0.1 to over 1.0 ppm. An
aggregated data set of two well-conducted studies (the 1980-1982
Wisconsin study and the 1980-1981 Clayton study described 1n this report)
has nearly 1,200 data points. The mean of that data set Is 0.43 ppm.
with a median of 0.31. This aggregated data set also contain home aye
values for every mobile hone sampled. The correlation coefficient of the
log-transformation exponential function describing the data Is 0.4,
Indicating that 40 percent of the variability In home levels Is
attributable to home age, while other factors control 60 percent of the
variability. The 0.43 ppm mean for the data set corresponds to a home
age of 246 days. The predicted average concentration of formaldehyde 1n
a mobile home over the first ten years of Us use is 0.19 ppm. A more
recent study. University of Texas (1982-1983) showed average levels of
12
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about 0.2 ppm In mobile homes built primarily during the 1980s but showed
little significant variation by home age. The data Indicate that
recently-built mobile homes may have lower Initial formaldehyde Ir.-vels
than homes built prior to 1980, but that the concentrations may not
significantly decline over time.
Potential Reductions In Exposure Levels
The exposure reduction that could result from the Implementation of
the control measures described m this report 1s difficult to determine.
The factors controlling formaldehyde concentrations 1n mobile and
conventional homes are complicated. Interdependent, and not well
understood. The available data on emissions reductions that can be
accomplished by various controls are sparse; the relatively few data are
often not comparable because of differences 1n measurement techniques.
Finally, the long-term effectiveness of the control options 1s not known.
and can only be speculated on.
There are. however, some simple tools that may Indicate the exposure
that may result from control of pressed-wood products containing UF
resins. Review of monitoring data for older homes 1n which formaldehyde
emission from pressed-wood products 1s probably limited to low levels of
hydrolysis products may be representative of situations In which other
sources predominate. Measured levels 1n conventional homes greater than
15 years old averaged 0.03 ppm 1n one study (Hawthorne et al. 1984). In
a study of various formaldehyde sources In homes (Traynor and Nltschke
1984). the control homes that had no Identified sources of formaldehyde
and the homes without pressed-wood products but with combustion sources
had formaldehyde levels ranging from 0.007 to 0.077 ppm. These are In
the reported range of levels 1n homes with pressed-wood products and are
not different from the average reported levels In conventional homes
(-0.05 ppm).
13
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and the homes without pressed-wood products but with combustion sources
had formaldehyde levels ranging from 0.007 to 0.077 ppm. These are In
the reported range of levels 1n homes with pressed-wood products and are
not different from the average reported levels In conventional homes
(~0.05 ppm).
The levels In mobile homes without pressed-wood products are more
difficult to determine, since virtually all mobile homes currently
constructed contain particleboard, HDF, and/or paneling as major
structural components. The decay function for the Clayton and Wisconsin
data, previously described, can be used to project levels Into the
future, when emissions from pressed-wood products may be relatively low.
This highly speculative approach to predicting exposure reduction Is not
specific to any particular control. The decay function predicts that a
concentration of 0.047 ppm would be present 1n a mobile home ten years
after construction assuming the Initial concentration 1n the new home was
0.50 ppm. This level might correspond to the levels that would be
reached by controlling pressed-wood product emissions 1n some fairly
effective manner. An error Inherent In using the decay function as
described Is that sources that would not release less over time (e.g.,
gas appliances and cigarettes) are decayed In the same manner as
pressed-wood products. This error can be corrected by adding a constant
to the decay function representing a background level attributable to
outdoor air, combustion products, etc.
Another simple approach to predicting exposure reduction 1s to
perform simple modeling calculations of Indoor air levels 1n homes,
factoring 1n emissions from all sources except pressed-wood products with
UF resins. A simple steady-state model developed at Oak Ridge National
Laboratory Is described In this report. Using that model, and emission
factors for new residential soun.es except UF resin bonded pressed-wood
products, yields an estimated steady-state concentration of approximately
0.07 ppm (at a typical mobile home air exchange rate of 0.35 ACH in a
volume of 175 m3).
14
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If controls on pressed wood products containing UF resins were 100
percent effective, these sample assumptions Indicate that levels 1n
mobile homes would drop from a current average of 0.2 to 0.5 ppm to less
than 0.1 ppm. Implementation of one or more controls with an
effectiveness of less than 100 percent would result 1n Incremental
Improvement between the current average and the projected levels.
There Is a high degree of uncertainty surrounding this prediction.
Current tools and data do not allow refinement at this stage. Ongoing
work on a more sophisticated model sponsored by CPSC and EPA should
produce a more reasonable approach to exposure prediction In the fall of
1985. This work Includes compilation of emissions data, study of the
factors affecting formaldehyde concentrations, and preparation and
validation of an Indoor air model applicable to this situation. The
model 1s described 1n this report, and will provide many of the answers
to questions that are now addressed by educated speculation. The current
work 1s, however, limited; still lacking are emissions characterization
for pressed-wood products that have been treated with specific control
options. There are no data that can be utilized 1n that model on
emissions from boards with known, low molar ratio resins; no data on
boards with specific scavengers; there are only emissions data on boards
characterized by Industry as either typical or low-emitting. These data
do Incljde emissions from Pf resin wood products, so that analysis of
exposure reduction resulting from product substitutions will be
possible. Further data development will, however, be required to
demonstrate exposure reduction from other control options scenarios.
IS
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1. INTRODUCTION
1.1 Background
On May 23, 1984. the U.S. Environmental Protection Agency (EPA)
decided that residents of manufactured and conventional housing could be
subject to a significant risk of cancer from exposure to formaldehyde. A
major source of formaldehyde In these homes Is construction material In
which urea-Formaldehyde resins are used. EPA at that time Issued an
Advanced Notice of Proposed Rulemaklng (ANPR) In which Initiation of a
full regulatory Investigation was announced; the purpose of that
Investigation Is to determine whether reasonable control options exist
for reducing formaldehyde exposure to this population.
As part of this regulatory Investigation, EPA 1s reexamlnlng
existing Information and 1s gathering and reviewing additional
Information on two general topic areas: (1) current levels of exposure
to formaldehyde In housing and the sources and factors that affect these
levels, and (2) reduction of exposure levels that could result if control
measures are Implemented. The purpose of this report 1s to summarize
current knowledge regarding these topic areas.
1.2 Report Organization
There are seven major sections to this report, which are summarized
below:
Section 2 provides a background discussion on formaldehyde emissions
from pressed-wood products containing urea-formaldehyde (UF)
resins. Included 1n this discussion are descriptions of the major
pressed-wood products and their uses 1n residential settings, the
mechanisms of Formaldehyde release, and the factors that affect the
rate of release. Section 2 also presents a background discussion on
formaldehyde emission rate testing methods. All methods used by
researchers to generate data discussed within this report are
described. Correlations between results generated by different
methods are, wrtere applicable, discussed.
Section 3 discusses the residential sources of formaldehyde (other
than pressed-wood products formulated with UF resins). Described
are urea-formaldehyde foam Insulation (UFF1). products made with
phenol-formaldehyde (PF) resins, consumer products made with UF
resins (textiles), Indoor combustion, and Infiltration
16
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of outdoor air. This section 1s concluded with a presentation of
data on the comparable strengths of various formaldehyde sources 1n
residential settings.
Section 4 presents a summary of monitoring data for formaldehyde 1n
homes. The results of a number of large-scale studies are
tabulated, and ongoing research projects are discussed. Also
Included Is a brief discussion of monitoring studies that were
designed to examine the factors that affect Indoor air levels of
formaldehyde 1n homes.
Section 5 describes the control options currently under
consideration by EPA for reduction of exposure to formaldehyde
emitted from pressed-wood products. Four types of controls are
described 1n terms of their projected short- and long-term
effectiveness: changes In UF resin formulation, post-cure board
treatme-ts, use of substitute resins, and use of substitute
products. Other potential controls, such as Increased room
ventilation, are discussed briefly. Section 5 also presents a
summary of quantitative data on formaldehyde emissions and exposure
levels resulting from the application of these control options.
Section 6 presents a summary of existing formaldehyde emissions and
exposure standards 1n the U.S. and 1n other countries.
Section 7 describes efforts to predict residential levels through
modeling. The Consumer Product Safety Commission (CPSC) and EPA are
supporting the development of a sophisticated formaldehyde model;
the status of model development and validation 1s a subsection In
Section 7. Simplified models or algorithms are also briefly
discussed.
17
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2. PRESSED-HOOD PRODUCTS CONTAINING UF RESINS
2.1 Product Descriptions
Pressed-wood products that utilize urea-formaldehyde resin as a
thermosettlng binder are used 1n flooring. Interior walls and doors,
cabinetry, and furniture construction; these relatively Inexpensive
pressed-wood products are a growing market share of the construction
products Industry (Meyer and Hermanns 1984a). The three major classes of
pressed-uood products containing UF resins are partlcleboard,
medium-density flberboard (HDF). and hardwood plywood.
2.1.1. Partlcleboard
The National Partlcleboard Association (NPA 1984) states that 28
firms, operating 45 plants, manufactured over 3 billion square feet of
partlcleboard In 1983 by the platen-press, or mat-forming, process. The
NPA (1984) defines the mat-forming process as one where resin-coated wood
particles are formed Into mats, which are pressed in a heated press
(platen) at elevated temperatures. These 45 plants account for an
estimated 96 percent of U.S. partlcleboard production capacity (NPA
1984). An estimated 10 plants with a total annual capacity of
approximately 50 million square feet manufacture partlcleboard by
extrusion of resin and wood Into mounted platens that serve as a die (NPA
1984). An additional 75 million square feet may have been produced by
the Mende Process (NPA 1984), which forms thinner partlcleboard by
pressing a ribbon of resin-coated wood particles. The average capacity
of each of the 45 plants Is 81 million square feet (NPA 1984).
Though three types of resin (UF, PF. and Isocyanate resins) are
suitable for use 1n partlcleboard, UF resin Is the primary adhesive used
1n 41 of the 45 mat-form process plants 1n the U.S. (NPA 1984). The four
remaining plants, three of which use phenol-formaldehyde (PF) resin and
one of which uses Isocyanate resin, constitute less than 10 percent of
total U.S. partlcleboard production capacity (NPA 1984. ICF 1984). Most
current F:U mole ratios for UF resins used In partlcleboard are claimed
18
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to be 1n the range of 1.15 to 1.3 (I.e.. 1.15 to 1.3 moles of
formaldehyde per mole of urea), down from about 1.6 In the late 1970s
(Podall 1984).
Partlcleboard produced with UF resin uses about S to 10 percent resin
by weight (Podall 1984). George (1977) describes the variations 1n UF
production techniques for resins with different end uses. The UF resin
he describes 1s a standard UF resin that 1s closely controlled for
viscosity: UF resin for partlcleboard 1s essentially monomeMc, for
enhanced solubility and ease of application (George 1977). Approximately
5 percent urea (by weight) 1s added to the resin mixture to control
polymerization; the final resin, 1n liquid form, Is 59 to 65 percent
solids (George 1977, Podall 1984).
NPA (1984) describes three major types of partlcleboard:
underlayment, mobile home decking, and Industrial board, Underlayment 1s
the least expensive type of partlcleboard and 1s typically used In floor
systems and for general applications. Mobile home decking, whose name
Implies Its use, 1s more expensive because 1t must be manufactured to
higher specifications of strength and stability. Industrial
partlcleboard. the most expensive. 1s often used as the base material 1n
cabinets and furniture and 1s the highest grade manufactured. The NPA
estimates that, 1n 1983, approximately 70 percent of partlcleboard was
used 1n furniture, fixtures, cabinets, etc., and that the remaining 30
percent was used for construction purposes (NPA 1984). Table 1
summarizes available Information on loading rates of pressed wood
products. Including partlcleboard. In residences. The average loading
rate of partlcleboard (underlayment. kitchen cabinet, and shelving) In
new conventional U.S. homes containing partlcleboard is reported to range
from 0.112 to 0.167 m /m (m of product surface ared/m of
Indoor air volume) (NPA 1984). while the average reported loading rate In
2 3
mobile hones Is 0.5 m/m .
19
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Table 1. Use of Pressed-Uood Products in Home Construction
Cateaorv Type of home*
SFO ffi SE ffi
Men Hangs (U.S.)a'b
Percent units containing
Hardwood plywood paneling 7.6 9.3 8.5 most
Particteboard underlayment 30.5 9.2 1.7 nost
Average loading rates.c (BrVn3)
Hardwood plywood paneling 0.066 0.059 0.049 1.0
Particleboard underlayment 0.118 0.092 0.033
Partlcleboard shelving 0.010 0.016 0.020
Particleboard kitchen cabinets 0.039 0.052 O.OS9
Total particleboard 0.167 0.160 0.112 O.S
Mew Hones (Canada)"
Percent units containing
Particleboard 100 100 100 100
Average loading rates (nfVtn3)
Total particleboard 0.145 0.100 0.079 0.479
Existing Homes (U.S.)8
Percent units containing
Manhood plywood paneling 35.5 — — most
Particleboard 90.3 — — most
Average loading rate (m2/^3)
Hardwood plywood paneling 0.098 — — 1.0
Particleboard 0.058 — — O.S
Note
Data reflect only interior uses of UF pressed mod products.
Loading rates are for those hones containing these products.
aSource: NPA (1984) and WNA (19B4) for conventional tanas - Based on
interpretation of the results of a survey of 900 hone builders (103
responses) regarding the extent of use of particleboard and hardwood
plywood paneling in new hones containing these products (NAHB 1984).
Source: Meyer and Hermanns (1984a), NAW (1984). MI (1984) for mobile
MOBS*
(Footnotes continued on next page)
20
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Table 1. Footnotes (continued)
Si£ of produce surface area/m3 of indoor air volume.
"Source: InterArt (1983) - based on in-home surveys at 9 SFD. 1 1H, 1 HF
and 1 RH. Total loading includes underlayment, shelving and cabinets.
SFO loadings ranged fron 0.028 to 0.491 nrVnr*.
eSource: Schutte (1981) - Based on in-home surveys at 31 SFD. Average
loadings based on hones containing these products.
f SFD = Single family dwelling
TH e Townhouse
HF = Hultifamily dwelling
HH = Mobile hone
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2.1.2 Medium-Density Fiberboard (MOF)
The NPA also represents manufacturers of medium-density flberboard,
which 1s composed of resin and sawmill residue fibers. Resin Is added to
comprise approximately 7 to 9 percent by weight of the mixture; the WOOL'
1s In the form of 0.2 to 0.8 mm fibers that are created by cooking or
shredding the raw wood material (Podall 1984. NPA 1984. Meyer 1979).
Essentially all medium-density flberboard 1s manufactured by
platen-pressing (mat-forming) (NPA 1984).
Ten companies with eleven plants currently produce MOF; the total
1983 production was 604 million square feet, with a total capacity of 760
million square feet (an average capacity per plant of 69 million square
feet) (NPA 1984).
Urea formaldehyde Is the only resin currently used In NDF production,
according to NPA (1984). with a typical mole ratio of F:U of 1.65 (Podall
1984). MOF requires a higher mole ratio resin because strong adhesion Is
more difficult to obtain than 1n partlcleboard manufacture (Podall
1984). Two factors contribute to this: (1) the lower moisture content
of the wood fibers (4 percent 1n HDF as opposed to 7 to 11 percent In
partlcleboard). and (2) there Is less 11gn1n and hemlcellulose In the
wood fibers, which normally aid the bonding process (Podall 1984). NPA
mentions experiments with PF and Isocyanate resins (NPA 1984), and Forss
and Fuhrmann (1980) discuss the use of ilgnln as a flberboard adhesive
(and compare the performance of llgnln-based boards to those manufactured
with PF). It appears that the exclusive use of UF In medium density
flberboard 1s not a result of technical necessity cf UF, but 1s probably
because of cost considerations. It Is widely recognized that UF 1s the
least expensive, most readily available resin for most pressed-wood
product applications.
Medium-density flberboard panels are homogeneous 1n texture and
color, and appear more like lumber when finished than other pressed-wood
products (NPA 1984). About 95 percent of production 1s directed to
22
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furniture, fixtures, doors, and cabinets, while 5 percent Is formulated
Into miscellaneous wood products (NPA 1984). In mobile homes. HOF 1s
also used as a decorative molding around acoustical ceilings (Meyer
1979). The differences 1n use patterns between MOF and partlcleboard are
largely attributable to the ability of HOF to accept machining of Its
edges, allowing 1t to be used directly as a finished product.
No data are available on the precise extent of HOF's use In either
mobile or conventional homes. The National Association of Hone Builders
(NAHB 1984) survey of new conventional homes revealed that 9.5 percent of
the components of kitchen cabinets are composed of MOF and that MDF
accounts for 0.7 percent of shelving In new homes. The use of MOF 1n
home construction Is probably highly variable, and 1t 1s likely used to a
lesser extent than Is partldebcard.
2.1.3. Hardwood Plywood
Hardwood plywood 1s a laminated product, unlike partlcleboard and
Hberboard, and contains only 2.5 percent UF resin by weight (Meyer and
Hermanns 1984a). It Is manufactured by cross-stacking three to five
layers of veneers, with UF resin and fillers between the layers (Meyer
1979). In some boards, veneers are applied to a core substrate of
partlcleboard or MOF (Smith 1982, 1983). The stack 1s then pressed at
temperatures up to 100°C and pressures up to 300 psl (Meyer 1979).
Nearly 2 billion square feet were manufactured 1n 1983 (HPMA 1984). It
Is used for Interior wall paneling (55 percent of production), furniture
and cabinets (30 percent of production), and door skins and laminated
flooring (15 percent of production) (HPMA 1984).
George (1977) describes the manufacture of UF resin for use 1n
plywoods. The major difference between UF resin designed for plywood
adhesion and resin for use 1n Mberboard or partlcleboard 1s that the
plywood resin 1s of higher average molecular weight (more completely
polymerized). The final resin can be a spray-dried powder or a syrup of
about 66 percent solid content (George 1977). Extenders (starch or
protein) may comprise up to 25 percent of the resin (George 1977).
23
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A substantial quantity of the hardwood plywood consumed An the U.S.
(about 75 percent of total consumption) 1s Imported Asian "lauan" plywood
that 1s preflnlshed by U.S. firms (Smith 1982). The faces of Imported
plywoods are either printed, stained, papered, or covered with a domestic
hardwood veneer to produce the finished product. Several varieties of
plywood are commercially available; all can be used In mobile or
conventional home Interiors. Printed paneling Is Inked In a decorative
pattern and accounts for 35 percent of plywood use; papered paneling Is
covered by wallpaper (40 percent of plywood use) or vinyl (7 percent nf
plywood use); natural hardwood or domestic paneling 1s plywood coversd
with a hardwood veneer, and accounts for 18 percent of all panels (HPNA
1984). The NAHB survey Indicates that plywood Is used for ?5.6 percent
of kitchen cabinetry and 7.2 percent of shelving In conventional homes.
Table 1 provides additional statistics on use of plywood paneling In
new home construction. Meyer and Hermanns (1984a) state that the average
loading rate In mobile hones 1s 1.0 m2/m . which Is appreciably higher
than that found 1n the NAHB survey of new conventional homes. However. It
should be realized that because sales of paneling for remodeling and repair
applications generally account for more than 20 times the sales of paneling
for new home construction, the actual loading rates of paneling 1n
conventional homes may be higher than those listed In Table 1.
Unfortunately, the average paneling use for remodeling or repairs 1n homes
1s not available (Matthews et al. 1983b).
UF resin Is the overwhelming choice of plywood manufacturers with
current formaldehyde:urea mole ratios reported to range from 1.2 to 1.5
or higher (Podall 1984. HPMA 1984). The Hardwood Plywood Manufacturers
Association (HPMA 1984) says that over 90 percent of hardwood plywood
produced uses UF resin and that phenol-formaldehyde resin Is used to
manufacture the balance (ICF 1984). Forss and Fuhronn (1980) describe
the use of Hgnln In Finnish production plants, but 1t seems unlikely
that 1t 1s currently used 1n U.S. plywood production.
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2.2 Sources and Mechanisms of Formaldehyde Formation and Release
This section Is excerpted from a recent draft report (Podall 1984) by
H. Podall of EPA's Office of Toxic Substances entitled "A Review of the
State-of-the-Art on Urea Formaldehyde Resins for Mood and Causes of
Formaldehyde Release." In addition to discussing sources and release
mechanisms, this report examines 1n depth: resin production; resin
composition and chemistry; resin use by board type and wood species; and
recent advances 1n UF resins.
The formation and subsequent release of formaldehyde from a UF-bonded
pressed-wood product Is due to two basic sources of latent formaldehyde:
1. "Free" formaldehyde arising from the UF resin prior to or during
the curing of the resin In the board.
2. Chemical species containing bound formaldehyde which liberate
formaldehyde as a result of their intrinsic Instability (and do
not require, stolchlometHcally, water, for the formation of
formaldehyde) and/or due to hydrolysis.
In order to understand the short- and long-term significance of these
formaldehyde emission sources, as well as to understand the effects
various control measures may have on reducing or eliminating these
sources, 1t 1s Important to:
• Define the actual species capable of producing formaldehyde.
• Assess their relative Importance as sources of formaldehyde by
Identifying the key reactions Involved 1n the formation of
formaldehyde.
2.2.1 Chemical Species Capable of Producing Formaldehyde
The "free" formaldehyde In a pressed-wood product presumably exists
as methylene glycol. low molecular weight formaldehyde oilgoners (e.g.,
HO-(CH2-0)n-H. where n » 2 to 4). and possibly some
paraformaldenyde. These chemical forms of formaldehyde may be
extensively hydrogen-bonded to the cellulose, hemlcelluloses, llgnln, and
25
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to the UF resin. In addition, they may be dissolved In the water
contained In the pores of the wood. The following components of the
cured UF resin can undergo hydrolytlc degradation to form formaldehyde:
N-me'.hylol urea, methylene ether urea, substituted urea, and methylene
urea moieties. Also, reaction of N-methyol urea moieties with the wood
cellulose and with formaldehyde (formed during cure) nay produce latent
formaldehyde moieties.
A list of the principal potential formaldehyde releasing moieties
believed to be present In a board bonded with a commercial 1.3:1 F/U mole
ratio resin and an estimate of the relative amounts of formaldehyde
present are given 1n Table 2. The reactions and assumed distribution of
products are given 1n the footnotes to Table 2. Although the assumptions
made are believed to be reasonable, 1t Is Important to recognize that
they represent major extrapolations of a given set of results for a
particular cured resin In the absence of wood.
2.2.2 Relative Importance of Chemical Species as Sources of
Formaldehyde
There appears to be available In the literature two sets of kinetic
data pertaining to the hydrolysis of structural moieties or components
present 1n UF resins. They are (1) dilute solution kinetics of
relatively simple model compounds, such as N.N'-dlmethylol urea, and (2)
more limited d» ca on the hydrolysis of UF-crosslInked cellulose and of
crosslInked UF resins, generally at very low pH and high temperatures,
ano' In certain cases employing a questionable analytical method for
formaldehyde.
Based on the available kinetic data and considerations of structure
reactivity, estimates were derived of the relative reactivities for the
structural species given In Table 2. These are given In Table 3,
together with estimated relative durations of formaldehyde releases.
A picture that emerges from the values estimated In Table 3 1s that
(1) next to the "free* formaldehyde, the formaldehyde bound to the wood
26
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Table 2. A Rough Estimate of the Relative Amounts of the Various Formaldehyde Derived
Special in a Cured Board with 1.3:1 F/u Mole Ratio Resin
Percent formaldehyde
Structural species
Prior to cure*
Cured
(neat resin)
Cured0'6
(in board)
OHjO dissolved in pores 0 0
°*2 ~ hydrogen bonded to wood
cellulose, etc. 0 0
CHjO in resin 0.5 0
cell-O-OfeW - -
cell-0-Q»2-0-ce11 — —
HOH
II
- N-C-M-CHjOH 43.8(c) 2.8
HOH
II
- M-C-W-CH2-0-CH2 29.0 44.3W)
HOH
II
- M-C-M-CH2- 26.6 52.8(d)
HOH
II
. N-C-N-CHj-O-cell — —
4.
HOH
II
Source: Podall (1984).
'Borden data (Hi 11 ions 1984).
DShou1d vary with board type (hardwood plywood, medium density fiberboard. or particleboard) and nith
furnish in particleboard.
'Percent available K-mettiylolurea (NHU) for reaction during cure • O.S * 43.8 = 44.31.
27
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Title 2. Footnotes (continued)
dPercent conversion available NKU to methylene ether urea = (44.3 - 29.0)x100/(44.3 - 2.8) =
15.3 x 100/41 5 = 37 percent. Percent conversion of available NNJ to methylone urea =
(S2.B - 2b.6) x 100/41.9 = 26.2 x 100/41.5 = 63 percent.
Assumptions regarding converstion of NHU:
el = 10 percent of the available mi reacts with wood = 4.4 percent.
& = 10 percent of the available NNJ nydrolyzes to GHjO «= 4.4 percent.
e3 = 2.S percent of the available NMJ does not react = 1.1 percent.
e4 = 77.5 percent x 0.443 of NNJ converts to 34.3 percent nethylene ether ureas 4- nethylene ureas
f f1 = Net increase in metnylene ether ureas = 34.3 x .37 = 12.7 percent.
f2 = Net increase in metnylene ureas •= 34.3 x .63 = 21.6 percent.
9Assune SO percent of CHjO from NKI reacts with cellulose = O.S x 4.4 = 2.2 percent and
SO percent remains as CHjO.
"Assume 75 percent of residual CH^ (1.7V becomes H - bonded to traod and 25 percent is in
pores (0.5 percent).
'Assures 60 percent of CHjO which reacts with wood (1.81) is converted to cellulose hemiformals and 20
percent is converted to cellulose formals (C.4 percent).
28
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Table 3. Relative Rates of Formation of Formaldehyde and Duration of
Release from a Cured UF Board
Structural moiety t as HCHO*
CHjO dissolved in pores 0.5
CHjO H-bonded to wood 1.7
cell-O-O^-O-H 1.6
H 0 H
II
- N-C-N-CHg-OH 1.1
cell-0-CHj-O-cell 0 4
H 0 H
II
- N-C-N-Gtj-O-O^ 42
H 0 H
II
- M-C-N-CHj-O-cell 4.4
H OH
- H-C-H-CHg 48
Source: Podall (1984).
aBased on estimates given in Table 2.
Initial
Relative relative
reactivity1' ratec
instantaneous 2,000
(4,000)
very fast 680
(400)
fast 36
(20)
moderate 1 . 1
(1.00)
moderate-slow 2
(0.5)
slow 4.2
(0.1)
slower 0.13
(0.03)
very slow 0. 10
(.002)
Estimated relative
duration of
release"1
0.0004 (instantaneous)
0.007 (instantaneous)
0.14 (short term)
2.4 (interned, term)
2.8 (interned, term)
60 (life of board)
126 (life of board)
3087 (life of board)
''Proportional to pseudo 1st order rate constants in sec"', pH 4 to 5, 25°C.
"•Initial relative rate ~ 1 as HOC x relative
^Estimated duration = t ~ 2.303 loq C.
reactivity.
t 2.303 : C. = i WHO:
krel.
= relative reactivity (see Podall 1984 for derivation).
29
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as hemlformals constitutes the most Important source of formaldehyde from
a rate standpoint. (2) over the long term, the formation of formaldehyde
appears to be largely determined by the concentration of methylene ether
urea functionalities. 1n spite of the greater reactivity expected for
N-methylol urea functionalities, and (3) the primary form of the resin.
viz., crossllnked methylene ureas, would appear to contribute very little
to the release of formaldehyde, even at pHs (of 4 to 5) conducive to
hydrolysis.
Thus, this picture appears consistent with a water transport
mechanism as being rate-determining for the Immediate through short term
release, and with the hydrolysis mechanism as rate-determining for the
Intermediate to long term release. The board may thus be viewed as
functioning as a tight reservoir for the formaldehyde formed from the
hemlformals of cellulose and related species, such as the hemlformal of
N-methylol ureas. Following the release of the "free" formaldehyde.
Initially present In the board after curing and from the facile
hydrolysis of the hemlformals, the formation of formaldehyde from such
sources as methylene ether ureas, N-methylol ureas, and the forma Is of
cellulose, become rate determining for the release of formaldehyde.
2.3 Factors Affecting Formaldehyde Release from Pressed Wood
Products
2.3.1 Product-Specific Factors
Many of the factors that dictate whether release occurs (and If so,
at what rate) are functions of the wood or resin and the manufacturing
processes used. Each factor discussed below 1s Important under at least
some circumstances; researchers have met with only limited success In
defining the controlling factor under circumstances of use In mobile or
conventional homes.
(1) Material Structure and Porosity. ChMstensen et al. (1981)
state that board porosity 1s a "major controlling factor 1n formaldehyde
emission* and that "the rate of formaldehyde release from partlcleboard
1s a diffusion controlled process." Meyer and Hermanns (1984a) agree
30
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that the formaldehyde emission rate Is strongly Influenced by the
structure and porosity of the pressed-wood product. This statement
refers to diffusion of unreacted formaldehyde from the core of the
product, though these parameters could conceivably affect resin
hydrolysis as well. Structure and porosity are c'.osely related
parameters.
Structure refers to the Inherent differences between a laminate.
such as hardwood plywood, and the true composite woods (flberboard and
partlcleboard). Some researchers have found formaldehyde emissions from
the laminated plywood to be lower than emissions from the same amount of
partlcleboard or flberboard. This Is easily explained by the fact that
the UF resin 1n plywood Is segregated In the glue layer between Intact
wood sheets, with little 1f any direct contact with air. Partlcleboard
and flberboard are, however, mixtures of wood and resin throughout;
though the residual formaldehyde 1s concentrated 1n the center by the
manufacturing process, free formaldehyde levels at the surface of these
pressed wood products can be half the elevated level 1n the center (Meyer
and Hermanns 19B4a). Thus, some free formaldehyde 1s available for
release from flberboard and partlcleboard Immediately.
Plywood 1s also less porous than flberboard or partlcleboard. The
speed of formaldehyde diffusion through pressed wood products has been
studied. Meyer and Hermanns (19B4a) report rate constants (1n meters per
hour) for the three types of products:
• 0.4 + 0.3 plywood
• 0.5 i 0.2 medium density flberboard
• 0.8 i 0.2 partlcleboard
The tests designed and performed by Chrlstensen et al. (1981)
generated data that compare (1) formaldehyde emissions from partlcleboard
surfaces and edges and (2) emissions from board surfaces of different
structure. The test involved a chamber containing the board sample.
31
-------
Into which was Introduced a calibrated flow of heated, water saturated
air. After the air exited the chamber. It was analyzed via the
chroraotropk add method. The purpose of creating the test was to
determine the extent to which the Increased edge area of board samples
commonly tested (Increased relative to surface area) dominate emissions
test data. Results are reported 1n units of rug formaldehyde/ft
board. The test was run by sealing either the edges or the surface with
a thick layer of epoxy resin.
Chrlstensen et al. found that the more porous partlcleboard edges
emitted formaldehyde at a rate of 2.1 times the surface emission rate. A
three-layered hardwood plywood was also tested, and the average ratio of
edge emissions to surface emissions was 4.9. These researchers also
found a correlation between density and surface emissions, with the most
dense (least porous) board composition emitting far less formaldehyde
than the two less-dense boards tested. Actual porosity (as measured by
resistance to air flow through the board under vacuum) also showed a
strong positive correlation with emission of free formaldehyde.
Matthews et al., 1n their work for ORNL, developed a diffusion-theory
approach that predicts formaldehyde emission rates as a function of
ambient concentration and a product's surface structure (Matthews et al.
1982, Report IV). They found that the macro-level surface
characteristics that affect boundary layer thickness and velocity of air
across the face have a direct, predictable effect on emission rate.
Products with relatively smooth surfaces produce, when tested, a linear
plot of emission rate versus concentration with a high negative value for
slope. Products with Irregular surfaces generally show linear plots with
low negative slope values.
The diffusion theory was borne out by tests and calculations, which
confirmed that:
• Mberboard and plain plywood, with smooth surfaces, will have
lower emission rates as concentration Increases.
32
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• Paneling, with alternating smooth and rough areas, will have a
range of emission rate/concentration relationships.
• The relationship between emission rate and concentration for
partlcleboard. with Its diverse mixture of surfaces. 1s not
linear over all ranges of emission rate and concentration.
(2) Type and Quantity of Resin Used As discussed 1n Section 2.2,
the F:U ratio 1n the resin strongly affects the presence and potential
release of formaldehyde. Other formaldehyde resin formulations (phenol-,
melamlne-, and tannin-formaldehyde are good examples) generally emit less
formaldehyde, either as unreacted residual or as a hydrolytlc product.
Figure I shows the low emission profile of PF partlcleboard relative to
UF partlcleboard. Hyers (1984a) presents a review of the literature on
the effect of mole ratio on formaldehyde emission rate. It describes the
relationships between F:U mole ratio, resin free formaldehyde (as
percent), and formaldehyde emission rate. Data from several
Investigators, as presented by Hyers (1984a). clearly show the positive
relationships between mole ratio and free formaldehyde and emission
rate. Hyers states that the exact-relationship 1s uncertain; other
variables (board manufacturing and aging) can affect the slope of these
lines. It 1s clear, however, that the type of UF resin (as defined by
mole ratio) strongly affects emission rates of formaldehyde.
Some inferences can be drawn from existing data on the effect of
resin quantity on formaldehyde emission rates. Researchers have shown
(Matthews et al. at ORNL and others) that emission rates for UF pressed
wood products can be generally described as:
HDF > partlcleboard » plywood
Numerous differences between these product types affect emission rate;
among those differences may be resin quantity. Recall from Section 2.1
that the weight percents of resin 1n the three product types are:
HDF - 7 to 9% w/w
Partlcleboard - 5 to 1OX w/w
Plywood - 2.SX w/w
33
-------
IN
r
I-
»0
o 14 «• n M in IM
Figure 1. Formaldehyde Release from UF and PF Partlcleboards
Measured by the NKI Method
Source: Roffael (1978).
34
-------
Plywood, with the lowest resin quantity, also has generally the lowest
emission rate; the distinction between partlcleboard and HOF Is less
clear.
(3) Manufacturing Conditions. A variety of manufacturing
conditions can affect the degree and uniformity of resin polymerization.
Incomplete polymerization leaves an excess of unreacted formaldehyde In
the pressed wood product, as well as Increased amounts of moieties that
can readily hydrolyze to release formaldehyde.
Meyer and Hermanns (1984a) and Meyer (1979) present discussions of
UF resin manufacture and formulation Into pressed wood products. Host
potential manufacturing variables that can affect formaldehyde release
are related to the complex resin chemistry:
• Use of non-uniform wood particles can lead to areas of Improper
resin:wood ratios and Incomplete cross-Unking of the polymer
(this refers largely to partlcleboard).
• Use of non-uniform wood particles, with spatially-varying water
content and pH, can also cause Incomplete polymerization In
partlcleboard manufacture.
• use of a UF resin with another chemical that may change the pH of
the wood-adhesive mixture can prevent proper polymerization.
Manufacturers are urged to test any change In catalyst or
reactant fully before changing the entire manufacturing process
(Meyer 1979).
• The length and magnitude of temperature and pressure during
manufacture affect polymerization and, therefore, free
formaldehyde levels. Myers (19B4a) shows that Increasing press
time and/or temperature lowers emissions, especially for high F:U
ratio resins.
• Manufacture may Include a final step designed to mitigate
formaldehyde off-gassing, such as treatment with scavengers or
Improved/extended curing.
The variables listed above are generalizations; Meyer (1979) lists the
following as manufacturing parameters affecting formaldehyde release:
35
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resin components
resin component ratio
resin application
hardener components
hardener quantity
press temperature
press duration
wood species
wood moisture
resin concentration
resin viscosity
wood chip size
wood chip diameter
Wood chip geometry was specifically studied by Chrlstensen et al. (1981)
as a factor In emission rate. Formaldehyde emission from partlcleboard
surfaces decreased in direct proportion to an increase in wood chip
particle size.
Not specifically listed above Is a parameter Hyers (1982a)
discusses: the curing process, a combination of the catalyst (or pH),
press time, press temperature, and other manufacturing conditions.
Myers1 review of the data was performed In an effort to re 1-lie cure with
releases by resin hydrolysis. Quadrupling curing tine (from 5 to 20
minutes) was found to decrease emissions approximately two-fold, by
resulting 1n 2 to 5 times stronger bonds In the cired resin. Decreasing
cure temperature from 40°C to 23CC resulted 1n a two-fold Increase In
bond stability with a corresponding six-fold decrease In formaldehyde
emission under test conditions. Increasing the pH from 3.0 to 6.5 caused
an Increase In bond strength of a factor of 10; the cured resin showed a
two-fold reduction In emissions.
(4) Age of the Product. Under normal use conditions, the release
of formaldehyde decreases with time, as discussed previously. Emission
reductions linked to product aging relate to a decrease over time In both
the formaldehyde present In the board as a residual from manufacturing
and the latent formaldehyde present In the board In hydrolytlcally labile
resin and wood components. The emission rate decay curve for a board Is
36
-------
apparently exponential with time; the residual formaldehyde 1s emitted at
relatively high rates followed by a slow release of latent formaldehyde.
Although the short-term emission rate behavior of boards has been
reported 1n numerous studies, little quantitative Information 1s
available on the long-term emission rates, as was discussed 1n Section
2.2.
Meyer and Hermanns (1984a) state that the emission rate may slow by a
factor of two within the first three weeks after a product 1s
manufactured (1f allowed to aerate properly). They present Figure 2 to
support this. The data upon which this figure 1s based were not
presented by the authors; the long-term emission rate beha- lor may well
be mathematically predicted.
ORNL 1s currently conducting experimental chamber studies for CPSC
designed to measure the decay of formaldehyde emissions from a
combination of partlcleboard, hardwood plywood paneling, and NOF under
controlled environmental conditions (23"C and SOX relative humidity) over
a period of one year. The board locations and loadings In the chambers
are designed to approximate consumer use conditions.
