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                                                                          Final
                       Assessment of Occupational Exposure to Formaldehyde From
                                                        Composite Wood Products

                                           U.S. Environmental Protection Agency
                                      Office of Pollution Prevention and Toxics
                                                   	Chemical Engineering Branch
                                                   	1200 Pennsylvania Avenue NW
                                                          	Washington, DC 20460

                                                                 6 October 2011
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Executive Summary
Introduction

This assessment of the occupational exposure to formaldehyde from composite wood products was developed to support EPA rulemaking under the Formaldehyde Standards for Composite Wood Products Act (FSCWPA).
In July 2010, President Obama signed into law the FSCWPA.  This law is an amendment to TSCA and directs EPA to regulate the formaldehyde emissions from hardwood plywood (HWPW), medium-density fiberboard (MDF), and particleboard (PB).  FSCWPA sets formaldehyde limits equal to the California Air Resources Board (CARB) Airborne Toxic Control Measure (ATCM) promulgated in 2007.  As part of the development of the rule under FSCWPA, EPA is conducting a cost-benefit analysis of implementing the formaldehyde limits cited by FSCWPA.  In support of this cost-benefit analysis, EPA assessed occupational exposure to formaldehyde during the life cycle of HWPW, PB, and MDF.
Purpose and Scope

The purpose of the assessment is, first, the prediction of baseline formaldehyde inhalation and dermal occupational exposures that are due to all sources of exposure (aggregate exposure) during the life cycle of composite wood products (CWPs), and, second, the determination of the effects on baseline exposures of the analytical options for limits on emission levels for off-gassing from HWPW, PB, and MDF.
The baseline occurs in the year in which EPA will promulgate limits under FSCWPA, which will be 2013.  The analytical options consist of the following limits on off-gassing emissions for HWPW, PB, and MDF:
Option 1: emission limits equal to the CARB ATCM Phase 1 limits;
Option 2: emission limits equal to the CARB ATCM Phase 2 limits (which are equal to the limits specified in FSCWPA); and
Option 3: emission limits equal to the no-added formaldehyde (NAF) limits specified in FSCWPA.
The assessed life cycle stages include the following:
      1. Manufacture of HWPW, PB and MDF within the United States (domestic manufacturing);
      2. Manufacture of products constructed with domestically-manufactured and imported HWPW, PB and MDF (secondary products) such as the manufacture of furniture (also referred to as composite wood product fabrication);
      3. Wholesale and retail of domestically-manufactured and imported HWPW, PB, and MDF and downstream products; and
      4. Office building occupancy and associated use of office furniture fabricated with domestically-manufactured and imported HWPW, PB, and MDF.

The following life cycle stages were not assessed due to data gaps in information needed for their assessment: the commercial use of HWPW, PB, and MDF and their secondary products in construction work, and the recycling and disposal of HWPW, PB, and MDF and their secondary products.
Approach

Inhalation exposure monitoring data were compiled for all of the assessed life cycle stages but were not deemed to be adequate for assessment purposes.  Time-weighted average (TWA) inhalation exposure monitoring data for sites in which the manufacture, fabrication, wholesale and retail of the three composite wood products likely occurs were compiled from the OSHA Integrated Management Information System (IMIS) database.  Inhalation exposure monitoring data for office buildings were compiled from EPA's Building Assessment Survey and Evaluation (BASE) study, which was conducted from 1994 through 1998.  As explained in Section 3.2, these monitoring data were deemed not adequate for the assessment of baseline exposures and the effects of the analytical options on baseline exposures, which were assessed using mathematical modeling where possible.  The compiled monitoring data are presented for perspective only.
Baseline average inhalation exposures in composite wood fabrication sites and in office buildings and the effects of analytical options on these inhalation exposures were assessed using mathematical models for the estimation of indoor air concentrations in combination with estimates of exposure duration (the hours of exposure per day) and frequency (the days of exposure per year).  For composite wood fabrication, exposure duration and frequency were estimated using census data on pre-baseline aggregate production hours.
Inhalation exposures in the manufacturing, wholesale, and retail life cycle stages were assessed qualitatively due to gaps in data needed for mathematically modeling indoor air concentration.
Dermal exposures to formaldehyde in liquid mixtures were quantitatively assessed using EPA dermal exposure models for CWP manufacturing for pre-baseline conditions only due to data gaps.  Dermal exposures to CWPs are not quantifiable using the EPA dermal exposure models for liquids and solids and, therefore, dermal exposure was not assessed for the CWP fabrication, wholesale, retail and office occupancy life cycle stages.
For all life cycle stages with the exception of occupancy of office buildings, the number of exposed workers was estimated based on aggregate census data (Census 2007a).  The number of exposed office workers was not determined due to data gaps.  The extent of use of personal protective equipment (PPE) was noted for manufacture and fabrication based on a review of OSHA inspection reports.  However, a limited number of inspection reports were available for review and a conclusion as to the prevalence of the use of respiratory protection in these life cycle stages could not be made.
Average formaldehyde indoor air concentrations in a CWP fabrication site and an office building were estimated using mathematical models that are based on the principle of mass conservation and the assumption that the work space is a well mixed box.  In these steady-state models the generation rate of formaldehyde due to off-gassing from CWPs is equated to the rate at which airborne formaldehyde is exhausted from the work space through ventilation with outdoor air to satisfy a formaldehyde mass balance on the work space.  The generation rate was expressed as the product of a formaldehyde off-gassing emission rate and an amount of emitting surface area.  The formaldehyde off-gassing emission rate was determined from average emission levels for the three composite wood products that would be domestically produced or imported at the baseline (provided in the EPA report Market Profile for Industries Potentially Affected by the Proposed Formaldehyde Standards for Composite Wood Products Rule (USEPA 2010a)) and under the analytical options (provided in the EPA report Formaldehyde from Pressed Wood Products: Exposure Assessment (USEPA 2009b)).
Method for Estimating Average Indoor Air Concentration in CWP Fabrication Sites
As discussed in Section 4.2.1, there are indications that sources of formaldehyde other than the off-gassing of formaldehyde from CWPs may exist in a CWP fabrication site.  Aggregate indoor air concentrations are the sum of the concentration contributed by off-gassing of the three CWPs, the concentration contributed by other formaldehyde sources in the workplace, and the concentration of formaldehyde in ambient outdoor air.  However, the extent to which sources in a CWP fabrication site other than off-gassing of CWP contribute to indoor air concentration in CWP fabrication sites is unknown.  Attempts to develop methods to estimate concentration contributions from other sources during CWP fabrication were not successful due to data gaps.  Therefore, only the contributions from off-gassing of the three CWPs and ventilation with outdoor ambient air were accounted for in the estimation of aggregate indoor air concentration in CWP fabrication sites.
Average indoor air concentration in a CWP fabrication site was calculated from the following mathematical model parameters:
Formaldehyde emission rate (off-gassing emissive flux) of the composite wood products;
Total emitting surface area of the composite wood products located in a CWP fabrication site;
Effective ventilation rate for an entire CWP fabrication site; and
The concentration of formaldehyde in the outdoor air for industrial land use areas.

The mathematical model is described in detail in Appendix E.  The literature search did not yield a CWP fabrication site population distribution for these mathematical model parameters, nor did it yield representative values for these parameters for CWP fabrication sites in general (with the exception of concentration of formaldehyde in the outdoor air).  Due to these data gaps with respect to the model parameters, what-if values for indoor air concentration were estimated.  This what-if analysis was accomplished by estimating the range of possible values for each model parameter (with the exception of outside air concentration) and calculating a range of what-if indoor air concentration values from the estimated ranges of the model parameters as discussed in detail in Section <IP_ADDRESS>.  A range of what-if indoor air concentration values was calculated assuming a CWP fabrication site contains only a single CWP type.  Each model parameter (except for outside air concentration) was varied between the two bounding values of its range (the low- and high-end values) while keeping the other model parameters constant at an average, a typical, or an intermediate value.  Section <IP_ADDRESS> describes in detail how an average, a typical, or an intermediate value was determined for each model parameter.  In this assessment report, an intermediate value is defined as a value in-between a low-end and high-end value.  This computational procedure resulted in three different low-end indoor air concentration values and three different high-end indoor air concentration values.  The broadest range of these calculated low- and high-end values constitutes a range of values for calculated indoor air concentration for a single CWP that is intended to be a broad range that accounts for uncertainty in coinciding values for the model parameters.  An indoor air concentration value was also calculated from the average, typical, or intermediate value of each model parameter.  These calculations were repeated for each CWP type: HWPW, PB, and MDF.
The low-end values of calculated indoor air concentrations for all three CWP types (a total of nine low-end values) were combined into a single range of low-end indoor air concentration values.  The same procedure was followed for the high-end values for all three CWP types, thereby yielding a single range of high-end values.  Finally, the intermediate values of indoor air concentration for each CWP type were also combined into a single range of intermediate values.  Therefore, three ranges of indoor air concentration values (one for low-end values, one for intermediate values, and one for high-end values) were obtained that account for any mixture of the different CWP types in a CWP fabrication site.
A final range of results for indoor air concentration was obtained by combining these three ranges into a single encompassing range and a best estimate for indoor air concentration was chosen as the midpoint of this overall range as discussed in Section <IP_ADDRESS>.  The resulting values in the estimated range for average indoor air concentration at a CWP fabrication site are characterized as what-if results because each concentration value in this range corresponds to combination of choices, or what-if values, for the model parameters.  Although the prevalence of the what-if values for each model parameter at actual CWP fabrication sites is unknown, the ranges of the model parameter values should be realistic such that any given choice, or what-if value, for any model parameter represents a possible value at actual CWP fabrication sites.
Method for Estimating Average Indoor Air Concentration in Office Buildings
Indoor air concentration in office buildings was estimated using a mathematical model for estimation of indoor air concentration resulting from off-gassing emissions from office workstations fabricated with the three CWPs.  This mathematical model was applied to two different office workstation types: open plan workstations and private office workstations.  Average indoor air concentration in an office building was calculated for each workstation type from the following mathematical model parameters:
Emitting surface area of panels in the workstation;
Emitting surface area of work surfaces in the workstation;
The outdoor air ventilation rate that affects the volume of the office building containing the workstation;
Emission rate (emissive flux) of the composite wood products used to construct the workstation panels and work surfaces;
The fraction of the panels' surface area that is finished, or overlayed, and the effectiveness of this finish or overlay as a barrier to off-gassing emissions from the CWP substrate;
Fraction of the work surfaces' surface area that is finished, or overlayed, and the effectiveness of this finish or overlay as a barrier to off-gassing emissions from the CWP substrate; and
Concentration of formaldehyde in the outdoor air for commercial land use areas.