One study, the •slow" decay study. Is being conducted with a
relatively low air exchange rate 1n the chamber (0.4 air changes per
hour). The elevated formaldehyde concentrations that are anticipated
with low ventilation should reduce the emission rates of the pressed wood
products and thus lengthen their decay period. (The effect of background
formaldehyde concentration on emission rates 1s explained In the
following section). Preliminary results Indicate that the decay period
to 1/e of the original chamber formaldehyde concentration (I.e.. 0.37) 1s
greater than one year (Matthews et al. 1982-1984).
The second study, the "fast* decay study, Is being conducted with
relatively high air exchange rates designed to keep the chamber
formaldehyde concentration at or below 0.1 ppm. The low background
formaldehyde concentration should Increase the emission rates and thus
37
-------
ppm
6 years 10
Figure 2. Predicted Formaldehyde Release as a Function of
Ags and Ventilation Rate for Two Partlcleboards.
One with an Initial Emission Rate of 1.0 ppm and One
with an Initial Emission Rate of 0.5 ppm
Source: Heyer and Hermanns (1984a).
38
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shorten the decay periods relative to those observed In the "slow" decay
study. Preliminary results Indicate that the decay periods to 1/e of the
original emission rates (I.e.. 0.37) are less than one year for most
boards tested (Matthews et al. 1982-1984).
2.3.2 Environmental and Architectural Factors
Factors not specific to the type of pressed-wood product may also
affect formaldehyde release and nay often be the overriding determinants
of release.
(1) Temperature and Humidity. The effect of temperature and, to a
lesser extent, the effect of humidity on formaldehyde emission from
pressed wood products have been Investigated by numerous researchers.
The results of these studies Indicate that formaldehyde emission depends
strongly on temperature and moderately on humidity. Most of the
Investigations have Involved emission rate testing of products within
laboratory chambers, although a few have Involved measurements of
temperature effects In homes. Nyers (1984b) recently reviewed all
available data that had been reported during the period 1960 through Hay
1984. The results of his review and analysis are summarized below. The
effects of temperature are addressed first, followed by the effects of
humidity.
Researchers, most notably Berge et al. (1980), have described the
temperature dependence of formaldehyde emission In exponential terns.
Hyers (1984b) concluded that an exponential Arrhenlus type expression
does provide adequate representation of this strong temperature
dependence.
or by rearrangement
Cc
39
-------
where
Cm » measured formaldehyde concentration
Cc = corrected formaldehyde concentration
R = temperature coefficient
Tm = measurement temperature (°K)
Tc a new temperature (8K)
Because of this strong temperature dependence, Myers (1984b)
concluded that meaningful comparisons of emission rate data or home air
levels necessitate that the measurements be made at a standard
temperature (preferably 25'C) or that the measured values be corrected to
the standard temperature using the equation above. Except for those
laboratories that have consistently observed a particular temperature
coefficient (I.e.. the R value) from board tests, Hyers (1984b)
recommends that a temperature coefficient of 8930 be used for correcting
measured home air levels and emission rate chamber data to a standard
temperature of 25°C. This value was obtained by a statistical analysis
of all chamber test data as a composite set (normalized to unity at
25°C), »,Uh - 95 percent confidence Interval of 8390 to 9470 (» 6 percent
relative error). Berge et al. (1980) reported a temperature coefficient
of 9799, which has been used by other researchers.
The statistical analysis also Indicated that, although the
temperature response of different boards can differ significantly, U 1s
not clear If there are significant differences In temperature response
between board types (I.e., partlcleboard versus hardwood plywood
paneling), between 'low* and 'high* emission boards, or between chamber
tests and homes.
Researchers have found that the humidity dependence of formaldehyde
emission Is much weaker than the temperature dependence and, at present,
can best be described In linear terms. Hyers (1984b) concluded that the
linear expression below does describe the humidity dependence based on
the limited data available and that a more complex model Is not warranted
at this time because of the uncertainties surrounding measurements of
humidity dependence.
40
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Cm = Cc x [1 * A (Hm - Hc)]
or by rearrangement
Cc = Cm [1 * A (Hc - Hm)]
where
C,,, = measured formaldehyde concentration
Cc * corrected formaldehyde concentration
A = humidity coefficient
H,, = measured relative humidity (X)
Hc . new relative humidity (X)
The response of board formaldehyde emission to humidity changes Is
more complex and less well understood than board response to temperature
change. Fewer Investigators have studied this dependence and Myers
(1984b) states that the tested boards may not have achieved equilibrium
or steady state by the time the concentration measurements were made.
because of the very slow (sometimes weeks or more) and erratic response
of boards to humidity change. This may explain, 1n part, the wide
variation (almost tenfold) 1n the humidity coefficients (I.e., A values)
measured In the various studies reviewed by Myers (1984b).
Similar to the statistical analysis performed on the temperature
dependence data, Hyers (1984b) performed an analysis on the humidity
dependence data (normalized to unity at SOX relative humidity) that
yielded a composite humidity coefficient of 0.0195 with a 95 percent
confidence Interval of 0.014 to 0.025 (± 28 percent relative error).
However, because of the large variations In the humidity coefficients
measured by different Investigators and between different boards. Myers
(1984b) expressed less confidence 1n the use of this humidity coefficient
to correct emission rate and In-home air measurements to standard
conditions than 1n the use of the composite temperature coefficient.
Berge et al. (1980) reported a humidity coefficient of 0.0175, which has
been used by other researchers.
41
-------
Table 4 provides an Indication of the variability 1n formaldehyde
levels that potentially could result from changes In temperature and
relative humidity.
(2) Barriers. Paints and coatings have long been used on flberboard
and partlcleboarC for decorating purposes and to render then somewhat
water-resistant; those substances are said to be effective barriers to
formaldehyde release (Meyer 1979. NPA 1984). Painting or coating a
surface effectively lowers the porosity of the material, hinders
diffusion of formaldehyde out of the wood, and slows moisture
accumulation In the wood (which may cause hydrolysis or transport of
formaldehyde with water vapor).
Meyer's 1979 publication also lists waxes; gypsum board; and paper,
plastic, and metal laminates as effective barriers to formaldehyde
emissions. These barriers may manifest themselves 1n homes as tile
flooring or simulated wood counter or furniture surfaces. In fact,
almost every overlayment (Including carpet) or surface treatment affects
formaldehyde release. Only In a very few cases has that effect been
quantified; systematic, complete data are not available.
Plckrell et al. (1984) do provide some quantitative data on the
effect of carpet and Insulation as barriers. The release rate of
carpeting over partlcleboard was 73 percent of the rate for partlcleboard
alone. Similar results were obtained for other product/barrier
combinations.
(3) Background formaldehyde concentration. The background level of
formaldehyde has been found to be a major factor affecting emission
rates. The primary factors controlling the background level are (1)
ventilation rates and (2) Interrelationships among numerous sources (and
sinks) of formaldehyde.
Mobile homes generally have low air exchange rates relative to
conventional homes, which exacerbates formaldehyde exposure. The average
exchange rate 1n mobile homes Is 0.35 changes per hour (University of
42
-------
Table 4. Potential Effects of Temperature and Relative Humidity
Changes or Formaldehyde Air Concentrations (ppro)*
Relative humidity
Temperature
59«F (15°C)
68"F (20°C)
77«F (2S»C)
86"F (30°C)
30&
0.08
0.1S
0.24
0.40
401
0.11
0.19
0.32
0.53
501
0.14
0.24
0.40
0.66
601
0.17
0.29
0.48
0.79
701
0.19
0.33
0.56
0.92
'Calculated using equations in Section 2.3.2(1) which were developed
primarily from data on ran pressed wood products and nen hones.
Assumes a temperature coefficient of 8.930 and a humidity coefficient
of 0.0195. Assures a base formaldehyde measurement of 0.40 ppm at 25°C
and 50 percent relative humidity.
43
-------
Texas 1983), while the rate 1n conventional homes may range from less
than 1 change to 10 changes per hour. Lower rates In localized areas
with poor mixing (such as closets) may lead to higher localized
formaldehyde levels.
Myers (1984c) and Myers and Nagaoka (IQBla) discuss the effect of
ventilation rate on formaldehyde air levels. Myers and Nagaoka
experimentally validated some predictive equations that show an
exponential decline 1n concentration with Increase In ventilation rate.
Myers1 (1984c) literature review points out that existing data must be
regarded as semi-empirical because most data are from controlled chamber
tests, and extrapolation to dwellings is not reliable. Moreover, test
results are almost exclusively for single products; actual hones will
have a complicating array of pressed-wood and other formaldehyde sources.
Ths Interrelationship between numerous formaldehyde sources In homes
Is not well-understood. Meyer And Hermanns (1984a) state that the
strongest-emitting product may be essentially the only active source of
emissions at some point 1n time, and that other UF-bonded products may
act as sinks by absorbing excess formaldehyde. If that source were
removed, then theoretically the next strongest formaldehyde emitter would
become the source rather than a sink. This Interrelationship Is one
subject of an ongoing research effort by the Consumer Product Safety
Commission. Products other than UF-contalnlng materials also can act as
formaldehyde absorbers or sinks. Formaldehyde Is such a reactive
chemical that an almost limitless variety of reactions with structural
components, consumer products, or Indoor air pollutants can be Imagined.
2.4 Formaldehyde Emission Rate Testing Methods
2.4.1 Background
There are five basic types of formaldehyde collection methods that
have b*en developed to measure formaldehyde emissions from pressed wood
products. These methods can be categorized as equilibrium, static,
dynamic air flow, distillation/extraction, and passive. The Hardwood
44
-------
Plywood Manufacturers Association (HPHA). National Partlcleboard
Association (NPA), and the Formaldehyde Institute (FI) Identified 34
potential testing techniques within these 5 basic method types In 1979
(HPNA. NPA. FI 1979). It 1s the purpose of this section of the report to
review the test methods most widely used today with regard to
formaldehyde collection and analytical procedures utilized and
advantages/disadvantages of the methods. Also, correlations between
methods, 1f any, will be discussed.
2.4.2 Methods
(1) Static test method. The static test method, or desiccator test.
Is a test method that has no air passed through for collection of
formaldehyde, but utilizes an aqueous medium for the collection of
formaldehyde. It 1s a destructive method 1n that 1t requires that small
samples be removed from large formaldehyde-bearling materials for
testing. In this test, formaldehyde 1s continuously emitted from the
samples and absorbed Into the aqueous medium, ihls type of test. In
particular the Japanese Industrial Standard (JIS) and a version of the
3IS (FTM-1), has been used extensively 1n the U.S. as a quality control
test method for wood products containing formaldehyde.
The desiccator test apparatus consists of a glass desiccator with a
secure, close fitting top; a sample rack to hold samples In the
desiccator; and a beaker or desiccator plate to contain the aqueous
collection medium (distilled water). The formaldehyde-containing samples
are placed 1n the rack above a specified quantity of distilled water.
Once the cover Is placed 1n position, the test Is underway. Figure 3
presents a view of the JIS desiccator test apparatus, which Is generally
representative of desiccator systems. The temperature of the system,
typically about 75°F, 1s maintained for the duration of the test period,
which may vary from 2 to 24 hours. Data are reported In units of
concentration, such as nlcrograms of formaldehyde per mllUllter of
distilled water. The total volume of water and mass of product tested
45
-------
Figure 3. JIS Desiccator Test Apparatus
Source: Ptckrell et al. (1982).
-------
must be known to convert results to mass formaldehyde per mass of
pressed-wood products.
Another static method, developed by Roffael (1978) and used widely In
Europe, 1s known as the NKI method. The HKI method apparatus Is a simple
one. consisting of a polyethylene bottle; a tight fitting bottle cap; and
an assembly with which to hold the material samples containing
formaldehyde 1n suspension within the sample bottle (see Figure 4). Two
samples of formaldehyde-bearing material are attached to the suspension
assembly and placed above 50 ml of distilled water contained within the
bottle. The distance between the suspended samples and the water surface
has not been deemed to be a significant factor for the experiment. The
samples should be cubes, with 2.5 cm (!') sides. When all apparatus are
1n place, the bottle Is tightly sealed with the bottle cap. The test 1s
performed at 40"C for different time Intervals. Roffael presented his
results In units of milligrams of formaldehyde per 100 grams of sample.
Advantages 1n using a static air test method Include ease of
operation, since neither air flow control nor actual experiment
observation 1s required. Manpower Is needed only for apparatus set-up
and analysis of data. Low levels of formaldehyde can be detected by
Increasing the duration of the test.
Disadvantages of this type of test Include the problem of Induced
high humidity 1n the sample chamber due to a stagnant atmosphere. This
may alter the moisture content of the sample, thereby causing a variation
1n formaldehyde emissions and the condensation of water vapor on the
walls of the chamber; test samples may also act as a formaldehyde sink
during the test. Care must be taken to ensure that particles from the
sample do not fall Into the collection medium, which would lead to
abnormally high formaldehyde concentrations 1n the collecting medium.
Because of the small size of the wood samples tested, an atypically large
amount of board edge surface 1s exposed; unless the edges are sealed, the
edge releases will dominate the test results. Finally, the test must be
47
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SAMPLES
DISTILLED
WATER
Figure 4. MKI Test Apparatus
Source: Roffael (1978).
48
-------
timed accurately to obtain proper results because formaldehyde
concentration In the collecting medium 1s a direct function of time.
The quantity of formaldehyde emitted from the sample, which would
eventually be absorbed 1n water medium, can be determined by one of four
analytical methods:
(1) Chromotroplc acid procedure
(2) Purpald procedure
(3) Acetylacetone procedure
(4) Pararosanlllne procedure
For static tests, depending on the application, any of the four tests can
be used. According to data presented by the Hardwood Plywood
Manufacturers Association (HPMA) 1n their July 1984 submission to EPA,
the Chromotroplc add and acetylacetone methods are used most 1n static
tests. All four tests are valid analytical techniques for formaldehyde,
though with different common detection limits and prone to different
Interferences. The Chromotroplc acid method Is subject to Interferences
from N02, alkenes. acroleln, acetaldehyde, and phenol; pararsoanlllne
has few (If any) Interferences: the purpald test may record higher
aliphatic aldehydes; and the acetylacetone test Is specific to
formaldehyde.
Formaldehyde data obtained from the desiccator and WKI tests may be
presented 1n units of formaldehyde concentration In solution or as an
average emission rate per mass of partlcleboardi.
(2) Dynamic test method. The dynamic air flow test method uses a
system that passes air at a controlled rate through a chamber containing
the samples to be tested. The released formaldehyde is carried by the
air out of the chamber. The dynamic test models the actual home air
contamination process by measuring the formaldehyde concentration In the
test chamber atmosphere. Therefore, this test constitutes a primary
characterization of formaldehyde emissions from formaldehyde-containing
49
-------
materials. Dynamic chamber tests may be conducted with large chambers,
capable of holding a full size sample of partlcleboard, or with small
scale-laboratory scale apparatus. Since many of the test procedures are
laboratory scale, this discussion will focus on the small-scale
laboratory apparatus and results obtained from a small-scale unit.
The apparatus for the dynamic chamber test consists basically of a
large standard desiccator within which the formaldehyde-bearing samples
are contained (see Figure 5). The desiccator Is fitted with a I1d
equipped with Inlet and outlet nozzles for the circulation of air.
During the experiment, air 1s pulled from the outside atmosphere Into the
chamber. This air mixes with the air 1n the chamber and exits the
chamber through the exit nozzle. The rate at which air 1s circulated
through the chamber 1s controlled to within *, 5 percent. A small fan or
stirring bar can be used to circulate air within the chamber. Dynamic
experiments are generally conducted under conditions of constant
temperature and humidity. Assuming that good gas mixing occurs within
the chamber, the effluent gas will fcs representative of the chamber gas.
At various time Intervals, the effluent gas 1s scrubbed through a
prescribed quantity of distilled water and the absorbed formaldehyde 1s
analyzed. Test results are reported In parts per million of formaldehyde
In chamber air.
A primary advantage of this type of test Is that, unlike the
desiccator test. It can be used to simulate real world conditions. The
dominant factors affecting the emission rate of formaldehyde from a given
board (I.e., temperature, humidity, product loading, and ventilation
rates) can all be varied using this method.
Disadvantages of this test Include the need for precise measurement
of air flow rate. A constant prescribed air flow rate must be
maintained; erroneous test results will otherwise be obtained. The
environmental conditions within the system must be maintained constant
throughout the test, thus making this test more manpower-Intensive than
the static test.
50
-------
To Impingers
Chamber
Exhaust
RH-Temp
Sensor
Humidified Air
— Support
Grate
Figure 5. Dynamic Chamber Test Apparatus
Source: Plckrell et al. (1982).
51
-------
The Impinged solution can be analyzed using any of the four
analytical methods mentioned previously. According to data presented by
the HPHA, the chromotroplc and purpald methods appear to be the most
widely used. Again, as with the static tests, the chromotroplc add
method has beer, recommended by HIOSH for the detection of formaldehyde.
(3) Dlstlnation/extraction test methods. The distillation/
extraction test method, also known as the perforator test method, Is
unlike either of the two previous test methods. Rather than using air as
a transport or collection medium, a boiling solvent such as toluene Is
used to capture formaldehyde. The system, as defined by Myers (1833),
Involves a 2-hour reflux In boiling toluene with a prescribed mass of
samples. The samples are placed 1n the boiling toluene, and the reflux,
which contains the formaldehyde, 1s bubbled through distilled water. The
distilled water extracts any formaldehyde In the toluene reflux. The
toluene vapor, which Is free of formaldehyde. Is then condensed and
returned to the boiling toluene pot. Final analysis of the water leads
to the perforator value, generally expressed as milligrams of free
formaldehyde per 100 g of dry board.
Advantages to this type of test Include the fact that test results
are generally reproducible, the test Is fast, and It requires no
preconditioning of the samples and no temperature or relative humidity
control. Also, considerable work has been done by the Europeans using
this test as a quality control and regulatory method.
Disadvantages 1n using this type of test Include the potential
generation of false formaldehyde results. Due to the rigorous test
conditions and high temperatures Involved, formaldehyde that under normal
ventilation situations would not be emitted may be released. Thus,
erroneous formaldehyde readings may be obtained. This was substantiated
by Roffael (1978) when he attempted to correlate his UKI method with the
perforator test. He stated that even In cases where no formaldehyde
binder was present 1n the sample, the perforator test still reported, or
52
-------
detected, formaldehyde In the sample. This fact, plus the Inability to
vary test procedures, are chief drawbacks to this test.
The water samples obtained with the perforator test can be tested by
any one of the four analytical methods. In his experiments, Myers (19B3)
used acetylacetone to obtain test results. He found that trloxane
emitted by the boards through the distillation process would be analyzed
as formaldehyde by the chromotroplc acid method, but not by the
acetylacetone method.
(4) Formaldehyde surface emission monitor (FSEH). The formaldehyde
surface emission monitor (FSEN) 1s a device that allows for the
non-destructive measurement of formaldehyde emission rates from
formaldehyde-bearing materials. The FSEH has been developed by Matthews
et al. (1983. 1984) to address a need for a semi-quantitative,
non-destructive measurement of formaldehyde emission rates from
full-scale formaldehyde bearing objects.
The main components of the FSEM (Figure 6) are a 20 cm brass
mechanical sieve, (No. 20 mesh- 0.0331 Inch openings) and a brass cover.
It Is within this compartment that the formaldehyde sorbent Is contained
when It 1s In operation. A circular flange, consisting of plexiglass and
neoprene. attached to the sieve provides for a seal between the outside
atmosphere and the test atmosphere. The separation distance between the
mesh surface and the emitting material 1s about 2.3 cm. The brass cover
Is mechanically clamped to the sieve to ensure that contamination of the
sorbent from the outside atmosphere 1s avoided. In order to use the
FSEN, the solid sorbent material 1s sprinkled 1n a uniform manner on the
screen of the mechanical sieve assembly. The sieve 1s then sealed for
the duration of the two-hour test period. At the conclusion of the test.
the sorbent Is washed with distilled water and the solution Is filtered
and assayed for formaldehyde content using a pararosanlllne method.
Results from this stage of the test are presented In grans of
formaldehyde per ml 111liter of solution tested. Matthews, concerned
53
-------
COVER
W/// WOOD PRODUCT
2,3 cm
Figure 6. FSEM Test Apparatus
Source: Matthews et al. (1984).
54
-------
primarily with emission rates, provided an algebraic relationship to
determine the emission rate:
Concentration of
formaldehyde found x Rinse volume
Formaldehyde emission rate = (ma/mil (mil
(mg/mz/h)
Sampling period (h) x Sample area (in2)
The major advantages to this test method are that 1t 1s
non-destructive and portable, thus potentially enabling emission rate
testing to be conducted on-slte (e.g., 1n the home). The major
disadvantage to this method Is that 1t has not yet been fully validated.
The effects of equipment design and environmental conditions on operation
results have not been completely resolved.
2.4.3 Inter-Method Correlations
Correlations or agreement between data generated by various test
methods are presented In this subsection. It should be noted In
reviewing the data that most correlations apply to specific test
conditions and specific sets of products. The exact correlation between
various test methods 1s complex and not yet fully established (Meyer et
al. 1983) The same correlation may not be valid when, for Instance, the
resin formulation Is changed, the wood species differs, the board finish
or top coat Is modified, the pre-test conditioning of the boards 1s
altered, or boards have been manufactured by different facilities (even
In similar manners) (Meyer et al. 1983).
In addition. It should be realized that the various test methods nay
very well be measuring formaldehyde emission generated by different
mechanisms (Myers 1983). The perforator method, according to Myers,
measures free formaldehyde but may also be measuring formaldehyde
generated by hydrolysis as a result of the testing. Desiccator tests
measure only the easily liberated portion of the free formaldehyde,
although the test, 1f sufficiently prolonged, may also cause resin
55
-------
hydrolysis. The dynamic tests measure varying combinations of Initial
free formaldehyde and hydrolytlcally produced Formaldehyde depending upon
exposure time and conditions (Myers 1983).
Although approximate linear correlations with relatively high
correlation coefficients have been found between various methods, large
deviations occured from the linear regressions. Myers (1983) concluded
that without large safety factors and/or much testing to clarify those
deviations neither the desiccator nor perforator test should be used as
product standard test methods; product standards should be based on
dynamic chamber tests.
Myers and Nagaoka (1980) summarized Inter-method correlations for six
formaldehyde emission tests: two desiccator tests (NPA and J1S). the
perforator test, the jar (WK1) test, a paper sorptlon test, and a dynamic
chamber method. They found nearly perfect cartesian correlation (r2 of
0.99) between results obtained via the two desiccator test methods.
Close agreement between different static tests 1s not unexpected; these
Investigators also found a close correlation (r2 > .96) for results
obtained via Jar and NPA 2-hour desiccator tests. An Interesting
correlation 1s found with the results of the seldom-used paper sorptlon
test and dynamic chamber test. The paper test Involved stacking filter
paper between wood samples, then extracting the formaldehyde from the
paper and using any of the common analytical methods. With ten data
points, a correlation coefficient of 0.99 was reported, with only 2
percent error; this was the closest correlation found by Myers and
Nagaoka (1980).
Data correlations between static and other formaldehyde test methods
have been developed by many scientists. Myers and Nagaoka (1980, 1981b)
have produced a relationship from data obtained In a JIS test and dynamic
test. Presented In Figure 7, these tests were conducted with fresh
partlcleboard at conditions of 25'C and 75 percent relative humidity (RH)
and displayed excellent agreement (r2 = 0.965) (Myers and Nagaoka
56
-------
Figure 7. Desiccator Test and Dynamic Test Data Correlation
Source: Myers and Nagaoka (1981b).
57
-------
1980). A similar correlation developed by Myers (1983) shows that data
obtained from a 2-hour desiccator test and a dynamic chamber test are In
close agreement (r2 =. 0.87). This correlation 1s given In Figure 8.
Test conditions were 2S°C and SO percent RH.
Roffael (1978) was able to correlate data obtained from his WKI
method and that of a dynamic chamber. Again, various partlcleboards
under similar conditions (23"C/45X RH) were tested. The results are
graphically presented 1n Figure 9.
Roffael also found that a correlation exists between data rbtalned by
the UKI test method and the extraction/distillation (perforator) method.
Using similar formaldehyde samples and testing for periods of 24- and
48-hours. two correlations were found to exist. They are given 1n
Figures 10 and 11.
A data correlation between the dynamic test method and the
extraction/distillation (perforator) method was also obtained by Myers
(19B3). At conditions of 25°C. 50% RH, and a board loading factor (N/L)
of 0.5, a near linear correlation was obtained and Is presented 1n
Figure 12.
Matthews (1984) Identified a correlation between his FSEM method and
that of a dynamic test chamber. Test conditions were set at 23°C and SO
percent RH. Graphed data results are given In Figure 13.
2.5 Fo:iiBldehyde Emission from Conventional Pressed-Mood Products
Numerous Investigators have measured formaldehyde emissions from
pressed-wood products over the past ten years. The changing nature of
pressed-wood products, however, renders data obtained prior to 1982
relatively obsolete In determining baseline formaldehyde emissions for
currently-marketed products.
During the period 1980 through 1983, three major surveys were
conducted to characterize formaldehyde emissions from pressed wood
products. NPA conducted Industry-wide surveys of partlcleboard and MOF
SB
-------
0 02 0.4 O£ Ofl 10 12 M
DYNAMIC CONCENTRATION AT N/L*O9(ptfn)
Relation iwtween Mwur desiccator values
•nd dynam,c concentration at 29' C/50% RM and MA,-0.5
(Groupi bearas- O-piywood: O»pwtideOoard.A=PF
particleboard.)
NOTE: ML 1s loading factor - N Is ventilation rate (HR~l), I Is
board loading (H2 board area/N3 chamber volume).
Figure B. 2-Hour Desiccator Test and Dynamic Chamber Test
Data Correlation
Source: Myers (1983).
59
-------
e n u «•
NOTE: Values on the Y-AXIS are net given. Roffael stated that he
was unable to provide these values due to an agreement between
himself and the German Partlcleboard Association.
Figure 9. HKI - Dynamic Chamber Correlation
Source: Roffael (1978).
60
-------
0 SO 4O 10 tO WO BO
met 'MCtHOD (TWENTY nm NOIMS)
Figure 10. WKI Method and Distillation/Extraction Method
Data Correlation (24 Hour Test Period)
Source: Roffael (1978).
61
-------
0 (0 40 W M
Figure 11. MCI Method and Distillation/Extraction (Perforator)
Method Data Correlation (48 Hour Test)
Source: Roffael (1978).
62
-------
- 20
0 0.2 04 0.6 QB LO 12
DYNAMIC CONCENTRATION
AT N/L-Ol5(ppffl>
Relation between perforator and dynamic
concentration at N/L=0.50. 2S*C/SO% RH. (Grouo 1
boards. O»plywood: O'particletward; A»PF par-
ticlaDoard)
Figure 12. Dynamic Test Method and Distillation/Extraction
Test Method Data Correlation
Source: Myers (1983).
63
-------
as
|0.6
I 0.4
\ I I
PARTICLEBQARO
PARTlCLEBOARO DECKING
PARTiaEBOARO UNOCRLAYMENT
INDUSTRIAL PARTICLE80ARJP
MEDIUM DENSITY FIBERBOARO (-31
HfROBOARD
SOFTWOOD PLYWOOD
u
MAKOWOOO PLYWOOD PANELING
a DOMESTIC VENEER
• PRINT OVERLAY
v PAPER OVERLAY
1
I
1
o tx2 0.4 oe ac u>
CM20 EMISSION RATE (m«/mzDr)- ENVIRONMENTAL CHAMBER
Figure 13. FSEM Test Method and Dynamic Test Method
Data Correlation
Source: Matthews et al. (1984).
64
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during 1980 and 1982. In 1983, CPSC conducted a survey of partlcleboard,
MOF, and harJwood plywood paneling produced by the top three
manufacturers of each product type. Although the three surveys used
different emission rate test methods aid, to a varying extent, tested
boards produced by different (and unidentified) manufacturers, the
results of these three surveys provide the best available Information
characterizing the extent of formaldehyde emissions from pressed wood
products marketed during the 1980's. The survey designs and results are
discussed below. Comparison of the NPA and CPSC results are made where
appropriate.
2.5.1 1980 and 1982 NPA Surveys (NPA 1984)
During 1980 and 1982, NPA requested partlcleboard and MOF samples
from members and non-members of NPA. Each participating plant was
requested to supply two samples of each of the major product types
produced by the plant. The samples were requested to be finished
products ready for sale and of recent manufacture.
A total of 47 products submitted by 32 different plants were tested
In the 1980 survey. A total of 62 products submitted by 38 different
plants were tested In the 1982 survey. Table 5 presents additional
Information on the number of plants producing various product types that
participated In the survey. The table also gives some Indication of the
extent of Industry participation 1n the surveys by comparing the number
of participants to the number of plants In the Industry. Because the
Identities of the participants are confidential, It Is not possible to
determine what percentage of actual Industry production volume or
capacity was represented by the surveys.
The 1980 survey was performed using the 24-hour tiesslcator test,
which was the standard test method for the Industry at that time. The
1982 survey was performed using the 2-hour desslcator test which, by
1982. had become the Industry standard test. In order to determine 1f a
correlation could be obtained between the results of the two test
65
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Table 5. Sutniry of Plant Participator! in NPA-s 1980 and 1962 Surveys'
Product type
Particleboard
(cabined)
-Mobile hone decking
- Underlayrcnt
- Industrial
HOP
Nende board11
No. participating
plants6 No. of repeats0*6
1980 1982
(27)
10
15
16
3
2
(32)
13
14
27
4
Z
(22)
9
9
15
2
2
No. of plants in
industry in 1963
MS)
unknown
unknown
unknown
11
8
•Source: NPA (1984).
bCoifcined ninter of particleboard plants is less than the sum of the individual
product plants because many plants supplied none than one product type.
'Indicates the muter of plants that definitely participated in both the 1980 and 1982
surveys.
°A type of particleboard defined by NPA (1984) as 1/8 to 1/4 inch thick
board produced by pressing a continuously moving ribbon of resin-coated
particles.
66
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methods, 56 of the 62 products collected 1n the 1982 survey were tested
using both the 2-hour and 24-hour test methods. A linear regression
analysis of these data yielded the following equation with a correlation
coefficient of 0.96:
(2-hour value) « 0.55 x (24-hour value) * 0.24
Using this equation, NPA predicted the 2-hour desslcator values for
the products tested 1n the 1980 survey. Table 6 provides a summary of
the average emission rates for each product type with all the
manufacturers' data combined for the two surveys. As can be seen 1n the
table, the average desslcator values, as well as the range of values,
decreased for all product types between 1980 and 1982. The average
decking, underlayraent and Industrial board test values decreased by 67
percent, 56 percent, and 61 percent, respectively. Figure 14 presents a
profile of the desslcator test values for the combined partlcleboard
subsets tested In the two surveys.
As Indicated In Table 5, 37 of the same plants that supplied samples
for the 1980 survey also supplied samples for the 1982 survey. The
boards from 28 of these plants had reduced desslcator values 1n the 1982
survey. Values Increased by 5 percent or less for 4 boards, Between 11
and 18 percent for 3 boards, and by greater than 100 percent for 2 boards.
2.5.2 CPSC Pressed-Wood Product Survey (Matthews et al. 1982-1984)
During 1983, the CPSC collected samples of six types of pressed-wood
products: partlcleboard underlayment, Industrial partlcleboar'd, MOP, and
hardwood plywood paneling (3 finishes - Ink print, paper, and domestic
veneer). Six boards were collected directly from one manufacturing plant
of each of the three U.S. manufacturers with the largest volume of sales
for each of the six product types. Thus, a total of 108 boards, 18 of
each product type, were collected.
The companies whose products were tested were selected because they
supply a large proportion of all the pressed wood products purchased by
consumers directly or as components of consumer products (e.g..
67
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Table 6. NPA 1980 and 1982 Survey Sunnry Results
Product type
Mobile hcne decking
Particleboard untier-
laynant
Industrial particle-
board
HOP
Nende board
Survey
1980
1982
1980
1982
1980
1982
I960
1982
I960
1982
Hunter of
sanples
10
13
IS
14
7
29
3
4
2
2
Test results (ugfol)*
mean Stnd. Oev. Range
3.61
1.18
3.99
1.74
5.05
1.99
7.56
3.77
5.64
3.B7
3.09
0.45
2.71
1.45
4.87
1.06
_
—
O.S7
0.41
1.11
0.57
0.78
0.78
1.49
1.36
5.53
3.22 •
-9.03
-2.01
- 10.6
-6.38
- 17.4
-4.9S
- 13.4
-4.92
-5.75
. 4.52
Source: NPA 0984).
"2-hour dessicator test results, values for 1980 survey are predicted; see Section 2.5.1
for details.
68
-------
li .
I I 1910 iain/oy boards
• 1982 survey tomb
I
o
•if-
0-1 l-I 1-11-4 4-4 S-6 fr-7 7-9 W 9-10 10-11 ll-U
•no inn tessiamn VMIIR
IT-IB
Figure 14. Profile of the Desiccator Values for the
Partlcleboard Products Tested In The 1980
and 1982 NPA Surveys
Source: NPA (1982).
69
-------
furniture). However, It was noted by CPSC that boards collected from the
top manufacturers may represent the state-of-the-art In terms of low
formaldehyde-emitting products rather than the actual range of
formaldehyde-emitting products on the market.
In order to obtain a random selection of boards available at a plant.
boards were selected from lots manufactured (or glued) on at least two
different dates. In addition, boards were selected at widely different
positions from a bundle of boards manufactured on a given date.
The samples were shipped to ORNL for emission rate testing with the
FSEH (see Section 2.4.2 for more Information about the FSEN). Prior to
testing, the partlcleboard and paneling samples were conditioned for 2
weeks at approximately 22°C, SO percent RH, and less than 0.15 ppm
background formaldehyde concentration. The HOF samples were similarly
preconditioned, except that the conditioning period lasted 3 to 4 weeks
Instead of 2 weeks. This extended conditioning time probably resulted In
a 10 to 20 percent lower formaldehyde emission rate 1n comparison to what
would have been measured after a 2 week conditioning period. Three FSEH
measurements were made on each board because of anticipated 1ntra-board
variation In emission rates. The paneling samples were tested on the
decorative side of the panel.
Table 7 presents a summary of the average emission rates for each
product type with all the manufacturer's data combined. For
partlcleboard, the mean emission rates of the underlayment and Industrial
subsets are very similar. In contrast, the mean emission rate of Ink
print paneling Is more than twice that of both the paper and domestic
veneer paneling products. On the average, the emission rates of uncoated
HOP beards are about five times higher than the emission rates of the
partlcleboard or paneling products.
Figure 15 presents a profile of the formaldehyde emission rates of
the combined partlcleboard and hardwood plywood paneling boards tested 1n
the survey. Figure 16 presents a comparative profile of the emission
rates of the tested HDF, partlcleboard. and paneling products.
70
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Table 7. CPSC Pressed-Uood Product Survey Emission Rate Sumary Results
Product type
Particleboard (contained)
- Underlaynent
- Industrial
Paneling (conblned)
- Ink print
- Paper
- Domestic veneer
IVF
No. of Samples
(36)
18
IP
(54)
18
18
18
18
Hean
(0.30)
0.30
0.31
(O.I?)
0.28
0.11
0.12
1.56
Emission rate Ong/nrVhr)
Stnd. Dev.
(0.18)
0.22
0.14
(0.14)
0.20
0.07
0.04
0.50
»
Range
(0.11 - 0.78)
0.11 -0.78
0.15 -0.62
(0.03 - 0.63)
0.05 - 0.63
0.03 - 0.27
0.07 - 0.24
0.57 - 2.30
Source: Matthews et «1. (1982-1984).
*FSEN measurement results.
-------
It
a ««
&
§
s
•
•
•
1
I 1 Mnfcnarf Mjm« «write|
• PanUlrkuriS
HUB
1
i^»-i 1
1
Ulil.n! 1 mnfli.i,, ..i.
Figure 15. Profile of the Formaldehyde Emission Rates of the
f'artlcleboard and Hardwood Plywood Paneling Boards
Tested In the CPSC Survey
Source: Matthews et al. (19BO-1VJ?).
72
-------
I ~1 -WF
g . ftirtlcltfaunJ
1223' -
iSO
. IS
10
0 . 0.1 O.J-41.6 0.4-0.« O.H.I 1.M.S I.&.I.8 1.1-1.1 Z. 1-2.4
: CHissm MK
Figure 16. Profile of the Formaldehyde Emission Rates of the
NOF. F«rt1cleboard and Hardwaod Plyvmod Paneling
Tested In the CPSC Survey
Source: Hatthews et al. (1980-1984).
-------
To evaluate the Interboard variability of measured emission rates for
products made by the same manufacturer, Matthews ee al. (1982-1984)
performed one-way analyses of variance on the emission rate data for each
manufacturer (I.e., test results on six boards per manufacturer). The
average coefficient of variation for Interboard variation was 11 percent
for partlcleboard (range of 0 to 22 percent), 43 percent for paneling
(range of 17 to 94 percent), and 18 percent for HDF (range of 12 to 24
percent). These results, summarized 1n Figure 17, Indicate that the
manufacturing processes of each of the partlcleboard and HOF plants
surveyed were reasonably consistent; however, the same was not true for
the paneling plants.
Comparison of the CPSC and NPA Survey Results
A qualitative comparison between the results of the CPSC survey and
the NPA surveys was made by Matthews (1982-1984) and 1s shown In Table
8. The Interlaboratory comparison suffers from: (1) a semi-quantitative
Intermethod correlation between the 2-hour desstcator test and the FSEN*;
(2) the change 1n formaldehyde emissions with newer products; and (3) the
possible bias of the CPSC survey towards sampling of state-of-the-art
boards rather than the entire range of products marketed In 1983. The
results of the comparison may Indicate significantly Improved products In
the 1983 CPSC survey In comparison to products tested 1n the 1982 NPA
survey.
*An approximate 1 to 1 correlation between the results of the 2-hour
desslcator test and the FSEH was found In testing at ORNL on nine
different products (Matthews et al. 1983).
74
-------
15 •
10 .
s
Hun
n
i
r I
I
Hiirdwod PlyMri
Rirtlelitoird
I
**•
OJ-M
M-W
tn-aa
u-u
U-IJ L7-L» Id-Li
u-u u-u >u
(Intra-Board Average Emission Rate)/(Inter-Board Average Emission Rate)
Source: Matthews et al. (1983),
Figure 17. Inter-Board Var atlon 1n the CPSC Survey
75
-------
Table 8. Caparison of 1980 CPSC and 1980, 1982 NPA Test Results
Product
Particleboard
underlaynent
Industrial
parti cleboard
Mobile hone
decking
NPA test results
1980
4.0 + 2.7
5.1 + 4.9
3.6 + 3.1
(ug/mL)a
1982
1.7 * 1.5
2.0 + 1.1
1.2 + 0.5
CPSC test results (ug/«L)D
1983
0.9 * 0.6
0.9 + 0.4
not tested
a2 hour dessicator test results: Mater sorbent, uneoated edges on test specimens.
bFSEH test results: molecular sieve sorbent. Results are selective to the QfeO emission
from the face of the product. An approximate 1 to 1 correlation between the results of the
2 hour dessicator test (units of ug CHjO/hiL HjO) and the FSEH (ug CHjO/mL HjO in the
sieve rinse solution) was found in ORNL tests.
76
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3. OTHER RESIDENTIAL SOURCES
Two major sources of formaldehyde emission In a residential setting
are pressed wood products and urea-formaldehyde foam Insulation (UFFI).
However, the formaldehyde concentrations 1n the hone may be attributable
to sources other than pressed-wood products containing urea-formaldehyde
(UF) resin and UFFI. The other sources can be characterized 1n the
following categories:
» Products with phenol formaldehyde (PF) resins
- softwood plywood
- hardboard
- waferboard
- oriented strand board
- fibrous glass Insulation
- fibrous glass celling tiles
• Consumer products that may contain formaldehyde resins
- Carpeting
- upholstery fabric
- drapery fabric
- other textiles
• Combustion products
- unvented kerosene and gas appliances
- smoke from tobacco products
- combustion of wood or coal In fireplaces
• Outdoor air
- ventilation system air exchange
The following sections will address these other residential formaldehyde
sources.
3.1 Urea Formaldehyde Foam Insulation (UFFI1
UFFI was Injected Into the sldewalls of buildings for Insulation
primarily 1n the 1970s. Formaldehyde 1s released from the UF foam In
varying concentrations and may arise from (1) excess
77
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formaldehyde 1n the original UF resin, some of which may be present just
after foaming, and (2) a continual generation and release due to
hydrolysis of the UFFI (Hawthorne et al. 1981). The add catalyst used
to complete the polymerization of the UFFI generates an acidic
environment. This circumstance tends to Intensify hydrolytlc
decomposition and therefore produces a continual release of formaldehyde
(Hawthorne et al. 1981.)
Levels of formaldehyde 1n the Indoor environment of both mobile homes
and conventional homes Insulated with UFFI tend to decrease over time
(Conn et al. 1984). The formaldehyde levels can vary with changes In
environmental conditions, such as the temperature and the relative
humidity. The age of the UFFI and the air exchange rates of the building
are also factors to be considered with the decrease In levels of
concentration. According to Anderson et al. (1983). not all UFFI emits
significant quantities of formaldehyde vapors. The concentration of
formaldehyde 1s much higher Immediately after Installation, and with
aging of the product less formaldehyde 1s emitted; the rate of decay of
the formaldehyde 1s not, however, well defined.
Conn et al. (1984) have gathered data from many studies of UFFI
residences within the United States and Canada. They have accumulated
1.164 data points, each of which 1s the average formaldehyde level
measured In a UFFI residence at the time of measurement; also listed Is
the age of the UFFI (with age defined as time lapsed between Installation
and measurement). Nearly all of the measurements were performed using
the chromotroplc add method. The data were grouped Into 10-week
Intervals by age of the UFFI home, and the average formaldehyde level for
all homes falling within each 10-week Interval was determined. The
average formaldehyde measurement ranged from 0.210 ppm In the first
10-week (0 to 71 days) Interval to 0.030 ppm 1n the last 10-week (3,011
to 3,080 days) Interval. The average formaldehyde level showed a
tendency to decline rapidly after the first 40 weeks and more slowly
thereafter (see Table 9).
78
-------
Table 9. Average Formaldehyde Measurement in UFFI Homes by Age
Days
0-71
141-210
211-ZBO
281-350
351-420
421-490
491-560
561-830
631-700
701-770
771-840
841-910
911-980
981-1050
1051-1120
1121-1190
1191-1260
1261-1330
1331-1400
1401-1470
1471-1540
1541-1610
1611-1680
1681-1750
1751-1820
1821-1890
1891-1960
1961-2030
2031-2100
2101-2170
2171-2240
2241-2310
2S21-2590
3011-3080
Hatter of
data points
63
76
51
58
72
55
68
45
49
70
37
54
45
44
66
30
46
29
22
22
8
6
15
9
14
4
5
4
5
4
4
1
* 1
2
Avg ppmNCHD
0.210
0.240
0.240
0.058
0.068
0.084
0.100
0.076
0.078
0.080
0.081
0.079
0.058
0.082
0.072
0.050
0.040
0.072
0.054
0.074
0.063
0.047
0.032
0.021
0.067
0.102
9.039
0.080
0.054
0.050
0.078
0.040
0.117
0.030
Source: Gatin et al. (1984)
79
-------
Limited measurements 1n other studies Indicate that, for homes
Insulated with UFFI, the range of formaldehyde concentrations 1s 0.01 to
4.1 ppm with an average concentration of 0.14 ppm (Gupta et al. 1982).
The Consumer Product Safety Commission (CPSC) In 1982 prohibited the
Installation of UFFI In residential buildings and schools. Although It
was later overturned by a Federal court, the CPSC ban of UFFI caused the
virtual elimination of the UFFI Industry (Formaldehyde Institute 1984).
There 1s considerable debate between the regulatory agencies and the UFFI
Industry as to the extent of long-term formaldehyde emission from UFFI
that 1s presently 1n place (Hawthorne ct al. 1983).
Detailed Information on UFFI can be obtained from the following
references:
1. Consumer Product Safety Commission 1982. Urea-formaldehyde
foam Insulation. Fed. Reg. 16 CFR Part 1306 47(64):14366
(1982).
2. Conn H. 1981. Revised carcinogenic risk assessment for
urea-formaldehyde foam insulation. Washington, DC:
Consumer Product Safety Commission.
3. Hawthorne AR, Ganmage RB, Matthews TG, et al. 1981. Oak
Ridge National Laboratory. An evaluation of formaldehyde
emission potential from urea-formaldehyde foam Insulation:
panel measurements and modeling. Oak Ridge. TN:
ORNL/TM-7959.
3.2 Construction Products Containing Phenol-Formaldehyde iff} Resins
Host structural pressed-wood products used In construction are
manufactured using PF resin adheslves Instead of UF resins. These
products Include softwood plywood, waferboard. hardboard, oriented strend
board, and structural phenolic partlcleboard. Other products that
contain PF are fibrous glass celling tiles and Insulation.
80
-------
1. Structural Mood Panel Products
Structural wood panel products are basically used In construction and
exterior applications that require water-proof boards. Common
applications Include roof and wall sheathing, subfloorlng. and siding.
Small amounts are used for shelving, cabinets, Indoor paneling, and
fixtures (APA 1984). Although formaldehyde Is used In the manufacture of
phenolic resins for the phenolic adheslves. Is 1s believed that virtually
all the formaldehyde reacts to form PF polymers. The small amount of
formaldehyde that 1s emitted from the panel products Is the result of
residual formaldehyde from the curing process; no release via resin
hydrolysis is expected (APA 1984).
There are several published studies on formaldehyde emissions from PF
pressed-wood panel products. The results of these studies, presented In
detail In Section 5.3, Indicate that PF pressed-wood products are not
likely to contribute more than 0.1 ppm to Indoor formaldehyde air levels
regardless of the product loading or air exchange rate.
2. Fibrous Glass Insulation and Celling Tiles
Other generic product lines containing phenol formaldehyde that are
used In construction applications are fibrous glass Insulation and
celling tiles. In 1983, as a result of a study on formaldehyde release
from consumer products, CPSC recommended further evaluation of fibrous
glass Insulation and celling tiles. In this study. Plckrell et al.
(1982) used desslcator tests to measure emission rates of 0.016 and 0.020
ng formaldehyde/or/hr for one sample each of fibrous glass Insulation
and celling panels, respectively. The CPSC provided! the samples,
presumably locally purchased. These products, when compared with other
products tested, were among the highest group of emitters. Concern arose
from the test results because of the high loading rates of these products
1n homes. Under normal use conditions (In attics). Insulation would be
subjected to temperatures much higher than normal room temperatures,
thereby Increasing potential formaldehyde emissions.
81
-------
Further Investigations on the emissions of formaldehyde from fibrous
glass Insulation and celling tiles were performed by Matthews and Westley
(1983) using both the FSEM and a small scale environmental chamber test.
FSEH measurements were performed on 9 Insulation products and 11 celling
tile products. Products from a total of 5 manufacturers were tested.
Products with the highest FSEN results were tested In the environmental
chamber. The samples were conditioned at 24°C. SOX RH and
-------
3.3 Consumer Products Potentially Containing Formaldehyde Resins
Consumer products found 1n a residential setting that may
contain formaldehyde resins Include carpeting, fabric (apparel end
non-apparel), and paper products. Plckrell et al. (1982) investigated
formaldehyde emissions from 28 different samples of these consumer
products using static desslcator tests. The Individual sample emission
rates are presented In Table 10. The emission rate values,
representative of each product group and approximating the median of
detectable and relevant values, are presented below. For comparison
purposes, the median emission rate values for the pressed-wood products
and Insulation products tested by Plckrell are also listed.
Product Emission rate (uq/m2/day)
Pressed-wood products -15,000
Wearing apparel (new, unwashed) ~400
Insulation products -400
Paper products -300
Fabric (non-apparel) »100
Carpet - 15
Most fabrics that contain cotton are finished with a formaldehyde-
containing crossllnklng agent for durable press properties. Formaldehyde
emission rates will, however, decrease with laundering*. The first home
*
laundering will greatly diminish the emission level.
Although carpets are listed as possibly containing formaldehyde
resins, an industry representative1" states that formaldehyde-emitting
resins have never been used by major carpet manufacturers, though small
'Personal communication between R. Relnhardt, USOA Southern Regional
Research Center, and P. Mood, Versar Inc., November 12, 1984.
tPersonal communication between Or. Donald Hayes. Burlington Industries
and G1na Dlxon, Versar Inc., January 2. 1985.
83
-------
Table 10. Release of Formaldehyde from Specific Consumer Products3
Product
Drapery fabric:
1001 cotton. Sample 1
1001 cotton, Sample 2
Blend (771 Rayon - 231 Cotton), Sample 1
Blend (77% Rayon - 331 cotton), Sample 2
Upholstery fabric:
100% Nylon, Sample 1
1001 Nylon, Sample 2
ion Olefln, Sample 1
ion Olefin, Sample 2
ion Cotton, Sample 1
ion Cotton. Sample 2
Latex-backed fabric:
Sample 1
Sample 2
Blend fabric:
Sample 1
Sample 2
Carpet:
Foam-backed, Sample 1
Foam-backed, Sample 2
Foam-backed, Sample 3
Sample 4
Samples
Samples
Sample 7
Clothes (new, unwashed):
(ten's shirts
(651 polyester cotton/351 cotton)
Ladies dresses
Girls' dresses (polyester/cotton)
Children;' clothes
(651 polyester cotton/351 cotton)
Paper products:
Paper plates and cups, Sample 1
Paper plates and cups, Sample 2
Paper plates and cups. Sample 3
ug/g/dayb
2.8 - 3.0
0.8 - 0.9
0.3 - 0.3
NO (0.01)
0.03 . 0.05
0.02 - 0.02
0 -0.02
NO (0.014)
NO (0.014)
ND (0.015)
O.S - 0.6
ND (0.015)
0.3 - 0.4
0.2 -0.3
0.05 - 0.06
0.006 - 0.01
0 - 0.002
0.0005 - 0.0009
0.0007 - 0.0009
0 - 0.0009
NO (0.043)
2.5 - 2.9
3.4 - 4.9
0.9 - 1.1
0.2 - 0.3
0.12'- 0.36
0.03 - 0.14
0.10 - 0.15
ug/mz/dayb'
(Range) (Mean)
330-350
90 - 120
50 -50
ND
7-11
6 - 7
0-5
ND
NO
ND
90-100
ND
20-30
20-30
60-65
8-13
0-2
0-4
0 - 1
0 - 1
ND
380-550
380 - 750
120 - 140
15 - 55
400-1000
75-450
330-335
340
100
50
ND
9
7
3
ND
ND
ND
100
ND
25
25
65
10
1
2
1
1
ND
470
570
130
35
680
260
330
•Preconditions = 25°C/100WH. loading of 21nrVm3.
bRange of 2 or more values.
ND a Not detected.
Source: Pickrell et al. (1982).
84
-------
amounts of formaldehyde were added as a dye stabilizer prior to 1979. It
was conjectured that glues used to attach carpet to flooring, or some
other component of the flooring system (such as partlcleboard
underlayment) may be responsible for emissions of formaldehyde attributed
to carpet. A*study conducted by the Ontario Research Foundation for the
Canadian Carpet Institute reported that formaldehyde 1s used as a
preservative In latex formulations used for foam backings on carpets
(Canadian Carpet Institute 1982). The amount of formaldehyde typically
used 1n commercial latexs was reported to be about 500 ppm. In order to
determine 1f the latex backing could be the cause of reported
formaldehyde emissions from carpeting, formaldehyde emission rates were
measured for carpet samples prepared with foam latex backing containing
500, 1000 and 10,000 ppm of formaldehyde. Emission rates for carpets
with latex backing containing 500 and 1,000 ppm of formaldehyde were less
than 14 ug/m /hr. Emission rates for carpets with latex backing
containing 10,000 ppm ranged from 56 to 162 ug/m /hr. These emission
rates are comparable In magnitude to the emission rates measured by
Plckrell et al. (1982) and Matthews et al. (1982-1984) for foam-backed
carpeting. As shown 1n Table 9, Plckrell et al. (1982) measured
significantly higher emission rates for foam-backed carpets than
non-foam-backed carpets. Matthews et al. (1962-1984) measured emission
2
rates of 14 ug/m /hr for a urethane foam carpet cushion and 6
ug/m /hr for a waffled sponge rubber carpet cushion.
3.4 Combustion
Unvented combustion appliances (such as gas ranges and heaters and
kerosene heaters) and tobacco smoking eml't formaldehyde as the result of
Incomplete combustion (Glrman et al. 1983). Several controlled chamber
studies have been conducted by Lawrence Berkeley Laboratory (LBL) to
determine formaldehyde emission rates from gas- and kerosene-fueled
85
-------
combustion appliances (Traynor et al. 1982, Glrman et al. 1983, Traynor
et al. 1983). Caceres et al. (1983) and Fortmann et al. (1984) have
determined emission rates by sampling appliance exhaust gases. The
results of these studies are summarized In Table 11. More recent studies
have been conducted at LBL but the results are not yet available.*
The results listed tn Table 11 Indicate that emission rates vary
considerably between different appliance types and are dependent, to a
large degree, on whether the appliance Is tuned and functioning
properly. Gas stoves, water heaters and furnaces are the most common
combustion appliances 1n general use. Formaldehyde was not detected 1n
fugitive emissions from water heaters or furnaces. Although the emission
rates for the oven and top burners of gas stoves can be relatively high,
the Intermittent use of gas stoves precludes them from typically being
significant sources of formaldehyde emission In the home.
Gas-fueled space heaters, on the other hand, are likely to be used
for longer durations of time and can have relatively high emission rates,
particularly 1f not well-tuned. Caceres et al. (1983) measured a
formaldehyde concentration of 0.24 ppm 1n a small room (21 m with an
air exchange rate of 0.5 hr ) containing a gas-fueled heater working
at full strength and 61rman et al. (1983) reported a concentration 1n
excess uF 1 ppm In a controlled field study with a poorly-tuned heater.
The emission rates for kerosene-fueled space heaters are generally much
lower than those from gas-fueled heaters.
Traynor and Nltschke (1984) surveyed Indoor air levels of
formaldehyde 1n 30 homes, stratified by presence o suspected emission
sources. Results Indicate no perceptible effect on Indoor levels by
combustion:
- Three homes with kerosene space heaters averaged 0.029 ppm.
- Three with wood-burning stoves averaged 0.026 ppm.
*Personal communication between J.R. Glrman, Berkley Laboratories and
P. Mood, Versar inc. on November 15, 1984.
86
-------
Table 11. Suimary of Formaldehyde Era)sston Rates from Unvented Conbustion Appliances
Appliance
Gas stove (age unspecified}4
Oven
Top burner
Older gas stove, cast ironc
burners
Older ovenc
Hen gas stove. steelc
burners
New ovenc
Gas space heater
Uell tuned11
Poorly tuned1*
Hell tuned6
Kerosene space heater
New convective*1
Mew radiant*
Radiant9
Hick8
Gas furnace0
Gas water heater0
No. of
appliances
tested
1
1
1
1
1
8
2
A
1
2
2
1
1
1
Emission factors (up/In)
Average Range
2.7
1.7
0.72f
0.19f
0.84r
1.5'
0.81
1.5
-
0.1?
0.52
_
-
<0.003r
<0.005f
2.4--?.4
O.f 0-2.5
NR
M>
m
MR
0.43-4.2
0.46-20.3
-
0.014). 42
0. 10-0.80
_
-
NR
NR
Fuel
consunption
(kj/h)
8.400
9,200
9.500f
G,030r
3,400f
9.300f
10,100-44,700
33,600-43,900
-
4.230-7,980
6.640-8,250
_
-
137.000r
45.500f
Emission rates (mq/hr)
Average
22.7
15.6
6.8
1.2
2.9
14.0
8.2-35.8
50.4-65.8
7.0
1.0
4.0
1.0
0.4
<0.4
<0.3
Range
20. 1-28.6
7.9-23.0
—
-
—
-
—
_
4.4-10.4
0.08-1.8
0.66-5.7
0.9-1.0
-
-
-
Source: 'Traynor et al. (1982).
tannin et al. (1983).
cFortiunnet al.(l984).
«*Traynor et al. (1983)
eCaceres et al. (1983)
rVatues originally reported in units of Kcal were converted to kj (1 KcaU4.187 KJ).
-------
- One with a coal-burning stove averaged 0.028 ppm, and one with &
coal-burning fireplace averaged 0.019 ppm.
- Two with gas-fired ranges averaged 0.046 ppm. and three with gas
furnaces averaged 0.030 ppm.
- The four homes with no Identified formaldehyde source averaged
.036 ppm (range of 0.007 to 0.077).
The University of Texas (1983), 1n their Indoor air quality study,
evaluated the effect of emissions from a propane stove on formaldehyde
levels 1n modlle homes with relatively high formaldehyde levels. The
appliance was operated both with and without an exhaust fan. They found
that levels did not change during and after stove use (mean levels
remained at 0.31 ppm) and concluded that the propane stove was not a
formaldehyde source In the two homes studied.
Leaderer et al. (1984) report similar results 1n their study of 55
homes 1n Connecticut. This study, conducted during the winter, found no
significant difference In the formaldehyde levels measured In homes with
gas stoves and/or kerosene heaters and In those homes without these
combustion sources. The authors concluded that the low formaldehyde
levels measured (average of 0.022 * 0.014 ppm) were not associated with
Indoor combustion of fuels.
Another possible source of formaldehyde emission 1n the Indoor
environment Is wood combustion In fireplaces and wood stoves. Llparl et
al. (1984) measured aldehyde emissions from wood-burning fireplaces.
Four different types of wood were tested, Including Jack pine, cedar, red
oak, and ash. Formaldehyde was one of the major aldehydes emitted.
Sampling was conducted using a freestanding fireplace Installed 1n the
laboratory. Samples were collected from the chimney port (not from the
ambient air of the laboratory) using Implngers containing
2,4-d1n1trophenylhydraz1ne (DNPH) 1n acetonltrlle. The aldehydes were
analyzed by high performance liquid chromatography. Formaldehyde
emissions ranged from 21 to 42 percent of the total aldehyde emission for
-------
each wood type tested with one exception. For the red oak, formaldehyde
emissions were 89 percent of the total aldehyde emission. The emissions
reported ranged from 0.089 to 0.708 g/kg (grains of formaldehyde per kg of
wood). There may be a relationship between wood type and formaldehyde
emission; however, scarcity of data prevents any conclusions (L1par1 et
al. 1984).
The literature reviewed presented disparate estimates of formaldehyde
enlsslons from burning cigarettes; published emission rates range from 20
to 1440 ug/clgarette.
Matthews et al. (1984). citing laboratory studies published by
others, derived an emission rate of 1.2 mg/cigarette. They based their
value on emission rates of 0.97 and 1.44 mg/hr published by other
Investigators. The value of 1.44 mg Is described as a rate per
unflltered cigarette.
Egle and Hudglns (1974) measured 4.1 ug formaldehyde per 40 ml puff;
assuming 30 puffs per cigarette, an emission rate of 1.2 mg/clgarette can
be calculated. This Independently-derived value agrees perfectly with
Matthew's value of 1.2 mg/clgarette.
Data presented by T1mm and Smith (1979) allow calculation of a
formaldehyde emission rate of 0.74 mq/dgarette. This value Is
3
calculated from the measured level of 0.26 ppm 1n a 45.8 m room 1n
which 20 cigarettes had been smoked. It was assumed that, during the
half-hour experiment, ventilation did not remove any formaldehyde.
Rlckert et al. (1980) measured total aldehydes 1n sldestream smoke
produced by a smoking machine, and calculated an emission rate of 0.912
mg total aldehydes per cigarette. The proportion of formaldehyde to
total aldehydes 1s not known.
Bardana (1984) cites the Surgeon General's 1972 report on smoking In
his derivation of a 0.57 mg/c1garette formaldehyde emission rate. The
Surgeon General's 1972 and 1984 reports, however, 11st emission rates of
89
-------
0.02 to 0.04 and 0.02 to 0.09 mg Formaldehyde per cigarette; Bardana
apparently cites a measured formaldehyde level 1n a room with cigarette
smoke and other sources to back-calculate the 0.57 mg emission factor.
Plckrell et al. (1982) reported that cigarette smoke contains up to
40 ppm formaldehyde; Ayer and Yeager (1982) measured 90 to 110 ppm In
sldestream smoke (a much more significant source of Indoor formaldehyde
than mainstream smoke). These levels are expected to diminish rapidly
with distance from the source. Traynor and Nltschke (1984) measured
levels 1n homes with smokers. Even with low air exchange rates (less
than 0.2 ACH), formaldehyde levels 1n these homes did not exceed 0.06 ppm
and were not significantly different from levels 1n homes with no
formaldehyde source.
3.5 Outdoor Air
The levels of formaldehyde 1n outdoor air are generally lower than
Indoor levels. Thus, as the air exchange rate Increases, there Is a
decrease In the level of formaldehyde Indoors. However, 1n cases where
formaldehyde levels outdoor are higher than levels Indoors, the Indoor
air can potentially be further polluted with ventilation air exchanges.
In outdoor air, formaldehyde can originate from Industrial plants and
from many combustion sources such as engine exhaust and Incinerators.
Singh et al. (i982c) used the chromotroplc acid method and the DNPH
method to analyze for formaldehyde concentrations In six urban areas of
the United States 1n 1980 and 1981. The reported concentrations are
presented in Table 12. Altschuller (1983) has summarized other ambient
air measurements for formaldehyde 1n urban areas 1n the United States.
The average concentrations range from 7.0 ppb to 70 ppb. These data are
also presented In Table 12. Measurements of formaldehyde In a nonurban
site were in the range of 0.1 to 0.8 ppb (Altschuller 1983).
90
-------
Table 12. ambient Air Measurements of Formaldehydn at Urban
Sites in the United states
Location
Dotmtotm Los Angeles,
CA
S. Pasadena. CA
DoMitom Los Angeles,
CA
Hun ting ton Park, CA
El Honte. CA
Los Angeles, CA
(Cal. State Univ.)
Los Angeles. CA
(Cal. State Univ.)
Clarenont, CA
(Harvey Hudd College)
Clarenont. CA
(Harvey Hudd College)
Clarenont. CA
(Harvey Nudd College)
Riverside, CA
(U. CA. Riverside)
Riverside, CA
(U. CA. Riverside)
Houston, TX
(Cratrford)
Houston, TX
(Clinton, or.)
Time of
Year
July. Nov. 1960
July. Nov. 1960
Sept.. Nov. 1961
Oct. 1966
Oct. 1968
June 1980
June I960
Oct. 1978
Aug.. Sept. 1919
Sept.. Oct. 1980
Oct. 1976
June. Aug. Oct.
1977
Sept., Oct. 1976
Sept., Oct. 1978
Tine of
Day
9a.m.
1p.m.
7 a.m.
7:40 a.m.
5-45 a.m.
morning-evening
morning-eveing
late morning-
late evrntng
morning-late
evening
morning-evening
late morning-
early evening
late norning-
evening
morning-early
evening
morning-noon
Concentrations (nob)
Average
45
30
40
70
50
21. 20
44
28
10
24
a
19
15
B
Maximum
130
70
160
135
90
3S, 39
71
71
22
48
14
38
25
28
91
-------
Table 12. (continued)
location
Houston, TX
(Parkhurst)
Houston, TX
(Fuqua)
Coluitus . OH
(Fort Hayes)
Coluifaus. OH
OCVO)
Atlanta, GA
(GA Tech)
Source: Altshuller
Denver. 00
St. Louis. HO
Chicago. IL
Pittsburgh, PA
Stated Is., NV
Riverside. CA
Tine of
Year
Sept., Oct. 1978
Sept., Oct. 1978
Sept., Oct. 1980
Sept., Oct. 1980
July, Aug. 1981
(1983)
June 1980
Nay 1980
April 1981
April 1981
April 1981
July 1980
Tine of
Day
morning-early
evening
morning-early
evening
early imrning-
early afternoon
early morning
6 a. m.
-
-
-
-
-
-
Concentrations
Average
7
11
8
10
8
12.3
11.3
12.8
20.6
14.3
19.0
(DOb)
Haiinun
IS
27
23
12
22
28.7
18.7
17.2
35.1
45.9
41.0
Source: Singh et al. (1982O
92
-------
Monitoring studies of Indoor residential levels of formaldehyde have
frequently reported the results of formaldehyde measurements performed
outside the residence. The results of several of these studies are
summarized below.
No. of Mean Concentration
Study Residential Sites (ppb)
Canada (UFFI/ICC 1981)
U.S. Nationwide (Singh et al. 1982a)
United Kingdom (Everett 1983)
Indiana (Konoplnsk! 1983)
Tennessee (Hawthorne et al. 1984)
Iowa (Schutte et al. 1981)
Texas (University of Texas 1983)
< 2.275
< 260
60
47
40
27
< 164
0.008
<0.02
0.006
0.005
<0.025
0.002
<0.02
It has been suggested that the atmospheric levels of formaldehyde
vary with seasonal Influence. Tanner and Neng (1984) observed strong
seasonal variations In the levels of formaldehyde. The maximum levels
were observed 1n the sunnier. The formaldehyde samples were collected, «*t
an unidentified northeast U.S. coastal site, using an Implnger containing
acetonltrlle and DNPH; they were analyzed by high-pressure liquid
chromatography. The concentrations ranged from 0.9 to 48 ppb with an
overall mean of 7.5 ppb. The monthly averages of ambient levels were as
follows:
Month Concentration fppbl
July - August 1982 15.8
October - November 1982 4.4
Harch 1983 3.8
April 1983 11.2
May 1983 12.2
93
-------
Formaldehyde 1s known to be produced 1n the atmosphere from photolysis of
hydrocarbons and ozone (HAS 1981). The Increased Intensity of sunlight
In warmer months may account for much of tMs observed seasonal variation.
3.6 Relative Significance of Sources on Air Levels Indoors
In order to compare the relative Impact of residential formaldehyde
sources on Indoor formaldehyde air concentrations, a simple steady-state
Indoor pollutant concentration model developed by Matthews et al. (1983)
can be used. This model Incorporates source emission algorithms for
combustion sources and formaldehyde resin-containing products. The
algorithms for res1n-conta1n1ng wood products assume a negative linear
dependence of emission rate on background concentration of formaldehyde
in air. The algorithms for combustion sources and resin-containing
products with low emission rates (e.g.. textiles) assume constant
emission rates unaffected by background formaldehyde concentration. The
model does not account for the effects of product aging and formaldehyde
sinks and assumes constant environmental conditions OF 23°C and 50
percent RH.
This model 1s a simplified version of a more complex model being
developed by Matthews that Incorporates algorithms to predict emission
rates, absorption by formaldehyde sinks, the effects of numerous sources.
tm> decay of emissions over time, and the effects of varying
environmental conditions to describe dynamic formaldehyde levels In
homes. This more complex model, as well as the algorlthr-s for
resin-containing wood product emissions used In the steady-state model,
are currently undergoing validation testing at the National Bureau of
Standards. Both models are discussed 1n more detail In Section 7 of this
report.
Matthews' steady-state model has been used to predict the potential
Impact of Individual emission sources on Indoor formaldehyde levels 1n a
3
dwelling with an Interior volume of 175 m . This size corresponds to
the the size of a single-wide mobile home or a small modular home or
apartment. Pressed-wood products were assumed to be present at the
loadings listed 1n Table 1 of this report for mobile homes and newly
94
-------
2
constructed single family conventional homes. An additional 3 m of
9
Industrial partlcleboard and 2 m of NDF are assumed to be present In
furniture. The loadings for other sources are based on assumed high
usage rates. For example, carpeting and celling tile were assumed to
cover the entire floor and ceilings, respectively. The air exchange
3
rates 1n the 175 m model mobile and conventional homes were assumed to
be 0.35 and 0.50 air changes per hour, respectively. The emission rate
data used for wood products and UFFI are based solely on average emission
rate data presented 1n Matthews et al. (1983). The emission rate data
for other sources are based on Information presented previously 1n this
section.
Tables 13 and 14 present the assumed source loadings and emission
rates used and the modeled changes In the Indoor formaldehyde
concentration from an assumed background level of 0.024 ppm. It was
conservatively assumed that the emission rate from each source was
Independent of emissions from other sources. The results Indicate that,
for both model homes under the assumed loading rates. UF resin-containing
wood products and UFFI are the major potential contributors to Indoor air
levels. Gas space heaters could also cause elevated levels 1f used For
long periods of time. A simplified ranking of the most significant
sources can be derived by setting the most Important source In each home
equal to 1.0. and scaling the other appropriately:
Mobile home
Hardwood plywood paneling (avg. of 3 types) a 1.0
Partlcleboard underlayment (carpet covered} = 0.55
Industrial partlcleboard 0.22
Gas space heater
MDF
Other combustion sources (combined)
All other Individual sources
0.19
0.17
0.12
<0.10
95
-------
Table 13. Potential Impact of PF Resin-Containing Products, Consumer Products, and
Cortmstion on Indoor Formaldehyde Concentrations9
Product
Construction products irith PF resins
PF plyMood flooring (uncovered)
Fibrous glass insulation
Fibrous glass ceiling tiles
Consumer products with OfrO resins
Carpeting
Upholstery fabric
Drapery Fabric
Apparel (unwashed)
GnriMistion sources (unvented)
Gas stove burners
Gas over
Kerosene space heater
• Oonvective (new)
Radiant (new)
Gas space heaters (Mell-tuned)
Cigarettes
Measured Assumed
emission rates'* emission rate1*
(units of rag/to2 hr) (units
0.01 - 0.02
0.008 - 0.022
o.ooa - o.on
(units of ug/m? day) (units
of mg/n? hr)
0.02
O.OII
0 009
of ug/m? day)
tt> - 65 13
NO- 1) 6
NO - 350 170
15-550 300
(units of mg/hr) (units of tng/hr)
2.9 - 16 8.6
1.2 - 23 13
O.OB - 1.8 1.0
0.66 - 4.0 4.0
4.4 - 36 10
0.02 - 1.44 mg/cig
1.2 mg/cig
Assumed
usagec
(units of ra2)
82
82
82
(units of of}
82
IS
IS
5
(units of hr/day)
1.0
0.7
8
8
8
10 cig/day
Modeled change in 24-Hr
average CHjO concentration
Mobile Hone Conventional Home
0.021
0.018
0.010
<0.001
<0.001
0.001
0.001
0.005
0.005
0.004
0.017
0.044
0.007
0.015
0.013
0 007
<0.001
<0.001
<0.001
<0.001
0.003
0.003
0.003
0.012
0.031
0.005
•Potential iopacts estimated using Matthews et al. (1983) Simple-Steady State Model (see Sections 3.6 and 7.2 for more details).
Mission rate data for PF resin products were obtained from Matthews et al. (1983). Matthews and west ley (1983). Emission rate data for consumer products
and combustion sources were obtained from Tables 10 and 11, respectively. The assumed emission rates for consumer products were obtained by averaging the
mean emission rates for those products with detected emission rates.
Section 3.6 for details.
exchange rate assuned to be 0.35 hr~' for a 175 m3 mobile home and 0.5 hr"1 for a 175 n1 conventional home.
-------
Table 14. Potential Impact of UF Resin-Containing Mood Products and Insulation on
Indoor Formaldehyde Concentrations*
Product
Furniture, cabinetry, and shelving
Industrial particleboard
HOP
Hardyood plywood paneling
Ink print overlay
Paper overlay
Domestic veneer overlay
Particleboard under! amen t
No cover
to Carpet and cushion cover
Tile cover
UTTl (in one exterior nail)
Measured Assured
emission rates'1 emission rate0
Ing/of hr) Gng/n2 hr)
0.15 - 0.62
O.ST - 2.3
0.05 - 0.63
0.03 - 0.27
0.07 - 0.24
0.11 - 0.78
—
—
0.05 - 0.80
0.31
1.5
0.28
O.It
0.12
0.30
—
—
0.23
Assumed
usaaec. m?
Mobile Hone
12
2
175
175
175
82
82
82
0
Conv. Home
12
2
12
12
12
21
21
21
20
Hodeled change in 24-Hr
averaoe CHyO concentration (pan)
Habile Home
0.051
0.040
0.340
0.188
0.183
0.222
0.130
0.002
Oonw. Hone
0.037
0.028
0.033
0.014
0.015
0.061
0.027
<0.001
0.054
•Potential impacts estimated using Matthews et al. (1983) Simple Steady-State Model (see Sections 3.6 and 7.2 for more details).
^Emission rate data as reported in Matthews et al. (1983) for products manufactured during 1983.
C5ee Section 3.6 for details.
dAir exchange rates assumed to be 0.35 hr"1 for a 175 m3 mobile hone and 0.5 hr'1 for a 175 m3 conventional home.
-------
Conventional home (excluding UFFI}
Industrial partlcleboard = 1.0
Gas space heater » 0.84
HOP = 0.76
Partlcleboard underlayment (carpet covered) = 0.73
Hardwood plywood paneling (avg. of 3 types) = 0.56
Other combustion sources (combined) = O.S6
All other individual sources » <0.40
98
-------
4.0 RESIDENTIAL MONITORING"DATA
The purpose of this section Is to summarize available formaldehyde
Indoor air monitoring data for domestic and foreign residences. Each
data set 1s accompanied by an overview of the study or project from which
It resulted. The format of each summary will Include, when available.
the following components: study name, applicable literature references.
monitoring dates, survey design (Including types of sampling and
analysis), and the results. Summaries are appropriately located In one
of the sections Immediately following.
4.1 Major Studies of Residential Levels
4.2 Studies Examining Factors Affecting A1r Levels
4.3 Ongoing Studies
4.4 European Studies
4.1 Ha.1or Studies of Residential Levels
Lawrence Berkeley Laboratory Study
Lawrence Berkeley Laboratory (LBL) has summarized formaldehyde
emission rates from a variety of combustion appliances. LBL Indoor A1r
Quality Group has also collected data on the formaldehyde concentration*;
observed in 40 residential Indoor environments 1n various studies since
1979 (Glrman et al. 1983). The combined data set (see Table 15) has been
tabulated from the results presented 1n several papers published In the
past few years. The data were obtained through the use of refrigerated
pump/bubbler samplers and a modified pararosanUlne analytical method
(GUinan et al. 1983).
The data presented In Table 15 Indicate that new energy-efficient
houses were generally found to have higher concentrations than those
observed In weather1 zed houses, with about a third being above the
American Society of Heating, Refrigeration, and A1r Conditioning
Engineers (ASHRAE) guideline. 100 ppb. The effect of ventilation rate on
99
-------
Table 15. Suimary of Formaldehyde Concentrations in Indoor Environments
Studied by the Laurence Berkeley Laboratory
Location
Ames, LA
Carroll Co., HO
Mission Vlejo.
CA
Hertford, OR
Midway, WA
Northfield, MN
Dundas, rM
Rio. HI
Cranbury. NJ
Eugene, OR
Rochester, NY
Sacramento, CA
No.
Type house buildings
Energy-efficient 1
Energy-efficient 1
Energy-efficient 1
Conventional, 2 (2)b
retrofitted for
energy-efficiency
Conventional , 12
retrofitted for
energy-efficiency
Energy-efficient, 1 (l)b
heat exchanger
Energy-efficient, 1 (l)b
mechanical
ventilation
Conventional , 1
retrofitted for
energy-efficiency
>IOO yrs, retrofitted 1
for energy-efficiency
Energy-efficient 2
Energy-efficent, 2
passive solar
Energy-efficient. 10 (6)b
mechanical
ventilation
Energy-efficient, 5
passive solar
Formaldehyde range Formaldehyde average
(pom) (ppn)a
0.028-0.061
0.044-0.148
0.066-0.214
O.OS1-0.068
0.005-0.079
0.069-0.013
0.064-0.080
0.053
0.019-0.022
0.037-0.073
0.082-0.112
O.005-0.064
0.098-0.127
NA
0.098
NA
NA
NA
0.070
0.072
0.063
0.021
NA
NA
0.029
NA
aKA indicates that neither an average concentration nor a set of data to calculate
an average Mas reported in the literature.