The mathematical model is described in detail in Appendix E.  Representative values for the emitting surface area of each workstation component (panel and work surface) and the work space ventilation rate were obtained from the Business and Institutional Furniture Manufacturer's Association (BIFMA) / American National Standards Institute (ANSI) M7.1-2007 standard test method.  The workstation component emission rates were estimated using CWP emission rates in combination with the extent of finishing or overlay on a workstation component and the reduction in the emission rate of the CWP due to the finish or overlay acting as a barrier to off-gassing emissions.
Information was not identified on the relative amounts of the three CWPs used in the fabrication of office workstations, representative values for the extent to which the workstation components are finished or overlayed, and the barrier effectiveness of the finish or overlay.  Due to these data gaps in information on representative values for these model parameters, what-if values for indoor air concentration were estimated.  What-if values for indoor air concentration were estimated by first estimating the range of possible values for the following parameters: extent of finishing or overlay of each workstation component and the barrier effectiveness of the finishing or overlay.  Next, these estimated ranges of parameter values were used in combination with the range of CWP emission rates obtained from the EPA reports mentioned above and the representative values for the remaining model parameters to estimate a range of what-if values for indoor air concentration in an office building due to each workstation type.  A range of what-if indoor air concentration values was calculated assuming a workstation consists of only a single CWP type.  Low and high ends of the range of what-if average formaldehyde indoor air concentrations in the building volume containing a workstation were estimated using the mathematical model and (1) the bounding values of the range of values for the model parameters for which ranges were estimated and (2) the representative values of the remaining model parameters so as to obtain a wide range of indoor air concentration.  Additionally, an intermediate what-if value of indoor air concentration was calculated using average or intermediate values for the model parameters for which ranges were estimated and the representative values of the remaining model parameters.  Section <IP_ADDRESS> describes in detail how an average or intermediate value was determined for each model parameter.  In this assessment report, an intermediate value is defined as a value in-between a low-end and high-end value.
These calculations were repeated for each CWP type: HWPW, PB, and MDF, thus resulting in nine values of what-if indoor air concentrations for each workstation type (a low-end, high-end, and intermediate value of what-if indoor air concentration for each of the three CWP types).  These values were then aggregated into low-end ranges, intermediate ranges, and high-end ranges to account for various mixtures of the different CWP types in each office workstation type.  The best estimate concentration was calculated as the average of the following two values: the midpoint of the intermediate range for open plan workstations and the midpoint of the intermediate range for private office workstations as discussed in Section <IP_ADDRESS>.
These calculated indoor air concentrations are initial steady-state concentrations resulting from off-gassing of office workstations fabricated from new CWPs.  Temporal decay in emission rates from the CWPs was not accounted for due to data gaps in information necessary for the modeling of the temporal decay of CWP emission rates in office buildings.
Results

The results for each assessed life cycle stage are summarized below.
Results for Manufacturing

At baseline, approximately all domestic production of HWPW, MDF, and PB will be in compliance with the CARB ATCM Phase 2 standard.  Only small fractions of HWPW and PB domestic production will not be in compliance with the CARB ATCM Phase 2 standard at baseline.  Hence, the CARB Phase 1 and FSCWPA/CARB Phase 2 analytical options will result in a negligible effect on baseline exposure levels for manufacturing.  Since approximately all domestic production of CWPs are expected to meet the CARB ATCM Phase 2 standard at baseline, only the NAF analytical option will affect baseline exposures.
NAF resins do not contain any formaldehyde.  Therefore, mills that use NAF resins in compliance with NAF standards should achieve a reduction in formaldehyde exposures due to the elimination of the formaldehyde content of resins.  However, wood naturally emits formaldehyde, and it is possible that workers in mills that use only NAF resins may still experience some formaldehyde exposures due to the natural emission of formaldehyde from wood.  Other sources of formaldehyde can exist for mills that apply value-added surfaces.  However, it is uncertain how many mills apply value-added surfaces.
Dermal exposures to workers during manufacturing can occur during unloading of liquid UF resin.  For the purpose of this assessment, EPA assumes a formaldehyde concentration of 0.59% in the UF resin.  The EPA/OPPT 2-Hand Dermal Contact with Liquid Model estimates a dermal exposure of 590 to 1,800 mg/day for exposure to a chemical at 100% concentration.  For the assumed formaldehyde concentration of 0.59%, the model estimates worker exposure of 3.5 to 10.6 mg/day.  This results in an estimated dose of 0.05 to 0.15 mg/kg/day for an average 70 kg worker.  It is uncertain how the free formaldehyde content of CWP resins will change as manufacturers adopt the CARB ATCM limits.  Therefore, both baseline dermal exposures and the effect of analytical options on baseline dermal exposures are uncertain and cannot be estimated.
Results for CWP Fabrication

The results of the assessment of indoor air concentrations in CWP fabrication sites at the baseline and the effect of the analytical options on baseline indoor air concentrations are presented in Table ES-1 through Table ES-4.  Table ES-2 provides a summary of the estimates of average indoor air concentration in a CWP fabrication site due to off-gassing from the three CWP types as a range of values and as a single best estimated value for the baseline and the analytical options.  Tables ES-3 and ES-4 provide average daily concentration (ADC) and lifetime average daily concentration (LADC) values, respectively, that correspond to the values given in Table ES-2.  The results show that the maximum formaldehyde indoor air concentration decreases as lower (more stringent) emission standards are implemented.  However, the CARB ATCM Phase 1 analytical option would result in little or no reduction in exposure from the baseline year because most composite wood products are expected to be already meeting more stringent standards by the baseline year (2013).  The minimum indoor air concentration is identical for all of the different analytical options because a small portion of the market is expected to be already meeting the NAF standards at the baseline.  The emission levels of NAF-compliant composite wood products were assumed to remain unchanged and not be affected by the analytical options.
Results for Wholesale and Retail

The formaldehyde concentration resulting from off-gassing is expected to decrease with the implementation of more stringent regulations.  However, as discussed previously, CARB ATCM Phase 1 analytical option would result in little or no reduction in exposure from the baseline year.  This effect is because most composite wood products in the market would already be meeting more stringent limits by 2013.
Results for Office Buildings

The results of the assessment of indoor air concentrations in office buildings at the baseline and the effect of the analytical options on baseline indoor air concentrations are presented in Table ES-5 through Table ES-8.  Table ES-5 provides for the baseline and each of the analytical options the three ranges of estimated indoor air concentration in an office building for each of the two types of office furniture workstations.  Tables ES-6 and ES-7 provide average daily concentration (ADC) and lifetime average daily concentration (LADC) values, respectively, that correspond to the values given in Table ES-5.  Table ES-8 presents the best estimated indoor air concentration values from among the results presented in Table ES-5.  Similarly as with the CWP fabrication results, the office building results show that the maximum formaldehyde indoor air concentration decreases as lower (more stringent) emission standards are implemented.  Again, the minimum indoor air concentrations remain constant throughout the different analytical options due to the presence of NAF-compliant products at the baseline.  The office building results in Table ES-8 show the most significant reduction in indoor air concentration from the NAF emission limits.

Table ES-1. Estimated Low-End, Intermediate, and High-End Ranges of Values for the Site-Average Indoor Air Concentration for CWP Fabrication at the Baseline and for the Analytical Options
                                     Case
                              Intermediate (ppm)
                                 Low End (ppm)
                                High End (ppm)
Baseline
                               0.0095  -  0.0181
                               0.0055  -  0.0092
                               0.0218  -  0.3934
Phase 1
                      0.0077 (-18.8%)  -  0.0176 (-2.7%)
                        0.0054 (-3.2%)  -  0.0092 (0%)
                      0.0111 (-49.3%)  -  0.3787 (-3.7%)
FSCWPA / Phase 2
                      0.0072 (-23.5%)  -  0.0175 (-3.2%)
                        0.0053 (-4.0%)  -  0.0092 (0%)
                      0.0084 (-61.5%)  -  0.3763 (-4.3%)
NAF
                      0.0064 (-32.0%)  -  0.0110 (-39.3%)
                        0.0052 (-5.5%)  -  0.0092 (0%)
                      0.0064 (-70.5%)  -  0.1807 (-54.1%)

Table ES-2. Estimated Overall Range and Best Estimate for the Site-Average Indoor Air Concentration for CWP Fabrication at the Baseline and for the Analytical Options
                                     Case
                              Overall Range (ppm)
                                Best Estimate
                             Concentration1 (ppm)
                                Reduction from
                                 Baseline (%)
Baseline
                               0.0055  -  0.3934
                                    0.1995
                                      --
Phase 1
                               0.0054  -  0.3787
                                    0.1920
                                     -3.7
FSCWPA / Phase 2
                               0.0053  -  0.3763
                                    0.1908
                                     -4.3
NAF
                               0.0052  -  0.1807
                                    0.0930
                                     -53.4
                        [1] The best estimate concentration is the midpoint of the overall range. The overall range is defined as the low-end value from the low-end range and the high-end value from the high-end range. The reduction from baseline, ADC, and LADC values are calculated from the best estimate concentration value.