"indicates hows in which the effects of ventilation were studied.
Sources: Girnan et al. (1983). Hollowe!! et al. (1982). Offer-man et al. (1982).
1UO
-------
formaldehyde levels was examined 1n ten houses. Variation In the
ventilation rate was'shown to have a predictable effect on formaldehyde
concentrations 1n seven of the houses studied, but had effects opposite
to those predicted 1n the other three houses.
Geomet Study
As part of the development of an Indoor air pollution model based on
outdoor pollution and air exchange rates, Geomet, Inc. studied the
patterns of Indoor aldehyde levels monitored In 17 houses and 2 mobile
homes 1n the U.S. These data can be useful If we assume formaldehyde
constitutes 60 percent of total aldehydes, based on LBL data.
In each of three Indoor locations, three 4-hour averages were
measured on each of 14 days. Outdoor concentrations were also observed
over a 24-hour period at one location per home.
The results In Moschandreas et. al. (1978) concluded that the 17
houses had an average aldehyde concentration of 0.09 ppm. and tne average
for the two mobile homes was 0.35 ppm. If we use the 60 percent factor,
the average formaldehyde concentration for the houses would be 0.05 ppm,
with 0.21 ppm for the mobile home*. The observed outdoor concentrations
of aldehydes were consistently lower than the Indoor levels, typically by
a factor of b and quite often by one order of magnitude. The results are
summarized In detail 1n Table 16.
University of Washington Study
The Department of Health, University of Washington (Breysse 1984),
along with a number of commercial laboratories, has monitored
formaldehyde In more than 1,000 conventional and mobile homes. For the
most part, sampling and surveying of these homes was Initiated by
residents1 complaints and/or formaldehyde exposure symptoms.
101
-------
Table 16. Summary of Observed Aldehyde Concentrations in
U.S. Homes Monitored by Garnet, Inc.
Concentration (pern)
Residence Avenqe Range
Denver conventloanl
Chicago Experimental I
Chicago Experimental II
Washington Conventional I
Baltimore Conventional II
Washington Experimental I
Baltimore Experimental I
Baltimore Experimental II
Pittsburgh Lou Rise I
Pittsburgh High Rise I
Chicago Conventional I
Chicago Conventional II
Pittsburgh Low Rise II
Baltimore Conventional I
Pittsburgh High Rie 11
Pittsburgh High Rise III
Pittsburgh Ion Rise 11
Pittsburgh Mobile Home I
Pittsburgh Mobile Home II
0.20
0.16
0.26
0.04
0.06
0.07
0.06
0.04
0.01
O.OS
0.04
0.04
0.06
0.12
0.10
0.12
0.09
0.38
0.31
0.01-0.50
0.11-0.24
0.20-0.45
0.02-0.12
0.03-0.12
0.01-0.23
0.01-0.13
>0. 01-0. 10
0.04-0.12
0.02-0.10
0.01-0.13
0.02-0.15
0.03-0.12
0.01-0.24
0.06-0.19
0.05-0.19
0.024.08
0.16-0.76
0.11-0.75
Range in 4-hour concentrations taken 3 tines/day over 14-day period.
Source: Hosehandreas et «1. (197B).
102
-------
After various methods of monitoring were reviewed, 1t was decided to
utilize the chromotroplc add method using one Implnger Instead of two.
No corrections were made for the use of only one 1np1nger. Temperature
and humidity were also monitored. Whenever possible, home owners were
requested to close all windows and doors and keep the temperature at 70
to 72°F the night before the survey was scheduled.
University of Washington sampled 244 homes Insulated with UFFI, 430
mobile homes, and 59 conventional homes or apartments. Table 17 presents
the number of samples In each of the formaldehyde concentration ranges
found during the study. Overall, average concentrations of formaldehyde
1n mobile homes were 2 to 10 times higher than concentrations In
conventional homes with UFFI.
In early 1983. three private Washington laboratories reported
formaldehyde monitoring results for 380 homes (see Table IS).
Approximately 52 percent of the samples exceeded 0.05 ppm with a maximum
of 5.3 ppm noted In a mobile home.
HHI Mobile Home Study
In 1984, tre Manufactured Housing Institute (HHI) had Conner Homes,
Inc. construct a single-wide demonstration mobile home unit for the
purposes of monitoring Indoor ambient formaldehyde levels (primarily to
see whether levels conformed to the new HUD target ambient formaldehyde
level of approximately 0.4 ppm).
The demonstration home was constructed 1n a fashion not dissimilar
from normally produced Conner mobile homes. This Included the use of
partlcleboard and hardwood plywood, and Interior features such as cabinet
doors comprised of medium density Hberboard. Specific loadings were not
available for the Individual board types but the researchers did caution
that they were unsure as to whether the home Included formaldehyde
emitting products 1n a manner generally representative of the Industry.
103
-------
Table 17. Nutter of Sanfcles in Formaldehyde Concentration
Ranges Found by University of Washington
Formaldehyde Habile hones UFF1 Hams & apts.
cone, (pan) (430) (244) (59)
> 1.0 37 15 2
X). 5-0.99 14T 10 2
>0.1-0.49 522 125 41
«0.l 116 370 68
Total 822 520 113
Source: Breysse (1984).
104
-------
Table 18. Umber of Samples in Formaldehyde Concentration
Ranges Found by Private Washington Laboratories
Lab I.D.
Ia
Iia
III-Nobila
-Com/en.
Total
No.
hones >1.0
215 2
121 1
19 4
25
380 T
Concentration ranges (DOTO)
0.99-0.50
2
3
3
2
9
0.49-0.1
34
39
31
9
113
0.09-0.05
112
94
1
45
252
<0.05
228
106
4
20
358
Total
378
242
43
76
739
aHcne Type (conventional or mobile) was not reported in the literature.
Source: Breysse (1984).
105
-------
Tests were conducted approximately three months after the
construction of the demonstration home. Readings were taken on five
separate days, all within a one-month period of time. Sampling stations
were located at 50-1nch elevations, drawing air through 20 ml of 1
percent aqueous sodium bisulfite solution at a rate of 1 liter/minute.
The chromotroplc add method was used for sample analysis.
The results for each of the five testing days are summarized In
Table 19 (Conners 1984). The overall average concentration observed was
0.34 ppm. Test details and environmental conditions on each
corresponding test day are also presented 1n Table 19.
Canadian National Testing Survey
The Urea Formaldehyde foam insulation information and Coordination
Centre (UFFI/ICC 1981) was established by the Canadian government 1n 1981
to handle all UFFI-related matters for the government. One of the
objectives of the Centre was to carry out a national testing survey that
would Involve monitoring nearly 2,300 Canadian homes.
Four different categories of homes were established from which a
total of 2.275 houses were selected: the first 100 represented houses
where Individuals had reported serious health problems or where residents
were forced to move from their residences; from the Canadian houses
Insulated under the CHIP (Canadian Home Insulation Program) program.
1,146 houses with UFFI and 37B houses without UFFI were selected; and
another 651 houses containing UFFI were selected from UFFI/ICC files and
provincial records, apparently at random.
The sampling and analysis Involved the NIOSH method (Lawrence
Berkeley Laboratory modified) using a sorbent tube containing a molecular
sieve. A1r was collected at a rate of 2 1/mln. for 15 minutes. For each
home, a minimum of two room air samples and one outdoor ambient air
sample was collected. The solid sorbent tubes were analyzed by the
modified pararosanlllne method. QA/QC was reportedly good.
106
-------
Table 19. NNI Habile Hone Study Test Results and Test. Details
2/15
Date of Measurement (1964)
2/16 2/27 3/1 3/2
Formaldehyde cone, (ppn)
Kitchen
First bedroom
Bid bedroom
Avg. cone.
observed (pom)
Average inside tenp. (°F)
0.41
0.43
0.45
0.43
78
0.41
0.43
0.45
0.43
77
0.26
0.24
0.28
0.26
74
0.28
0.36
0.30
0.28
76
0.31
0.30
0.32
0.31
78
Average cone, (ppm)
adjusted to 77°F
and SOIRH*
0.4S 0.39
0.35
0.34
0.36
Time test initiated
ll:20*n 10:26am 11:31*. 9:SSam 9:40am
Sampling duration tain.) 45
45 45
Inside m
451 551 431 42U 391
Outside tenp. (°F)
SO
55
Outside conditions
rain 1001 1001 Sunny Partly
overcast overcast cloudy
Outside HOC (ppm)
0.01 <0.01 0.03 <0.01 4.01
Source: Conner* (1984).
•Concentrations adjusted using equations presented in Section 2.3.2 and
equation coefficients reported by Myers (1984b).
107
-------
The results of the averaged concentrations found In each of the four
categories are presented 1n Table 20. Results from three of the
categories, the Ron-complaint UFF1 and the non-UFFI homes, are broken out
In more detail tn Table 21.
Clayton Study
In 1980, Clayton Environmental Consultants, Inc. was contracted by
the U.S. Department of Housing and Urban Development (HUD) to conduct
several research projects related to formaldehyde contamination In mobile
hone Indoor air (Singh et al. 1982a). Both occupied and unoccupied
mobile homes were selected for this study (approximately 260). and all
were voluntarily enrolled (I.e., they were primarily 'non-complaint*
homes). The testing involved homes 1n Florida, Georgia, Texas,
California, Indiana, Michigan, and Minnesota, covering a spectrum of
climatic conditions.
The testing took place between September 1980 and October 1981.
Three measurements were typically taken In each single-wide home (usually
1n the kitchen, living room, and master bedroom). Four measurements were
made In each double-wide home (usually the kitchen, living room, master
bedroom, and second bedroom or den). Outdoor Formaldehyde concentrations
were measured 1n each area to account for the Formaldehyde present 1n the
background ambient air. No results were presented for outside levels
since all values were less than the detection limit of the analytical
method used. A variety of factors that affect the Indoor levels oF
formaldehyde were also measured at each sampling event, Including age of
the mobile home, temperature, relative humidity, and occupancy.
The test procedure used was the pararosanlllne method.
Concentrations of formaldehyde were determined from standard curves
prepared dally. QA/QC was good 1n that either complete analysis
(Including spectrophotometrlc evaluation) was performed on site or good
sample preservation techniques were employed to ensure the Integrity of
all transported samples.
108
-------
Table 20. Suimry of Results of Canadian National resting Survey
Formaldehyde results
Using house average Using house naxinun
indoor readings indoor readlras
Sample* Number of Average0 1 at or Average 1 at or
categories houses (pom) over 0.1 pom (ppn) over 0.1 pom
First one hundred 100 0.139 (0.139) 47% 0.174 571
(conpldint nones)
UFFI/ICC Files 651 0.040(0.041) 5.11 0.048 8.61
UFFI CHIP 1.146 O.OS4 (0.054) 10.2% 0.067 16.5%
Control CHIP 378 0.034 (0.035) 2.6% 0.042 4.8%
Average outdoor
readings (ppn)
0.007
0.003
0.009
0.007
aSee accompanying text for details on sample categories.
''Values not in parentheses Mare calculated assuming "not detected" results are equal to zero.
Values in parentheses Mere calculated assuming 'not detected* results are equal to the detection
limit (0.01 ppn).
Source: UFFI/ICC (1981).
109
-------
Table 21. Comparison of Canadian Home Populations by
Average Formaldehyde Concentration
Average
formaldehyde
concentration (pom)
<.01
.01-.025
.025-040
.040-.055
.OSS-.070
.070-.085
.085-. 10
. I-. 15
. IS-.20
>.2
Control CHIP
(non-UFFI)
37B hones
Percentage
12.7
29.4
25. 7
17.7
7.9
40
—
2.4
0.3
—
emulative
percentage
12.7
42.1
67.8
85.5
93.4
97.4
—
99.8
100.1
—
UFFI/ICC Files
(UFFI-non complaint)
651 hems
Percentage
11.1
26.3
24.6
14.3
9.8
4.9
4.0
3.8
1.1
0.2
emulative
percentage
11.1
37.4
62.0
76.3
86. 1
91.0
95.0
98.8
99.9
100.1
UFF I/CHIP files
1,146 hones
Percentage
4.2
16.0
22.2
20.0
13.9
8.7
5.2
7.6
1.4
0.9
emulative
percentage
4.2
20.2
42.4
62.4
76.3
85.0
90.2
97.8
99.2
100.1
Source: UFFI/ICC (1981).
110
-------
For the 259 observations, formaldehyde levels were adjusted to
standard conditions (25°C and 50 percent relative humidity) using Serge's
formula. The adjusted le*«1s ranged between 0.02 and 2.9 ppm (see Table
22 for more details), with a mean of 0.62 ppm (std. dev. = 0.58) and a
median of 0.38 ppm. A statistical analysis done by Versar correlating
the formaldehyde levels with the mobile home ages 1i presented 1n
Section 7 of this report.
Wisconsin Study
In March of 1980, the Wisconsin Division of Health. Madison.
Wisconsin, Initiated an Indoor air quality study to characterize Indoor
formaldehyde concentration variations 1n mobile homes 1n terms of the
effects of home age, temperature, and humidity (Anderson et al. 1983).
The project design utilized a stratified random sampling procedure to
Identify and voluntarily enroll 137 homes 1n the study. The enrolled
homes were sampled once a month for six or more consecutive months
followed by a final sample at the one year anniversary.
Originally, 976 data points were collected from 137 mobile homes
voluntarily enrolled 1n the study. Upon review of the data supplied by
Wisconsin. 56 points were found missing (53 concentrations and 3 home
ages), leaving 920 full observations. Each remaining data point
consisted of a formaldehyde concentration value In ppm (adjusted to 25°C
and 50 percent humidity via Berge's formula) and the corresponding age of
the mobile home monitored. All the mobile homes In the study were
categorized as 'non-complaint11 homes.
Formaldehyde samples were collected 1n two rooms (usually the kitchen
or living room and bedroom) using personal sampling pumps (HtA model S
and Bendlx BOX 44). Air was drawn through midget 1mp1ngers containing IS
to 20 mis of one percent sodium bisulfite absorbing reagent. Pumps were
run at a flow rate of 0.7 1/minute for approximately one hour. Gas
111
-------
Table 22. Huiter of Observations Found In Concentration
Intervals by Clayton Environmental Consultants
Concentration
interval
(ppn)
0.0
.11
.21
.31
.41
.51
.61
.Jl
.81
.91
1.1
2.1
- .10
- .20
- .30
- .40
- .50
- .60
- .70
- .80
- .90
- 1.00
- 2.00
- 3.00
Total
Muter of
observations
21
51
3T
24
13
12
12
10
10
20
38
Jl
259
Source: versar statistical analysis of data supplied by Singh
et al. (1982).
112
-------
appliances were shut off, and smoking was discouraged during the sampling
period. Windows were closed approximately one-half hour prior to
sampling. Samples were analyzed at the Wisconsin State Laboratory of
Hygiene using the NIQSH chromotroptc add procedure (Anderson et al.
1963). QA/QC was reportedly good.
The results of the monitoring study revealed an average concentration
of 0.31 ppm (std. dev. = 0.3}. The values ranged from 0.02 to 2.26 ppm
with a median value of 0.3 ppm; these data are presented 1n greater
detail 1n Table 23.
The results of the statistical analysis done by Versar correlating
the Formaldehyde levels with the mobile home age are presented In detail
In Section 7.3 of this report.
ORNL/CPSC 40 Tennessee Homes Study
From April to mid-December 1982, Oak Ridge National Laboratory (ORNL)
with the U.S. Consumer Product Safety Commission (CPSC) studied indoor
air quality In 40 east Tennessee homes. The objective of the study was
to Increase the data base of formaldehyde monitoring 1n a variety of
American homes and further examine the effect of housing types,
Inhabitant lifestyles, and environmental factors on Indoor pollutant
levels.
Homes selected for study were restricted to residential urban and
semi-urban areas of Oak Ridge and west Knoxvllle. Selection was
stratified to ensure a good representation of house ages. Insulation
material used, and heating sources. Hawthorne et al. (1984) did not
specify whether any of the homes were 'non-complaint,11 although all homes
were enrolled voluntarily. No mobile homes were monitored 1n the study.
Eleven of the homes contained urea-formaldehyde foam Insulation (UFFI).
Formaldehyde measurements were made using passive membrane samplers.
Twice a month, four samplers at each location monitored formaldehyde
levels In three rooms and outside the house. Samplers were exposed to
the air for 24-hour periods. No modifications to the residents' life
113
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Table 23. Winter of Observations Found in Concentration
Intervals by Wisconsin Division of Health
Concentration
interval
(Pf»0
(Hissing
0.0 -
.11 -
.21 -
.31 .
.41 -
.51 -
.61 -
.71 -
.81 -
.91 - 1
Values)
.10
.20
.30
.40
.SO
.60
.10
.80
.90
.00
1.1 -2.00
2.1 - 3
.00
Total
Mnber of
observations
53
85
199
180
137
90
78
51
35
21
7
37
_!
976
Source: Versar statistical analysis of data supplied by
Wisconsin Division of Health (1984).
* The S3 missing values uere excluded from the statistical
analysis described in Section 7 of this report.
114
-------
styles were requested during these measurements. The sorbent was
subsequently analyzed In the laboratory using the pararosanlllne
colorlmetrlc method; the detection limit using this procedure Is
approximately 25 ppb. Calibration measurements weie conducted 1n an
exposure chamber using a dynamic formaldehyde generation facility.
Quality control measurements were conducted approximately once per month
using a refrigerated Implnger unit operating for 24 hours 1n one room of
a house concurrently being monitored with the passive units.
From the resulting 5,900 measurements, the overall average
formaldehyde concentration equalled 0.062 ppm. A more detailed
presentation of these results 1s found In Table 24. Table 25 presents a
comparison of formaldehyde levels observed 1n houses with and without
UFFI. Preliminary analysis of the formaldehyde measurements In the
40-home east Tennessee study led to the following major conclusions :
1. The average formaldehyde levels exceeded 100 ppb (0.1 ppm) In
25 percent of the homes.
2. Formaldehyde levels were found to be positively related to
temperature In hones. Houses with UFFI were frequently found to
exhibit a temperature-dependent relationship with measured
formaldehyde levels.
3. Formaldehyde levels generally decreased with Increasing age of the
house. This 1s consistent with decreased emission from materials
due to aging.
4. Elevated levels were found 1n new houses that did not contain UFFI.
5. Formaldehyde levels were found to fluctuate significantly both
dlurnally and seasonally for homes of all ages.
It should be noted that considerable Information concerning
temperature, humidity, air exchange rates, combustion sources, and
various housing structural characteristics was also gathered during this
study. Detailed analyses to determine any correlation between the
variables and measured formaldehyde levels have not yet been completed.
115
-------
Table 24. ORNL/CPSC Mean Formaldehyde Concentrations (ppn)
as a Function of Age and Season (Outdoor Means Are
Less Than 25 ppb Detection Limit)
Age of house
Season
all
0-5 years
5-15 years
older
0-5 years
5-15 years
older
all
all
all
all
all
spring
suimer
fall
spring
sinner
fall
spring
sinner
fall
spring
sinner
fall
0.062
0.084
0.042
0.032
0.087
0.111
0.047
0.043
0.049
0.034
0.036
0.029
0.026
0.062
0.083
0.040
o.or?
0.091
0.042
0.042
0.093
0.102
0.055
0.040
0.048
0.035
0.051
0.037
0.023
0.076
0.091
0.047
5903
3210
1211
1482
1210
1069
931
626
326
259
757
341
384
2593
1736
1574
40
18
11
11
Note: x = mean concentrations.
s • standard deviation.
m = nuttier of measurements.
n a muter of hones.
Includes homes with and without UFFI.
a Not detected values Mere assured to be equal to 12.5 ppb
(e.g., one-half the detection limit).
Source: Hawthorne et al. (1984).
116
-------
Table 25. ORNL/CPSC Formaldehyde Levels Qbservod in
Houses with and without UFFI
Hean
No. of concentration
Age of house Type of house houses (ppn)
2 to 5 years UFFI - prefit 7 0.090
15 to 35 years
(UFFI age: 2-4 years) UFFI - retrofit 4 0.055
2 to 5 years noMJFFI 5 0.115
all non-UFFI 29 0.060
Source: Hawthorne et aI. (1984).
117
-------
Minnesota State Health Study
The Minnesota State Health Department reported data from 109 mobile
homes sampled over a nine-month period following the department's
educational programs Instituted to Inform physicians and the public about
potential Formaldehyde exposure symptoms. Mobile homes sampled are
considered "complaint" homes In that monitoring was requested by the
occupants or family physician. Data Included age of the mobile home,
measured level of formaldehyde, and symptoms reported on a detailed
questionnaire. The average age of the sampled mobile homes was less than
2 years, and the average formaldehyde level was less than 0.61 ppm. The
formaldehyde levels were Inversely related to the age of the mobile homes.
The only Information available on the results of the study was found
1n a Technology & Economics, Inc. Report (Stone et al. 1961) and Is
presented 1n Table 26.
Tennessee Department of Health and Environment Investigations
During the period of March 1982 through September of 1983, the
Tennessee Department of Health and Environment sampled 132 mobile homes
where physicians had Indicated that the homeowners were experiencing
symptoms consistent with formaldehyde exposure. Two-hour samples were
collected and analyzed In each home using the NIOSH P&CAN 125 method.*
The results of the Investigation are summarized In Table 27 (from
Hodges 1984) for the 55 sampled hones for which mobile home age
Information 1s available. The average formaldehyde concentration
measured In another 77 mobile homes for which no age information is
available was 0.30 ppm (range: 0.02 to 1.43 ppm). Formaldehyde was
detected In all 132 sampled homes.
'Personal communication between G. Schweer (USEPA/OTS) and R. Foster
(Tennessee Department of Health and Environment) on October 24, 1984.
118
-------
Table 26. Sumnary of Formaldehyde MOD Her Ing Data from Caiplaint HOBK
Collected by the Minnesota State Health Department
Cases reported 109
Duration of sanple (norths) 9
Percent of Habile hones
< 1 year old 37
1-2 years old 24
2-3 years old 13
Percent of Mbile hones with levels
Below 1 ppm 83
Average formaldehyde
level in all sanple (ppn) 0.61
Average formaldehyde level
for mobile Domes < 2 years old (ppn) 0.83
Source: Stone et al. (1981).
119
-------
Table 27. sunmary of Formaldehyde Concentrations featured in Conplaint
Mobile Homes in Tennessee From March 1982 through September 1983
Habile hone
Aje (Yrs)
<2
2
2.5
3
4
5
6
7
B
9
10-13
All
Hunter of hones
sampled
9
14
4
9
3
5
1
3
1
6
ss
Nean cone.
(PIW)
0.225
0.310
0.288
0.383
0.190
0.122
0.091
0.068
O.OS6
0.058
0.233
(tin. cone.
(PP"|)
0.11
0.063
0.043
0.132
0.137
0.018
.
0.091
0.094
0.056
0.033
0.018
Max. cone.
(PPO
0.459
1.92
0.483
0.814
0.283
0.264
_
0.091
0.090
0.056
0.10
1.92
Source: Hodges (1984).
120
-------
Kentucky Department for Health Services Investigations
During 1979-1960. the Kentucky Department for Health Services
received 139 formaldehyde-related complaints from residents of mobile
homes of which 103 were Investigated and sampled (Conyers 1984). With
the exception of one home that was sampled during September of 1979, all
samples were collected 1n 1980. Formaldehyde was detected 1n all but two
of the homes. The average level of formaldehyde detected was 0.43 ppn
with a range of 0.01 to 1.99 ppm. Over half of the samples collected
were above 0.3 ppm. Samples were collected from mobile homes
manufactured 1n 1969 through 1980. The majority of samples were obtained
from homes manufactured during the period 1978 through 1980. Data
compiled In Kentucky are further detailed 1n Table 28.
SAI California Formaldehyde Survey
In an effort to assess the overall formaldehyde exposure problem In
California, the California A1r Resources Board contracted Science
Applications. Incorporated (SAI, 1984) to evaluate formaldehyde emission
from all sources, and estimate resulting airborne concentrations and
human exposure. As part of the study 73 residences (64 non-mobile homes.
6 "new" non-mobile homes, and 3 mobile homes) were passively sampled for
Indoor Formaldehyde levels — mean concentrations found were 0.05, 0.08.
and 0.11 ppm, respectively.
The Lawrence Berkeley Laboratory Passive Diffusion Sampler was used
to monitor all the residences for one week periods (168 hours). Results
were reported as tine-weighted average concentrations. Other variables
evaluated In each home during the monitoring period Included:
Residence type (single or multiple unit)
Owner/Renter occupied
Urban/rural
Geographic location (within California)
Age of residence
Type of heating
Type of Insulation
Age of furniture (I.e.. cabinets, carpeting)
Number of rooms
121
-------
Table 28. Sunnary of Formaldehyde Concentrations Measured in
Coqplaint Habile Hones in Kentucky from Septentar 1979
through Oecester 1980
Year of Number of homes Mean cone. Hln. cone. Max cone.
manufacture saipled (ppm) (pen) (ppm)
1980 8 0.85 0.63 I.S3
1979 31 0.73 0.14 1.99
1978 17 0.44 0.01 0.87
1977 7 0.28 0.10 0.72
1976 10 0.25 0.08 O.S3
1975 5 0.11 0.04 0.23
1974 8 0.12 0.04 0.31
1973 7 0.11 0.04 0.28
1972 3 0.10 0.01 0.22
1971 2 0.06 (0.04)* <0.04 O.OB
1970 1 0.01 0.01 0.01
1969 4 0.08 (0.07)* <0.04 0.19
All 103 0.43 0.01 1.99
Source: Gonyers (1934).
* Values in parentheses indicate mean concentrations when "not detected* values are
assuaed to be zero
122
-------
• Amount of cooking performed
• Window use
• Fireplace use
• Cigarettes smoked
No Information was reported on types or amounts of formaldehyde emitting
materials (I.e., pressed-wood) present 1n the monitored residences. In
addition. Infiltration rates, which can be critical In determining Indoor
air pollutant concentrations, were not measured.
The statistical evaluation of many of the variables with correlative
formaldehyde levels had limited significance. In general, hones with gas
cooking and cigarette smoking (12 homes) were found to have significantly
higher formaldehyde concentrations (by 0.02 ppm on average) than homes
with electric cooking and no smoking (16 homes). The curve of
formaldehyde concentration to age of home showed erratic decay (instead
of a steady concentration reduction) for both the mobile and non-mobile
homes monitored.
The mean formaldehyde concentration for the 64 non-mobile home
residences was 0.0498 ppm, with a standard deviation of 0.021 ppm.
Concentrations ranged from 0.018 to 0.120 ppm. Concentrations In the 6
"new" non-mobile home residences ranged from 0.046 to 0.153 ppm. The
mean and standard deviation were 0.0845 and 0.037S ppm, respectively.
Formaldehyde concentrations In the three mobile homes ranged from 0.06B
to 0.144 ppm and had a mean and standard deviation of 0.114 and 0.0404
ppm. respectively.
Naval Housing Study
The U.S. Department of Energy sponsored measurements of Indoor air
quality and air Infiltration 1n recently constructed government housing.
123
-------
The study (Parker et. al. 1984) Included three units of a rnultlfamily
housing complex at the Naval Submarine base 1n Bangor, Washington, over 5
consecutive days during the heating season of 1983. Three dwelling units
of Identical size constructed 1n 1978 were monitored, each in a separate
two-story four-unit complex. Two of the units were occupied by smokers.
None of the units had combustion appliances.
Formaldehyde was measured Indoors and outdoors using an A1r Quality
Research Inc. PF-l passive integrated monitor. The monitor 1s capable of
detecting formaldehyde concentration as low as 0.001 ppm over a 7-day
exposure period. In addition to monitoring of other conventional Indoor
air pollutants. Indoor and outdoor temperature and windspeed were also
recorded. Indoor air exchange was measured about three times during each
24-hour period, using a perfluorocarbon tracer with automatic tracer
sampling.
Average formaldehyde concentrations measured Indoors at the three
homes ranged from 0.005 to 0.124 ppm. The only outdoor formaldehyde
value reported In the literature (Parker et.al. 1984) was 0.01 ppm. The
dally average air exchange rates ranged from 0.22 to 0.91 air changes per
hour (ACH).
Houston Housing Survey
As part of a pilot study to determine the quality of Indoor air for a
cross section of housing types In southern urban areas, the University of
Texas. School of Public Health (Stock and Mendez 1985) conducted a study
of formaldehyde concentrations Inside 78 homes In the Houston, Texas,
area during the sunnier of 1980. Mobile homes and residences with
urea-formaldehyde Insulation (UFFI) were not Included 1n the study. No
homes characterized by occupant complaints were used.
124
-------
Air sampling was performed by means of a specially designed
multl-pollutant sampling unit which consisted of the following
components: a high-flow personal sampling pump with a high capacity
battery pack, a six-port stainless steel sampling manifold, and an
1mp1nger sampling tratn for formaldehyde collection. A1r sampling and
analysis for formaldehyde were performed according for the chromotroplc
acid procedure.
Indoor concentrations range from below the limit of detection
(approximately 0.008 ppm) to 0.29 ppm, with an average value of 0.07 ppm
for detectable concentrations (N=75). Only 8 of 13 outdoor measurements
resulted 1n a detectable concentration; the average of these was 0.02
ppm. The difference between the Indoor and outdoor means was
statistically significant (p<0.05). A probability plot presented In the
literature (Stock and Hendez 1985) Indicates that the Indoor formaldehyde
concentrations can be reasonable approximated by a log-normal
distribution.
Energy efficient condominiums had, as a housing category, the highest
mean level (0.18 ppm). Condominiums, apartments, and energy-efficient
houses represented the mid-range with mean levels of 0.09, 0.08, and 0.07
ppm, respectively; the mean In conventional houses was 0.04 ppm. Home
formaldehyde levels declined with home age.
Wagner 16 California Home Study
As part of a H.S. thesis at the University of California, Berkeley,
the author (Wagner 1982) monitored Indoor air quality 1n IB California
homes that fell Into a prescribed 'worst case* category of building and
occupancy characteristics. The worst case criteria Included: low
Infiltration rate, low natural ventilation rates, presence of gas stoves,
and new construction.
1Z5
-------
Monitoring took place between January 13 and February 24, 1982.
Formaldehyde sampling was conducted using the LBL sodium bisulfite
passive formaldehyde monitor and conventional bubblers. Time-weighted
weekly average formaldehyde concentrations 1n twelve low Infiltration
homes, measured by passive samplers, ranged from 0.078 to 0.163 ppm.
Formaldehyde values from the remaining houses were not reported In the
lUeidture. Average Infiltration rates for the heating season ranged
from 0.19 to 0.50 ACH, In all cases well under the projected design rates
of 0.6 and 0.9 ACH estimated for California's new building standards.
4.2 Studies Examining Factors Affecting Air Levels
Dutch Study with Coated Partlcleboard
J.F. Van der Wai (1982) of the TNO Research Institute for
Environmental Hygiene (The Netherlands) measured formaldehyde
concentrations In Dutch homes where partlcleboard was used. In response
to Inhabitants' complaints, 36 houses were monitored during the period
1977 to 1980. The objective of the study was to Investigate the number
of homes that violated the 1978 Threshold Limit Value (and legal celling
2
value) of 120 ug/m (0.1 ppm) set by the Dutch, and to evaluate the
effectiveness 1n reducing formaldehyde levels of coating the
partlcleboard with a special vinyl-toluene paint.
Analysis was performed using the pararosanlUne method. The
reprodudblHty was reported to be *. 10 percent at 100 ug/m , with a
detection limit of 5 ug/m . Temperature, relative humidity, and
ventilation rate were also measured. The following efforts were made In
an attempt to standardize the environmental conditions In each home ai
the time of sampling:
• Room temperatures were manually adjusted to fall as close to 20°C
as possible 12 hours before each measurement.
126
-------
• Ventilation rate was adjusted manually (opening and closing
windows) to fall between 0.5 and 1.0 changes per hour.
• Relative humidity was not adjustable, and regulation was not
attempted.
• Presence of alternative formaldehyde sources was prevented as much
as possible. Smoking, use of natural gas burners, detergents,
shampoos, etc., were not permitted.
Table 29 presents the highest formaldehyde concentrations measured 1n
the Dutch houses. Of the 36 houses Investigated, only 7 had a •
formaldehyde concentration throughout (1n every room sampled) less than
3 3
the 120 ug/m (0.1 ppm) celling. The highest value was 1.8 mg/m
(1.4 ppm). Neither a complete range of measured concentrations nor a
mean value was reported 1n the study.
Table 30 presents results of coating the partcleboard used In Inner
walls and roof plates of five of the Dutch homes. Formaldehyde
concentrations were decreased by a factor of 1.5 to 3.0. Van der Mai
concluded that when accounting for all the factors Influencing Indoor
concentrations in this study, diffusion-retarding paint coating on
partlcleboard will not decrease Indoor formaldehyde concentrations by
more than about SO percent.
University of Iowa Study
The University of Iowa Study (Schutte et al. 1981), performed for the
Formaldehyde Institute, monitored 31 conventional, detached homes not
containing urea-formaldehyde foam Insulation (UFFI) for formaldehyde
concentrations In the Indoor air. Samples were evaluated 1n relation to
outdoor formaldehyde concentrations, age of the home, and other
environmental factors monitored at each of the sampled homes.
127
-------
Table 29. Highest Measured Formaldehyde Concentrations in Dutch Houses
Fora. cone.
Location
Oudenbosch
Haarlem, house 1
Haarlem, house 2
Haarlem, house 3
Haarlem, house 4
Orach ten
lesuarden. house 1
leeMarden, house 2
Leewarden. house 3
Leeuarden, house 4
Leewarden, house 5
Leewarden, house 6
Leevarden, house 7
Leewarden. house 8
Leeuarden, house 9
LeeMarden. house 10
Eiimen, house 1
Omen, house 2
Ernnen, house 3
Enrnen, house 4
Schoonebeck
Dlenen. house 1
Dienen. house 2
Lelystad. house 1
Lelystad, house 2
Uaddncyeen
Monster
Zaandan, house 1
Zaandam, house 2
Zaandm. house 3
Zaandam, house 4
Zaandam, house 5
Zaandam. house 6
Zaandam, house 7
Hellendm
up/a?
300
820
960
1800
1100
290
250
540
750
250
220
200
280
390
ISO
330
290
ISO
70
30
60
40
290
220
250
320
ISO
230
350
140
110
170
150
110
150
90
ppm
0.241
0.658
0.770
1.444
0.882
0.233
0.201
0.433
0.602
0.201
0.176
0.160
0.225
0.313
0.120
0.265
0.233
0.120
0.056
0.024
0.048
0.032
0.233
0.176
0.201
0.257
0.120
0.184
0.281
0.112
0.088
0.136
0.120
0.088
0.120
0.072
ROOK where highest cone.
was measured
attic
bedroom
bedroom
hall
bedroom
living room
bedroom
uedroon
. — .Inil nilll
ocuroon
bedroon
bedroon
living room
attic
attic
attic
ocdrooB
living roan
attic
bedroon
hflhjI^MMWk
DCflroon*
bedroon
tiinl^ii^
DQQnJOffl
attic (bedroon)
attic (bedroom)
study
tetfrooD
living room
bedroom
bedroom
attic (bedroom)
tedroon
attic (bedroon)
h*i al^xi^
DeorooD
t, n .«.„. i^—
ocuraan
bedroom
attic
Remarks
not inhabited
not inhabited
not inhabited
shoM house
Source: Van der Hal (1982).
128
-------
Table 30. Formaldehyde Levels In Dutch Houses Before and After Panel Coatings
Before coatina
HCHO
cone.
House
Leeuarden
house 2
house 4
house 6
house 7
Diemn
house 1
Roan
bedroom 1
living roan
h n itfutf^tt 1
oearoan i
living roan
attic
living room
attic
living roan
living room
bedroom Ist
stock
attic bedroon
northern side
attic badroon
southern side
ug/n3
ISO
400
220
80
280
180
390
130
60
100
290
190
pom
0.602
0.321
0.176
0.064
0.225
0.144
0.313
0.104
0.048
0.080
0.233
0.152
Trap
°C
19
21
18
19
18
22
17
23
21
23
23
24
RH
1
43
54
57
58
56
SI
54
55
60
62
55
53
ACH
IT'
0.5
0.4
0.9
0.7
1.6
0.6
O.b
1.0
1.1
0.2
0.3
1.0
After coatina
HCHO
cone.
ug/n?
430
170
130
70
180
60
230
90
60
100
210
120
pom
0.345
0.136
0.104
0.056
0.144
0.048
0.184
0.072
0.048
0.080
0.168
0.096
Tanp
•C
21
19
19
20
18
19
19
22
23
25
24
24
RH
1
54
60
60
68
S3
55
50
SO
66
72
66
62
ACH
I.-'
1.0
0.4
0.9
0.5
0.9
0.4
0.5
0.9
0.4
0.2
0.6
0.7
Source: Van der Wai (1982).
Note: RH = relative humidity;
ACH = air exchange rate (exchanges per hour)
129
-------
Twelve 8-hour formaldehyde samples were taken 1n each dwelling, using
the modified NIOSH PCAN #125 method (1 percent bisulfite absorber and
dual Iraplngers). Samples were taken at different positions in each house
including the kitchen, living room, bedroom, and family room.
The results of the formaldehyde monitoring are presented 1n
Table 31. The average Indoor concentration found 1n the homes was 0.063
ppm (std. dev. = 0.064) with a range of 0.013 to 0.34 ppm. The average
outside formaldehyde concentration was 0.002 ppm (std. dev. = 0.0013).
In addition, the correlation (from a linear regression) of the natural
log [CH-0] versus age of the home resulted In a correlation
significance at the 95 percent confidence level (R = -0.42). This Is
comparable to the statistical analysis performed by Versar on the
Wisconsin and Clayton formaldehyde 1n mobile home data (see Section 7.3
of this report). Fitted coefficients were not provided by the University
of Iowa study, however, so comparison of actual decay curves Is not
possible without evaluating all the raw data.
In addition to age of the hone, several other parameters were tested
for correlation with home formaldehyde concentration. The following
correlations were significant at the 95 percent confidence Interval:
number of occupants; hours of home occupation; and Inside relative
humidity. The linear regression slopes of the above three parameters
with formaldehyde level were negative. Although significant correlations
were not observed between partlcleboard and paneling loading rates and
formaldehyde levels for all homes combined, significant correlations (at
the 95 percent confidence Interval) were observed for (1) paneling In
those homes which when tested had their windows closed and air
conditioning systems on and (2) for partlcleboard In those homes which
when tested had either their windows open or closed and air conditioning
130
-------
Table 3V Formaldehyde Concentrations Found in Conventional
Homes Monitored by the University of lews
Home*
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Source:
Average hone Q^O
concentration
(ppm)
0.048
0.037
0.025
0.013
0.017
0.01B
0.038
0.084
0.063
0.045
0.018
0.014
0.047
0.040
0.044
0.050
0.068
0.019
0.043
0.340
0.061
0.027
0.100
0.058
0.069
0.200
0.043
0.120
0.034
0.120
0.054
re 0.063
Sa 0.064
Range ° 0.013-0.34
Schutte et al. (1981)
Outside CHjO
concentration
(ppm)
0.001
0.001
—
0.003
0.001
—
—
0.004
0.004
0.002
0.001
0.001
0.002
0.003
0.003
_
0.003
<0. 001
0.003
0.002
0.003
0.001
0.006
0.004
0.003
0.004
0.003
0.001
0.002
<0.001
0.003
X = 0.002
S = 0.001
Range <* 0.00041-0.0056
131
-------
systems off. In general, 1t was found that alteration of homes from high
ventilation (open windows) to low ventilation (closed windows) resulted
In an approximate doubling of Indoor Formaldehyde concentration.
Indiana Studies
A report by Virgil J. Konoplnskl (1983) of the Indiana State Board of
Health summarizes the results of a series of Investigations conducted
from 1979 through 1983 to determine formaldehyde levels In conventional
homes In Indiana. The purpose of the 1983 report was to compare the
levels found 1n homes with urea-formaldehyde foam Insulation (UFFI) to
the levels found 1n those homes using other types of Insulation.
Airborne formaldehyde was sampled using a midget Inplnger sampling
train and by taking area samples. The Implnger sampling was done using a
battery powered vacuum pump capable of sampling for at least eight hours
duration; actual sample time for this study was two hours. The pump was
fitted with a 'liquid trap and calibrated for an airflow of 1 liter per
minute. Air samples were collected 1n a 1 percent bisulfite absorbing
solution. Sample volume varied from 30 to over 100 liters with a sample
volume of 45 to 60 liters for most samples. Formaldehyde samples were
analyzed following the procedures outlined 1n NIOSH Method 125.
chromotroplc add procedure.
Table 32 summarizes the results of the Indiana Board of Health
monitoring study. A total of 239 homes were sampled for formaldehyde,
119 of which contained UFFI and 120 of which contained some other type of
Insulation. Health problems were reported by the occupants of 103 of the
homes (66 UFFI homes and 37 non-UFFI homes). Neither the age of the home
nor the age of the UFFI Installations was reported. It should be noted
that UFFI was not considered the sole source of formaldehyde 1n those
132
-------
Table 32. Formaldehyde Levels Found in Indiana Study
Residences with Residences without
UFFI UFFI
ttnter of samples
Mean concentration of
formaldehyde-con3
Naxioun concentration of
fomldehyde - ppn
Ninioun concentration of
formaldehyde - ppm
Hunter of nondetectable
situations
119
0.05
0.18
Not detectable
18
120
0.09
1.35
Not detectable
35
Source: Koneplnski (1983).
'•Not detected* values Mere assigned a zero concentration for
calculation of mean concentrations
133
-------
homes containing It. The outdoor concentration of formaldehyde was also
measured 1n 47 situations; the mean concentration was 0.005 ppm. There
were 28 Instances of non-detectable formaldehyde for outdoor measurements.
Godlsh (1983) reported the results of monitoring for formaldehyde In
28 residences containing UFFI. but no partlcleboard flooring, and 29
residences that contained neither UFFI nor partlcleboard flooring,
cabinetry or paneling. Ninety minute air samples were collected and
analyzed using the modified NIOSH bubbler/chromotroplc add procedure.
Formaldehyde levels In the UFFI residence ranged from 0.02 to 0.13 ppm
with mean and median values of 0.07 ppm. Levels In conventional
residences containing miscellaneous low-level sources (e.g., carpeting,
upholstery, furniture) but no partlcleboard or UFFI had a range of 0.03
to 0.07 ppm with mean and median values of O.OS ppm.
Hever and Hermanns Studies Showing Effect of Temperature In and
Around Mobile Homes
Meyer and Hermanns (1984b) reported the result of field studies on
diurnal fluctuations In formaldehyde Indoor air concentrations In a
mobile home In Florida during the summer. They found substantial
variations, and related those variations to changes In Indoor wall
temperatures as a function of solar radiation or simply ambient outdoor
temperature. They describe peaks In Indoor air levels corresponding to
times of the day when the sun strikes the mobile home; levels declined
when the temperature dropped. There was an approximately one-hour time
lag between the temperature peaks and concentration peaks. Figure IB
Illustrates the calculated time-weighted levels as a function of time of
day. It Is not clear from their report whether the Indoor air
temperature was allowed to vary with the ambient temperature. Figure 19.
reproduced From Meyer and Hermanns (1984a), Illustrates temporal
variability In data reported by George Myers for an unoccupied mobile
home.
134
-------
1.25 -F
FORMALDEHYDE
6/2/84
8 12 16 20 24
DAY TIME
Figure 13. Calculated Time-Weighted Average Formaldehyde Levels
In a Mobile Home
Source: Meyer and Hermanns (1984b).
135
-------
28
24
20
PC)
16
12
«
3JO
1.0
ppm
I I
TEMPERATURE
Jnside
\ outside
x
FORMALDEHYDE
air level
corrected rote
FIRST DAY
SECOND DAY
i i
Gam 10 2pm 6
(a)
8pm 12 4
Figure 19. Formaldehyde Levels In a New, Unoccupied Mobile Home as a
Function of Time of Day and Temperature
Source: Meyer and Hermanns (1984a).
136
-------
A similar study was recently conducted 1n Texas during the summer
months using two mobile homes (University of Texas 1984). The Indoor
temperature of one mobile home was allowed to vary with ambient
temperature while the temperature In the other home was maintained at
about 22°C with air conditioning. The results reported for the first
home are very similar to the results of Meyer and Hermanns (1984b).
However, the controlled temperature home had much lower variation In
formaldehyde concentration throughout the day, presumably due to an
Increased air exchange rate caused by the air conditioning and the
Indoor/outdoor temperature differential.
Fleming and Associates Study
The objective of this study (Traynor and NUschke 1984) was to
monitor residences for nitrogen dioxide, carbon monoxide, formaldehyde.
resplrable suspended particles, and air exchange rates where suspected
combustion-related Indoor pollution sources could be readily Identified.
These sources and associated formaldehyde levels are summarized 1n Table
33. The average formaldehyde level observed In all the test homes was 40
ppb; a high value of 151 ppb was found 1n one of the tested residences
categorized as containing new furnishings and new paneling as a suspected
pollution source.
Formaldehyde was monitored In thirty New York state homes for
forty-one one-week periods. The sampling was performed primarily during
the winter months when the usage of some of the suspected sources was
greatest. Formaldehyde was monitored with a passive diffusion sampler
developed at Lawrence Berkeley Laboratory. A1r exchange rates were
monitored using passive perfluorocarbon emitters and collectors.
This study was funded by a private power utility In New York
specifically to Investigate the role of conbustlon-related appliances In
Indoor pollution. The Investigators, contacted by phone, acknowledged
that lUtle more was to be done on the project other than submitting a
final report to the utility. A copy of the draft report will be made
available to the EPA In early 1985.
137
-------
Table 33. Sirmary of One-Week Average Indoor Formaldehyde Data
Observed in the Fleming and Associates Study
Source/house
code
Air exchange
rate3 (Ir1)
House volume
HOC*
(Ppm)
Mo source
14
16
24
50-1
Hex furnishings
23
45
61
Smokers (S)
02-1
02-2
36
50-5
0.11
0.24t>
0.40*
0.15
0.25
0.13
0.26b
0.17
0.16
0.37
0.12
Kerosene-fired space heater (KM)
20 0.30*
32-1 0.19
50-2 0.13
Mood-burning stove OS)
25 0.10
44 0.10»
51-1 0.12
Coal-burning stove (CS1
31 0.11
Fireplace M/nood (FW)
350
SOB
329
644
429
483
480
473
473
45S
644
70)
644
733
606
443
1020
0.077
0.026
0.034
0.007
0.061
0.015
0.023
0.060
0.056
0.040
0.032
0.031
0.032
0.025
0.031
0.036
0.012
0.028
4}
50-3
0.15
0.16
433
644
0.019
0.018
138
-------
Table 33. (continued)
Source/house Air exchange House volute HCHO2
code rate2 Or') (m3) (ppn)
Fireplace n/coal (FC)
50-4 0.11 644 0.019
Gas-fired range CCS)
05-2 0.28 472 0.056
50-6 0.13d 644 0.036
Gas-fired furnace (ft
01 0.30 315 0.026
21 0.32 379 0.048
43 0.32° 652 0.017
Oil-fired furnace (OF)
17 0.35 682 0.023
38 0.06 798 0.027
56 0.32° 588 0.022
Coafcination of sources
03 (S, MS)
05-1 (MS, GR)
10 (OF. SU)
18-1 (S. KH, GR)
18-2 (S. KH, GR)
22 (CS, WS)
32-2 (US, KH)
32-3 (CS, KH)
33 (WS, KH)
51-2 (WS. GR)
55 (S. AC)*
60 (S. GR. GF)
0.27
0.33
O.OT8'
0.57
0.57C
0.17°
0.33
0.14
0.24
0.13
• 0.09
0.11°
289
412
690
441
441
697
701
701
579
443
270
468
0.024
0.0(2
0.064
0.039
0.032
0.020
0.046
0.053
0.022
0.013
0.047
0.059
aReported standard deviations, based on multiple measurements at different
indoor locations, Here not included in this table.
bBased on average ratio of the measured air exchange rate to the air exchange rate
at 50 pascals (0.049 * 0.029).
'Average air exchange rate of house measurements made during other tine periods.
"Attached garage.
Source: Traynor and Hitschke (1984).
139
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4-3 Ongoing Monitoring Studies
California Mobile Home Survey
Th« California Department of Health Services 1s currently analyzing
the results of a large formaldehyde monitoring survey of 700 mobile homes
conducted during August and September of 1984. This 1s apparently the
largest coordinated survey of mobile home formaldehyde exposures ever
undertaken 1n the United States. The survey was designed to be as
"random" as possible and to be stratified by age of mobile home.
Approximately 60 percent of the sampled homes were less than three years
of age. Thus, the results should be useful In determining whether
current efforts (I.e., within the last several years) by Industry to
reduce formaldehyde emissions from pressed wood products have been
successful 1n actually reducing In-home formaldehyde exposures.
Monitoring w&s performed using the five- to-seven-day exposure Air
Quality Research passive dosimeters.
The preliminary results of the survey will not be available until the
first quarter of 1985. The California Department of Health Services
hopes to repeat the survey of the sane homes In February of 1985 so as to
obtain winter indoor air levels that can be compared to the summer Indoor
air levels obtained 1n the first survey. The results of this second
survey will not be available until the third quarter of 1985.
Bonnevllle Power Administration Surveys**
The Bonnevllle Power Administration (8PA) In the State of Oregon Is
initiating two large-scale surveys of the levels of Formaldehyde and
*Personal communication between G. Schweer (USEPA/OTS) and Or. K.
Sexton (California Department of Health Service) on 10/17/84.
"Personal communication between G. Schweer (USEPA/OTS) and R. Rothman
(Bonnevllle Power Administration) on 7/2«/84 and 11/19/84
140
-------
several other pollutants 1n conventional housing. Tne goals of the
surveys are to determine the effects of energy conservation techniques on
Indoor pollutant levels both 1n new and existing electrically heated
housing.
Approximately 150 existing homes (typically 5 years or older) and as
many as 600 new homes will be screened for formaldehyde levels using the
Air Quality Research/Lawrence Berkeley Laboratory passive dosimeter
(which measure five to seven days' exposure). Approximately 40 existing
homes and 100 new homes will be selected for more 1n-depth testing of the
effects of various energy conservation retrofit techniques and
ventilation controls Including air-to-air heat exchanges. Preliminary
results are not expected before the spring of 1985. The studies will
probably continue through the winter of 1985/1986.
DIMardl/Rush-Hampton House Study
The D1Nard1/Rush-Hampton house 1s a 3600 square foot contemporary,
passive solar house located 1n Amherst, Massachusetts. This house 1s
Instrumented for the continuous analysis of hydrocarbons, formaldehyde,
carbon monoxide, Infiltration, ambient meteorological conditions,
Insolation, energy consumption, and Indoor thermal comfort parameters.
The overall project has many objectives, all focusing on the effect
of different factors on Indoor air contaminant levels. The factors being
considered range from broad-based spatial, temporal, and seasonal
variations to the very specific Infiltration rate, temperature, and
Inhabitant living activities. For formaldehyde specifically, the study
hopes to compare several different analytical techniques used by their
laboratories (I.e.. the NIOSH chromotroplc acid method, the DNPH2 method.
and an automated pararosanlllne analyzer), as well as to evaluate the
effectiveness of several Indoor air treatment regimes on low-level
formaldehyde concentrations (I.e., air-to-air heat exchangers and air
ventilator/washers).
141
-------
Air sampling. Including tha. for formaldehyde, Is accomplished with a
sample Inlet connected to a 5-po1nt all Teflon sequential sampling system
which 1s controlled automatically by the microprocessor 1n the data
acquisition system. The sampling lines are 1/4 Inch Teflon tubing
extending from the 5-polnt sampling system In the laboratory to sampling
ports located 1n various rooms throughout the house. The locations
sampled with this system are zero air. permeation calibration source.
master bedroom, kitchen and ambient (OINardl et al. 1984).
According to the researchers , the data on formaldehyde levels In
the DINardVRush-Hampton house collected during the last heating season
(last winter) are still being evaluated. Preliminary results, however,
show formaldehyde levels (hourly averages) tn the range of 3D to 80 ppb
(0.03 to .OB ppn). The data will be Formally presented and available for
distribution 1n early 1985.
Future plans Include one more study, from January to March 1985.
evaluating Indoor formaldehyde levels and comparing analytical techniques.
Texas Indoor Air Quality Study
The Texas Indoor A1r Quality Study, being performed by the University
of Texas, School of Public Health (1983), Is an ongoing, 1n-depth Indoor
air monitoring study Involving a total of 164 "non-complaint* mobile
homes 1n four Texas counties. In addition to providing one of the
largest data bases on formaldehyde levels In mobile homes, this study
will ultimately provide Information on many related Issues, such as:
effects of air exchange; comparison of long- and short-term formaldehyde
levels; a study of air filter Intervention; a cooking fuel emission study
(see Section 3.0 for a summary of preliminary results on this); a
comparison of four types of formaldehyde monitoring methods; an
architectural study of mobile home designs and furnishings; and a study
'Personal communication between S.R. D1Nard1. university of
Massachusetts, and T. Chambers, Versar Inc. November 29, 1984.
142
-------
of the effects of temporal and environmental factors. As stated 1n the
report, "any conclusions drawn from the data produced by this study at
this time may be subject to revision upon further analysis — The
Influence of specific architectural characteristics of the homes on the
observed formaldehyde levels has yet to be determined* (University of
Texas 1983).
The sampling for formaldehyde (as well as resplrable suspended
partlculates, aeroallergens. and other volatile organlcs) was performed
from October 1982 through August 1983. On a typical sampling day.
monitoring equipment would be assembled Inside the mobile homes by about
11 a.m.; the monitoring period would begin by 12 p.m. and finish at about
7 p.m. Mean dally levels of formaldehyde were measured with the
CEA-TGH-555 continuous monitor and are presented 1n Table 34 by age of
mobile home within each county. The overall mean for sample sets
equalled 0.12 ppm. All mobile home age groups In El Paso have
approximately the same mean formaldehyde concentration during the first
sampling period of 0.05 to 0.07 ppm, as well as the lowest levels
measured 1n all counties. This Is most probably explained by the
predominant use of evaporative air coolers (In use In 98 percent of the
mobile homes) during April; these significantly Increase the air exchange
rate. Although 49 percent of the mobile homes 1n Midland also use
evaporative coolers, sampling was performed during March, when they would
not be In use.
To determine the variability of formaldehyde concentrations over
short time periods and the factors potentially affecting the levels.
sequential measurements were taken dally over two one-week periods.
One-Week Study I was done during June T983, and One-Week Study II was
performed during September 1983. During both studies, a two-hour dual 20
ml (one percent bisulfite) Implnger sample was collected at ISO ml/mln.,
at approximately 8 a.m. and 4 p.m., and dry and wet bulb temperatures
were recorded for four consecutive days. On the third day of each study.
samples were collected for two hours every four hours for 24 hours.
143
-------
Table 34. indoor nean Formaldehyde Concentrations Measured in
164 Mobile Hones by the Texas Indoor Air Quality Study
(Preliminary Results).
Mobile hone
location/age
Harris Co
< 1 year
1-2 years
2-3 years
3-4 years
> 4 years
Group mean
Tarrant Co.
< 1 year
1-2 years
2-3 years
3-4 years
> 4 years
Group nean
Midland Co.
< 1 year
1-2 years
2-3 years
3-4 years
> 4 years
Group nean
El Paso Co.
< 1 year
1-2 years
2-3 years
3-4 years
> 4 years
Group mean
Firs
Nean (ppn)
.21
.20
.20
.14
.14
.18
.35
.19
.23
.21
.22
.24
.13
.09
.09
.04
.11
.07
.05
.06
.06
.06
t s*n>l
«d
.11
.12
.12
.05
.10
.11
.21
.11
.13
.06
.07
.15
.07
.04
.04
.06
.05
.05
.05
.04
.05
inq survey Reoeat sample
H Sanpling dates Nean (ppra) »sd N Sampling dates
9 October August 1983
12 1982 - .17 .OS 3
3 Hay 1983
5
9 .04 .01 3
38
10 February 1983
13
11
5
3
42
19 March 1983
18
3
1
41
10 April 1983 .04 .02 4 July 1983
12 .12 .14 2
12 .25 .15 2
4
.03 1
38 .10 .12 9
144
-------
Table 34. (Continued)
Habile hone First sanding survey Repeat sample
location/age Mean (ppm) »sd N Stapling dates Man (ppn) *sd N Saddling dates
All Counties Except
El Paso
< 1 year
1-2 years
2-3 years
3-4 years
>! years
tiroup mean
0.21 -
0.1S -
0.20 —
0.16 -
0.16 -
0.18 -
38
43
17
11
12
121
Source: University of Texas (1983).
N • number of samples
sd o standard deviation
145
-------
starting with the 8 a.m. sample. During One-Meek Study I, samples were
collected simultaneously in the living room, main bedroom, and second
bedroom. Samples were collected 1n the living room area only during
Study II.
Over the three-month period between the One-Week Studies, the
formaldehyde concentration decreased by approximately 0.1 ppm. Table 35
shows the comparison of the total one-week formaldehyde concentrations
and temperature measurements for the two studies. The Indoor
temperatures In mobile home No. 1 and 2. were similar for bcih studies .
However, from One-Week Study I to II 1n mobile home No. 1. the
formaldehyde level decreased from 1.29 ppm to 1.12 ppm. and 1n mobile
home No. 2. from 0.36 ppm to 0.24 ppm.
University of Wisconsin Survey
The University of Wisconsin, under a grant from the Wisconsin Power
and Light Company, 1s Investigating the Influence of a residential
weatheHzatlon program on Indoor sir quality (Quackenboss et al. 1984).
Fifty homes, belonging primarily to low-Income or elderly Individuals,
are being weather1 zed at no cost to the homeowners.
Prior to the Initiation of home weatherlzatlon activities, each home
was sampled three times during the 1982 to 1983 heating season to
determine the levels of Indoor air pollutants and air Infiltration
rates. A1r Quality Research passive dosimeters were employed for
monitoring formaldehyde concentrations over week long periods. The
available published results of the pre-weatherlzatlon sampling Indicate
an overall average formaldehyde concentration of 0.031 ppm (standard
deviation of 0.016 ppm) In the 50 homes and a median concentration of
0.028 ppm (Quackenboss et al. 1984). (Additional unpublished Information
on the Individual home formaldehyde levels has been requested frnm the
•
researchers ).
'Personal communication between Or. 3araes Quackenboss, University oF
Wisconsin, and G. Schweer. USEPA-OTS, on 10/1/84 and 12/27/84.
146
-------
Table 35. Mean Formaldehyde Concentration and Temperature
Heasurenents for Texas Indoor Air One Week Study I and II
One Meek Study I One Meek Study II
Wan formaldehyde Mean Mean formaldehyde Nean
concentration temperature concentration tenperature
(ppnfesd (°C)±sd (ppm)*sd (°C)«4d
Mobile hone
No. 1
Mobile hone
No. 2
1.29 * 52 31.9 * S.2 1.2 » .33 32.7 «• 4.0
0.36 * .07 22.9 ± 1.6 0.24 * .03 22.4 j. 0.8
NOTE: Indoor air temperatures in mobile hone No. 1 were allowed to fluctuate tilth ambient outdoor
teoperatures. Indoor air temperatures in Mobile hone Ho. 2 were controlled with air conditioning.
Thus, due to the higher indoor/outdoor tenperature differential In mobile home No. II and the use
of the air conditioner, air exchange rates Mere probably higher in this hone. This nay account for
the lower levels in Home No. 2.
sd » standard deviation
147
-------
In addition to formaldehyde and air Infiltration measurements,
Information was also gathered on the building materials, physical layout,
and furnishings of each home as well on occupant activities that may
Influence formaldehyde levels (e.g.. smoking and use of combustion
appliances}. This Information has not yet been published .
4.4 European Studies
Switzerland
In a study done by the Swiss Federal Institute of Technology,
Department of Hygiene and Applied Physiology, Zurich. Switzerland (Kuhn
and Wanner 1984), the formaldehyde content In room air was measured 1n 8
one-family houses and 38 multiple dwellings. *
Formaldehyde was measured with two consecutive gas-washing bottles
(mldget-lmplnger) containing an aqueous solution of methyl-
benzthlazolon-hydrazon (HBTH), called a TOMA." The color Intensity of
the reaction mixture was subsequently evaluated spectrophotometrlcally.
In the spring (before occupancy), the residential concentrations
ranged from 0.2 to 0.7 ppm; a year later, measured concentrations were
reduced by about one-half. Table 36 summarizes mean concentrations
measured during four seasonal periods.
Holland
In a study performed by the Product Analysis Agency, Haarlem
District, the Netherlands, formaldehyde concentrations were measured 1n
49 houses and 3 homes for the elderly In which partlcleboard was
specifically not used as a building material and 1n which no
urea-formaldehyde foam Insulation was used. The formaldehyde
concentration, the ventilation flow, the temperature, and the relative
humidity were measured 1n the living rooms, kitchens, and the bedrooms
(as well as the approximate age of each building). The analysis was
Personal conrounlcation between Or. James Quackenboss, University of
Wisconsin) and G. Schweer USEPA/OTS on 10/1/84 and 12/27/84.
148
-------
Table 36. Formaldehyde Measurements in Swiss Houses over
Four Seasonal Periods (ppn)
Spring I Sinner Winter Spring IX
x sd x sd x sd x sd
One-fanilj 0.29*0.12 0.33+0.04 0.15+0.04 0.1440.03
houses
Multiple family 0.37*0.18 0.4G+0.19 0.24+O.OJ 0.18+0.05
dwellings
Source: Kuhn and Wanner (1984).
X o Mm concentration
sd = Standard deviation
149
-------
Intended to provide an Insight Into the usual concentrations of
formaldehyde 1n homes In which the residents have made no complaints and
In which any formaldehyde emanates from self-Introduced sources, such as
smoking, floor coverings, curtains, gas-powered appliances, open
fireplaces, cleaning products, and partlcleboard-contalnlng furniture.
The Investigative monitoring was performed between April 1981 and
April 1982. Concentration measurements were taken 1n two-day periods.
Preparation Involved standardizing the Indoor environment to
approximately 18" to 22eC, 0.5 to 1.0 air changes per hour. .Five hours
before measurement, the areas to be measured were ventilated thoroughly
and then the windows and doors were kept closed; no smoking was
permitted. The chromotroplc acid method and the fluorescence method with
acetyl-acetone (Hatzseh reagent) were both used In the analysis. An
average of two values per room per sampling event was reported.
The data presented 1n the study documentation (Cornet 1983) are too
voluminous to reproduce In this report. In the documentation, sets of
tables are presented for each of the three rooms: living, kitchen, and
bedroom. Data include location and age of home, number of residents.
smoking behavior or residents, home renovations, outdoor wind speed, wind
direction, outdoor temperature, and weather conditions. Also reported
are indoor temperature, relative humidity, ventilation rate, materials
used for walls, floors, and ceilings, surface and finishing of sheet
material, type of heating, usual day and night temperatures, wall cavity
material, and secondary formaldehyde sources (such as boilers). Table 31
summarizes the data by presenting average, median, 10th and 90th
percentlles, and highest and lowest formaldehyde values found in the
three rooms. The average concentration of formaldehyde observed by the
study was 0.054 ppm.
ISO
-------
Table 37. Average, Median, 10th and 90th Percentiles and Highest and
Lowest Values Found in Haarlem District Study (The Netherlands)
Measurement
Chrortptropic acid method
Formaldehyde concentration
standard measurement.
living roan, in ug/m*
in ppm
Formaldehyde concentration
standard nvKunaient kitchen
in ug/m3
in ppm
Formaldehyde concentration,
standard measurement, bedroom
in ug/m3
in ppm
Fluorescence method
Formaldehyde concentration.
standard measurement, living n
in ug/m3
In ppm
Formaldehyde concentration,
standard measurement, kitchen
In ug/m3
in ppm
Formaldehyde concentration,
«Aiutopff iMJiuiramnt tuMtmm
in ug/m3
in ppm
Average
61
0.049
60
0.048
68
0.055
DOB
66
0.053
69
0.055
77
0.062
Median
50
0.040
54
0.043
48
0.038
63
0.061
64
O.OS1
59
0.047
10th
Percenti le
32
0.026
31
0.025
24
0.019
33
0.026
26
0.021
26
0.021
90th
Percentile
93
0.075
108
0.087
155
0.124
108
0.087
121
0.097
161
0.129
Lowest
value
20
0.016
3
0.002
15
0.012
17
0.014
7
0.006
9
0.007
Highest
value
152
0.122
•
149
0.119
288
0.231
146
0.117
203
0.163
280
0.225
Source: Garnet (1983).
151
-------
Germany
Formaldehyde Indoor air concentrations are also reported for German
homes In a study by Schulze (1975). The results are presented In
Table 38. No other Information on the study was available.
Sweden
Indoor air formaldehyde concentrations were presented by Sundln
(1978) from monitoring performed from September 1975 to October 1977 In
319 Swedish homes. Formaldehyde levels found In the homes tested were
attributed to partlcleboard use and a new type of celling panel utilizing
an Improper glue application technique. Approximately 75 percent of the
homes contained the celling panels. Also, more than 90 percent of the
tests could be categorized as coming from complaint homes.
All analyses were made with the chromotroplc add method, which Is
the official test method 1n Sweden for quantitative determination of
formaldehyde In the air. No other testing conditions or procedures were
available from the related literature. Results ranged from 0.1 to 2 ppm;
the average being 0.58 ppm. The results are further summarized in
Table 39.
Denmark
Andersen et al. (1975) sampled indoor formaldehyde concentrations In
25 rooms of 23 dwellings (19 houses and 4 flats) from February to
September 1973 In suburban areas of Jutland. Denmark. The objective was
to evaluate Indoor air concentrations In homes that exclusively used
chipboard (or partlcleboard) 1n walls, floors, and ceilings (with U:F
molecular ratios of approximately 1:1.4). Other environmental factors
considered In this study Included age of house, temperature, humidity,
and air changes. The average concentration was 0.50 ppm with a range of
0.06 to 1.79 ppm. A complete summary of results Is presented In Table 40.
152
-------
38. Formaldehyde Concentrations in German Homes Cppm)
Kitchen
First MM building 0.129
Second new building 0.068
Old building -
Range = 0.06 - 0.20
Overall average = 0.12
Living roan
0.081
0.060
0.19S
Average
0.105
0.064
0.195
Source: Schulze (1975).
153
-------
Table 39. Frequency Distribution of Formaldehyde
Concentrations of Swedish Hones
Concentration Hatter of
interval houses Percent
(ppn)
Less than 0.30 . 72 £.6
0.30-0.39 60 18.8
0.40-0.69 100 31.3
0.70-0.99 49 15.4
More than 0.99 38 11.9
Average = O.S8 pom
Total nutfcer of houses a 319
emulative
percent
22.6
41.4
72.7
88.1
100.0
Source: Sundin (1978}.
154
-------
Table 40. Fornaldehyde Concentration in Danish Homes
Roan
no.
I
2
3
4
S
6
7
a
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
House
age
(months)
0.3
0.3
0.3
0.3
0.3
5.0
5.0
5.0
5.0
5.0
S.O
29
29
29
29
2
0.2
0.2
36
42
42
56
54
0.2
0.2
Rooffl
volune
en?)
20
20
20
97
97
14
12
14
14
14
14
14
14
14
14
16
16
16
22
18
18
21
15
21
21
p/V*
1.6
1.6
1.6
1.1
1.1
1.7
1.1
1.7
1.1
1.7
1.7
0.4
0.4
0.4
0.4
1.3
1.3
1.3
1.8
1.1
1.8
0.3
0.3
1.0
1.0
Tenper-
ature
(«C)
17.1
21.4
8.6
20.1
36.8
26.1
25.4
22.5
23.3
23.0
23.8
21.4
26.8
31.1
24.4
26.0
25.9
19.6
21.6
23.3
25.8
22.3
21.6
22.1
19.4
ttmidity
(g/kg air)
6.0
4.7
4.8
4.9
9.5
5.6
5.0
5.9
6.7
8.0
6.5
4.8
4.8
5.4
4.2
7.3
10.2
7.7
6.6
9.7
10.7
9.4
7.1
8.7
8.5
Air
changes
(per hour)
0.5
0.5
0.4
0.9
0.8
1.2
2.3
0.9
0.3
1.2
0.6
1.3
0.9
1.1
4.6
0.4
0.1
_
0.3
0.2
_
0.3
0.6
0.4
1.4
WHO
concentration
(PP»)
0.54
0.64
0.36
0.74
1.87
0.28
0.28
0.50
0.57
0.59
0.48
0.07
0.17
0.22
0.08
O.S6
1.08
0.56
0.41
0.8B
0.9B
0.35
0.30
0.62
0.17
* Surface area of parti cleboard per net volute of roan.
Source: Andersen et al. (1975)
155
-------
According to the study documentation, houses sampled were selected at
random. The only criterion was to Include houses with different contents
of partlcleboard. Partlcleboard was used as a construction material In
11 rooms and for fixtures only 1n eight rooms.
Samples were taken by drawing 50 liters of room air through two
washing bottles. The laboratory analysis was carried out with the
chromotroplc add test method with a reproduclblHty of *. 5 percent at
0.8 ppra and a detection limit of 0.08 ppm.
UK Study
Over a two and a half year period, the Building Research Station,
England (Everett 1983) made over 2,000 measurements of formaldehyde
levels In some 120 homes and 58 other buildings. The overall objective
of the study was to compare measured formaldehyde levels In houses with
and without urea formaldehyde foam Insulation (UFFI). and to compare
levels In houses before and after Installation of UFFI. The buildings In
the main survey and In the more detailed monitoring exercises were
selected because of Important design features, and Included buildings
where occupants had reported some discomfort as well as those where no
complaint had been made.
The study provides results 1n the following areas:
• Outdoor formaldehyde levels
• Indoor formaldehyde levels, for
- Buildings with uninsulated walls or V.sulants other than UFFI
- Buildings with UFFI
- Houses monitored before and after installation of UFFI
- Houses of conventional (all masonry) construction
- Houses of prefabricated concrete construction
• Formaldehyde levels in wall cavities
Unfortunately, sampling and analysis procedures used In the study
were not described In the available documentation. Only a summary of the
sampling results and a comparison to the results of the Canadian UFFI/ICC
156
-------
study were provided 1n Everett (1983). These are presented 1n Table 41.
The average outdoor concentration found across bO sites, regarded by the
author as typical for normal urban environments 1n the UK. was 0.006 ppm
(std. dev. of 0.004 ppm).
4.5 Summary of Monitoring Data
Table 42 briefly summarizes the formaldehyde monitoring 1n residences
reviewed within this section. It Is divided between conventional and
mobile homes for ease of comparison.
The studies performed by the Lawrence Berkeley Laboratory, the
Consumer Product Safety Commission, the government of Canada, and
researchers 1n Iowa and Indiana are the most recent studies of
conventional homes and are not generally based on homeowner complaints.
The age and construction of the home appear to be major determinants of
the formaldehyde concentration. Newer, energy-efficient homes tend
toward higher levels, likely due to the low air exchange rates of
energy-efficient housing. Comparison of these data with data collected
prior to 1980 Indicates that there has been little change In conventional
home formaldehyde levels since 1978.
Initial levels In new mobile homes are less well-defined, but appear
to have declined 1n recent years. The Clayton study and the Wisconsin
study, conducted prior to 1982, sought to define mobile home levels by
age. The mean of an aggregated data set of these two studies (with
nearly 1,200 observations - see Section 7.3) 1s 0.43 ;ipra, corresponding
to a home age of less than one year. The more recent Texas study of
formaldehyde levels In mobile homes of various ages found that levels In
homes less than one year old averaged 0.21 ppm, and that the average
levels were essentially the same for the l-to-2, 2-to-3, and
3-to-4-year-old age groupings.
157
-------
Table 4). Sumary of U.S. Study and Caparison with
Canadian UFFI/ICC Data
Arithmetic Standard Standard
mean, ppm deviation, ppn error
Candlan data
I. Control (no UFFI) 0.034 0.029 O.OOtS
II. 100 problen houses 0.139 0.281 0.0281
III. UFFI houses (UFFI/IOC files) 0.040 0.036 0.0014
IV. UFFI houses (CHIP files) 0.054 0.044 0.0013
UK data
SO control buildings (no UF foam) 0.047 0.042 0.0020
Foam insulated buildings 0.093 0.099 0.0026
Source: Everett O9B3)
158
-------
Table 42. Svmary of Residential Formaldehyde nonitoring
Study/date(s)
Hunter of hares Muiter of samples
Hem (ppn) or
range of means
Range (ppm)
Consents
OONVENIIOUL HONES
Fleming 8 Associates
New York study
(Traynor * Nitschke 1984)
Univ. Washington (1982-1963)
(Breysse 1984)
IBL (1919-preswit)
(Giman eta). 1983)
(1978)
(Noschandreas el a). 1918)
«g Canadian UFFI/IOC <19B1)
(UFFI/ICC 1981)
ORNL/CPSC 40 Tennessee hone
Study (1982)
(Hawthorne et al. 1984)
Private Washington labs (1983)
(Breysse 1984)
UK study (-1980-1982)
(Everett 1983)
Outcti study (1977-1980)
(Van der Mai 1982)
30
58
24 (EE)
16 (U)
17
378
29
25 specified
conventional
SO
113
~714
16
0.040 0.007-0.151
<0.1 to> 1.0
O.005 to 0.214
O.005 to 0.079
0.02 to 0.16 <0.01 to 0.50
0.05 (overall)
0.034
0.060
O.01 to < 0.20
O.025 to > 0.25
<0.05 to >O.S
0.047
0.032 to 1.444
(range of
maxinms)
Non-ccmplaint hones.
Primarily cenplaint hones. Only 4 of 113
measurements >0.5 poo.
Includes energy-efficient (EE) and older.
ueatherized (W) nm-cojplaint nones around
the U.S.
Includes conventional, "experlnental', and
apartment hones around U.S. Hon-coBplaint
hones. Assuring 601 of total aldehydes is
formaldehyde.
study of UTI and non-UFFl hones; mean is
for non-UFFl hones. (Hean H/UFFI = 0.054
ppn for 1.897 hones).
Study of UTI and non-UFFl hones: nean is
for non-UFFl homes. (Hean u/UFFI . 0.077
ppm for 11 hones).
None exceeded 1.0 ppa. 45 of 76 between
0.05 and 0.09 ppn.
Study Mas of UFF1 and non-UFFl hones; nean
is for non-WFI hones. (Nean u/UFFI = 0.093
ppn).
Prior to control inplenentation. Largely
conplaint hones.
0.048 to 0.602 After panel coating.
-------
Table 42 (Continued)
Stody/date(s)
Munber of hones milter of samples
Bean (ppm) or
range of means
Range (ppn)
Gonnents
leua studjy (1980)
(Schutteet a). 198?)
SAI California survey (1984)
(SAI 1964)
Indiana Board of Health
study (1919-1983)
(Konopimki 1983)
Godtsh (1983)
Cohn (19B1)
Swiss hones (1983)
(Kuhn and Manner 1984)
Netherlands study (1981-196?)
(Cornet 1983 - Holland study)
(1975)
(Schulza I97S)
Swedish hones (1915-1971)
(Sundin 1978)
Danish nines (1973)
(Andersen et al. 1975)
NDB1U NONES
31
6
64
120
312
103
46
52
3
319
23
0.063
0.084
O.OSO
0.09
0.05
0.027
0.013 to 0.34 Non-conplaint hones.
0.046 to 0.153 New, non-cooplaint homes.
0.018 to 0.120 Older, non-conplaint hones.
NO to 1.3S Study of UFFI and non-UFFI hones; Bean is
for non-VTI hones; includes some ceoplaint
hones. Mean w/UFFI = O.OS pan for 119
hones).
0.03 to 0.07 Study of IJFFI and non-UFFl taaec; Mean is
for non-UFFl hones containing no
particleboard flooring, cabinetry or
paneling. (Mean w/UTTI » 0.07 ppn for 28
hones). .