Table ES-3. Overall Range and Best Estimate ADC for CWP Fabrication at the Baseline and for the Analytical Options
                                     Case
                           Overall Range (ug/m[3])
                         Best Estimate ADC (ug/m[3])
Baseline
                                1.556  -  110.4
                                     56.0
Phase 1
                                1.506  -  106.3
                                     53.9
FSCWPA / Phase 2
                                1.494  -  105.6
                                     53.5
NAF
                                1.471  -  50.71
                                     26.1

Table ES-4. Overall Range and Best Estimate LADC for CWP Fabrication at the Baseline and for the Analytical Options
                                     Case
                           Overall Range (ug/m[3])
                         Best Estimate LADC (ug/m[3])
Baseline
                               0.8894  -  63.08
                                     32.0
Phase 1
                               0.8607  -  60.72
                                     30.8
FSCWPA / Phase 2
                               0.8536  -  60.34
                                     30.6
NAF
                               0.8407  -  28.98
                                     14.9

Table ES-5. Summary of Formaldehyde Indoor Air Concentrations for Office Buildings at the Baseline and for the Analytical Options
                            Open Plan Workstations
                                     Case
                              Intermediate (ppm)
                                 Low End (ppm)
                                High End (ppm)
Baseline
                                0.0265 - 0.0732
                                0.0035 - 0.0053
                                0.2002 - 1.0089
Phase 1
                       0.0167 (-37.0%) - 0.0705 (-3.7%)
                           0.0035 (0%) - 0.0053 (0%)
                       0.0729 (-63.6%) - 0.2833 (-71.9%)
FSCWPA / Phase2
                       0.0143 (-46.0%) - 0.0701 (-4.2%)
                           0.0035 (0%) - 0.0053 (0%)
                       0.0414 (-79.3%) - 0.167 (-83.4%)
NAF
                       0.0099 (-62.6%) - 0.0346 (-52.7%)
                           0.0035 (0%) - 0.0053 (0%)
                       0.0184 (-90.8%) - 0.0728 (-92.8%)
                          Private Office Workstations
                                     Case
                              Intermediate (ppm)
                                 Low End (ppm)
                                High End (ppm)
Baseline
                                0.013 - 0.0332
                                0.003 - 0.0036
                                0.0719 - 0.3555
Phase 1
                        0.0087 (-33.1%) - 0.032 (-3.6%)
                           0.003 (0%) - 0.0036 (0%)
                       0.0273 (-62.0%) - 0.1011 (-71.6%)
FSCWPA / Phase2
                       0.0077 (-40.8%) - 0.0318 (-4.2%)
                           0.003 (0%) - 0.0036 (0%)
                       0.0163 (-77.3%) - 0.0603 (-83.0%)
NAF
                       0.0058 (-55.4%) - 0.0165 (-50.3%)
                           0.003 (0%) - 0.0036 (0%)
                       0.0082 (-88.6%) - 0.0273 (-92.3%)
                  Note: Values in parentheses are the percent reductions in the indoor air concentration from the baseline value.

Table ES-6. Summary of Formaldehyde Exposure Concentrations for Office Buildings as Average Daily Concentrations at the Baseline and for the Analytical Options
                            Open Plan Workstations
                                     Case
                            Intermediate (ug/m[3])
                              Low End (ug/m[3])
                              High End (ug/m[3])
Baseline
                                 7.44 - 20.54
                                  0.98 - 1.49
                                 56.17 - 283.1
Phase 1
                                 4.69 - 19.78
                                  0.98 - 1.49
                                 20.46 - 79.49
FSCWPA / Phase 2
                                 4.01 - 19.67
                                  0.98 - 1.49
                                 11.62 - 46.86
NAF
                                  2.78 - 9.71
                                  0.98 - 1.49
                                 5.16 - 20.43
                          Private Office Workstations
                                     Case
                            Intermediate (ug/m[3])
                              Low End (ug/m[3])
                              High End (ug/m[3])
Baseline
                                  3.65 - 9.32
                                  0.84 - 1.01
                                 20.17 - 99.75
Phase 1
                                  2.44 - 8.98
                                  0.84 - 1.01
                                 7.66 - 28.37
FSCWPA / Phase 2
                                  2.16 - 8.92
                                  0.84 - 1.01
                                 4.57 - 16.92
NAF
                                  1.63 - 4.63
                                  0.84 - 1.01
                                  2.30 - 7.66

Table ES-7. Summary of Formaldehyde Exposure Concentrations for Office Buildings as Lifetime Average Daily Concentrations at the Baseline and for the Analytical Options
                            Open Plan Workstations
                                     Case
                            Intermediate (ug/m[3])
                              Low End (ug/m[3])
                              High End (ug/m[3])
Baseline
                                 4.25 - 11.74
                                  0.56 - 0.85
                                 32.1 - 161.8
Phase 1
                                  2.68 - 11.3
                                  0.56 - 0.85
                                 11.69 - 45.42
FSCWPA / Phase 2
                                 2.29 - 11.24
                                  0.56 - 0.85
                                 6.64 - 26.78
NAF
                                  1.59 - 5.55
                                  0.56 - 0.85
                                 2.95 - 11.67
                          Private Office Workstations
                                     Case
                            Intermediate (ug/m[3])
                              Low End (ug/m[3])
                              High End (ug/m[3])
Baseline
                                  2.08 - 5.32
                                  0.48 - 0.58
                                11.53  -  57.00
Phase 1
                                  1.39 - 5.13
                                  0.48 - 0.58
                                 4.38 - 16.21
FSCWPA / Phase 2
                                  1.23 - 5.10
                                  0.48 - 0.58
                                  2.61 - 9.67
NAF
                                  0.93 - 2.65
                                  0.48 - 0.58
                                  1.31 - 4.38

Table ES-8. Summary of Best Estimate Results for Office Buildings at the Baseline and for the Analytical Options
                                     Case
                      Best Estimate Concentration1 (ppm)
                          Reduction from Baseline (%)
                                 ADC (ug/m3)
                                 LADC (ug/m3)
Baseline
                                    0.0365
                                      --
                                     10.23
                                     5.85
Phase 1
                                    0.0320
                                     -12.3
                                     8.97
                                     5.13
FSCWPA / Phase 2
                                    0.0310
                                     -15.1
                                     8.69
                                     4.97
NAF
                                    0.0167
                                     -54.2
                                     4.69
                                     2.68
                              [1] The best estimate concentration is the average of the following two values: the midpoint of the intermediate range for open plan workstations and the midpoint of the intermediate range for private office workstations. The reduction from baseline, ADC, and LADC values are calculated from the best estimate concentration value.

Uncertainties

There is uncertainty in the values of the parameters of the mathematical model for the estimation of average indoor air concentration in a CWP fabrication site.  In particular, as discussed in Section <IP_ADDRESS>, there is considerable uncertainty in the range of values for emitting surface area, and some uncertainty in the range of values for effective ventilation rate.  Therefore, there is uncertainty in the calculated range of baseline indoor air concentration.  It is not possible to determine the direction of uncertainty (i.e., whether the estimated values for indoor air concentration are an underestimate or an overestimate).  Furthermore, as discussed above, if sources other than off-gassing from CWPs are present in a CWP fabrication site, then the calculated indoor air concentrations would not be representative of aggregate indoor air concentrations.
The composition of composite wood products used in office furniture was not determined and, therefore, panels and work surfaces of office workstations were assumed to be entirely composed of CWPs.  Furthermore, the type and extent of coverage by finishing or overlay materials on the CWPs used to fabricate office workstations were also not determined, and a range of values was assumed for these parameters.  This assumption introduces uncertainty into the calculated indoor air concentrations.  Furthermore, the mathematical model for the estimation of indoor air concentrations in an office building simplifies the complex nature of office building ventilation systems.  Typically in these systems, outdoor air is mixed with a recirculation stream of indoor air prior to being supplied to the various ventilation zones.  The return air from these ventilation zones is mixed and then a stream is split for recirculation and mixing with the outdoor air while the balance is exhausted.  Therefore, the office environment model neglects the effect of one exposure zone on another resulting from the recirculation of indoor air or the movement of air directly between exposure zones without passing through the ventilation system.  The uncertainty in the results due to neglecting the effect of one exposure zone on another is uncertain and cannot be quantified without a detailed, rigorous mathematical model with detailed supporting monitoring data.  It is not possible to determine the direction of uncertainty in the estimated results for indoor air concentration in office buildings.

                               Table of Contents

1.	Introduction	1
2.	Purpose and Scope of Exposure Assessment	1
2.1	Manufacturing	9
2.2	Composite Wood Product Fabrication	9
2.3	Wholesale	10
2.4	Retail	10
2.5	Commercial Use	10
2.6	Disposal and Recycle	10
3.	Exposure Assessment Method	11
3.1	Literature Search	12
3.2	Compilation of Pre-Baseline Exposure Monitoring Data	13
3.3	Exposure Assessment Methods and Assumptions	17
3.3.1	Estimation of Indoor Air Concentrations Related to Baseline and Analytical Options for CWP Fabrication and Office Buildings	18
<IP_ADDRESS>	Method for Estimation of Indoor Air Concentration for CWP Fabrication	19
<IP_ADDRESS>	Method for Estimation of Indoor Air Concentration for Office Buildings	27
3.3.2	Estimation of Dermal Exposures to Formaldehyde in Liquid Resin	37
4.	Exposure Assessment By Life Cycle Stage	37
4.1	Exposure Assessment for Manufacturing	37
4.1.1	Description of Life Cycle Stage	37
4.1.2	Production Volumes and Number of Establishments, Workers, Production Hours, and Work Days	41
4.1.3	Pre-Baseline Exposure Monitoring Data	43
4.1.4	Respiratory Protection Usage During Manufacturing	47
4.1.5	Baseline Exposure and the Effect of Analytical Options on Baseline Exposure for Manufacturing	48
4.1.6	Dermal Exposures during Manufacturing	49
4.2	Exposure Assessment for Composite Wood Product Fabrication	50
4.2.1	Description of Life Cycle Stage	50
4.2.2	Number of Establishments, Workers, Production Hours, and Work Days		53
4.2.3	Pre-Baseline Exposure Monitoring Data	57
4.2.4	Respiratory Protection Usage During Composite Wood Product Fabrication	57
4.2.5	Baseline Exposure and the Effect of Analytical Options on Baseline Exposure for Composite Wood Product Fabrication	59
<IP_ADDRESS>	Results for Indoor Air Concentration Calculation Trials and Sensitivity Analysis	59
<IP_ADDRESS>	Estimation of a Range of Values for the What-If Low-End and the What-If High-End Indoor Air Concentrations that Account for All CWP Types	60
<IP_ADDRESS>	Final Results for the Estimation of What-If Indoor Air Concentrations	61
<IP_ADDRESS>	The Assessment of Exposure Level for the Baseline and the Analytical Options	63
4.2.6	Dermal Exposures during Composite Wood Product Fabrication	69
4.3	Exposure Assessment for Wholesale	69
4.3.1	Description of Life Cycle Stage	69
4.3.2	Use Volumes and Number of Establishments, Employees, Employed Hours, and Work Days	69
4.3.3	Pre-Baseline Exposure Monitoring Data	70
4.3.4	Baseline Exposure and the Effect of Analytical Options on Baseline Exposure for Wholesale	71
4.3.5	Dermal Exposures during Wholesale	71
4.4	Exposure Assessment for Retail	71
4.4.1	Description of Life Cycle Stage	71
4.4.2	Use Volumes and Number of Establishments, Employees, Employed Hours, and Work Days	72
4.4.3	Pre-Baseline Exposure Monitoring Data	73
4.4.4	Baseline Exposure and the Effect of Analytical Options on Baseline Exposure for Retail	75
4.4.5	Dermal Exposures during Retail	75
4.5	Exposure Assessment for Office Workers during Commercial Use	75
4.5.1	Description of Life Cycle Stage	75
4.5.2	Use Volumes and Number of Establishments, Employees, Employed Hours, and Work Days	75
4.5.3	Pre-Baseline Exposure Monitoring Data	76
4.5.4	Baseline Exposure and the Effect of Analytical Options on Baseline Exposure for Office Buildings	77
<IP_ADDRESS>	Determination of a Best Estimate for Indoor Air Concentration	77
4.5.5	Dermal Exposures during Commercial Use	81
5.	Uncertainties In Assessment Results	82
5.1	Uncertainties in Assessment Results for Composite Wood Product Manufacturing, Fabrication, Wholesale, Retail, and Office Buildings	82
5.1.1	Uncertainty in the Estimates of Indoor Air Concentration for Composite Wood Product Fabrication	82
5.1.2	Uncertainty in the Estimates of Indoor Air Concentration for Office Buildings	83
5.2	Uncertainties in Pre-Baseline Monitoring Data	84
5.2.1	OSHA IMIS Data	84
5.2.2	BASE Study Monitoring Data	92
5.3	Uncertainty in Number of Production Workers and Employees	93
6.	References	94

Appendix A: Definition of Terms
Appendix B: Data Quality Acceptance Criteria Specifications
Appendix C: Existing Formaldehyde Occupational Exposure Limits and Formaldehyde Off-Gassing Emission Standards for Composite Wood Products
Appendix D: Formaldehyde CWP Off-Gassing Emission Level Data for the Pre-Baseline Period, Baseline, and the Analytical Options
Appendix E: Modeling Methodology for Estimating Indoor Air Concentrations Related to Baseline and Analytical Options
Appendix F: Pre-Baseline Formaldehyde Exposures from OSHA IMIS by Worker Activity and Industry Sector for Composite Wood Product Fabricators
Appendix G: Summary of OSHA Inspection Reports
Appendix H: Summary of Additional Exposure Monitoring Data from Manufacturing
Appendix I: Model Results for Indoor Air Concentrations at CWP Fabrications Sites using Pre-Baseline Emission Rates
                                List of Tables

Table ES-1. Estimated Low-End, Intermediate, and High-End Ranges of Values for the Site-Average Indoor Air Concentration for CWP Fabrication at the Baseline and for the Analytical Options	viii
Table ES-2. Estimated Overall Range and Best Estimate for the Site-Average Indoor Air Concentration for CWP Fabrication at the Baseline and for the Analytical Options	viii
Table ES-3. Overall Range and Best Estimate ADC for CWP Fabrication at the Baseline and for the Analytical Options	viii
Table ES-4. Overall Range and Best Estimate LADC for CWP Fabrication at the Baseline and for the Analytical Options	ix
Table ES-5. Summary of Formaldehyde Indoor Air Concentrations for Office Buildings at the Baseline and for the Analytical Options	ix
Table ES-6. Summary of Formaldehyde Exposure Concentrations for Office Buildings as Average Daily Concentrations at the Baseline and for the Analytical Options	x
Table ES-7. Summary of Formaldehyde Exposure Concentrations for Office Buildings as Lifetime Average Daily Concentrations at the Baseline and for the Analytical Options	xi
Table ES-8. Summary of Best Estimate Results for Office Buildings at the Baseline and for the Analytical Options	xi
Table 2-1.  NAICS Industry Sectors Identified for the Life Cycle Stages of HWPW, MDF, and PB	6
Table 3-1.  Pre-Baseline Formaldehyde Emission Levels for Domestically-Produced Composite Wood Products	15
Table 3-2. Summary of What-If Method for the Estimation of the What-If Range of Average Indoor Air Concentrations of Formaldehyde at CWP Fabrication Sites	21
Table 3-3. Matrix of Ventilation Rates and Mixing Factors	22
Table 3-4. Estimated Values for Parameters in the Mathematical Model for Average Indoor Air Concentration at a CWP Fabrication Site for the Baseline and the Analytical Options	26
Table 3-5. Data Sources for the Estimation of Parameters of the Mathematical Model for Average Indoor Air Concentration at a CWP Fabrication Site	27
Table 3-6. Summary of What-if Method for the Estimation of the What-if Range of Average Indoor Air Concentrations of Formaldehyde in Workstation Volumes	30
Table 3-7. Comparison of ASTM E1333 Parameter Values with Typical Office Environment Properties	33
Table 3-8. Estimated Values for Parameters in the Mathematical Model for Average Indoor Air Concentration Resulting from Emissions from Private Office and Open Plan Workstations for the Baseline and Analytical Options	34
Table 4-1.  U.S. Hardwood Plywood Production Data and Number of Mills	42
Table 4-2.  U.S. Reconstituted Wood Product Production Data and Number of Mills	43
Table 4-3.  Summary of 2007 Economic Census Data and Exposure Frequency and  Duration Calculated from These Data for U.S. Manufacturing Mills	43
Table 4-4.  Summary of Formaldehyde Inhalation Monitoring Data for Hardwood Plywood Manufacturing Mills from the OSHA IMIS Database	44
Table 4-5.  Summary of Formaldehyde Inhalation Monitoring Data for Reconstituted Wood Product Manufacturing Mills from the OSHA IMIS Database	45
Table 4-6.  Summary of 2007 Economic Census Data and Exposure Frequency and Duration Calculated from These Data for Composite Wood Product Fabricating Sites	54
Table 4-7.  Summary of All IMIS TWA Personal Monitoring Data for Industries Within the CWP Fabricator Life Cycle Stage	57
Table 4-8. Results for the Calculation Trials for the What-If Low- and High-End Baseline Indoor Air Concentrations	64
Table 4-9. Results for the Calculation Trials for the What-If Low- and High-End CARB Phase 1 Indoor Air Concentrations	65
Table 4-10. Results for the Calculation Trials for the What-If Low- and High-End FSCWPA / CARB Phase 2 Indoor Air Concentrations	66
Table 4-11. Results for the Calculation Trials for the What-If Low- and High-End NAF Indoor Air Concentrations	67
Table 4-12.  Estimated Low-End, Intermediate, and High-End Ranges of Values for the Site-Average Indoor Air Concentration at the Baseline and for the Analytical Options	67
Table 4-13. Estimated Overall Range and Best Estimate Site-Average Indoor Air Concentration at the Baseline and for the Analytical Options	68
Table 4-14. Overall Range and Best Estimate ADC at the Baseline and for the Analytical Options	68
Table 4-15. Overall Range and Best Estimate LADC at the Baseline and for the Analytical Options	68
Table 4-16.  Summary of 2007 Economic Census Data for Wholesale Facilities	70
Table 4-17. Summary of Formaldehyde Inhalation Monitoring Data for Wholesalers from the OSHA IMIS Database	71
Table 4-18.  Summary of 2007 Economic Census Data for Retail Facilities	73
Table 4-19.  Summary of Formaldehyde Inhalation Monitoring Data for Retailers from the OSHA IMIS Database	74
Table 4-20.  Overview of General Characteristics of the 100 BASE Buildings	76
Table 4-21.  Summary of Formaldehyde Inhalation Monitoring Data for Office Occupational Settings and Outdoor Measured Concentrations from the BASE Study	76
Table 4-22.  Results for Calculation of What-If Indoor Air Formaldehyde Concentrations for Each Analytical Option	79
Table 4-23.  Combined (for All CWP) Results: Calculated What-If Indoor Air Concentrations at the Baseline and for the Analytical Options	80
Table 4-24.  Combined (for All CWP) Results: Calculated What-If Indoor Air ADCs at the Baseline and for the Analytical Options	80
Table 4-25.  Combined (for All CWP) Results: Calculated What-If Indoor Air LADCs at the Baseline and for the Analytical Options	81
Table 4-26.  Best Estimate of What-If Formaldehyde Exposure Concentration at the Baseline and for the Analytical Options	81
Table 5-1.  Number of OSHA Inspections at CWP Fabrication Facilities Compared to the Maximum Number of Facilities from the U.S. Economic Census	85

                                List of Figures

Figure 2-1. Life Cycle and Market Distribution of HWPW	3
Figure 2-2.  Life Cycle and Market Distribution of MDF	4
Figure 2-3.  Life Cycle and Market Distribution of PB	5
Figure 4-1. Comparison of Model Results for Ranges of What-If Indoor Air Concentrations using Pre-Baseline Emission Rates with OSHA IMIS Data	62
Figure 5-1.  TWA Exposures from OSHA IMIS for a Single Inspection for Armstrong Cabinets (NAICS 337110)	88
Figure 5-2.  TWA Exposures from OSHA IMIS for a Single Inspection for Mid Continent Cabinetry (NAICS 337110)	88
Figure 5-3.  TWA Exposures from OSHA IMIS for a Single Inspection for Benvenuti and Stein (NAICS 337122)	89
Figure 5-4.  TWA Exposures from OSHA IMIS for a Single Inspection for Ameriwood Industries (NAICS 337122)	89
Figure 5-5.  TWA Exposures from OSHA IMIS for Two Inspections for The Gunlocke Company (NAICS 337211)	90
Figure 5-6.  TWA Exposures from OSHA IMIS for Two Inspections for Silver Street (NAICS 337211)	90
Figure 5-7.  TWA Exposures from OSHA IMIS for a Single Inspection for The Commercial Furniture Group (NAICS 337127)	91

                             List of Abbreviations

ADC				Average daily concentration
C&D				Construction and demolition
CARB P1			California Air Resources Board Formaldehyde Regulation Phase 1
CARB P2			California Air Resources Board Formaldehyde Regulation Phase 2
CFM				Cubic feet per minute
CWP				Composite wood product
FSCWPA			Formaldehyde Standards for Composite Wood Products Act
HWPW			Hardwood plywood
HWPW-CC			Hardwood plywood  -  composite core
HWPW-VC			Hardwood plywood  -  veneer core
LADC				Lifetime average daily concentration
MDF				Medium-density fiberboard
MF				Melamine formaldehyde
MSW				Municipal solid waste
NAF				No-added formaldehyde
OSHA				Occupational Safety and Health Administration
PB				Particleboard
PF				Phenol formaldehyde
pMDI				Poly(methylene diphenyl diisocyanate)
PPE				Personal protective equipment
PVA				Poly(vinyl acetate)
tMDF				Thin medium-density fiberboard
TWA				Time-weighted average
UF				Urea formaldehyde
ULEF				Ultra low emitting formaldehyde