"O.I to 0.7 Highest level prior to occupancy.
0.048 to C.055 —
0.12 0.06 to 0.20
O97B)
(Itocchandreas et al. 1978)
84
0.58
1.44
0.21
Hones without particleboard, as Bcouired by
the ehronotropic acid Method.
Few details available.
0.1 to 2.0 Feu details available.
0.01 to 1.87 Hones known to have particleboard
construction materials.
0.07 to 0.46 Assuring 601 of total aldehydes is
fomldehyde. Non-conplaint hones.
-------
Table 42. (Continued)
Study/da te(s)
Univ. Washington (1982-1983)
(Bneysse 1984)
MI (1984)
(Comers 1984)
Clayton (1930-1981)
(Singh et al. 19B2a)
Wisconsin (1980)
(Anderson et al. 1983)
Minnesota (1980-1981)
(Stone et al. 1981)
Tennessee (1982-1983)
(Hodges 1984)
Kentucky (1979-1980)
(Cssgers !9M»
Texas study (1982-1983)
(Univ. Texas 1983)
SAI California survey (1984)
(MI 1984)
Nunber of hones
430
1
259
137
109
71
55
103
121
3
Mean (ppn) or
Hunter of samples range of means
822 —
15 0.34
— 0.62
(adjusted)
920 0.38
0.61
— 0.30
— 0.23
- 0.43
- 0.18
— 0.114
Range (ppn)
<0.1 to>1.0
0.24 to 0.46
0.02 to 2.9
(adjusted)
0.02 to 2.26
__
0.02 to 1.43
0.02 to 1.92
0.01 to T.99
0.04 to 0.35
0.068 to 0.144
Convents
31 of 822 measurements >1.0 pan. Complaint
hones.
3-month old home btult specifically for test.
Nan-complaint, occupied and nonoccupied.
Concentration by home age evaluated.
Hon-ecnplaint. occupied hones.
Concentration by hone age evaluated.
Average home age <2 yrs. Conplaint hones.
Gonplaint hones; no age data.
Complaint hones, see T.ible 27 for data by
how age.
CBoplaint hunes. see Table 28 for data by
hose ago.
Non-conplaint hares. Excludes results fro*
one county (El Paso) where evaporative
coolers were in use.
Passive LBl sanpler: one week; non-coaplaint.
- Insufficient data in reviewed literature to report value.
Mtm mi Detectable, or Below Detection itait
-------
5. SHORT- AND LONG-TERH EFFECTIVENESS OF FORMALDEHYDE CONTROL
OPTIONS
This section discusses many of the control options that are
promising for reduction of formaldehyde exposure In residential
settings. Some options that have been evaluated or described by
Investigators are not discussed; among these are air cleaners (discussed
by AOL Inc. 1981) and some esoteric chemical treatments and resins. This
section describes the potential options, discusses the basis for the
formaldehyde reduction effect, and presents available data on
effectiveness.
In general, there are limited data demonstrating the effectiveness of
the formaldehyde emission control options described In this report. Host
of the available data concern only short-term effectiveness In reducing
emissions of the residual free formaldehyde from boards. Virtually no
information Is available concerning the effectiveness of any technique 1n
reducing formaldehyde emissions over months or years of product life.
For those techniques Investigated (see Table 43 for a summary of
available Information), the usefulness of the results 1s further limited
by the absence of correlation between Independent testing methods and
conditions. The available data on control options effectiveness
summarized 1n this section reflects only those data that were measured,
not estimated. Any modeled or otherwise estimated values for control
effectiveness were omitted from this summary.
5.1 Changes In UF Resin Formulation
Two major classes of control options fall under this category:
variation of the ratio of formaldehyde to urea In UF resins, and adding
chemicals to the resIn/wood system to act a* scavengers of excess
formaldehyde, preventing Its release.
162
-------
Table 43. Suimary of Data on Formaldehyde
Emission Control Options*
Control option
Board type
and thickness
Test type
Test results
Reference
Changes \n UF Resin
Formulation
Reduction in FU Ratio
U:F ratio in resin
1:1.20 Particleboard
1:1.30
1:1.40
1:1.65 HDF
1:1.26
1:1.20
1:1.05
Formulation of Scavengers
Into the Resin/Wood System
Sodium sulf ite
scavengers
Plywood
Perforator
desiccator
Perforator
Desiccator
Perforator
Desiccator
Perforator
Desiccator
Perforator
Desiccator
0.025-0.0351 released
0.04-0.05% released
0.06-0.11 released
1.64.4 ug/ral
80 mg/lOOg board
1.4 uo/nl
34 ng/1009 board
O.Ruo/nl
23 ng/lOOg board
0 36 ug/tal
9.3 mj/IOOo. board
0.00 pom (1001 improvement)
0.2S pom (981 Improvement)
0.34 pen (971 Improvement)
0.26 pom (981 improvonent)
Pizzi (1963)
Meyer et al.
(1983)
Urea scavengers
(unspecified)
Kenosize FR4514
urea scavenger
Plywood
22 on
parttcleboard
Desiccator
Perforator
HK1 (nodifed)
Swedish chamber
after S ninths
0.07 ppn (<
IZng/lOOg
911^
0.29 pom
0.4Sppn
Iteyer (1979)
Meyer (1979)
Johansson (1932)
163
-------
Table 43. Sumntry of Data on Formaldehyde
Emission Control Options* (continued)
Control option
Board type
and thickness
Test type
Test results
Reference
Post-Cure Board Treatments
Ammonia Funigation
Verkor FD-a Parttcleboard
Plywood
Perforator
Desiccator
RYAB
Particleboard
10 nm
19 ran
22 mn
10 Am
19 nm
22 on
10 nm
19 am
22 BIB
Swedish charter
Perforator
M(l (modified)
5.5 rug/100 gr. board (971
improvement) 4.4 no/100 gr.
board (861 improvement).
0.15 pom (991 improvement)
0.37 ppm (971 inprovenent)
0.01 ppm (1001 improvement)
0.64 ppn (951 improvement)
0.14-0.39 ppm
<0.1 ppm
0.71 opm
Mmg/IOOg.
13 mo/100 9.
19 mg/100 g.
Simon (1980)
Oohanswm (1982)
IKmg/m2
164
-------
Table 43. Suimary of Data on Formaldehyde
Emission Control Options'* (continued)
Control option
Board type
and thickness
Test type
Test results
Reference
Particleboard
10 nm
Ifam
22 am
10 BID
19 rrm
22 cm
10 RIP
19 nm
22 nm
Particleboard
10 nn
28m
36 m
Johansson (1982)
Swedish chanter
Perforator
MCI (modified)
Perforator
8 ao. after production
10 m Perforator
28 on
36 nm
Ueyerhauser in-home
fumigation N/A
Indoor air levels
<0.1-0.32 pom
0.25 ppn
0.22 pqn
IS na/100 g.
14 mo/100 g.
14 gig/100 9.
166 mg/100 g.
79 rag/100 9.
113 mg/100 g.
9 mg/100 g.
12 no/100 g.
8 mg/100 g.
S mg/100 g.
13 mg/100 g.
b og/100 g.
0.074.26 pom
(up to 8S1 reduction)
SMdspan (undated}
Oewll (1982)
165
-------
Table 43. Surmary of Data on Formaldehyde
Emission Control Options* (continued)
Control option
Hon-scavenaer
emission barriers
Nelamine-containing
surface coating
Falima-F (coating)
Valspar 50100
Nitrocellulose surface
coating
Polyurethane surface
coating
Hall paper
Hacore overlay
Varnish
Overlay paper
Decorative vinyl
overlay
Board type
and thickness
Particleboard
Particleboard
PlytMod
(Unspecified)
PlyNood
(Unspecified)
(Unspecified)
(Unspecified)
(Unspecified)
Plyuood paneling
Test type
Perforator
Dynamic Chanter
(emission rate)
Dynamic Chanter
Desiccator
JIS Desiccator
(Unspecified)
(Unspecified]
(Unspecified)
(Unspecified)
Large chanter
2-hr desiccator
Test results
0.02 ppm (981 improvement)
0. 10 ppm (921 improvement)
0.03 ppm (971 improvement)
25.4-70.8 ug/hrVhr
0.3 ppm (901 improvement)
0.09 ppm (921 improvement)
0.02 ppn (981 improvenent)
0.5 ppm (961 improvement)
331 improvement
841 improvement
sc-3o> inprovsnent
931 inprovenent
0.04. 0.75 ppn
O.S3 - 3.04 ug/ml
Reference
Meyer (1979)
Nolhave (1983)
nyers (1982b)
ICF (1984)
Neyer (1919)
Meyer (1979)
Groan (1984)
166
-------
Table 43. • Summary of Data on Formaldehyde
Emission Control Options* (continued)
Control option
Board type
and thickness
Test type
Test results
Reference
Substitute Resins
Phenol-formal Jehyde
resin adhesives
Other Controls
Board aging
30 days
60 days
15 days
Pine plywood
Fir plywood
Oriented strand
board
Parti cleboani
Uaferboard
2-hr desiccator
Dynamic chamber
2-hr desiccator
Dynamic chanber
2-hr desiccator
Dynamic chamber
2-hr desiccator
Dynamic chanber
2-hr desiccator
Dynamic chanter
Particleboard
Fir plywood
Fir/hemlock plywood
water-board
Pine plywood
Hardwood plywood Dynamic charter
24-Hr desiccator
0.08-0.34 g/ml
0.011-0.04 ppn
0.1B 9/ral
0.017-0.05 ppn
0.02-0.14 gAnl
0.03-0.07 pom
0.15-0.51 g/ml
0.01-0.03 pen
0.03-0. IB g/ml
0.01-4. OB ppm
APA (1984)
3 85 x
2.50 x 10-*hg/nil
1.30 x 10-^ng/nl
1.45 x I0-*ihg/m1
1.35 x 10-*lng/bl
0.31 ppn (90S improvement)
<0.01 ppn (1001 improvement)
931 inproyenent
Meyer (1981)
Myers (I982b)
•Further details on tasting nethocH, conditions, and results can be found in tie following text
in this section and in the references cited. Many references cited are secondary sources.
167
-------
5.1.1 Reduction 1n the F:U Ratio
Resin formulation has changed dramatically over the past decade. In
the 1970s, a resin molar ratio of 2.0 parts formaldehyde per part urea
was not uncommon; current (I.e., mid-1984) mole ratios commonly reported
range from 1.15 to 1.3 for partlcleboard. 1.2 to 1.5 for hardwood plywood
paneling, and In the vicinity of 1.65 for MDF (HPMA 1984. NPA 1C84.
Podall 19B4). This change has occurred, at least 1n part. 1n response to
the public's and regulatory agencies' concern about formaldehyde
exposure. Lessening the amount of formaldehyde In a pressed-wood
product, as through this measure, 1s effective In the short term In
reducing formaldehyde release. The long-term stability of these low
ratio resins has, however, been questioned; It 1s possible that even
though Initial emission rates may be dramatically lower, a similar amount
or even more formaldehyde could be released over the life of a low F:U
ratio board, via increased hydrolysis, than from a board made with more
conventional resin formulations (Swedish Partlcleboard Association, Or.
Gfeller (Novopan AG), and Or. Roffael (Ullheln Klaudltz Institute) as
reported by Gaudert et al. 1983). Roffael (1918) states that the water
solubility of cured resins Increases with a decrease In F:U. Meyer
(19B4) demonstrated a slight Increase In emission rate from a low mole
ratio partlcleboard over a three-year test period; experts agree,
however, that long-term effectiveness and emissions characteristics are
not known for this control (Meyer 1984, Gaudert et al. 1983).
Myers (1984a) points out that mole ratio affects not only the rate
and magnitude of formaldehyde release from pressed-wood products but 1s
also a major determinant of the structural properties of the product.
His literature review concluded that direct correlation of board
properties with UF resin formulation yas net possible with existing data,
as there was too much variation be ^«n Investigators' test methods and
materials. He did present the following criteria as limitations on the
F:U ratio 1n partlcleboard:
168
-------
F:U must be less than 1.1 to 1.2 to meet the West German
formaldehyde emission standard for E-l partlcleboard (I.e.. less
than 0.1 ppm 1n a specified chamber test).
F:U must be less than 1.2 to 1.3 to meet the HUD emission standard
for partlcleboard In mobile homes (I.e.. 0.3 ppm In a chamber test).
F:U must be more than 1.2 to provide sufficient bending strength.
F:U must be more than 1.1 to 1.2 for Internal strength of bonds.
F:U must be more than 1.2 to 1.3 for control of thickness swell.
These conflicting standards Illustrate the difficulty with using low mole
ratio resins to meet formaldehyde emission standards.
The mole ratio of the UF resin 1s correlated with the free
formaldehyde content of pressed-wood products, which Is a determinant of
the emission characteristics of the product at least during the early
part of the product life. Nyers (1984a) collected data from numerous
published studies and produced a correlation with a wide range of values
around the curve. This is reflective of the other parameters affecting
free formaldehyde content (press time and temperature, amount of
catalyst, and other manufacturing variables).
Nyers also states that F:U ratio 1s a determinant of the hydrolytlc
stability of resin bonds, thus affecting another potential mechanism of
formaldehyde release (Nyers 1982a). He measured the hydrolysis rates of
two resins of different mole ratios, keeping other parameters constant.
He found that resin variation strongly affected hydrolysis rate and
consequent formaldehyde release when the cure was more complete (higher
press time and temperature), and that et less-complete cure conditions
resin mole ratio did not affect hydrolysis. The resin with a mole ratio
of 2.0 exhibited more hydrolysis over the test period than did the resin
of mole ratio 1.4. The usefulness of these results Is somewhat
169
-------
diminished by the fact that this test was performed on resin only; no
wood was Incorporated, so that the object was not a pressed-wood
product. In addition, the low mole ratio resin used (1.4) 1s at the
upper end of the range of low mole ratio resins used commercially during
19B4. Furthermore. Meyer et al. (1983) have reported results somewhat
contradictory to this theory on the effect of molar ratio.
The constraints listed previously limit the lowering of mole ratio
much below 1.2 for particleboard resins. The NPA states that current
mole ratios In partlcleboard range from 1.15 to 1.25 (NPA 1984), thoi-qh
the USDA reports that resins with an F:U ratio of 1.05 have been tested
that do not cause excessive sacrifice In product properties (USDA 1984).
The data that have been reported for the use of low mole ratio
resins In HOF Indicate that low mole ratios do diminish emissions; no
data on board properties are. however, available. It has been stated
(NPA 1984) that NDF 1s more sensitive to low mole ratio UF resin than Is
partlcleboard, and that successful formulations require a ratio of 1.2 to
1.4. HPNA (1984) states that mole ratio resins as low as 1.2 to 1.4 are
being used In the manufacture of hardwood plywood paneling.
The results of emission characterization surveys conducted by NPA
Indicate that Initial emissions (I.e.. desslcator results for fresh
boards) from mobile home decking, partlcleboard underlayment. and
Industrial partlcleboard decreased, or the average, by 67 percent, 56
percent, and 60 percent, respectively between 1980 and 1982 (NPA 19B4).
Reduction In F:U resin mole rations was cited as being responsible for
most of the observed decrease In emissions. NPA Is currently conducting
Its 1984 emission survey (see Section 2.S).
The Improvement 1n formaldehyde emission Is accomplished by varying
the amount of excess formaldehyde. The results of two such studies are
presented In Tables 44 and 45. Neyer et al. (1983) tested seven
adheslves by manufacturing HDF and measuring resultant formaldehyde
110
-------
2877H
Table 44. Caparison of Formaldehyde Emission fran
Partlcletooard Prepared trith UF Resins of
Different telar Ratios
U/F oolar Percent CHjO released
rat to (perforator method) (ng/lOOg)
1:1.4 -1.5 80-100
1:1.3- 1.35 40-50
1:1.2- 1.25 25-35
Source: Pizzi (1983).
171
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2877H
Table 45. Comparison of Formaldehyde Emission from
NT Prepared with UF Resins of Different
Holar Ratios
Resin adhesive4
F:U
(1:l.BS)e
(l:1.65)d
(l:l:6S)e
(l:1.6S)e
(l:1.26)e
(l:1.20)e
(1:1.05)"
2-Mr desiccator value0
(mlcrograns/ml)
3 Days
__
4.8
5.6
2.6
2.5
1.4
0.54
6 Merits
8.4
2.3
3.0
1.6
1.4
0.72
0.36
5Hos.
_
2.0
2.3
0.86
0.85
0.62
0.38
10 fcs. f
4.4
1.9
2.0
O.TO
0.71
0.59
0.40
Perforator
(ng/IOOg)
6 techs
_
63
80
—
34
23
9.3
a Boards tare manufactured witli dimensions 0.9 n x 0.9 m x 16 ran.
Kenosfze MM dispersion (contains a scavenger) was added to each
resin at I ut V
b Board sample edges Mere not sealed. Average values for at least
thru boards for each resin type.
e Gomerclal domestic resins.
d lab-cade resin
e Oomercial European resins
f Samples cut one day before testing from center of boards.
Source: Meyer and Hermanns (1984*); Meyer et al. (1983): Meyer et al.
(1984).
172
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emissions. Two of the resins were commercial UF preparations with a mole
ratio of 1.65. One resin was a UF-urea scavenger mixture, also with a
mole ratio of 1.65. The four remaining resins were manufactured 1n
Sweden, and had mole ratios of 1.65. 1.26. 1.2U. and 1.05. As seen In
Table 45. emissions declined with declining F:U ratio. The structural
properties of these boards were not reported.
Data are also available on the combined effect of varying F:U molar
ratios 1n resin adhesive; with other formaldehyde emission control
options discussed 1n this report. These data are presented 1n Tables 46
and 47.
5.1.2 Formulation of Scavengers Into the UF ResIn/Wood System
Reactive chemicals, which will react with excess or free
formaldehyde present 1n pressed-wood products, can be added to the resin
formulation or the wood or one of the fillers (like wax) prior to cure.
These chemicals are often sulfurous or nitrogenous compounds that form
stable complexes with formaldehyde 1n the resin. Other carconaceous
compounds, such as resprclnol derivatives (Oletrlck and Terbllcox 1983)
may also be effective.
Champion International, Union Camp, the Polatch Corp., the MPA, and
other Industry representatives provided the EPA with comments regarding
this proposed control option, discussing both the effectiveness and costs
(economic and 1n terms of reduced properties). These comments and the
review report of Myers (1984d) state that scavengers can be effective but
add cost and can be deleterious to the finished product. The most
popular scavenger Is urea, added as an aqueous solution or as a dry
compound. The effect of this action 1s the same as a variation 1n the
formaldehyde:urea ratio. In terms of lessening emissions as well as
reducing strength (Champion 1984. Potlatch 1984). An overaddltlon of
scavenger like urea can prohibit the proper cure of the resin during
173
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Table 46. Contained Effect of Aging and Varying Molar
Ratios In Adbesives on Formaldehyde Emissions
from Parti detain)
Test
(Units)
MCI
(mS/lCOg)
terfordtor
(ma/lOOg)
2-Hour
desiccator
(ug/W.)
Hale ratio
F:U
1.27
l.SS
1.40
1.60
1.60
1.6
1.8
1.0
1.2
1.3
1.6
Aging
condition
ftenD./MO
20*C/6S1>
Probably
20BC/6S1
Probably
anbient
Aging
tine
1 day
6 Heeks
1 day
6 weeks
7 weeks
15 months
7 weeks
15 Months
7 weeks
15 months
0
8 days
0
8 days
Iday
IS days
Iday
IS days
1 day
IS days
Iday
IS days
Test
values
83
49
127
78
80
48
139
60
ITS
72
100
73
125
85
0.8
0.4
1.4
0.8
3.0
1.1
8.0
4.3
Source: Dyers (19B4a).
174
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Table 41. Cnftined Effect of Press Tanperature/Ttae and
Varying Molar Ratios In Adhesive; on
Formaldehyde emissions fran Particleboard
Mole ratio
F:U
1.40
1.60
1.80
1.27
I. SO
1.2S
1.37
1.53
Varvino cress ten
Press
tenpcrature/tlrae
("C/rain.)
140/8
180/8
140/8 *
180/8
140/8
180/8
1800.2
220/3.2
180/3.2
220/3.2
npratuTQ
Perforator
value
Gng/lOOg)
48
3)
85
65
1ST
110
27
IB
59
40
Varying Prats
Press
unperauire/tiBe
(°OMn.)
180/5
180/8
180/5
Ian/a
180/5
180/8
220/2.1
220/3.2
224)72.1
220/3.2
170/2.S
110/4.2
170^.5
170/4.2
IKV2.S
170/4.2
Tina
Perforator
value
(hg/IOOg)
41
40
80
70
150
110
26
18
57
40
28
17
47
30
84
55
Source: nyers (M84a).
-------
press; any formaldehyde scavenger can Interfere to some extent with
proper curing by removing essential formaldehyde. The Hardwood Plywood
Manufacturers Association states that scavengers are less effective when
used with low molar ratio resins than with more conventional resin
formulations (HPNA 1984). evidently because there Is less free
formaldehyde for the scavenger to react with when the resin has a low F:U
ratio.
The National Partlcleboard Association (NPA) discusses the use of
annonlum compounds, and adds that Inclusion of the scavenger as a
component 1n the wax sizing Is probably the most effective method of use
1n partleleboard manufacture; Myers (I984d) also concluded that this nay
be the most effective scavenger technique. NPA lists the following as
useful scavengers: urea, protein, llgnosulfonates. and ammonium
carbonate. The usefulness of a urea 1n wax formulation Is confirmed by
reports that European manufacturers (Casco and BASF) have produced boards
that meet emission standards by using this control (Gaudert et al. 1983.
Myers I984d).
Johansson (1982) evaluated the effectiveness of Kenoslze FR 4514, a
urea scavenger that 1s formulated Into the wax added to the resin/wood
system. Use of the Kenoslze reduced emissions, as measured by the
perforator method, from 26 mg/lOOg (control board} to 12 mg/lOOg (treated
board). Even though resin weight, as a percent of the board, must' be
increased somewhat with the use of Kenoslze (Shields and Serveau 1983),
this control was found to be the most effective of the four reviewed by
Johansson (two ammonia treatments, a low molar ratio resin, and the
scavenger). Long-term effectiveness of this control was measured by
chamber tests. Johansson reported that measurements five months after
treatment showed Increased emissions (0.45 ppm} over emissions
Immediately after treatment (0.29 ppm).
Myers (1984d) summarized the rather limited Information available on
ttie effectiveness of scavenger additions to wood furnish or veneer. He
divided the various treatment techniques reported 1n the literature Into
176
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four basic approaches: (1) addition of llgnocellulosU materials
Impregnated with scavengers (e.g., nelamlne and urea) to the furnish
before resin addition; (2) spraying furnish or veneer with simple
formaldehyde-reactive chemicals (e.g., ammonium carbonate, ammonium
llgnosulfonate) before of after resin addition; (3) spraying furnish with
an aqueous wax or polymer dispersion containing urea; and (4) using a
urea scavenger 1n conjunction with a non-UF adhesive 1n the middle layer
of the furnish.
Table 48 summarizes the results of the various studies reported In
the literature for these four approaches. The data for Approach 3
compare well with the data of Johansson on Kenoslze scavenger discussed
above. Although critical evaluation of the results was difficult because
of the limited amount of Information, Myers concluded that the use of
scavengers, 1n conjunction with resins having F:ll mole ratios of about
1.4, can lower the formaldehyde emission of boards by about SO to 70
percent, although often at some sacrifice In the physical properties of
the boards. Thus, other complementary measures may be needed to provide
additional reduction In emission while maintaining or even Improving
physical properties.
This option Is obviously potentially useful as a method of achieving
short-term reductions 1n formaldehyde emissions, as can be seen In Tables
48 and 49. Johansson (1982) alludes to the longer-term effectiveness of
this control, and her data are promising. Sundln (1985) has measured
formaldehyde levels 1n a home with Kenoslze-treated partlcleboard as Its
only pressed wood product. The loading rate of partlcleboard in the home
* a
1s 1.1 m /m . The highest level measured 1n the home was found
immediately after construction, and was around 0.1S ppm. The home has
been monitored six times In the five years since construction, and only
once did the level exceed 0.10 ppm. A sample of the partlcleboard was
removed from the home In 1982 (three years after It was built) and
emissions measured via the perforator method. Sundln reports a very low
177
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Table 48. Formaldehyde Emissions fnm Boards Formulated with Scavengers
Approach Illustrative board variations'
1 51 of niddle layer furnish with 601
aelanine; F/U 1.5
F/U 1.4; 51 fiber; -21 urea
F/U 1.4; 141 fiber; 41 urea
F/U 1/4; 21 of urea-treated papnr
fibers; 0.81 urea
2 AnonitB acetate "tapregnted
veneer"
NaNSOj • Impregnated veneer"
Urea-'iprayed veneer;
3-ply plywood
(.51 If resin; - 1.21 llgnowlfonate
on furnish
F/U i/4; an OeVgcoa
F/U 1.4; 0.6M (UX4)2CO,
F/U 1.2; 0.341 (HH4)2003
F/U 1/2; 0.611 W^tfOj
CMjO value Data adequacy0
(oercent of control)
5.0 ccc Low. Few details. Significance of
(53) CHgO test not clear.
<10 as/100 sd High
(«2S)
<10 ng/10011
(<25)
20 ng/100 a* High
2.6 og/mle Low-aedlun
O.S ug/tol
-0.5 ug/ml
13 ng/100 a> Low
(SO)
20 •g/10Qd High
(62)
I2ae/100g
OT)
9.S ng/100 9
(58)
7.0 H9/100 9
(43)
-------
Table 48. (continued)
Approach
Illustrative board variations'
CHgO value
(percent of control)
Data adequacy"
-41 of seven different
dispersions on furnish; 1 41 urea
F/U 1.4; -3* of one dispersion
system; It urea
F/U 1.4; -41 of two dispersions;
0.81 urea
F/U 1.2; 1/21 Kenosize dispersion In
middle layer and 0.671 in surface
layer
-11 Kenosize dispersion; control
perforator ~ 31 mg/100 g
-11 Kenosize dispersion; control
perforator —IS ng/lOOg
31 isocyanate and 31 urea in middle
layer. F/U 1.4
Middle layer with 21 isocyanate
and 21 urea. F/U 1.4
10 to 20 mg 100d
(25 to 50)
20 mg/100 gd
(50)
20 mg/1 100 gd
(29)
12 mg/100 gd
(46)
12 rag/100 gd
(40)
8 mg/100 gd
(SO)
IS mg/100 gd
(54)
14 mg/100 d-h
High
Nedium
Lou
High
'Concentrations based en dry furnish unless stated otherwise. UF = urea-formaldehyde, MUF = melmlne urea-
formaldehyde. F/U = formaldehyde-to-urea mole ratio.
Subjective judgment by Myers (19B4d). H - high, N - iclium, L = low.
cSample in sealed container 2 hour, 70°C, 501 relative humidity. Formaldehyde and air purged, collected, analyzed.
^Perforator test. Analysis of formaldehyde removed by 2 hours in boiling toluene.
'Japanese dessicator test). Measure of formaldehyde transferred from boards through air into dish of water,
all within a sealed vessel.
f"Bonding strength* after 3 hours of water iimvrslon, 60"C.
•Ground sample, 100°C, 3 hours. Evolved formaldehyde trapped in cold water.
''Control Is board with same Isocyanate and no urea.
Source: Myers (1984d).
-------
Table 49. Effect of Several Pre-Press Scavengers
on Formaldehyde Emissions from Plywood
Scavenger
Control
Urea COON.H^)
Amnoniun sulfite ((HH.)-SO.)
Sodiun sulfite (Na.SOJ
Sodiun bisulfite (NaNS03)
Sodiun hydrosulfite (Na S 0 )
Sodiun metabisulfite (Na.S.0.)
ftmoniun bicarbonate (W^HCOg)
Amnoniun thiosulfate ((NH ) S.O.)
Atnoniun sulfamate (NH 050.NH )
CH;0 Emission
desiccator method
(ppro)
13.20
0.07
0.1S
0.00
0.25
0.34
0.26
0.37
0.01
0.64
Percent
inprovonent
_
99
99
100
98
97
98
97
100
95
Source: Meyer (1979).
180
-------
perforator value of 8.6 mg/lOOg for that sample. Sundln (1985) also
reports a 22-week study In a manufacturing plant.using Kenoslze FR 4514
1n a 1.2 mole ratio resin. Emissions, measured by the Swedish chamber
test, steadily declined from 0.14 mg/m3 at 23°C/50X RH to 0.08 mg/rn3
ever the test period.
One non-Industry commenter on EPA's 4(f) rule stated concern over
emission of reaction products or the scavenger Itself. The reaction
product of formaldehyde and a urea scavenger 1s hexamethylenetetramlne;
the stability of that compound over a matter of years 1s questionable.
The exact reaction products of formaldehyde and other scavengers varies,
but there exists the possibility that they could break down and emit
formaldehyde over extended periods of use.
5.2 Post-Cure Board Treatments
5.2.1 Ammonia Fumigation
Several researchers have evaluated the use of ammonia fumigation as
a control for formaldehyde emissions from pressed-uood products. There
are numerous permutations of the ammonia fumigation process; variations
exist In the ammonia concentration, the method of application, and the
duration of treatment. Few data exist, however, to quantify the
effectiveness of this option 1n controlling emissions over the long terra,
regardless of the actual fumigation process used. Very few data on the
relative effectiveness of this control on different wood products are
available, though existing data do pertain to a wide variety of
products. Only medium-density flberboard appears never to have been
tested Individually.
The fumigation process can be performed either on manufactured
pressed-wood products or on entire homes containing those products. The
National Partlcleboard Association (NPA 1984) states that. In this
country, ammonia fumigation 1s used primarily as a retroactive treatment
for complaint homes, largely 1n mobile homes. The production line
181
-------
processes, the Verkor, Swedspan, and RY AB methods, are used primarily In
Europe; no domestic manufacturer mentions their use 1n U.S. plants.
Regardless of whether the process 1s Intended for control 1n homes or 1n
production, the basis of the control option remains the same. Ammonia 1s
introduced to the wood product as a gas. which binds with the free
formaldehyde present 1n the wood, forming hexamethylenetetramlne (Smith
1983, Simon 1980).
The Verkor FO-EX method, as described by Simon (1980), Is Intended
for large-scale production applications. Figure 20 Illustrates the
treatment apparatus. It 1s designed specifically to control free
formaldehyde, and Simon claims a permanent reduction 1n formaldehyde
emission. The fumigation takes place In a series of two
carefully-controlled, sealed chambers. In the first, ammonia Is
Introduced as a gas; the concentration of ammonia Is determined by the
mass of wood to be treated, the formaldehyde:urea ratio of the resin In
the wood, and the volume and residence time In the chamber. Residence
time ranges from 4.5 minutes for thin partlcleboard to over 10 minutes
for hardwood plywood. The second chamber Is used to eliminate free
ammonia from the surface layers of the boards by employing controlled
ventilation (Simon 1980). Some excess ammonia 1s left 1n the boards to
allow continued scavenging of formaldehyde, although formic acid Is added
after ventilation to neutralize some ammonia and reportedly to reduce the
chance of future hydrolysis (ICF 1984).
Figure 21 presents the measured effectiveness of the Verkor method.
Very high short-term effectiveness levels (1n terms of absolute reduction
over uncontrolled boards, as a percent) were iaported by Simon (1980).
He measured the effectiveness of the treaui^.it Immediately following
ammonia application and up to three years later. That three-year later
measurement 1s apparently the basis for the permanent reduction claim.
though comments by the NPA (NPA 1984) state that the reduction may not be
182
-------
VERKOR'eHHEX CHAMBER •**«<«»
1. Particle boards
2. FwKJer.
3. Inlet chamber.
4. InsWe transportation syatam, 7. PERFORATOR GRADE stamping roll.
5. VEHKOR's FD-EX CHAMBER. 8 Stacker
6. Outlet chamber. 9. Control panal.
10. Automatic analyMr-controller.
Figure 20. The Verkor FD-EX Chamber
Source: Simon (1980).
183
-------
1 - Wood particlaboard. thickness 20 mm. density 600 kg/m3
la - Same board as 1. tested 14 months after treatment
• Flax-shive board. thickness 20 mm. density 500 kg/ma
- Ftax-shive board. thickness 20 mm. density 400 kg/md
- Wood particteboard. thickness 6 mm. densrty 750 kg/m3
Pwfortfor wahM 0.03*
FO-CX TREATMENT TIME
Figure 21. Effectiveness of FD/EX Treatment
Source: Simon (1980).
-------
permanent. Simon's study was extremely limited; only four boards were
tested, and retestlng was conducted only a few times (seven data points
were reported) over the three-year period of the experiment. Results are
therefore far from overwhelming.
Little Information 1s available on the RYAB method of fumigating
wood products with ammonia, a method known to be used 1n Finland (Gaudert
et al. 1983) and Sweden (ICF 1984). That method employs pressure to
Introduce ammonia Into the boards (see Figure 22); the ammonia therefore
enters deeper into the board, scavenging a greater proportion of the
formaldehyde present. A pressure differential of 5.8 to 13 psl is
employed (ICF 1984). Quantitative efficiency data are available from
Johansson (1982). She evaluated the RYAB treatment by comparing
emissions, measured by the perforator test, from treated board to
emissions from control boards. Table 50 lists these data, along with
data for Swedspan treatment efficiency.
The ASSI method mentioned by Smith (1983) Is the Swedspan method, a
production-stage fumigation method. This method involves spraying of
ammonia compounds (carbonates, bicarbonate;, sulfates, or acetates)
between boards as they are stacked after production (see Figure 23).
Smith reports a BO percent reduction In emissions 44 weeks after
treatment, with a reduction of up to 88 percent Immediately following
spraying. This method may not be expected to be as effective as the
Verkor or RYAB methods, mainly because the treatment 1s more surflclal.
The data 1n Table 50 do not bear this out, however. In direct
comparison. Swedspan was more effective 1n controlling emissions.
Neither the RYAB nor the Swedspan method was as effective 1n the long
term (5 month chamber tests) as In the short term, as measured by
perforator emissions. Additional data on the efficiency of the Swedspan
method are presented 1n Table 51. This manufacturer claims continued
effectiveness of up to 89 percent after 5 months and 75 percent after B
185
-------
1 - Upper chamber
2 = iou pressure zone
S = frame
4 - Pneumatic rolls
4a= Compressor
5 = 7 = Injection
6 = Vacuum pimp
S = Rolle
3 s Jrvfection of amOKta
20 = Particltboard
Source: Jewell (1982).
Figure 22. RYAB's Gassing Equipment
186
-------
Table SO. Effectiveness of RYAB and Suedspan Amnonia Funigatlon of Boards
Boards manufactured by RVAB Boards manufactured by Snedspan
Property RVAB Swedspan Control RVAB Suedspan Control
method method method method
Chanter emissions, ppm
imned after manufacture 0.35 0.66 1.40 —
5 mo. after manufacture 0.48 0.69 0.98 —
Perforator Value.
019/100 g parti cleboard
22 no board 19 14 26 _
19 im board — — — 13
10 on board 10 9 27 11
UK1 (modified) results
mj/ta2, 24 hr
22 can board IBS 113 178
19 im board — — — 110
— —
- —
•4 28
IS 36
— —
79 214
Source: Johansson (1982)
-------
Swedspan method
1 Cooler
2 Application of chemicals
3 Stacking and conditioning
4 Sanding
5 Cutting
Source: Swedspan (undated).
Figure 23. The Swedspan Aimonla Treatment Hodel
188
-------
2877H
Table 51. Effectiveness of Swedspan Method for
Formaldehyde Emission Reduction
Board thickness (type unsoacified)
10 mm 28 im 36 n
One week after Perforator values (ma/lOQa)
manufacture
Untreated 25 29 21
Treated 9 12 8
Percent reduction 64 59 62
8 months after
manufacture
Untreated 20 28 20
Treated 5 13 6
Percent Reduction 75 55 70
Source: Swedspan (undated)
189
-------
months. The best emission reduction Is at the surface, but an Initial
reduction of SO percent 1n formaldehyde emission potential from the core
of a treated 28 mm board has been measured by Swedspan (undated). No
loss of properties 1s said to occur as a result of treatment. All
ammonia treatments are potentially applicable to composition boards and
plywood.
Available data on In-home treatment with ammonia are relatively
limited. Some work has been done by Meyerhauser, as reported In Jewell
(1980a, 1982) and In their comments on the 4(f) notice. In addition.
Smith (19B3) evaluated the efficiency of ammonia treatment of a
four-year-old trailer used as an office building.
The method of In-home ammonia treatment as described by Jewell
(1982) and Meyerhauser (1984) Involves vacating the residence, then
placing pans of 29 percent ammonia throughout the dwelling. The home Is
sealed, and the Indoor temperature Is raised to 80 degrees Fahrenheit to
Increase the rate of vaporization. The fumigation 1s allowed to continue
for at least 12 hours; at that time, the home can be thoroughly
ventilated and reoccupled. The Manufactured Housing Institute (MHI 1964)
cites an effectiveness of 70 percent for reduction of Initial emissions.
Weyerhauser (198*) reports an average Initial reduction of Indoor
formaldehyde levels by 75 percent 1n 12 ammonia-treated mobile homes
(treatment performed In 1979 and 1980); however, air sampling performed
several weeks after treatment In five of the mobile homes Indicated that
formaldehyde air levels were Increasing (although not to the
pre-treatment levels). Table 52 presents these data.
Jewell (1982) has also studied the effectiveness of ammonia
treatment of boards (both lauan plywood and 5/8 Inch partlcleboard). The
large Initial effectiveness of his fumigation treatment Is not seen 10
weeks after treatment, when emissions from treated boards are only
slightly less than emissions from control boards.
190
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Table 52. Results of Ammonia Fumigations of 12 HobUe Hones1
Type of
Mobile
Ham?
single-U
Double-*!
Single-*
Single-W
Single-U
Single-*
Single-U
Single-U
Office
Double-W
Single-W
Double-*
Oouble-u
Location
Alabama
Hash.
Hash.
Mash.
Kentucky
Florida
Wash.
Illinois
Oregon
Oregon
Florida
Florida
Before Fun.