Introduction
In March 2008, the Environmental Protection Agency (EPA) was petitioned by the Sierra Club and other signatories under Section 21 of the Toxic Substances Control Act (TSCA) to adopt nationally an Airborne Toxic Control Measure (ATCM) promulgated by the California Air Resources Board (CARB) in 2008 that establishes maximum formaldehyde emissions from the three types of composite wood products: hardwood plywood (HWPW), medium-density fiberboard (MDF), and particleboard (PB).  As described in EPA's Advance Notice of Proposed Rulemaking (ANPR) published in December 2008 (73 FR 73620) and in response to this petition, EPA investigated whether regulatory action, including possible action under TSCA Section 6, or non-regulatory action might be appropriate to control the levels of formaldehyde emitted from composite wood products.
In July 2010, President Obama signed into law the Formaldehyde Standards for Composite Wood Products Act (FSCWPA).  This law is an amendment to TSCA and directs EPA to regulate the formaldehyde emissions from HWPW, MDF, and PB.  FSCWPA sets formaldehyde limits equal to the CARB ATCM standards.  It also requires EPA to promulgate implementing regulations by January 1, 2013.  As part of the development of a rule under FSCWPA, EPA is conducting a cost-benefit analysis of implementing the formaldehyde limits cited by FSCWPA.  In support of this cost-benefit analysis, EPA assessed occupational inhalation and dermal exposure to formaldehyde during the life cycle of HWPW, PB, and MDF.
Purpose and Scope of Exposure Assessment
The purpose of the assessment is, first, the prediction of baseline formaldehyde inhalation and dermal occupational exposure that is due to all sources of exposure (aggregate exposure) during the life cycle of composite wood products (CWPs), and, second, the determination of the effect on baseline exposure of the analytical options for limits on emission levels for off-gassing from HWPW, PB, and MDF.
The baseline occurs in the year in which EPA will promulgate limits under FSCWPA, which will be 2013.  This document discusses various analytical options for limits on emission levels for off-gassing from HWPW, PB, and MDF (i.e., various emission standards) simply for informational purposes.  The breadth of the discussion here should not imply that EPA necessarily has corresponding flexibility in implementing the statute.  The following specific analytical options were assessed in support of the cost-benefit analysis for the formaldehyde rulemaking activity:
Analytical Option 1: a scenario in which EPA would implement maximum formaldehyde emission limits equal to the CARB ATCM Phase 1 limits;
Analytical Option 2: a scenario in which EPA would implement maximum formaldehyde emission limits equal to the CARB ATCM Phase 2 limits (which are equal to the limits specified in FSCWPA); and
Analytical Option 3: a scenario in which EPA would implement maximum formaldehyde emission limits equal to the no-added formaldehyde (NAF) limits specified in FSCWPA.
Figure 2-1, Figure 2-2, and Figure 2-3 depict the life cycle and market distribution for HWPW, MDF, and PB, respectively.  Manufacture, import, and export volumes are expressed in cubic meters of composite wood products and are annual volumes for the year 2005 (Table 2-5 of USEPA 2010a).  Market distributions are expressed as percentages that represent the amounts of North American produced CWP that are sold to the various CWP fabrication industry sectors and directly to retail (section 2.3.2 of USEPA 2010a).  The market distributions of imports are unknown.  Percentages may not sum to 100 percent due to rounding.  The description of the life cycles, i.e., the markets and market channels, were obtained from the Hardwood Plywood and Veneer Association (HPVA) (for HWPW) and the Composite Panel Association (CPA) (for PB and MDF) (HPVA 2009a; CPA 2008a).
This assessment assesses potential worker exposure to formaldehyde from the following life cycle stages of HWPW, PB and MDF:
Manufacture of HWPW, PB and MDF within the United States (domestic manufacturing);
Downstream manufacture of products constructed from domestically manufactured and imported HWPW, PB and MDF (e.g. manufacture of furniture using HWPW, PB and MDF), referred to in this report as composite wood product fabrication;
Wholesale and retail of domestically manufactured and imported HWPW, PB, MDF, and downstream products fabricated from these CWPs; and
Occupancy by office workers of office buildings containing domestically manufactured and imported HWPW, PB, MDF, and downstream products fabricated from these CWPs.
The life cycle stages not assessed due to major data gaps include the following:
Commercial construction using HWPW, PB, MDF, and products fabricated from these CWPs; and
Recycling and disposal of HWPW, PB, MDF, and products fabricated from these CWPs.
The life cycle stages that are assessed as well as those that were not assessed are further discussed below in Sections 2.1 through 2.6.  Table 2-1 summarizes the applicable NAICS codes for the assessed life cycle stages.

Figure 2-1. Life Cycle and Market Distribution of HWPW

Figure 2-2.  Life Cycle and Market Distribution of MDF

Figure 2-3.  Life Cycle and Market Distribution of PB

Table 2-1.  NAICS Industry Sectors Identified for the Life Cycle Stages of HWPW, MDF, and PB
                               Life Cycle Stage
                             Included NAICS Codes
                   Corresponding NAICS Industry Descriptions
HWPW Manufacturing
                                                                         321211
Hardwood veneer & plywood manufacturing
MDF Manufacturing
                                                                         321219
Reconstituted wood product manufacturing
PB Manufacturing

Composite Wood Product Fabrication
                                                                         321911
Wood window & door manufacturing

                                                                         321918
Other millwork (including flooring)

                                                                         321991
Manufactured home (mobile home) manufacturing

                                                                         321999
All Other Miscellaneous Wood Product Manufacturing

                                                                         336213
Motor Home Manufacturing

                                                                         336214
Travel Trailer & Camper Manufacturing

                                                                         337110
Wood kitchen cabinet & counter top manufacturing

                                                                         337121
Upholstered household furniture manufacturing

                                                                         337122
Non-upholstered wood household furniture manufacturing

                                                                         337124
Metal Household Furniture Manufacturing

                                                                         337127
Institutional furniture manufacturing

                                                                         337129
Wood television, radio, & sewing machine cabinet manufacturing

                                                                         337211
Wood office furniture manufacturing

                                                                         337212
Custom architectural woodwork & millwork manufacturing

                                                                         337214
Office Furniture (except Wood) Manufacturing

                                                                         337215
Showcase, partition, shelving, & locker manufacturing

                                                                         339950
Sign Manufacturing
Wholesale
                                                                         423210
Furniture merchant wholesaler

                                                                         423220
Home furnishing merchant wholesaler

                                                                         423310
Lumber, plywood, & wood panel merchant wholesaler

                                                                         423320
Brick, stone, & construction material merchant wholesaler

                                                                         423330
Roofing, siding, & insulation material merchant wholesaler

                                                                         423390
Other construction material merchant wholesaler

                                                                         423440
Other commercial equipment merchant wholesalers

                                                                         423450
Medical, dental, & hospital equipment & supplies merchant wholesalers

                                                                         423490
Other professional equipment & supplies merchant wholesaler

                                                                         423510
Metal service centers and other metal merchant wholesalers

                                                                         423610
Elec. equip. and wiring merchant wholesalers

                                                                         423620
Electric appliance, TV & radio merchant wholesalers

                                                                         423710
Hardware merchant wholesalers

                                                                         423720
Plumbing equip. merchant wholesalers

                                                                         423730
HVAC equip. merchant wholesalers

                                                                         423740
Refrigeration equipment and supplies merchant wholesalers

                                                                         423830
Industrial machinery & equipment merchant wholesalers

                                                                         423850
Service establishment equipment & supp merchant wholesalers

                                                                         423910
Sporting & recreational goods & supplies merchant wholesalers

                                                                         424610
Plastics materials and basic forms and shapes merchant wholesaler

                                                                         424950
Paint, varnish, and supplies merchant wholesalers
Retail
                                                                         441210
Recreational vehicle dealers