HCHO
(UL/L)
1.0
1.1
0.71*
0.89
0.65
0.41
0.93
0.56
0.68
1.0
0.51
0.41
Weeks After Anmonia Treatnent HCHO (uL/LI
1 1 1 1 1 1 1 1 1 1 1 1 1
0 5 1015202530354045505560
0.26* 0.26 0.24 0.28* 0.19
0.17*0.23 0.20
0.07 0.17 0.19* 0.30*
0.13* 0.27* 0.42*
0.23*
0.11
0.16* 0.37* 0.36* 0.57*
0.31* 0.25*
0.20*
0.13
o.ie*
0.12
' Formaldehyde measurements made using a modified NIOSH ehrontropic acid method.
* Data temperature corrected using the mathematical nodel of Berge, et.al. (1980).
H • Hide
-------
The study by Smith actually simulated In-home fumigation rather than
being a full-scale field study. He Identified the highest formaldehyde
emitter In the mobile homes that had been converted Into offices, then
removed that source (paneling) and fumigated the panels with ammonia. He
was able to correlate emission reduction with both ammonia concentration
and duration of exposure to the ammonia. This study obtained
formaldehyde emission data for a period of 48 days following treatment
and observed no reduction In effectiveness. Smith's 1983 thesis does,
however, raise the question of the long-term effectiveness of the
treatment, citing the potential for uncontrolled resin hydrolysis to
evolve formaldehyde.
The effectiveness of this control option, both 1n the short and long
term. Is a function of the chemistry of the ammonia-formaldehyde reaction
and the characteristics of the remaining formaldehyde 1n the resin.
Neither of those parameters Is particularly well-characterized,
necessitating speculation regarding their Importance.
As stated previously, the reaction between ammonia and formaldehyde
results 1n the formation of hexaraethylenetetramlne, which Is said to be a
stable adduct (Smith 1983, Weyerhauser 1984). It 1s conceivable that
there could be degradation of that complex over periods of tine not yet
measured by Investigators. In addition, the ammonia treatment may be
effective only for free formaldehyde present 1n the pressed-wood product
at the time of treatment and not for any formaldehyde liberated by resin
hydrolysis or other mechanisms (unless an excess of ammonia could be
maintained to act as a continuous scavenger).
The Information presented In this discussion does not provide
unequivocal evidence of the long-term effectiveness of this control
option. The treatment Is, however, apparently effective for months or
possibly years; Weyerhauser suggests repeated use to ensure reduced
exposure to mobile home residents (Meyerhauser 1984).
192
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An Important consideration in the evaluation of control option
feasibility is the effect of a treatment on the physical characteristics
of the pressed-wood product. Little research has been reported In this
area, but one Investigator has shown that ammonia fumigation does not
adversely affect partlcleboard shear strength (Myers 1982b). No data
were found regarding the effect of ammonia fumigation on aesthetic
properties of pressed-wood products (primarily color changes).
5.2.2 Post-Cure Board Treatments with Other Scavengers
A variety of post-cure scavengers can be applied as coatings
(paints, varnishes, etc.) or as aqueous solutions. The chemicals most
often tested are sulfur and nitrogenous compounds, which act similarly to
ammonia In that they react chemically with free formaldehyde to produce a
more stable complex.
Geomet (1980) summarized literature available at that time regarding
the effectiveness of various scavengers applied to pressed-wood products
as coatings. Sundln (1978) tested a urea-based paint and found that It
reduced formaldehyde emissions by nearly 75 percent. Those results must
be termed short-term effectiveness; no long-term emission testing was
undertaken.
Smith's (1983) literature review discusses the work done by Japanese
scientists on formaldehyde emission reduction by use of surface
scavengers. It 1s Implied that these applications are not 1n paints but
rather are directly-applied solutions of scavenger. Ammonium salts.
guanldlne derivatives, amides, and urea have been tested and all found
effective 1n the short term to some extent. Smith concludes that this
control option has as yet undeveloped potential.
Barghoorn (1979, In Meyer 1979) presented results showing a
reduction In formaldehyde emissions from partlclebcard treated with
various surface coatings containing formaldehyde scavenging chemicals.
The procedure Involved a chamber test that compared the value of an
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untreated board (1.20 pprn) to the values of coated boards. Boards were
tested with and without edges sealed, at a loading of 0.6 m /m . one
air change per hour, and sample dimensions equal to 1 x 2 m. Results
showed that the edge finish alone reduced emissions by a factor of ten.
One coating tested was a melaralne-contalnlng coating which, with sealed
edges, reduced test chamber concentrations to 0.02 ppm (a 98 percent
reduction); with exposed edges, It reduced formaldehyde concentrations to
G.10 ppm (a 92 percent reduction). Fallma-F, a commercially available
scavenger- containing coating of undisclosed composition reduced dynamic
test chamber concentrations from 1.20 (untreated) to 0.03 ppm (a 97
percent reduction). No long-term effectiveness data were available.
Mo1have et al. (1983) examined the emission rates of formaldehyde
from partlcleboards treated with Fal1ma-F surface coating. Under
standard conditions (23°C, 45 percent relative humidity), with an air
2 3
exchange rate of 3.25 and a loading of 2.2 m /m . emission rates
varied 38 percent (standard deviation) 1n the range 25.4 to 70.8
ug/m /hr. Emission rates for control boards (I.e.. not coated) were
not provided for comparison.
Another coating tested was Valspar 50100. a urea-containing wood
product surface coating. Myers (1982b) compared dynamic test results
between untreated commercially unfinished lauan plywood (5.6 mm thick).
deliberately selected because of Its high formaldehyde emission, with
Valspar treated boards. Samples were cut to 50 x 125 mm sizes and had
their edges sealed. Results at 35°C and 60 percent relative humidity
showed a ten-fold (90 percent) reduction In formaldehyde emissions from
3.00 ppm to 0.3 ppm. Scavengers are also sprayed over newly pressed
boards, usually In an aqueous solution to facilitate their absorption
Into the board.
Myers (I982b) found that the Valspar varnish acted both as a barrier
to reduce water and formaldehyde transmission across the board surface
and as a scavenger. The control was about 90 percent effective in
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reducing emissions. He cites continued reduction after 30 days as
evidence of the long-term effectiveness of the treatment. Little Is
known about the effects of surface scavengers on board properties, though
little effect Is expected. Scavengers are used to react with free
formaldehyde; when the scavenging chemical Is used 1n a post-cure
treatment, as 1n a varnish, the effects on resin bonds should not be
significant.
The Dutch have also tested the effectiveness of a vinyl-toluene
paint by coating the Inner walls and roof plates (made from
partlcleboard) of experimental houses 1n Haarlem District, the
Netherlands (Van der Wai 1982). Although little 1s stated about the
conditions of the boards and the testing Itself, detailed results were
provided. These were summarized 1n Table 26 this report. Overall, the
painting reduced formaldehyde concentrations by a factor of 1.5 to 3.0
(1n the short term).
Use of scavengers with boards of low F:U ratio will not be as
effective as with boards of higher F:U, simply because there would be
less free formaldehyde for the scavenger to remove (as Indicated by
comments by the HPMA). The long-term effectiveness of this treatment 1s
essentially unknown. Union Camp (1984) specifically questions the
effectiveness of this metho'1..
5.2.3 Non-Scavenger Emission Barriers
The primary function of non-scavenging surface coatings 1n the
treatment of formaldehyde emitting boards 1s to prevent the absorption of
water by the boards thereby mitigating subsequent resin hydrolysis and
formaldehyde off-gas. Since none of the studies cited 1n this subsection
referred to their results as being long term. It 1s assumed that all of
the effectiveness Indications are reports of short term emission tests.
There do not appear to be any data on the long-term effectiveness of
these coatings.
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ICF (1984) reports that the use of nitrocellulose coatings decreases
measured formaldehyde emissions (desiccator method) From 1.20 ppm to
0.09 ppm (92.5 percent) and 0.02 ppm (98 percent) for boards with exposed
and sealed edges, respectively. Meyer (1979) reports studies that
Indicate 96 percent emission reductions (13.2 to 0.5 ppm JIS desiccator
method) for plywood treated wUh polyurethane applied at a rate of 100
grains per square meter.
Other surface coatings tested for effectiveness on partlcleboards 1n
chamber tests (1 air change/hr; 0.6m/hi), also reported 1n Meyer
(1979), include: wallpaper with sealed edge, 33 percent reduction
(untreated board caused 1.20 ppm); macore overlay with coated edge, 84
percent reduction; varnished surface with coated edge, 98 percent
reduction; varnished surface with uncoated edge, 92 percent reduction;
and overlay paper with sealed edge. 93 percent reduction.
Kazakevlcs (1984) evaluated the effect of emission barriers (paints
and wallpaper) on formaldehyde release from partlcleboard. The barriers
he evaluated successfully reduced emission rates below his method
detection limit (0.01 mg/ni2/hr).
The effect of a decorative vinyl overlay on formaldehyde emissions
was studied by Groah et al. (1984). The study examined large chamber and
2-hour desiccator tests on 4.0 mm thick plywood paneling with a 2 mil
(0.002 Inch) vinyl film adhered tc one panel face. Average
concentrations found In the large chamber tests were 0.75 ppm when both
vinyl faces and unfinished backs were exposed, and 0.04 to O.OB ppm when
only vinyl faces were exposed. Average desiccator test values were, for
exposed Faces and backs. 2.06 ug/ml; For vinyl faces only, 0.13 ug/ml;
and for unfinished back only, 3.04 ug/ml.
Hardwood plywood wall paneling Is almost always produced with a
factory applied finish; the user does not have to paint or decorate the
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panel after Installation. With the reduction 1n emissions from UF
adhesive systems. 1t has become apparent that the Impact of the coating
system has become more Important. Over the past 5 to 10 years, the flat
wood paneling Industry has been changing from solvent to water-base
coat'iigs to reduce volatile organic emissions (VOC) so as to meet ambient
air quality guidelines for atmospheric releases from manufacturing
p'.ant:. Some water-based systems now contdn formaldehyde 1n order to
Minimize VOC emissions, to achieve a decorative finish with appropriate
application characteristics, and to provide for a product with suitable
durability and with aesthetic and surface properties acceptable to the
consumer. Therefore, some coatings may even enhance the formaldehyde
emissions. It 1s not known at this time whether formaldehyde emitted
from the top coat of water-based finishes has significant Impact on long
term formaldehyde concentrations In living spaces (HPHA 1984).
The Council of Forest Industries of West Germany (1981) lists over
14 approved coatings or finishes for reduction of formaldehyde emissions
from untreated partlcleboard of emission categories E2 and E3 (see
Section 6.3 for definition of these codes). Those finishes and their
application rates Include:
melamlne resin Inpregnated paper
laquer coating on film underlay (>250 g/m2)
polyester (styrol) varnish (>250 g/m2)
2-component polyurethane varnish (>300 g/nr^)
oil-based alkyd resin paint (>230 g/m2)
veneers (walnut, makore. oak. pine) plus nitrocellulose
(>34 g/m2), polyurethane (>30 g/m2). or polyester (>35 g/m2)
Fallma - F coating (200 g/m2)
Fallma - 271 coating (200 g/m2)
0.5 mm plastic laminate
Rigid PVC film (100 - 180 mm)
PVC film. 18X plastlclzer (0.08 - 0.1 mm)
Laminated plastic on unsaturated polyester (O.S mm)
PVC film. 16X plastlclzer (0.18 mm)
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Use of any of these coatings or finishes will produce boards conforming
to German El standards, discussed further In Section 6.
5.3 Substitute Resins
Much work has been done on substituting other resins for the
urea-formaldehyde now used In pressed-wood products. Potential
substitute resins Include tanning-formaldehyde (Forss and Fuhrmann 1980,
Coppens et al. 19BO); melamlne formaldehyde, resorclnol formaldehyde, and
polyvlnyl acetate adheslves (NPA and HPHA 1984); spent sulfUe liquor
adhesive (Shen 1983) or Ugn1n-UF-PF combinations (FoMntek 1983); and
urethane or polyester binders (White 1979). There are, however,
technological or cost restraints severely restricting the use of any of
the above-listed adheslves. This report will discuss only the most
promising substitutes for urea formaldehyde 1n pressed-wood products —
phenol formaldehyde resin and Isocyanate resin.
5.3.1 Phenol Formaldehyde Resin as a Substitute for Urea Formaldehyde
Resin
Of all the substitute resin mixtures known, phenol-formaldehyde
resins have been studied most extensively. From collective testing, the
pressed-wood product Industry Is convinced that phenolic panel products
(pressed-wood products made with phenol-formaldehyde resin adhesive)
(1) emit very little formaldehyde 1n the long or short tern and
(2) Insignificantly affect the formaldehyde levels found Indoors and
outdoors. Their large test chamber studies have shown that even freshly
manufactured phenolic panel products produce formaldehyde levels at less
than 0.1 ppm (American Plywood Association 1984). Monitoring conducted
1n three mobile homes containing only phenolic panel products showed
formaldehyde levels to be less than 0.1 ppm (average levels ranged from
0.02 to 0.07 ppm) (Singh et al. 19B2a).
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Phenol 1s more reactive with formaldehyde than Is urea; the resultant
resin Is therefore more durable and emits considerably less formaldehyde
according to the American Plywood Association (APA 1984). The
formaldehyde that Is released 1s the small amount of free formaldehyde
present after manufacture, and no release via resin hydrolysis 1s
expected (APA 1984). The substitution of PF resin thus represents a
viable short- and long-term emission reduction option. This control
option could Include substitution of PF resin 1n products now formulated
with UF resin or actual product substitution (I.e., use of PF-bonded
softwood plywood In place of hardwood plywood made with UF). The latter,
product substitution, Is discussed separately In Section 5.4 of this
report. Phenol-formaldehyde 1s currently used by a small number of
partlcleboard manufacturers, accounting for about 6 percent of 1983 U.S.
partlcleboard production capacity (ICF 1984) and Is the sole adhesive
used by makers of softwood plywood (APA 19B4). Maferboard, hardboard,
and orlented-strand board are also based on phenolic resins and are
consequently low formaldehyde emitters.
Phenol formaldehyde 1s a suitable resin for substitution In
essentially all pressed-wood products that now use UF. The NPA cites
some difficulties with PF (low tack, loss of dimensional stability), and
the Manufactured Housing Institute adds that PF partlcleboard 1s. by
necessity, of costly tongue-and-groove construction (HHI 1984). An
additional consideration Is that PF resins cause certain light-colored
woods to be darker than they would be If UF resin were used, thus
limiting Its applicability In some furniture and fixture construction
(Champion 1984). The major drawback cited by Industry 1s the higher cost
and limited availability of PF resin, which stems from the general
economic Instability of all petroleum-based products (Including phenol).
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It appears from all relevant data that PF could be substituted 1n
pressed-wood products for UF as follows:
Partlcleboard - Phenol-formaldehyde can be substituted for urea
formaldehyde In all types of partlcleboard except for panels thicker
than 1 3/4 Inches, according to Champion (1984). The limiting
factor on thicker partlcleboard was not stated, but relatively
little partlcleboard Is manufactured thicker than 3/4 Inch.
Medium-density flberboard - No data specific to this product were
found. It 1s likely that applications similar to those for
partlcleboard would be feasible. The NPA (1984) states only that
limited experimentation has been performed with this resin-wood
combination, but cites no technological factors that would render
this use nonfeaslble.
Hardwood plywood - Many manufacturers submitted comments on EPA's
proposed 4(f) rule addressing this substitution. Hardwood plywood
made with PF Is said to exhibit a tendency to warp or expand In high
humidity environments, necessitating very careful Installation (NHI
1984); that problem may be solved by proper formulation of the resin
with waxes and other fillers, according to Champion International
(1984). The only situation In which PF Is an Inappropriate resin Is
1n the veneering of light colored woods, such as oak, or when thin
veneer of porous woods like elm, birch, hickory, and pecan are to be
glued to the surface (HPMA 1984, Champion 1984).
Myers and Nagaoka (1981b) measured emissions from two sets of
phenolic partlcleboards made with varying press times. Dynamic chamber
tests were performed involving one ventilation rate (1.15 air changes per
2 3
hour), a chamber loading of 19.2 m /m , and two sets of atmospheric
conditions (25°C/75 percent RH and 40°C/7S percent RH). Results averaged
only slightly above 0.1 ppm at 25°C and only approached 0.2 ppm at the
higher temperature, despite the very high chamber loading.
Meyer (1981) evaluated formaldehyde emissions from four plywood
samples, a 3/4 Inch partlcleboard. and a waferboard, all manufactured
with PF resins. Highest emissions (3.85 x 10~6 mg formaldehyde/ml test
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solution, as measured by a perforator test were from the PF
partlcleboard. A Douglas fir plywood released 2.5 x 10 mg/ml; that
same type of wood product, after accelerated aging, released only 0.22 x
and
-6
10" mg/ml. Releases from the waferboard, a southern pine plywood, and
a fir/hemlock plywood were nearly equal at 1.45, 1.35, and 1.30 x 10
mg/ml, respectively.
Meyer used these data to predict equilibrium Indoor air formaldehyde
levels that could result from the use of these PF-resIn pressed wood
products 1n a home. At a loading rate of 1.18 mZ/m3 and no air
changes, the predicted formaldehyde level resulting from the use of the
highest emitting product (partlcleboard) was 0.05 ppm; at 0.5 ACH. the
predicted level was 0.0025 ppm.
Myers (1983) reported very low perforator and 24-hour desiccator
measurements for four PF partlcleboards. Perforator values ranged from
1.1 to 1.4 mg/lOOg; 24-hour desiccator values ranged from 0.12 to 0.26
ug/ral. Myers (1984c) measured the formaldehyde concentrations resulting
from different air exchange rate/loading combinations of a PF
partlcleboard 1n chamber experiments. At a partlcleboard loading rate
typical for mobile homes. Myers reported formaldehyde concentrations of
0.02 ppm for an air exchange rate of 0.5 per hour and 0.04 ppm for an air
exchange rate of 0.25 per hour.
Matthews et al. (1982-1984) applied several test methods to phenolic
hardboard and softwood plywood panels (as well as to other pressed-wood
products) to Investigate the dependence of emission ra..j on the
background concentration of formaldehyde. Interpretation of the curves
plotted Indicates that averaged emission rates were essentially zero when
background formaldehyde levels were about 0.1 ppn. The results of the
tests Indicate that these phenolic boards could produce, at most, an
Indoor air level of about 0.1 ppm formaldehyde regardless of the board
loading rate or air exchange rate.
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Manufacturers' data on phenolic pressed-wood products are also
available. Champion International Corporation has published the results
of large chamber tests for their phenolic plywood, uaferboard, and
partlcleboard. At a chamber loading of 0.43 m2/m3. a relative
humidity of 50 * 2 percent, a temperature of 24 t TC (75 ± 2"F). and an
air exchange rate of 0.5 changes per hour, formaldehyde levels In the
test chamber are shown to be less than 0.1 ppm for all three types of
phenolic panels. Even lower levels are shown for a ventilation rate of 1
air change per hour and for products covered with either a resilient
floor cover or a pad and carpet (Champion International 1984).
Table 53 summarizes the results of a large study done on several
phenolic products by the American Plywood Association (1984). In this
Investigation, formaldehyde emissions from most major types of phenolic
panels were measured using large-scale dynamic chambers and two-hour
desiccator tests. Table 54 summarizes additional emission data which
have been furnished to the American Plywood Association (19B4) by various
phenolic panel manufacturers. Data from both large-scale dynamic chamber
and two-hour desiccator tests are again provided. The data from both
Tables 53 and 54 seem to confirm that phenolic products are not likely to
contribute more than 0.1 ppm formaldehyde to Indoor air levels.
5.3.2 Isocyanate Resins
Isocyanate resins contain no formaldehyde, making their use by
definition an effective short and long term control measure. The
presence of formaldehyde 1n Isocyanate partlcleboard and 1n wood chips
may be due to partial degradation of I1gn1n or carbohydrates during the
drying process (Roffael 1978). This Incidental level of emission 1s
demonstrated graphically In Figure 24. These resins are similar In cost
to phenol-formaldehyde resins, and the major disadvantages to their use
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Table 53. Suimary of Formaldehyde lest Data from Various Phenolic-Bonded Panel Products
Measured by Dr. W.F. Lehnann of Ueyerhaeiiser Go.
M
O
2-Hour Initial test
Products
Southern pine plywood
13 mn. 4-ply
Douglas-fir plywood
14 an. 5-ply
Oriented strand board No.
12m
Oriented strand board Mo.
(Sanple Ho. 1) 12 mn
Oriented strand board Ho.
(Sample No. 2) 12 on
Uaferboard (Sanple No. 1)
12 irn
Uaferfaoard (Sample No. 2)
12 am
Particleboard
19 nm, tat-mlt coating
(a) Test conditions: 25 »
desiccator Panel age
ug/ol (days)
0.03 32
0.18
-------
Table 54. Results of Large-scale Dynamic Chanter Tests and Tta-ttour Desiccator Tests on
Various Types or Phenolic Panel Products'"'
Chanfcer test parameters
Age at Precondition
Product test time(c)
type (Days) (Days)
So. pine ply.
23/32". 4-ply •- 8
So. pine ply,
5/8-. 5-ply •- 8
So. pine ply,
5/8". 5-ply - 8
D.-fir ply.
1/2" — 8
Particleboard.
5/8" - 2
so. pine ply.
5/8". 5-ply <30 2-3
GOHPLV,
5/8" <30 2-3
UaFerboard.
5/8" 22 2-3
Uaferboard
5/8" — 2-3
Parllcleboard
3/4" - :(M
Particleboard,
3/4" -- j"'
Particleboard
3/4" • - '^
So. pine ply,
15/32- -- 2
Loading
i-ate(d]
(orVm3)
0.95
0.95
0.95
0.95
0.49
0.49
0.43
O.S2
O.S2
0.43
0.43
0.43
0.43
Temp.
(C)
23 t 0.5
23 * 0.5
23 » 0.5
23 » 0.5
24* 1
24 t 1
24 * 1
24 t 1
24 * 1
24 * 1
24 » 1
24* 1
25 * 1
Relative
humidity
0.04
0.17 0.03-0.04(9) 0.03
0.18 0.03-0.04(9) 0.05
0.22 0.01 0.04
0.17 0.01 0.05
0.20 0.01 0.04
0.34 - 0.04<'>
-------
lable 54. (Continued) - Footnotes
(a) Ventilation rale IMS 0.5 air changes per hour for all clunber tests. Chrcmotropic acid was used for Formaldehyde analyses, unless
noted otherwise. Different test chanters were used by each of the conpantes represented.
(b) So. pine ply = southern pine plywood; 0-Hr ply » Douglas-fir plywood.
(c) Specimens Mere preconditioned at the same temperature, and relative (timidity as is given for the test chanter.
(d) Loading is given in terms of square feet of panel surface per cubic feet of air volume in the chanter.
(e) All desiccator tests were performed in accordance with the procedures given by the National Particleboard Association, Test Method
riH-1, with edges unsealed unless noted otherwise.
(f) Pararosanlline was used for formaldehyde analysis, rather than chrarotrapic acid, using the same panel specimens as those used in
the test whose results are reported directly above.
(g) Range typically encountered at this test facility.
(h) Background formaldehyde level in conditioning area was O.OB pom.
(i) Background formaldehyde level In conditioning area was 0.03 pom.
(j) Background formaldehyde level In conditioning area was O.OS ppm.
(k) Average of four tests involving samples from two separate panels;'for each panel samples for one test had sealed edges, while
those for the other tests were unsealed. Rang* = 0.29 - 0.43.
(II Average of four measurements made on four consecutive days. Range was 0.02 - 0.05.
Source: American Plywood Association (1984).
-------
aaoerwun SBMO
wooowumojs
71 M
Source: Roffael (1978).
Figure 24. WKI Method Test Results for Cured Resin/Mood
Composites and Dried Wood Particles
206
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are (as 1n the case of PF) related to Increases "in resin and finished
product costs. An additional consideration cited by many In Industry Is
the paucity of knowledge about the health effects of exposure to
Isocyanate resins and their byproducts; available data Indicate potential
problems with their use. Isocyanate resins Include, as a class, a large
number of compounds differing In cost and properties. Host Investigators
consider NOI (4,4'-d1phenylmetnanedl1socyanate) to be the most promising
as a wood adhesive.
Oeppe (1977) was the first to publicize the feasibility of Isocyanate
binders for use In pressed-wood products In the U.S. He compared the use
of Isocyanate to PF resin 1n partlcleboard and reported an Increase 1n
shear strength, a decrease 1n thickness of swelling, and comparable
properties for other parameters.
Wilson (1981) and Adams (1980) discuss three varieties of MOI
Isocyanate binders. Polymeric HOI, or PHDI, 1s the resin currently used
by manufacturers that make Isocyanate based pressed-wood products.
Einulslflable HOI (EHDI) and monomerlc HOI are also discussed as potential
adheslves. He found that PHDI and EHDI are approximately equal In
strength properties, and performed better than UF resin pressed-wood
products, but that polyols of those resins were actually the best
adheslves. All other resins tested performed better than monomer1c HOI.
Elllngson Lumber Co. presently manufactures a partlcleboard bound
with Isocyanate (PNOI) (Elllngson 1984). They state that the resultant
product Is competitive with traditionally-manufactured partlcleboard and
medium-density fiberboard (HDF) for many applications, Including as
underlaynent. This report supports the theory that there are no
technological restrictions on the substitution of HDI for UF, at least In
partlcleboard manufacture. It 1s likely that HDI would also be suitable
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for use 1n HOP, and the NPA reported limited testing of that combination
but no commercial manufacture (NPA 1984). Wilson (1980) states, however.
that the low tack properties of HDI may render 1t unsuitable for many
types of plywood.
5.* Substitute Mood Products
EPA Is considering several material substitutions as potential
control measures for lessening formaldehyde exposures In residences.
Some of these substitutes are products with no formaldehyde, while some
are low-emitting products. These options are described below.
5.4.1 Hardboard
Hardboard Is. 1n most Instances, manufactured with PF resin and Is a
low-level formaldehyde emitter. It Is used In the following
applications: exterior siding. Interior paneling, household and
comnerclal furniture, and Industrial board (American Hardboard
Association 1984). it competes with both hardwood plywood and softwood
plywood, but 1s not more extensively used at this time because of cost
considerations. Hardboard currently makes up 23 percent of the market
for residential paneling and 1s the leading component of exterior siding
(AHA 1984).
It thus appears that the value of this control option lies In Its
potential use as a substitute for hardwood plywood that Is formulated
with UF resin or for HDF or partlcleboard used In furniture and
cabinets. The potential utility of hardboard as a substitute for
partlcleboard underlayraent and similar applications 1s less clear.
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5.4.2 Gypsum Board
Gypsum board Is considered a viable alternative to hardwood plywood
1n the manufactured housing market, and Is currently gaining favor (NHI
1984). Gypsum board contains no formaldehyde, which would lead one to
believe that this substitution would be an entirely effective control
option. Recent studies Indicate that gypsum board 1s a strong absorber
of cormaldehyde in the atmosphere, and can emit that absorbed
formaldehyde if other sources are temporarily controlled (Plckrell et al.
1984, Weyerhayser 1984). The effectiveness of this option therefore
depends to a great extent on the presence of other formaldehyde sources
within the home.
5.4.3 Other substitutes
Softwood plywood Is, as discussed previously, a potential substitute
for hardwood plywood under some circumstances of use. It Is viable for
some Interior paneling uses (those not Involving hardwood veneering) and
for use as decking. Like gypsum board, softwood plywood bonded with PF
resin may be a formaldehyde absorber and can become a source under some
circumstances. There are also formaldehyde emissions, though slight,
associated with PF resin products like softwood plywood.
5.5 Increased Room Ventilation
Conroenters on the Advanced Notice of Proposed Rulemaklng (ANPR) for
the formaldehyde 4(f) Investigation mentioned that ventilation, or
Increasing a home's air exchange rate, may be an effective means of
controlling formaldehyde levels (Weyerhauser 1984, NPA 1984). An
increase in ventilation rate will reduce the formaldehyde concentration,
though unlike many other Indoor air pollutants the reduction will not be
In direct proportion to the ventilation change (NPA 1984); the lowering
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of the ambient concentration will trigger an Increased emission rate.
The NPA states that doubling the ventilation rate will cut the
formaldehyde level by only one-third. A marginal Increase In exposure
reduction may be achieved with air-to-air heat exchangers when used with
Increased ventilation (HHI 1984, Weyerhauser 1984).
Myers (1984b) critically reviewed the available literature concerning
the effect of ventilation rate and pressed-wood product loading on Indoor
formaldehyde concentrations. Although a large number of studies of
formaldehyde levels have been reported for a variety of buildings, Hyers
found that very few of these studies report measurements of ventilation
rates 1n the buildings. Of these few studies, Myers determined that only
three (Jewell 1980b; Moschandreas and Rector 1981; and Singh et al.
1982b) provide sufficient data to permit even a semlquantltatlve
evaluation of ventilation rate effects.
Based on the concentration data and air exchange rate and product
loading Information given In the studies. Myers fit the three data sets
to the HBF equation so as to have a basis for consistently evaluating
the studies' results. Myers found that'the calculated (and observed)
changes 1n formaldehyde concentration with Increasing ventilation rate
were within the ranges seen In controlled chamber tests with pressed-wood
products. A doubling of the air exchange rate from 0.25 to 0.50 ACH (air
changes per hour) decreased the formaldehyde concentration by as little
as 8 percent to as much as 37 percent.
The HBF equation 1s a model developed by Hyer (1984b) based on
research by Hoetger, Berge, and FuJII. The HBF equation, like the
emission rate models being developed by ORNL for CPSC (see Section 7.1).
Is an expression that linearly relates the steady-state concentration of
formaldehyde 1n a chamber to the air exchange rate and loading of the
pressed-wood product.
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Increasing the air exchange rate from 0.50 to 1.0 ACH decreased the
concentration by 9 to 42 percent. Increasing the air exchange rate from
0.25 to 1.0 ACH decreased the concentration by 17 to 63 percent.
Thus, as has been found In chamber tests with pressed-wood products,
Increasing the ventilation rate will reduce formaldehyde concentrations,
but the reductions achieved will typically not be as large as one might
expect; that Is, a simple doubling of the air exchange rate will not
necessarily reduce the concentration by 50 percent, but rather by about
one-third or possibly less. The emission rate of formaldehyde from a
pressed-wood product Is a function of the concentration of formaldehyde
1n the ambient air surrounding the board. The emission rate will
decrease as the ambient air concentration Increases, and 1t will Increase
as the ambient air concentration decreases.
5.6 Presale Storage (Board Aging)
Aging boards under conditions that promote formaldehyde emission,
before they are sold, has been shown to be an effective option for
controlling consumer exposure. Although this process Is not under active
consideration by EPA at this point, many data are available and reported
1n this section.
Kazakevlcs (1984) performed a five-year study on the effects of board
aging on formaldehyde emission. Soon after manufacture, emissions were
10 to 100 times higher than after five years. Partlcleboards with
emissions of 12 mg/n /hr were tested five years later and emitted 0.1
2
to 1.1 mg/m /hr. Kazakevlcs found that emissions from boards of F:U
1.0 to 1.5 leveled off from high levels of 'free formaldehyde0 to lower
levels of "hydrolysis products* at approximately 12 months. Fluctuations
were attributable to changes 1n the climate 1n which the boards were
stored.
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Nyers (1982b) presented the following testing results of aging on
hardwood plywood board samples. After a 30-day aging at 75aC and 50
percent RH, the mean formaldehyde air concentration 1n a dynamic testing
chamber was reduced by 90 percent (3.0 to 0.31 ppm). After two such
aging periods, the mean concentration dropped by 100 percent (3.0 to
<0.01 ppm or below the detection limit). Twenty-four hour desiccator
tests on similar board samples after Identical aging conditioning showed
a 93 percent reduction 1n formaldehyde emission after only a 15-day aging
period.
Testing results 1n Nyers (1982b) also showed how presale board aging
could be used effectively with other control options, for example,
hardwood plywood board samples treated with a urea-containing surface
coating were measured 1n dynamic testing chambers at a mean value of
0.3 ppm. After one 30-day aging period (75°C and SO percent RH) measured
formaldehyde concentrations were reduced to 0.039 ppm (87 percent
Improvement). In the same study, the combined effect of board aging and
ammonia scavenging was evaluated. In a 24-hour desiccator test, aging
had a much greater Impact on the untreated plywood (3.9 to 0.3 ug/ml or
92 percent Improvement) than on the ammonia treated plywood (0.06 to 0.05
ug/ml or 17 percent Improvement). In the dynamic chamber test,
ammonia-treated plywood samples, Initially measured for very low
formaldehyde emissions (<0.01 ppm), increased slightly after aging. It
was suggested that this Increase was due to a loss of sorbed ammonia
during aging and, thereby, a loss of scavenging capability.
Forlntek (1983) evaluated the effect of board aging on formaldehyde
emission rates from partlcleboard and hardwood plywood. They performed
desiccator tests dally for a period of 60 to 223 days, then plotted the
ln(CH20) vs time. This confirmed that the half-life of partlcleboard
emissions Is around 8 to 9 months, and Indicated that after 60 days of
storage, emissions decline at the rate of 1 percent per day.
212
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5.7 Approaches to Reducing Formaldehyde Emissions from UF Bonded
Wood Products Based on Resin Chemistry
This section basically consists of excerpts from a recent draft
report by H. Podall of EPA's Office of Toxic Substances entitled "A
Review of the State-of-the-Art on Urea Formaldehyde Resins for Wood and
Causes of Formaldehyde Release" (USEPA 1984).
Any approach regarding physical/chemical changes In the resin,
treatment of the board, the curing step, or in the final board treatment
or finishing, aimed at reducing Initial formaldehyde emissions, must also
take Into account the long-term hydrolytlc stability of the resin/wood
composite. Although our understanding of the exact sources and
mechanisms of the releases Is not complete, the following approaches
appear desirable for reducing the long-term, as well as the Initial,
releases of formaldehyde from UF-bonded wood products:
(1) Requirement of lower ratio F:U resins In Imported hardwood
plywood boards, comparable to those products manufactured \u the
U.S.
(2) Storage of resins In dry forms (where storage 1s required) to
reduce the decomposition of the resin to formaldehyde.
(3) Moisture-proofing of furnishes In composition boards or of
veneers 1n hardwood plywood to reduce affinity for moisture.
(4) Minimize or avoid addition of other acidic components (such as
formic acid) to the resin formulation or to the wood, 1n order
to minimize long-term hydrolysis of resin components to
formaldehyde.
(5) Use of a minimum amount of NH4C1 or (NH4)2S04 as acid
catalyst (hardener) for cure.
(6) Production of tighter boards to reduce permeability of moisture
1n board and hence displacement of formaldehyde.
213
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(7) Treatment of cured board with an appropriate base of sufficient
strength (possibly sodium b1carbonete or trlethanolamlne ) to
reduce the free acid concentration In the board to a pH of
about 7.
(B) Coating of edges of board (and both sides - particularly for
composition boards) with a moisture-Impervious coating to reduce
diffusion and escape of formaldehyde, eliminate displacement of
formaldehyde by moisture, and to reduce and/or eliminate mid- to
long-term hydrolysis of various formaldehyde-releasing species.
(9) Use of low F:U mole ratio resins (e.g.. 1:1) which do not
require an add hardener for curing.
(10) Use of veneers for hardwood plywood or furnishes for composition
board whose wood 1s approximately neutral (pH 7).
(11) Use of appropriate external crossllnklng agents, such as
tr1methoxymethylmelam1ne, added to the resin formulation to
facilitate curing (to the desired three-dimensional network)
and/or to obviate the requirement for an acid hardener.
214
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6. FORMALDEHYDE STANDARDS FOR MOOD PRODUCTS AND INDOOR AIR
Many European countries, and recently the United States (through the
Department of Housing and Urban Development), have promulgated standards
that limit formaldehyde emissions from wood products and/or set maximum
allowable Indoor air concentrations for formaldehyde. Table 55 lists the
standards and the associated analytical test methods for determination of
emission potential.
As can be seen 1n the table, the analytical test methods upon which
the standards are based Include chemical extraction (I.e., perforator),
static chambers (JIS and TNO), and dynamic chamber methods. The
oerforator methods vary little among European nations, and the results
are 1n general directly comparable. The static chamber methods are
difficult to Interrelate because of variable testing conditions (Matthews
et al. 1982 Report V.) The dynamic chamber methods are also difficult to
compare because they differ 1n air exchange rate, loading factor,
pre-conditioning of boards, and measurement procedures. In 1978, the
European countries formed an official Technical Committee (CEN TC 91) In
an attempt to develop standardized dynamic chamber test methods and
preconditioning methods that would be used by all countries (Gaudert et
al. 1983). The work of this committee apparently came to a halt In 1983
*
before a standardized method had been developed.
Details on the standards of several countries are presented below.
6.1 Denmark
All pressed-wood products used for construction purposes (e.g.,
particleboard, plywood, waferboard, hardboard. MDF) are governed by the
standards. The maximum allowed perforator value for any board 1s
25 ing/100 g. Any board that Is to be used In places that people
•Personal communication between G. Schweer (USEPA/OTS) and P. Gaudert
(National Research Council of Canada) on October 30, 19B4.
215
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Table SS. International Indoor Air Standards for Formaldehyde and Standards for Formaldehyde
Emission from Pressed Hood Products a
Nation
Belguim
Denmark
Finland
France
Italy
Japan
Netherlands
Norway
Spain
Sweden
Switzerland
United Kingdom
United States
west Germany
Product type
Particleboard
Class 1
Class 2
Class 3
All pressed wood products
All pressed wood prxxfcrts
Parlicleboard
Particleboard
Particleboard
Particleboard
Particleboard
Particleboard
Particleboard
Particleboard
Particleboard
Particleboard
Hardwood plywood
Particleboard (El)
Particleboard (E2)
Particleboard (E3)
Use(s)
Indoor Use
Homes, schools, etc.
Non-home, etc.
Indoor Use
Indoor Use
Government-
subsidized housing
Indoor use
Indoor use
Indoor use
—
—
Mobile homes
Habile homes
Indoor use
Indoor use
Indoor use
Standard or
Guideline c
14mg/IOOg
2Bmg/100g
42 mg/lOOg
0.12 ppm
ZSmg/lOOg
30 mg/100 g (mean)
SO ing/ 100 g (mean)
50 ing/ 100 g
5.0 ugAnl
10 mg/100 g
30 mg/100 g
SO mg/100 g
40 mg/100 g
(under development)
SO mg/100 g (mean)
70 mg/100 g (max.)
0.3 ppm
0.2 ppm
<0.1 ppm
X).l to <1.0 ppm
>1.0 to <2.3 ppm
Standard Indoor air Standard
test method or Guideline0
Perforator
Dynamic chamber 0.12 ppm (law)
Perforator
Perforator 0.12 to 0.24 ppm (guideline)0 •
Perforator
Perforator
0.10 ppm (guideline)
Static JIS method
Perforator 0.10 ppm (guideline)
Perforator
Perforator
Perforator 0.4 ppm (guideline)
- 0.2 ppm4 (law)
Perforator
Perforator
Dynamic chatter
Dynamic C .inter
Dynamic chanter 0.10 ppm (guideline)
Dynamic chanter
Dynamic chanter
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Table 55. Footnotes
'Based on information reported in Qaudert et al. (1983). Matthews et al. (1981-1982 Progress Reports IV, V), and Sundin (1985).
pSee Section 6.2 for additional details.
clisted values are standards in Denmark, Finland, Sweden and the U.S. Listed values for Uest Germany and the Netherlands are guidelines. The legal
status of the listed values for the other countries is uncertain.
^Personal eonnunication between G. Schueer (USEPA) and Or. B. Gfeller (Novopan-Ketler AC), January 22, 1985.
cThe indoor air standards refer to neasurenents conducted under "normal indoor conditions*. The criteria for determining "normal indoor
conditions" vary from country to country but are within the following parameter ranges: temperature - 20 to 24°C; relative humidity - 40 to 601; and air
exchange - 0.5 hr-' (Sundin 1982).
-------
normally Inhabit (e.g., homes, schools) must also either result in an air
level of 0.12 ppm formaldehyde or less 1n the Danish Chamber Test or be
treated 1n a manner approved by the Danish authorities (e.g., surfaces
covered with PVC foils, melamlne paper, veneers, or formaldehyde
absorbing paints) so that the emission value does not exceed 0.32 ppm
(Matthews et al. 1982 Report V) Denmark has also promulgated an Indoor
ambient air strr.dard of 0.12 ppm formaldehyde (Gaudert et ai. 1983).
6.2 Finland
Finland has established an Indoor ambient air guideline of 0.12 ppm
of formaldehyde for new buildings (I.e.. constructed during or after
1983) and 0.24 ppm for old buildings (Nlenela and Topplla 1984).
6.3 Mest Germany
West Germany has a graded product standard 1n place for partlcleboard
used for construction and In kitchen cabinetry. The standard was
Initially a national guideline but has been adopted as local law
throughout the country. Products with formaldehyde chamber values less
than or equal to 0.1 ppm can be used, uncovered, 1n the home; these are
termed El boards. Boards with chamber values ranging from >0.1 to <1.0
ppm, called E2 boards, must have exposed surfaces covered prior to use 1n
homes. Boards with chamber values ranging from >1.0 to <2.3 ppm, E3
boards, can be used only with both surfaces and edges covered. Boards
with chamber values 1n excess of 2.3 ppm cannot be used Indoors (Gaudert
et al. 1983).
6.4 Netherlands
The Netherlands has established an Indoor ambient air formaldehyde
limit value of 0.1 ppm (Gaudert et al. 1983). For schools and houses far
rent the limit value has a legal base. The Netherlands Is 1n the process
of establishing a legally binding product standard for partlcleboard
Including furniture of 10 mg/lOOg (perforator).
218
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6.5 Sweden
In June of 1977, the Swedish government proposed an Indoor ambient
air Interim standard for formaldehyde of 0.4 ppm with a planned final
standard of 0.1 ppm. Apparently, this standard 1s still a proposal and
has not been promulgated. However, the Interim standard Is regarded as
semi-official and remedial measures are required by local building boards
when It is found to be exceeded (Gaudert et al. 1983).
6.6 United States
On August 9, 1984. the U.S. Department of Housing and Urban
Development (HUD) published final regulations limiting formaldehyde
emission from partlcleboard and hardwood plywood used for construction
purposes 1n mobile homes (49 FR 31996). The regulations became effective
on February 9, 1985. Hardwood plywood Is limited to a maximum emission
value of 0.2 ppm by a dynamic chamber method, and partlcleboard 1s
limited to a value of 0.3 ppm.
The American Society of Heating. Refrigerating and A1r Conditioning
3
Engineers (ASHRAC) recommends a Unit of 0.12 mg/m (0.1 ppm) of
formaldehyde 1n Its "Ventilation Standard for Acceptable Indoor Air
Quality" (Standard 62-1981).
219
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7. MODELING FORMALDEHYDE RELEASE FROM PRESSEO-WOOD PRODUCTS AND
EXPOSURE IN RESIDENTIAL SETTINGS
The following sections discuss efforts by CPSC and EPA to model
formaldehyde release from pressed-wood products and subsequent exposure.
Different Investigators and research projects have focused on different
segments of the chain of events that lead to residential formaldehyde
exposure. One Investigator may. In addition, create multiple "modeIs" of
varying complexity and precision.
The first subsection (7.1) describes the ongoing research, funded by
CPSC, designed to produce an accurate predictive model for estimating
formaldehyde exposure due to emissions from pressed-wood products. The
CPSC model 1s the most complex of those discussed herein; 1t Incorporates
algorithms to predict emission, absorption by (and subsequent emission
by) formaldehyde sinks, the effect of numerous products, the decay of
emissions over tine, and the effects of varying environmental conditions
to describe dynamic formaldehyde levels 1n homes.
Section 7.2 describes a simplified version of the CPSC model; 1n this
report, the model 1s termed "Matthew's Steady-State Model." It
Incorporates emission predictions for one or more sources but neglects
sinks. Matthews proposes this model as a tool to compare the relative
Impact of residential formaldehyde sources on Indoor air levels.
Section 7.3 does not discuss a model per se; 1t describes the
mathematical prediction of long-term levels resulting from 'slow*
formaldehyde decay. The substance of this section 1s a
statistically-derived equation that represents the "best-fit* for a large
collection of long-term formaldehyde monitoring data In mobile homes.
Numerous statistical examinations of this data collection are described.
This discussion 1s Included here because It Is a logical extension of the
previously-discussed models. The use of a decay curve such as that
described In Section 7.3 can provide Integrated, long-term exposure
estimates. However, the major disadvantage to this curve 1s that 1t 1s
220
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based on historical monitoring data collected In mobile homes containing
pressed wood products that were not manufactured with the low F/U ratio
resins In use today. Thus. 1t may not accurately reflect the decay rates
of these new resins.
7.1 CPSC Indoor A1r Quality Model
The U.S. Consumer Product Safety Commission (CPSC), through
Interagency agreements with Oak Ridge National Laboratory (ORNL) and the
National Bureau of Standards (NBS) has been developing a sophisticated,
computerized Indoor air quality model to accurately predict expected
formaldehyde levels 1n housing, given the emission source
characterization and the other physical parameters upon which the
concentration 1s based. It 1s anticipated that this model, after Its
development and validation (expected 1n early 1985), will yield Indoor
formaldehyde estimations representative of pressed-wood product loading
scenarios observed In the field. This Is a requirement for accurate
results 1n the subsequent exposure and risk analysis proposed for ongoing
regulatory Investigations.
CPSC has developed and 1s refining computer programs for a
two-compartment model for Indoor air quality based on the "mass balance*
principle. This principle, simply stated, 1s that the mass flow Into and
out of the compartment must be equal and that the rate of change of the
pollutant level 1s determined by the rate of generation and rates of
removal. As 1t 1s described by Mulligan (1983)*. the formaldehyde mass
balance equation calculates the rate of change of the air concentration
1n a single compartment of specific volume by considering the:
Mixing Factor
Formaldehyde contribution from outside air
Filter efficiency of the ventilation system
A1r and pollutant removed from the compartment
Emission source term
Sink term
*Much of this Section (7.1) Is excerpted directly from Mulligan's (1983)
description of the CPSC Indoor A1r Quality Model.
221
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In the two-compartment model, one of the compartments only exchanges
air with the other compartment. This would usually result 1n better
prediction of the concentrations 1n one compartment as opposed to an
average concentration for the whole house. The sophistication of the
model 1s related to the additional factors augmenting the simple mass
balance function. Because formaldehyde emission from pressed wood and
other products Is complex and because formaldehyde Is In equilibrium In
the Indoor air column, one must Incorporate Influential factors Into the
overall model In order to obtain accurate estimates. Three such factors
that will be addressed by the model are non-uniform air Infiltration,
mixing, and air exchange. Other factors that will allow the
sophisticated model to better simulate real life situations (such as
homes of varying ages, homes where sources have been covered or masked,
or homes where disproportionate amounts of sources are found) are
currently being researched In support of the model development.
The Oak Ridge National Laboratory (ORNL) has been conducting
research on the formaldehyde emissions from pressed wood for the CPSC for
the past two years. This research Is specifically designed to support
the development of portions of the CPSC model; for example, the emission
model, barrier model, decay model, etc. The current efforts at ORNL are:
1. Emission characterization of partlcleboard, paneling and MDF
(medium density flberboard), which represents a random sampling
of products produced at the end of 1982.
2. Sorptlon/desorptlon characterization of gypsum wallboard.
3. Decay studies of formaldehyde emission from pressed wood products.
4. The effects of permeation barriers on formaldehyde emission from
partlcleboard.
5. The Inter-laboratory testing of the formaldehyde surface emission
monitor.
222
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In order to predict formaldehyde concentrations In homes, It Is
necessary to have the data upon which a model of these emissions can be
derived and verified. ORNL has developed a chamber test method which
allows the emissions to be measured as a function of temperature,
relative humidity, and background formaldehyde concentration. Using this
method 1t 1s possible to develop sub-models (I.e., equations) for the
emission characteristics of the various pressed wood products. ORNL has
developed two emission models. The current testing Is Intended to
confirm the physical bases for these models and also yield coefficients
representative of the pressed wood products on the market at the end of
1982.
While the pressed wood 1n homes can act as the source of
formaldehyde, the gypsum wallboard can act as a sink which removes
formaldehyde from the air. However, under certain circumstances (e.g.,
reduced background levels of formaldehyde) the sink can Itself become a
source releasing previously absorbed formaldehyde. These actions combine
to make prediction more complex and Interactive, but they make the
resulting real room concentrations less subject to wide variations than
could theoretically result from short- term variations 1n environmental
conditions. ORNL has developed an experiment to characterize the
behavior of wallboard both In the sorptlon and desorptlon cycles.
The emission characteristics of pressed wood vary with time, and
ONRL 1s therefore measuring the emission rate change. Two experiments
are being undertaken. The first, referred to by ORNL as the "fast*
decay. 1s conducted under a low background concentration of formaldehyde
(-0.1 ppm). It 1s expected that this will result In rapid decay of the
emission rate. The second experiment 1s being conducted under a high
(approximately 0.5 ppm) background concentration of formaldehyde. This
experiment Is expected to yield Information on the slow decay of emission
rates.
223
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The emission of formaldehyde from pressed-wood products Is affected
by any coverings over the pressed wood. The effect of these barriers Is
being measured at ORNL 1n a two-part experiment. The first part, which
has already been completed, was a dual desiccator setup for measuring the
transport coefficient. The resulting data Indicate that the rate of
emission from pressed-wood products can be expected to be lowered by the
presence of barriers. The second, ongoing tests are chamber tests using
pressed wood as the source of formaldehyde. In these tests, a teflon
lined chamber 1s placed over the rug/pad/partlcleboard combination, and
the concentration 1n the chamber Is measured. Initial results from these
dynamic tests Indicate that 1n actual use the transport of formaldehyde
through carpets and padding will result in emission rates slightly lower
than Indicated by the desiccator tests. This Is probably due to a
suppression effect at the partlcleboard/pad Interface.
A major element of the successful development of the CSPC Indoor air
quality model 1s Its validation. The National Bureau of Standards (NBS)
has been contracted (under Interagency agreement) to support the research
necessary to validate the model. The focus of their effort Is to
Investigate, experimentally and theoretically, the behavior of
formaldehyde-emitting pressed-wood products In simulated and real homes.
This effort will be used to validate both the ORNL developed pressed-wood
product emission sub-models and the overall Indoor air quality computer
model.
The NBS controlled experiment consists of emission rate
measurements, 1n 4 x 8 x 2 ft teflon chambers, of the various pressed-
wood products to be used In a two compartment, 10 x 20 x 8 ft test
chamber. Both of these measurements are being made 1n a large
environmental chamber capable of maintaining the requisite temperatures
and humidities. Once the emission rate has been determined, the products
will be Installed in the two-compartment chamber, 1n a manner that
simulates their use In a home. A prediction of the expected formaldehyde
224
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concentration will be made, and this prediction will be compared to the
actual measurements. Final modeling adjustments will be made 1n
accordance with these experiments.
7.2 Matthews et al . Simple Steady-State Hodel for Indoor
Formaldehyde Concentrations
Matthews et al. have simplified the CPSC model described In Section
7.1 to evaluate the relative importance of a variety of formaldehyde
emission sources In a single compartment. The following discussion 1s 1n
large part excerpted from Matthews et al. (1983b).
At steady-state, the formaldehyde concentration 1n a single
compartment may be expressed as:
[CH20]SS = [CH20]0 + CK2OER/(C x ACH x VOL) (1)
where
[CH2n]ss = steady-state concentration Inside the compartment (mg/m3),
» steady-state concentration outside the compartment (mg/m3),
CHjOER = the emission rate of formaldehyde sources Inside the
compartment (mg/h) ,
C = the fraction of air coming Into the compartment that mixes within
the volume (I.e.. the mixing factor),
ACH o tne flow rate of air through the compartment 1n compartment volume
per time (hr"1), and
VOL « the volume of the compartment (m3).
The multiplicative product of C and ACH Is termed by Matthews et al. as
PEX, the effective pollutant exchange rate (In units of hr"1).
Equation 1 therefore becomes
[CH20]SS = [CH20]0 + CH2OER/(PEX x VOL) (2)
Application of the model as expressed In Equation 2 1s simplified by
assuming that all parameters In the equation remain constant (at
steady-state) and that there are no permanent losses of formaldehyde due
to Irreversible sorptlon to sinks.
225
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Equation 2 must be rewritten to accomodate the different
characteristics of various sources of formaldehyde emissions; emission
rate expressions are substituted for CHgOER 1n the equation. The three
types of formaldehyde emissions, each of which Is treated somewhat
differently by the model, are:
(1) Solid emission sources In direct contact with Indoor air (such
as hardwood plywood paneling).
(2) Solid emission sources that have a barMer. reducing emission
rate, between the source and the Indoor compartment (for
example, particleboard underlayment with a carpet barrier).
(3) Combustion sources (cigarettes, gas appliances, etc.)
The first two types of sources listed above are area-dependent 1n that
the magnitude of the emission 1s a direct function of the surface area of
the source In the compartnent. The equivalent of Equation 2 for
area-dependent sources 1s
[CH20]SS = [CH20]0 + CH2OER'. Area/(PEX x VOL) (3)
with CHjOER1 1n units of mg/m2hr and area 1n ra2.
The third, combustion sources, may be modeled with Equation 2
(assuming that the emission rate 1s constant over time). The emissions
expressions for the area-dependent sources, both with and without
barriers, are discussed below.
Pick's Law describes the bulk-vapor Interphase at the surface of a
solid emission source. If one assumes that the mass transport
coefficient and the formaldehyde concentration In the bulk phase are
independent of the formaldehyde concentration 1n the vapor phase, the
emission rate of a solid source Is:
226
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CH2OER' ~ -m [CH20]W * b (4)
where
m = the mass transfer coefficient (m/hr)
[CH20]V = the CH20 concentration In the vapor phase (mg/m3)
b = a constant; the emission rate at zero CH20 concentration In
the air (mg/m2hr)
Therefore. Equation 5 (Equations 3 and 4 combined) Is used to calculate
the concentration Inside a single compartment with
-------
CH2OER' = (b-m x [CH2Q]SS)/1 + m/k) (B)
The concentration Inside a single compartment with this type of
source 1s calculated via Equation 9:
[CH20]Ss = fArea/fPEX x VOLn x b * M «• (m/IO x fCHyO^l (9)
1 t (m/K) * m
-------
of formaldehyde levels versus time (with time 1n weeks, months, or
years), an exponential type of decrease, or decay, 1s exhibited (Meyer
and Hermanns 1984a,b; Hyer 19B4b). This 1s termed slow decay, and a
mathematical description of the correlation can-be a valuable predictive
tool for long-term estimates of exposure In residential settings. Models
such as the CPSC model (discussed In Section 7.1) provide a starting
point, or an Initial formaldehyde level; equations derived From the decay
curve Function can Integrate levels over extended time periods.
This section discusses the development of a best-fit decay curve for
a combined data set of formaldehyde observations over time for
representative (I.e., noncomplalnt) homes. The combined data set Is
composed of two surveys, known as the Clayton study and the Wisconsin
study. The following sections describe each data *ct and present results
of statistical data analysis on 4ac
-------
The home age ranges from 0 to 2894 days. Homes less than three years
old had an average formaldehyde level of 0.73 ppm, while homes over three
years old averaged 0.1B ppm. Information was provided on temperature and
humidity conditions. Homes tested were primarily "non-complaint11 homes.
and QA/QC was reportedly good. Figure 25 presents a plot of the data
points as mobile home age (X) versus formaldehyde concentration (Y).
(2) Wisconsin Survey Data. This data set contains 920 data points
from 137 mobile homes; 56 of the original 976 observations were missing
values from lost samples and similar experimental problems. The
formaldehyde levels have been standardized for constant temperature and
relative humidity by the Wisconsin Division of Health. The standardized
concentrations ranged from 0.02 to 2.26 ppm. The mean for the
distribution 1s 0.38 ppm, and the median Is 0.3 ppm. The 75th percentlle
1s 0.51 ppm while the 90th percenllle Is 0.72 ppm. The standard
deviation 1s 0.3 ppm. and the coefficient of variation is 79 percent.
The home ages range from 30 to 3360 days. Homes less than three
years old had an average formaldehyde level of 0.45 ppm, and homes over
three years old averaged 0.15 ppm. Homes tested were primarily
non-complaint homes. Figure 26 presents a plot of the Wisconsin data
points as mobile home age (X) versus formaldehyde concentration (Y).
(3) Aggregated Data (Clayton and Wisconsin). The two data sets
(Clayton and Wisconsin) were combined to obtain a new data set that has
1179 values. The concentrations range from 0.02 to 2.9 ppm. The mean
for this distribution Is 0.43 ppm. the median 1s 0.31 ppm. the 75th
percentlle Is 0.55 ppm. and the 90th percentlle 1s 0.89 ppm. The
coefficient of variation 1s 90.6 percent.
The home age ranges from 0 to 3360 days. Homes less than 3 years old
have an average Formaldehyde level of 0.51 ppm. and homes over three
years old averaged 0.15 ppm.
230
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PLOT OF Y"X LEGEND: A = 1 DBS. B • t ODS. ETC.
I I
3.08 »
I
I A
I
2.75 «
I B
I
2.SO i
I
IB
U
t.25 »
U A A
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t.OO »A
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u
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U A
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'
1.50 |C
i»
10 A A
1.25 »
ICAA B
|OB A A A A
I
1.00 •! AAA A B
IECA
ICA A A
1C A A
0.75 <«F A A
ICAA AA A
IB A A
(AOAA AA A
B.50 «AA A A A AS A
IOC . A
IBA A AAB A AB A
U A • A A BA A AA AA A A
P.2S
-------
PLOT OF Y«X lEGEtO: A s 1 BBS. B » Z DBS, ETC.
Z.25
2.00
1.13
o
-------
Each of the data points has the following characteristics:
• Formaldehyde was measured by the chromotroplc acid method or by
the pararsoanUlne method.
• Each data point Is the average of measurements taken on a
particular day, and the age of the mobile home at the time of
measurement 1s given.
Figure 27 presents a plot of the aggregated data points as mobile home
age (X) versus formaldehyde concentration (Y).
7.3.2 Results of Statistical Analysis of the Decay Function
Based on the three plots (Figures 25, 26, and 27}, It Is clear that
the initial average level of formaldehyde declines with the Increase In
the ages of homes. Consequently, the exponential and power mathematical
models were evaluated to determine the function of the curve that best
describes (or fits) the data.
The evaluation of these models Involved developing several different
statistical approaches for manipulating the data under the exponential
and power laws. The description and results of these statistical
evaluations are detailed 1n Section 7.3.3 of this report. The final
determination was to select the exponential model as the best fit for the
combined data. The resulting decay function follows:
In Y = -.684 - .OOQ65X
Y « e--684 e--G0065X
Y * .504 e -.00065X
7.3.3 Statistical Analysis of Separate and Combined Data Sets
The two models considered to best Fit the available data sets are the
exponential and the power mathematical models.
233
-------
PLOT OF »»X LECEM): A B I DBS, B = 2 OBS. ETC.
V I
3.00 •
I
I A
I
2.75 I
I
I
2.50 •
I
IB
lA
2.25 I A
U A A
I* A
_ I A
§. Z-OO lA A
I A A
S lA
° 1.75 » A
£ lA A A
£ 1C A A
•g I A A
0> 1.50 »C A AA
K) G ' » •
we |AB AA
* ° lo AA B
* 1.25 » AB
^ ICAA A A AA BA
flOBA a M A« A
I A AAC A
•T 1.00 «E AC AAAB BB
1 IGB A A A
t |CA A AAAE* A
Ik 1C A ABBA AABACB A AA
„ 0.75 »DE AA A CB«OB BAB
IDA A ODCBDABFCDBA B A A
*• IB AACBOBBCC6BAC A A A
ICOB AC6CCei eoo «oo 600 eoo 1000 120
X « Age of Mobile Home, Days
igure 27. Plot of Combined Data Set
-------
An exponential model for the regression of Y on X has the form:
y = a ebx
which Is transformed by taking logarithms to obtain
Iny = Ina * bx
setting Y s Iny, A = Ina, Bob. and X = x, produces the linear
expression:
Y = A » BX
used In the analyses.
The power model has the form
Y * a xb.
which 1s transformed by taking logarithms to obtain
Iny a Ina + b Inx
setting y » Iny, A = Ina, B • b, and X = Inx results 1n the linear
expression:
Y . A + BX
used in the analyses.
In both the power and exponential forms, x equals the age of the home (1n
days) and y equals the measured level of formaldehyde 1n the Indoor air
(1n ppm).
The nature of the data and the models considered Indicated, that the
data points for days 0 and 1 significantly deviated from an otherwise
good fit. Consequently, both models were tested with a data set minus
one or both of these days. Two basic types of statistical analyses,
described below, have been performed.
235
-------
(1) Analyses of Individual Observations. For all observations
reported In the three data sets (Clayton, Wisconsin, and the combined
data} the following three analyses were performed:
Analysis 1 - The observations that had 0 age values were excluded.
Analysis 2 - The observations that had 0 or 1 age values were
excluded.
In addition, the original plot of the data set Indicated that 1f the data
set was split at what appeared to be the elbow 1n the curve, two linear
functions, one for each subset, might best describe the entire data set.
Moreover, this split could reflect the cutoff point between the two types
of formaldehyde emission from pressed-wood products. Consequently, a
third analysis would test both curve models and a linear model with the
data split at the value X = 575.
Analysis 3 - The data set (0 and 1 omitted) was split Into two parts,
with regression analysis performed on each.
The results of these three analyses on the various model options are
summarized below and 1n Table 56 and Figure 26 for the Clayton data; 1n
Table 57 and Figure 29 for the Wisconsin data; and in Table 58 and
Figure 30 for the combined data set.
• Analysis of the Clayton Data (zero age values excluded). The R*
(the coefficient of determination) values and the mean square errors
are very close for both models. The probability (0.1499) for
testing the first parameter of the power model shows that It 1s not
significantly different from 0. This means that parameter A • 1.
• Analysis of the Clayton Data (age of zero and 1 excluded!. The
R* values and the mean square errors are very close for the two
models. The probabilities of each model show the significance of
the two parameters.
• Analysis of the Split Clayton Data. For the first data region, the
power model fits slightly better than the others. For the second
data region, all the models fit equally well. The estimates for the
model parameters (A, B) change dramatically from first to second
data regions.
236
-------
Table 56. Results of Statistical Analyses of Clayton Data
Goodness of fit
Hotel Parameter A
Analysis 1 (zero excluded)
Exponential -0.533
Power 0.112
Analysts 2 (zero and 1 excluded)
Exponential -0.53
Power 0.47
Analysis 3 (split data set)
First data region:
Exponential -0.37
Power 0.09
Linear 0.44
Second data region:
Exponential -1.41
Power O.SS
Linear 0.27
Significance9
Yes
Mo
Ves
Yes
Yes
No
Yes
Yes
No
Yes
Parameter B
-0.00076
-0.24
-0.00076
-11.41
-O.COI
-0.16
-O.Oui
00.0002
-(1.32
-0.00005
Significance
Yes
Ves
Yes
Yes
Yes
Vss
Yes
Yes
Ves
Yes
«Eb
.66
.67
.66
.63
.76
.73
.35
.34
.34
.01
R*
.32
.32
.33
.36
.05
.09
.06
.07
.06
.07
•significance determined by the probability level using the T-test cnpared at the 991 level.
fcfean square error.
'Percent of variation explained by model.
-------
PLOT OF Z»X
PLOT OF PRfOHTBX
LEGENDI A » I OBS, B = 2 085.
SYMBOL USED IS •
ETC.
B
oa
2.0 »
I.S
i.o * B
1C
|C AA A
lA A
_ 0.5 «0 AA
t IBB
01 10 A A
ICCAA A A
g 0.0 «HA AAA A
-Z P IFCA A
*J fl JCEA A A
u E ICBA AA A
•g 0 -O.S *CBA AB A A
0» I |AB*A«>» A
g C IAA A ABBBBIBI
o T IAC •
0 * C -1.0 «8A A AAB A
« 0 |A ABA
'S. I A A A A
•<= V lA B A B
•5 A -1.5 «A AB AC
« l •
1 U lA A A
£ E lA A A A
u. -2.0 • B A
e> I*
O I AA A
J lA
• -2.5 • A
-3.0
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IB
-4.0 »
DEP VARIABLE! Z~
SOURCE DP
MODEL I
ERROR 257
C TOTAL 250
ROOT NSE
OEP HEikit
C.V.
VARIABLE OP
IHTERCEP 1
X 1 -0.
SUN OF
SQUARES
79.715957
182.496
262.212
0.642675
-0.92BI61
-90.7693
PARAMETER
ESTIMATE
-0.526906
000766414
MEAN
SQUARE
79.715957
0.71010!
R-SQUARE
AOJ R-Sfl
STANDARD
ERROR
0.064511
.00007233544
f VALUE
112.260
0.3040
0.30IS
T FOR HO I
PARAMETERS
-0. 199
-10.595
PROB>F
0.0001
PROB > ITI
0.0001
0.0001
•• AB
BBIBABB A AA AA
BBBBA A AA
•• ••»
A A «A
A A
ABA
A
AC
A A
A A
B BIBB
•B *H
A A •
AAA A
B
A
A A
A
A
• •
AA
A «A
A
BB
A • •
A
A
A
0 200 400 600 000 1000
X =» Age of Mobile Home. Days
IEOO
1400
1600
ISOO
EOOO
2ZOO
2400
2600
2600
3000
Figure 28. Regression Analysis of Clayton Data - Exponential Model
-------
Table 57. Results or Statistical Analyses of Wisconsin Data
w
w
\o
Goodness of fit
ftxfel
Analysis 1
Exponential
Power
Analysis 2
Exponential
Power
Analysis 3
First data
Exponential
Power
Linear
Parameter A
(zero excluded)
-0.748
2.14
(zero and 1 excluded)
-0.748
Z.14
(split data set)
region
-0.881
-0.568
0.524
Significance
Yes
Ves
Ves
Yes
Yes
No
Yes
Parameter B
-0.0006
-0.531
-0.0005
-0.531
-0.00027
-0.0700
-0.00017
Significance
Ves
Ves
Ves
Yes
No
No
No
"*
.38
.41
.38
.41
.42
.42
.09
R2C
.4
.3
.4
.3
.002
.001
.002
Second data region
Exponential
Power
Linear
-0.732
4.57
0.468
Yes
Yes
Ves
-0.0006
-0.869
-0.0001
Yes
Yes
Yes
.3
.3
.03
.4
.5
.3
NOTE: Analyses 1 and 2 are the same for the Wisconsin data; there were no 0 or 1 age values .
•Significance determined by the probability level using the T-test compared at the 951 level.
t>Mean square error.
cpereent of variation explained by nodel.
-------
PLOT OF Z"X
PLOT OF PREOHT'X
LEGEND: A = I OBSi B
SYMBOL USED IS •
= 1 DBS, ETC.
0.5
0.0
B
i.
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c
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-3.5
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A
A A
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BA A
A AAB A
ABA
A AAABA
A AAA ABAA
A A ACAB B A
A AAA
AABA BABDAOB A AA
AAAA ACBABACAB A B
A ABBBCD BBBACAAA B A A
BCABGDCCBBOBC AAA A
B AAACCBCAOEFAABBBABA A A
AAAAAC CABACCADBBAAA A A
•••A« C BDCBEAAF ACB AA B BA
A B"«C*A COECEAAOA BCAA
ACBAOEFCBAAAE CD
DEP VARIABLE I 2
SOURCE OF
•BOIL |
ERROR 910
C TOTAL 919
ROOT NSE
DIP HCAM
C.V.
VARIABLE OF
(NTERCEP I
* 1 -0.
CACOCFFEBCOAEACAMAA A A A A AA A A
ABBBFOBABBAA A AAA" • A A B AA A AA
AAB CAADBD AEAAB BA ••••A A AA AAAA A 1
BABBC BAD AC A A A «••" A A A AA
SIRI OF MEAN
SQUARES SQUARE F VA
191. 9B1 193.903 51 I.I
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54Z.42S
0.616090 R-SQUARE 0.3!
-1.252734 ADJ R-SQ 0.1!
-49.1796
PARAMETER STANDARD T FOR Ht
ESTIMATE ERROR PARAMETER
-0.74B119 0.030IBO -24.7
000601972 .00002662796 -22.6
A
IA
A A
BA ABB BABDDAAA C A AA A A »A«« A AA BBA A AA A A
A AAA AA A B AA A A A A ••••"•A A AAA ABAA A
A AAAOA AB B A A A A A A«AA" B A A
A A A AA BBA A AAA •••A"A AA AA AB
A A BA AB AA A A A A AA AA BBBA'A A
A
AAA A
A A
A A AAAAAABA A AAA A"" »AABB
AAAAA A A- AAAAA A«»A« A A A
AA AA A BBAAAA
A A A AB A A AB AA AA
AA A A A A A A
A A B
A A AAA A B
B A A
AA A A
A A A
A A A
A A
A
A
A
»
A«»
BA A
A A •«
A •••••
A n'
A
A
A
30 210 390 570 750 930 1110 1290 1470 1650 1030 2010 2190 2370 2550 2730 2910 3090 3270
X a Age of Hoblie Home. Days
Figure 29. Regression Analysts of Wisconsin Data - Exponential Model
-------
Table 58. Results of Statistical Analyses on the Aggregated Data Set
Goodness of fit
Model
Analysis 1
Exponential
POMP
Analysts 2
Exponential
Power
Analysis 3
First data
Exponential
Power
Linear
Parameter A
-0.690
0.598
-0.693
0.92
region
-0.54
0.096
0.441
Significance
Yes
Yes
Yes
Yes
Yes
No
Yes
Parameter B
-0.00064
-0.296
-0.00064
-0.346
-0.001
-0.18
-0.0002T
Significance
Yes
Yes
Yes
Yes
Yes
Yes
No
HSEb
.44
.50
.43
.48
.50
.49
.33
R2C
.4
.3
.4
.3
.1
.1
.001
second data region
Exponential
Power
Linear
-0.85
4.03
0.266
Yes
Yes
Yes
-0.0006
-O.F97
-0.000046
Yes
Yes
Yes
.32
.32
.07
.4
.4
.06
•significance determined by the probability level using the T-test compared at the 95 percent level.
btean square error.
cPercent of variation explained by model.
-------
PLOT OF 2"X
PLOT OF PREOHT»X
UGENDl A = I DBS. B = 2 DBS. ETC.
STHQOL USED IS •
I
a.
§
2
s
§
w
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?
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1.5
1.0 «AA
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I AA* AAA AAB AAA BA A
lA A AA A
-2.5 » AAAA A
AA A A A
A A
B
-1.0 A
A
A A
-1.5
IB
OEP VARIABLE: Z
SOURCE OF
MODE I 1
ERROR 1177
C TOTAl 1178
ROOT USE
OEP MEAN
C.V.
VARIABLE OF
INTERCfP 1
X 1
sun OF
SQUARES
209.045
536.813
025.920
0.675154
-1.101419
-97.164
PARAMETER
ESTIMATE
-0 .604452
-0.000641618
11EAM
SQUARE
209.095
0.4S6103
R-SQUARE
ADJ R-SQ
ST AWARD
ERROR
0.027O66
.00002566457
F VALUE
613.030
0.3500
0.3495
T FOR HOi
PARAMETERS
-24.562
-25.176
PROB'F
O.0001
PROS > ITl
0.0001
0.0001
A
AA
AA A
A AA A AAA A
A AA A AAU
AAAA A AAAABA
••«»• AA AB A
BAA»» AAA BB AA
B A
BA
AA
A
AA
AA
BAA
AA A
A A
A A
ACAAA
AA A«A«B A B AA A A
ABA A ••••A* A C AA ABAAA A
A A AAAA BBBAA A BA A
AA A A A A B AAAA»l»AAC
A A A BA BAA A BA«"»A» A
A AB A A AB B AAA BA •••••A
A A AAA AAAAA
A A A A AAA
A A A C
AA A A A
A AAA
A A
A
A A
A
A
A
A
A
A A
A A A
._«..
ZOO
.-»—
400
__«._
600
000 1000 1200 1400 1600 I BOO 2000 2EOO 2400 2600 2800 3000 3200 3400 3600 3BOO 4000
X » Age of Mobile Home. Days
Figure 30. Regression Analysis or Combined Data Set - Exponential Model
-------
• Analysis of the Wisconsin and Aggregated Data (zero age values
excluded)"The R* value for the exponential model of 0.4 (r »
-.6) is larger than the R2 for the power model of 0.3 (r > -.5).
The mean square error for the exponential model Is less than the
mean square error for the power model.
• Analysis of the Wisconsin and Aggregated Data (age of zero and 1
excluded).The R2 value for the exponential model Is larger than
the R* for the power, and the mean square error for the
exponential model 1s less than the mean square error for the power
model.
• Analysis of Split Wisconsin and Aggregated Data. For the first data
region, both the models fit equally well. For the second data
region, the power model fits better than the exponential.
Splitting the data set did not Improve the fit for any of the models.
even through using two equations for two regions should better describe
the data set (the R values are very small for both regions In the
Clayton data and 1n the first region 1n the Wisconsin data).
From the above discussion and the results of the three analyses, the
exponential curve Is determined to best describe the decay of the average
formaldehyde level in the mobile homes for the entire period.
(2) Analysis of Data Aggregated by Range of Age of Homes at
Observation. An approach to analyzing formaldehyde decay by aggregating
data was reported 1n Cohn (1384). In Conn's approach, the data were
grouped and the average formaldehyde level (or the mid point of each
group) was used 1n subsequent equation derivator). The results of this
approach, as expected, showed a high value of ft (good fit) because
variability (which decreases R2) was reduced by averaging data ranges.
Similar analyses of the Clayton, Wisconsin, and combined data are
described herein. The data are grouped by 10, 25, SO, 100, and 200 day
Intervals, and the average of concentration over these periods 1s used 1n
the mathematical analysis (Table 59 summarizes the results). It Is
obvious that grouping the data creates a better fit line.
243
-------
Table 59. Analysis of Data Grouped in Two Intervals
EXPONENTIAL
Interval , N
daw
0
10
25
50
100
200
1178
159
117
64
32
17
R2
.4
.6
.7
.8
.8
.9
Estimate
a b*10~*
-0.684
-0.683
-0.696
-0.675
-0.641
-0.611
-*.4J
-5.96
-5.66
-5.77
-5.74
-5.78
Sid
error of
estimate
a 5*10-*
.027
.066
.067
.078
.065
.099
2.57
4.05
3.70
4.17
4.53
5.04
POUER
Std error of
R?
.3
.6
.7
.8
.8
.9
Estimate
a b
0.598
1.8
2. IBS
2.449
2.54
2.943
-.296
-0.486
-.535
-.537
-.581
-.634
estimate
a b
.089
.215
.234
.276
.302
.296
.014
.031
.033
.038
.042
.041
-------
Table 59 shows that grouping the data reduces the number of data
observations and greatly Increases the standard errors of the estimates.
2
A model with high standard errors Is unreliable; furthermore, the R
and the estimates change with the changing of the grouping structure
which shows the Instability of modeling by thts approach. The effect of
data grouping 1s especially pronounced at the low age values, where
formaldehyde levels range from 0 ppm to 2.9 ppm.
7.3.4 Conclusion
The exponential model of the full data set. chosen as the best
1
,2
2
description of the decay curve, has an R value of 0.35. This R Is
consistent with that shown for analysis of each data set. Since R
denotes the amount of variability In the values that 1s attributable to
the variables modeled, It Is apparent that the age of the home determines
35 percent of the home formaldehyde level. Other variables (type and
amount of product, other formaldehyde sources, measurement error, etc.)
account for the remaining 65 percent of the level. This confirms the
complexity of formaldehyde emission and the factors that control It.
245
-------
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Everett LH. 1983. Urea formaldehyde foam and formaldehyde emission, UK
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forlntek Canada Corp. 1983. Process Improvement for reducing
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