                                                                         442110
Furniture stores

                                                                         442210
Floor covering stores

                                                                         442291
Window treatment stores

                                                                         442299
All other home furnishings stores

                                                                         443111
Household appliance stores

                                                                         443112
Radio, television, & other electronics stores

                                                                         443120
Computer & software stores

                                                                         444110
Home centers

                                                                         444120
Paint and wallpaper stores

                                                                         444130
Hardware stores

                                                                         444190
Other building material dealers

                                                                         444210
Outdoor power equipment stores

                                                                         444220
Nursery, garden center, & farm supply stores

                                                                         445110
Supermarkets and other grocery (except convenience) stores

                                                                         448110
Men's clothing stores

                                                                         448120
Women's clothing stores

                                                                         448130
Children's and infants' clothing stores

                                                                         448140
Family clothing stores

                                                                         448150
Clothing accessories stores

                                                                         448190
Other clothing stores

                                                                         451120
Hobby, toy, and game stores

                                                                         451130
Sewing, needlework, and piece goods stores

                                                                         452111
Department stores (except discount department stores)

                                                                         452112
Discount department stores

                                                                         452910
Warehouse clubs and supercenters

                                                                         452990
All other general merchandise stores

                                                                         453110
Florists

                                                                         453210
Office supplies and stationery stores

                                                                         453220
Gift, novelty, and souvenir stores

                                                                         453920
Art dealers

                                                                         453930
Manufactured (mobile) home dealers

                                                                         453998
All other miscellaneous store retailers (except tobacco stores)

                                                                         454113
Mail-order houses

                                                                         454390
Other direct selling establishments
   Source: EPA market profile (USEPA 2010a)

Manufacturing
The term "manufacturing" in this report refers specifically to the manufacture of HWPW, MDF, and PB (and is also referred to as "primary manufacturing").  The scope of this assessment includes the domestic manufacture of these products themselves but excludes any part of the upstream supply chain for the manufacture of these products such as resin or veneer manufacturing.  Occupational exposures of formaldehyde in UF resin manufacture is covered under the "Draft Final Occupational Exposure and Environmental Release Assessment of Formaldehyde in Urea-Formaldehyde Resin Manufacture and of Substitute Technologies to Reduce Emissions from Composite Wood Products" (USEPA 2011a).  The manufacture of imports, i.e., the manufacture of HWPW, MDF, and PB in countries outside of the U.S., is not included in the scope of this assessment.
The NAICS code 321219 - Reconstituted Wood Product Manufacturing includes both the manufacture of PB and MDF.  It also includes the manufacture of composite wood products not included in the scope of this assessment, such as hardboard, oriented strandboard, and waferboard (Census 2007a).
The NAICS code 321211 - Hardwood Veneer and Plywood Manufacturing includes the manufacture of hardwood plywood.  It also includes the manufacture of hardwood veneer (Census 2007a).  These veneers are typically not manufactured at the same facilities that manufacture hardwood plywood.  Therefore, hardwood veneer manufacturing facilities would not be subject to any requirements under the proposed FSCWPA rule (USEPA 2010a).  Therefore, hardwood veneer manufacturing facilities are not included in the scope of this assessment.
Composite Wood Product Fabrication
HWPW, MDF, and PB may be converted into articles or other products.  For example, HWPW may be pressed into panels and plywood components (e.g., curved HWPW, seat backs, chair arms, etc.) or used for furniture, cabinets, architectural millwork, paneling for commercial buildings, flooring, store fixtures and doors (OAQPS 2000b).  Similarly, MDF and PB are used in the manufacture of many products including virtually every application where interior panels or strips are required, especially in furniture and cabinetry.  However, MDF is not used as floor underlayment or decking except on special request (Kirk-Othmer 2011a).  In addition to furniture and cabinetry, PB is used as floor decking in manufactured homes, underlayment in conventional homes, shelving, countertops, door cores, stair stepping, door frames, and many other products that require small flat parts as a starting point.  A small portion of PB is also extruded or molded into furniture parts, paper roll plugs, brush bases and toilet seats (Kirk-Othmer 2011a).
Composite wood products also may have "value-added surfaces" added to the panel product.  "Value-added surfaces" include decorative finishes or overlays and coatings, which may be applied at a "sister" facility of the manufacturer or at unaffiliated finishing sites (CPA 2007a; CPA 2009a).  A technical bulletin published by the Composite Panel Association (CPA) further discusses the types of value-added surfaces (CPA 2007a).
Wholesale
Wholesalers buy products from manufacturers in bulk for the purpose of resale to various industries and individuals.  Wholesale products may include CWP fabrication products as well as composite wood products (i.e., panels).  A single wholesaler may sell many different types of composite wood products (Census 2007a).
Retail
Retailers operate from fixed locations and sell products for direct consumption by the purchaser (individuals or businesses).  These retailers may receive HWPW, MDF, or PB directly or as components in CWP fabrication products.  Like the wholesale sector, the retail sector is not distinguished by composite wood product type (Census 2007a).
Commercial Use
The commercial use of composite wood products includes (1) the use of composite wood products in on-site construction, and (2) the occupancy by office workers of workplace buildings (commercial buildings) containing composite wood products.  CWP fabrication products such as furniture and cabinets, in addition to composite wood products, are present in commercial buildings.
Data gaps for on-site construction using HWPW, PB, and MDF include the following:
The volumes of HWPW, PB, and MDF used during on-site construction could not be determined.
The number of sites and workers engaged in on-site construction could not be determined.  Therefore, the size of this life cycle stage and the number of workers exposed during this life cycle stage are unknown.
Formaldehyde monitoring data for on-site construction could not be determined.  Therefore, the range of potential exposures that occur during this life cycle stage is unknown.
Due to these data gaps, this assessment does not include an occupational exposure assessment of formaldehyde during on-site construction.
Disposal and Recycle
At end of life, composite wood is either disposed of as municipal solid wastes (MSW) or construction and demolition (C&D) debris materials, or recycled into new products.
A total of 15.84 million tons of wood MSW was generated (before recycling) in 2009 in the U.S.  Of these 15.84 million tons, 10.08 million tons were from wood pallets and wood crates (USEPA 2010b).  Wood pallets and wood crates are likely not constructed of CWPs and are outside the scope of this assessment.  Of these 15.84 million tons of wood MSW, the remaining 5.76 million tons of wood were from furniture and furnishings (USEPA 2010b).  As discussed in this report, CWPs are used in the fabrication of furniture; therefore, an unknown fraction of the 5.76 million tons of wood likely consists of CWPs.  EPA reports that the only identified recovery of materials from MSW composed of furniture and furnishings was mattress recovery (USEPA 2010b).  Of all MSW discarded in 2009 (after recovery for recycling and composting), 82% was landfilled or otherwise disposed and 18% was incinerated for energy recovery (USEPA 2010b).  Therefore, it is likely that CWPs in furniture that enters the MSW stream are not recovered and are discarded via landfilling or incineration.
C&D materials consist of the debris generated during the construction, renovation, and demolition of buildings, roads, and bridges, which can include wood materials (USEPA 2011c).  The majority of building-related C&D materials come from building demolition and renovation with the remainder from new construction (USEPA 2011c).  A report from 2003 estimated that 20% to 30% of building related C&D debris generated was wood (USEPA 2011c).  However, it is unknown what fraction of wood C&D debris consists of CWPs.
In 1995, the Department of Agriculture estimated that 3.96 million tons of wood products were recovered for recycling into miscellaneous uses (USDA 1996a).  The sources and types of the recovered wood products referred to here were not given, and it is unknown whether the recovered wood material includes CWPs.  The term "miscellaneous uses" was not explicitly defined in the text but referred to examples such as insulation, molded pulp products, hardboard, insulating paperboard, and composite wood panels.  More recently, of the 10.08 million tons of wood MSW from wood pallets and wood crates, 22% were recovered for recycling as mulch and bedding material (USEPA 2011b); however, as stated above, wood pallets and wood crates are likely not constructed of CWPs.  Several existing and developing technologies exist for producing composites using recycled wood-based fiber.  These composites include dry-formed wood composites, wet-formed structural fiber products, wood-plastic composites, and wood-inorganic composites (Hamilton 1996a).
Data gaps for the disposal and recycling of HWPW, PB, and MDF include the following:
The volumes of HWPW, PB, and MDF disposed of as waste and recycled could not be determined.
Formaldehyde monitoring data for the disposal and recycling of composite wood products could not be determined.

Due to these uncertainties, this assessment does not include an occupational exposure assessment of formaldehyde during disposal and recycling.  It is noted that due to the decay of formaldehyde emission rates from CWPs with time (see Section <IP_ADDRESS>), CWPs can have reduced emission rates and, therefore, a diminished contribution to exposure concentrations when disposed or recycled at their end of life.
Exposure Assessment Method
This section describes the data collection efforts and the methods used for assessing occupational exposures, and their underlying assumptions.
Literature Search
This exposure assessment relied on the use of readily available data, including exposure monitoring data and mathematical modeling data.  A comprehensive literature search of readily available government, industry, and academic sources was conducted, which included sources from EPA, OSHA, NIOSH, the California Air Resources Board (CARB), SRI International, and the Organization for Economic Co-operation and Development (OECD), as well as industry websites, academic journals, and other publications.  Additionally, submissions in response to EPA's ANPR (73 FR 73620) were reviewed.  The ANPR review included 123 public submissions to Docket Number EPA-HQ-OPPT-2008-0627 and 30 public submissions to Docket Number EPA-HQ-OPPT-2008-0267.  Also reviewed were regulations, such as the National Emissions Standards for Hazardous Air Pollutants (NESHAP) for plywood and composite wood products and the Housing and Urban Development (HUD) Rule on formaldehyde emissions from certain wood products in manufactured homes (24 CFR § 3280.308).
The following specific databases and studies were searched for formaldehyde air monitoring data:
OSHA's Integrated Management Information System (IMIS);
EPA's Building Assessment Survey and Evaluation (BASE) study;
The Relationship of Indoor, Outdoor, and Personal Air (RIOPA) project;
The International Agency for Research into Cancer (IARC) Formaldehyde Monograph (Volume 88); and
The Detroit Exposure and Aerosol Research Study (DEARS).
The literature search did not yield any formaldehyde air monitoring data that are directly relevant to this exposure assessment.  Data from OSHA IMIS and EPA's BASE study were the most relevant data obtained and were used in this assessment to provide perspective as discussed in Section 3.2.  Additionally, other exposure monitoring studies of CWP manufacturers from the literature are cited in this assessment, but data from OSHA IMIS are more comprehensive and more relevant to this exposure assessment than these additional studies as OSHA IMIS contains only U.S. data.  A summary of the abstracts of these additional CWP manufacturer studies are provided in Appendix H.  Some of these additional studies are from monitoring studies of CWP manufacturing mills outside the U.S.
The IARC study cited exposure monitoring studies for various types of settings (including offices, homes, and institutional and public buildings) in various countries (including countries in North America, Europe, South America, Asia, and Australia).  Monitoring data for U.S. office buildings from the IARC study were not used because they were not recent data (they were dated prior to 1990).  The RIOPA data were not used as the RIOPA project focused on individuals' exposures through-out their day.  Although limited information was collected to estimate an individual's exposures during their occupations, occupational exposures were not the focus of the project.  The DEARS also focused on personal, residential, and outdoor monitoring.  Occupational exposures were not the focus of DEARS.  In contrast, OSHA IMIS and EPA's BASE study are both focused on occupational exposures.  Recent data on formaldehyde concentrations in Hong Kong office buildings were reported in Wong et al. (Wong 2006a).  The minimum of the range of these concentrations is similar to the lowest value reported in the BASE study (BASE 1998a), while the maximum of the range is over twenty times greater than the maximum reported in the BASE study.  However, these Hong Kong data were not used because they may not be relevant to exposure in U.S. office buildings.  Specifically, it is unknown how determinants of formaldehyde inhalation exposure in Hong Kong office buildings compare to those in U.S. office buildings, such as sources of airborne formaldehyde including the amount of CWP present in office buildings and their formaldehyde emission rates and ventilation rates.  As compared to the above mentioned studies, the BASE study results are the most relevant to this assessment of formaldehyde inhalation exposure in office buildings and are adequate and sufficient for the purpose of providing perspective on the results of this exposure assessment.  Therefore, the BASE study results are presented in this assessment while information from the other studies is not included.
Dermal exposure was not included in data searches.  Instead, this assessment has relied solely upon mathematical modeling for dermal exposure assessments.
Appendix B of this report presents the quality criteria used during the literature search and data compilation.  These quality criteria represent the preference for selecting data.  The collected data used in this assessment meet these quality criteria.
Compilation of Pre-Baseline Exposure Monitoring Data
Baseline formaldehyde occupational exposure monitoring data are not available because the baseline occurs in the future in the year 2013.  As described in Section 3.1, a literature search for pre-baseline exposure monitoring data was conducted as part of the data gathering for this assessment.  Pre-baseline exposure monitoring data from OSHA IMIS and the EPA BASE study were compiled and evaluated for adequacy for use in the assessment of baseline exposure and the effect of analytical options on baseline exposure.
The compiled inhalation exposure monitoring data, which are described below, were not used in the assessment of exposure at the baseline or for the analytical options.  The reasons that these data were not used to assess exposure are discussed below.  However, these data are still considered useful for reasons also discussed below.
Manufacturing, Composite Wood Product Fabrication, Wholesale and Retail
Pre-baseline formaldehyde exposure monitoring data for manufacturing, fabrication, wholesale and retail facilities were obtained from the OSHA IMIS database (OSHA 2009a).  At the time the OSHA IMIS data were obtained (June 2010), the most current data were from 2009.  Of the collected IMIS data, only data from the period of 2002 to 2009 were considered for use in the assessment because some information on the production-weighted average emission levels and the range of emission levels of domestically-produced CWP during the pre-baseline period of 2002 to 2009 is available.  This information is presented in Table 3-1; as seen in this table, the production-weighted average emission levels for CWP domestically-produced during the period of 2002 to 2009 were close to the CARB Phase 1 limits, especially after 2008.
The pre-baseline OSHA IMIS inhalation exposure monitoring data were determined to not be adequate for the assessment of baseline exposure concentrations and the effect of the analytical options on baseline exposure concentrations due to the following three reasons:
   1. The extent to which exposure levels reported in OSHA IMIS will be affected by the limits on CWP formaldehyde emission rates set by FSCWPA is uncertain;
   2. The OSHA IMIS data may not be representative of exposure levels that are associated with formaldehyde off-gassing emissions from the three CWPs with emission rates equal to baseline or analytical option emission rates; and
   3. It is unknown whether the OSHA IMIS exposure monitoring data are representative of the exposure of the entire population of exposed workers during the pre-baseline period of time associated with these data.
The above three reasons are further discussed below.
First, the extent to which the sources of exposure associated with the compiled OSHA IMIS monitoring data will be affected by the FSCWPA is uncertain.  OSHA's occupational exposure limits apply to aggregate exposure and not to exposure due to any specific source.  Accordingly, the OSHA IMIS, which is described in Appendix F, does not contain information on the sources of formaldehyde that contributed to the observed exposure concentrations, which are a measure of aggregate exposure where more than one source of exposure existed.  As discussed in Section 4, sources other than the off-gassing of formaldehyde from the three CWPs may contribute to formaldehyde occupational exposure during the life cycle of CWPs.  Therefore, the compiled OSHA IMIS monitoring data may be associated with sources of exposure other than off-gassing from the three CWPs.  The contributions of any such sources to the observed inhalation exposure concentrations are not expected to be affected by the limits on CWP formaldehyde emission rates set by the FSCWPA.  Hence, EPA is not able to use the OSHA IMIS data to accurately assess the effect of analytical options on baseline exposure because the extent to which the exposure levels reported in OSHA IMIS will be affected by the CWP emission rate limits set by FSCWPA is uncertain.
Second, the pre-baseline OSHA IMIS data may not represent baseline or analytical option exposure levels.  Levels of formaldehyde in U.S. workplaces across multiple industries have decreased from 1979 to 2001 according to a 2008 study of IMIS data (Lavoue 2008a).  This decrease in formaldehyde levels could be due to OSHA's implementation of a formaldehyde PEL of 1 ppm in 1987 and implementation of the current PEL of 0.75 ppm in 1992 (Lavoue 2008a).  Manufacturers reduced formaldehyde emissions from composite wood products by 80 to 90 percent from the levels of the early 1980s (CPSC 1997a).  A decline in emission levels also occurred during the last decade as illustrated in Table 3-1.  As discussed above, this table contains emission level data for domestically-manufactured CWPs during the pre-baseline period of 2002 to 2009.  The emission level data in Table 3-1 indicate that domestic manufacturers produced national production-weighted average emission levels close to the CARB ATCM Phase 1 limits in 2002; however, the manufacturers also produced CWPs with a wide range of emission levels.  Furthermore, the emission levels of domestically-manufactured CWPs were trending towards a greater adoption of the CARB ATCM Phase 1 limit between 2002 to 2009, but a high percentage of CARB ATCM Phase 1 adoption was not expected until 2009.  Therefore, to the extent that the compiled OSHA IMIS pre-baseline inhalation exposure monitoring data are associated with off-gassing of formaldehyde from the three CWPs of interest, these data are associated with pre-baseline emission rates for these CWPs.  Therefore, the OSHA IMIS exposure levels may not be representative of exposure levels resulting from off-gassing of formaldehyde from CWPs with baseline or analytical option emission rates.
Third, it is uncertain whether the OSHA IMIS data are representative of the exposure concentrations for the entire population of exposed workers during the pre-baseline period of time in which exposure monitoring to obtain these data occurred.  For some life cycle stages, very few monitoring data were compiled.  However, even if an adequate amount of data were available, it is uncertain whether the inspected facilities in which the exposure concentrations were observed were selected randomly.  Therefore, it is unknown whether such exposure monitoring data are representative of the exposure of the entire population of exposed workers during the pre-baseline period of time associated with these data.
Due to the three considerations discussed above, the OSHA IMIS monitoring data were not used to assess baseline exposure concentrations and exposure concentrations for the analytical options.  Due to lack of adequate exposure monitoring data, baseline exposure and the effect of analytical options on baseline exposure are assessed using mathematical modeling as described in Section 3.3.  However, the monitoring data are still useful.  The monitoring data can provide a perspective as to observed formaldehyde exposures in industries.  Additionally, monitoring data obtained from OSHA IMIS provide exposure measurements by worker activity and thereby provide perspective as to the different worker activities in each industry that can result in formaldehyde exposure.
Table 3-1.  Pre-Baseline Formaldehyde Emission Levels for Domestically-Produced Composite Wood Products
                                    Timeline
                               Information Source
                                    HWPW [a]
                                     PB [b]
                                     MDF [b]
2002
CARB survey
                          Production-Weighted Average

                                   0.09 ppm
                                   0.18 ppm
                                   0.25 ppm

                     % of Production Represented in Survey

                                      73%
                                      53%
                                      83%

                           Range in Survey Responses

                               0.07 to 0.75 ppm
                               0.13 to 0.24 ppm
                               0.03 to 0.31 ppm
End of 2008 / Beginning of 2009
ANPR Submissions
75% of domestically-produced CWP were CARB Phase 1 compliant
96% of domestically-produced CWP were CARB P1 compliant
96% of domestically-produced CWP were CARB P1 compliant
Later in 2009
ANPR Submissions
90% of domestics expected to be CARB P1 compliant
                                      --
                                      --
 a  -  A submission from HPVA in May 2008 estimated that domestically-produced HWPW will be in compliance with CARB Phase 1. Phase 2 limits require new technologies, which have not been in commercial use and some only recently invented and patented. Additionally, a submission from HPVA in February 2009 estimated that 75% of North American HWPW was CARB certified and soon 90% or more will be CARB certified. "CARB certified" is assumed to mean CARB Phase 1 per the statements made in the May 2008 submission. The term "soon" is uncertain; therefore, the point in time in which 90% of domestics were expected to meet CARB Phase 1 is uncertain.
 b  -  A submission from CPA in May 2008 stated that "almost all" domestic production is expected to be compliant with CARB Phase 1 and 2. The volume related to "almost all" is uncertain. This submission also states that "eventually" this rate of compliance would be reached; the time frame associated with "eventually" is uncertain. CPA did estimate that 96% of domestics were Phase 1 compliant by the end of 2008.

Commercial Use (Office Buildings)
For office buildings, formaldehyde inhalation exposure monitoring data were obtained from the EPA Building Assessment Survey Evaluation (BASE) study.  The BASE study was a five-year study to characterize determinants of indoor air quality (IAQ).  The BASE study collected indoor air quality data from 100 randomly selected public and commercial office buildings in 37 cities in 25 states from 1994 to 1998.  The buildings were all occupied buildings randomly selected from cities with populations greater than 100,000 within ten climatic regions.  The studied buildings were primarily (73%) located in urban surroundings.  Ninety-eight percent of the buildings had mechanical ventilation and 44 percent had operable windows.  Within each building, a test space with a target population greater than 50 occupants, residing on no more than three floors, and served by no more than two air-handling units was randomly selected.  Buildings with highly publicized indoor environmental quality problems were excluded.  The data compiled through the BASE study include general information regarding the building itself, area monitoring of indoor pollutant concentrations, basic occupant statistics, occupant health symptoms and perceptions of indoor air quality, and information about the design, maintenance and operation of building heating, ventilating, and air conditioning (HVAC) systems.  A summary of the results of the BASE study is given in Section 4.5.3.
The BASE study does not contain any information on the sources of the monitored formaldehyde indoor air concentrations.  Even while assuming that CWPs were the main source of monitored formaldehyde, the BASE study inhalation exposure monitoring data are not adequate for assessing exposure concentration in this assessment because the emission levels of such CWPs in the studied buildings are unknown.  As indicated in Table 3-1 and discussed in the subsection above, the formaldehyde emission levels of new CWPs have been decreasing with time and, therefore, the emission levels of new CWPs depend on their date of manufacture.  Furthermore, formaldehyde emission levels of CWPs decay with time and, therefore, the emission level of aged CWPs depend on the emission level when manufactured and the duration of time they have been in use.  Although the BASE study was conducted in 1994 to 1998, the vintage of the office furniture (i.e., the year in which the office furniture were built), which may contain CWPs and are a likely source of formaldehyde emissions as further discussed in this document, is unknown for each studied building.  Therefore, the emission levels of any CWPs that are components of office furniture in the monitored office buildings at the time the monitoring occurred are unknown.
Exposure Assessment Methods and Assumptions
This section describes the methods used for assessing baseline exposures, which are due solely to off-gassing from CWPs and ventilation with ambient air, the effect of the analytical options on these baseline exposures, and the assumptions underlying the assessment methods.
Baseline indoor air concentration and the effect of the analytical options on baseline indoor air concentration were assessed for CWP fabrication and office buildings; the methods for these assessments are discussed below.  Baseline indoor air concentration and the effects of the analytical options on baseline indoor air concentration were not assessed quantitatively for the CWP manufacturing, wholesale and retail life cycle stages due to data gaps, and only qualitative assessments were made.
The goal of this assessment was to assess aggregate formaldehyde indoor air concentration in each assessed life cycle stage.  Aggregate indoor air concentration is the sum of the concentration contributed by off-gassing of the three CWPs, the concentration contributed by other formaldehyde sources in the workplace, and the concentration of formaldehyde in ambient outdoor air.  However, due to data gaps, this assessment only assesses formaldehyde indoor air concentration that is due to off-gassing of the three CWPs and the concentration of formaldehyde in ambient outdoor air.
For CWP fabrication sites, as discussed in Section 4.2.1, there is indication that sources of formaldehyde other than the off-gassing of formaldehyde from CWPs may exist.  However, the extent to which other sources of formaldehyde contribute to worker exposure in CWP fabrication sites is unknown.  Attempts to develop methods to estimate concentration contributions from other sources during CWP fabrication were not successful due to data gaps.
On the other hand, in homes the most significant sources of formaldehyde are likely to be CWPs made from UF resins (USEPA 2011b).  The literature search did not identify information to indicate that sources of formaldehyde in office buildings are significantly different than in homes.  Therefore, it is assumed that CWPs are the most significant source of formaldehyde in office buildings.  It is noted in this regard that the concentration of airborne formaldehyde tends to be lower in office buildings as compared to residential structures.  EPA compiled residential indoor air formaldehyde monitoring data (USEPA 2009b).  A comparison of these data with the monitoring data of the BASE study (BASE 1998a) shows that the central value of the indoor air concentrations in office buildings are for the most part lower than the central values of residences.  This observation is also indicated by a Health Effects Institute report (HEI 2007a).  However, this comparison neither supports nor detracts from the assumption made here about the predominant type of emission source in office buildings because airborne concentration is a function of not only the type of emission source, but also its quantity as well as the ventilation rate.  These last two factors are not expected to be similar for office buildings and residential structures.
Dermal exposures to formaldehyde in liquid mixtures were quantitatively assessed for manufacturing.  Dermal exposures were assessed only qualitatively for the CWP fabrication, wholesale, retail, and commercial use life cycle stages.  Due to data gaps, quantitative dermal exposure estimates for manufacturing were only made for pre-baseline conditions; baseline and analytical option dermal exposures could not be estimated.  The qualitative dermal exposure assessments for CWP fabrication, wholesale, retail, and commercial use were made for baseline and analytical options.
The use of respirators as personal protective equipment (PPE) for CWP manufacture and fabrication was considered based on the review of OSHA inspection reports.  However, a limited number of inspection reports were available for review and a conclusion as to the prevalence of the use of respiratory protection in these life cycle stages could not be determined.  OSHA guidance on safe practices in the woodworking industry was also considered and is summarized in this assessment report.
Exposure duration (the hours of exposure per day) and frequency (the days of exposure per year) for all assessed life cycle stages with the exception of office buildings were assessed based on census data on pre-baseline aggregate production hours.
The number of exposed workers in each life cycle stage with the exception of office buildings was estimated to be equal to the pre-baseline number of production workers according to census data.
Inhalation exposure results for baseline and each analytical option are presented as average daily concentration (ADC) and lifetime average daily concentration (LADC).  The equations for ADC and LADC are presented in Appendix E.  ADC and LADC are used as measures of exposure when considering non-cancer and cancer risks, respectively (USEPA 2009a).  Formaldehyde may result in both non-cancer and cancer health effects (ATSDR 1999a; ATSDR 2010a).
The assessment results are presented in Section 4.
 Estimation of Indoor Air Concentrations Related to Baseline and Analytical Options for CWP Fabrication and Office Buildings
This section discusses the mathematical models used for estimating baseline indoor air formaldehyde concentrations due to off-gassing of CWP in CWP fabrication sites and office buildings, and the effect on baseline indoor air concentrations of the FSCWPA analytical options.  As discussed in Section 3.2, the OSHA IMIS and BASE data are likely not representative of exposure concentrations at baseline or for the analytical options.  Therefore, mathematical modeling was used to estimate indoor air concentration for the baseline and the analytical options.
The mathematical models for the estimation of formaldehyde indoor air concentration in CWP fabrication sites and office buildings are presented in this section, while a detailed description of these models and their underlying assumptions is included in Appendix E.  These models are based on the principle of mass conservation.  As further discussed below, the generation rate of formaldehyde in these models is expressed as the product of a formaldehyde off-gassing emission rate and an amount of emitting surface area.  This generation rate is used in combination with the rate of ventilation of the work space area containing the CWP emitting surface area.  This section also contains a discussion of the determination of the values of these and the other model parameters of these models and the use of the models for estimating what-if values of indoor air concentration at CWP fabrication sites and office buildings.  Mathematical modeling was not applied to other life cycle stages because data were not available to estimate the model parameters for the other life cycle stages.
Method for Estimation of Indoor Air Concentration for CWP Fabrication
At steady-state, a mass balance equates the formaldehyde generation rate due to off-gassing from HWPW, PB, and MDF present at a CWP fabrication site to the rate at which airborne formaldehyde is exhausted from the CWP fabrication site through ventilation with outdoor air.  As further discussed in detail in Appendix E, the mathematical model for indoor air concentration, which is derived from the mass balance, is as follows:
					C=FxAQeffective+Coind			Eqn (1)
where:
      C	=	Average airborne formaldehyde concentration in a CWP fabrication site (ug/m[3]);
      F	=	Emission rate (off-gassing emissive flux) of formaldehyde from the composite wood product (ug/m[2]-h);
      A	=	Total emitting surface area of the composite wood products located in a CWP fabrication site (m[2]);
      Qeffective	=	Effective volumetric ventilation rate for an entire CWP fabrication site (m[3]/h); and
      Co[ind]	=	Concentration of formaldehyde in the outdoor air for industrial land use areas (ug/m[3]).

The literature search did not yield an exposure site population distribution for the input parameters of Equation 1, nor did it yield representative values for these input parameters for CWP fabrication sites.  Due to these data gaps with respect to the model parameters, what-if values for indoor air concentration were estimated.  This what-if analysis was accomplished by estimating the range of possible values for each model parameter (with the exception of outside air concentration as further explained below) and calculating a range of what-if indoor air concentration values from the estimated ranges of the model parameters as further discussed below.  The resulting values in the estimated range for average indoor air concentration at a CWP fabrication site are characterized as what-if results because each concentration value in this range corresponds to combinations of choices, or what-if values, for the model parameters.  Although the prevalence of the model parameter what-if values at actual CWP fabrication sites is unknown, the ranges of the model parameter values should be realistic such that any given choice, or what-if value, for any model parameter represents a possible value at actual CWP fabrication sites.  However, as further discussed below, the ranges of the model parameters were estimated with varying levels of accuracy.
What-If Method for Calculating Indoor Air Concentration
The ranges of possible values for the model parameters were estimated as further discussed below.  These ranges consist of low- and high-end values and average, typical, or intermediate values, which are presented in Table 3-4.  For the purpose of this assessment, "intermediate" is defined as a value in-between the low-end and the high-end estimates.  Low and high ends of the range of what-if average formaldehyde indoor air concentrations in CWP fabrication sites were estimated using Equation 1 from what-if values of the model parameters that are within the estimated ranges for these parameters and that result in a wide but realistic range of indoor air concentration.  Due to data gaps with respect to the relative amounts of the three CWPs used at fabrication sites, this what-if approach for estimating indoor air concentration was applied to three limiting cases for the type of CWP that is present at CWP fabrication sites: only HWPW, only PB, or only MDF.  The results of these three limiting cases are combined into ranges to account for mixtures of different CWP types as discussed in Section 4.2.5.
To estimate the what-if low-end indoor air concentration, three estimates of indoor air concentration are calculated, and the minimum value is used as the estimate for the what-if low-end indoor air concentration.  The three estimates are calculated by using the low-end value for one parameter and the average, typical, or intermediate value for the two other varying parameters and repeating this twice with a different parameter having a low-end value each time.  The estimate of the what-if high-end indoor air concentration was similarly calculated.  The what-if estimation method is summarized in Table 3-2.  An intermediate indoor air concentration was also calculated for each of the three limiting cases for CWP type from the typical, average, or intermediate values of the model parameters.  Due to varying uncertainty of the representativeness of the estimated typical, average, or intermediate values of the model parameters, the extent to which these calculated intermediate indoor air concentrations are representative of all exposure levels is unknown.
The model results for the range of average formaldehyde indoor air concentration at CWP fabrication sites for the three limiting cases are presented in Section 4.2.5.

Table 3-2. Summary of What-If Method for the Estimation of the What-If Range of Average Indoor Air Concentrations of Formaldehyde at CWP Fabrication Sites
                          Limiting Cases for CWP Type
   Method for Calculating What-if Low- and High-End Indoor Air Concentration

Determination of What-if Values of the Indoor Air Concentration Model Parameters that Result in a What-if Low-End Indoor Air Concentration
Determination of What-if Values of the Indoor Air Concentration Model Parameters that Result in a What-if High-End Indoor Air Concentration
A total of three cases: HWPW only, PB only, or MDF only is used at a fabrication site
What-if low-end indoor air concentration is estimated as the minimum value from amongst three low-end estimates of indoor-air concentration that are calculated from the following three combinations of parameters:
   1. High-end ventilation rate, intermediate emitting surface area, weighted-average emission rate, and average value for the ambient air concentration of formaldehyde;
   2. Low-end emitting surface area, typical ventilation rate, weighted-average emission rate, and average value for the ambient air concentration of formaldehyde;
   3. Low-end emission rate, typical ventilation rate, intermediate emitting surface area, and average value for the ambient air concentration of formaldehyde.

What-if high-end indoor air concentration is estimated as the maximum value from amongst three high-end estimates of indoor-air concentration that are calculated from the following three combinations of parameters:
   1. Low-end ventilation rate, intermediate emitting surface area, weighted-average emission rate, and average value for the ambient air concentration of formaldehyde;
   2. High-end emitting surface area, typical ventilation rate, weighted-average emission rate, and average value for the ambient air concentration of formaldehyde;
   3. High-end emission rate, typical ventilation rate, intermediate emitting surface area, and average value for the ambient air concentration of formaldehyde.

The basis for the ranges of values of the indoor air concentration model parameters is discussed below and summarized in Table 3-5.
Range of Values for Effective Ventilation Rate
Industrial ventilation rates for all industries, including those unrelated to CWP, vary from 500 to over 10,000 cubic feet per minute (cfm) with a typical value of 3,000 cfm (USEPA 1991a).  The adopted range for this analysis is 500 cfm to 10,000 cfm.  A mixing factor is applied to account for non-ideal mixing of air; the mixing factor is multiplied by the ventilation rate to estimate an effective ventilation rate.  The value of the mixing factor ranges from 0.1 (worst-case) to 1 (ideal mixing) with a typical value of 0.5.  The various combinations of ventilation rate and mixing factor are given in Table 3-3 and the resulting range of effective ventilation rate is 50 to 10,000 cfm.  The final values of effective ventilation rate selected for use in the mass balance equation are the following three values from Table 3-3: 50 cfm (low-end value), 1,500 cfm (typical value), and 10,000 cfm (high-end value).

Table 3-3. Matrix of Ventilation Rates and Mixing Factors
                            Ventilation Rates (cfm)
           Effective Ventilation Rates for each Mixing Factor (cfm)

                           Worst-Case Mixing Factor
                             Typical Mixing Factor
                           Ideal (no mixing factor)

                                      0.1
                                      0.5
                                       1
10,000 (high end)
                                     1,000
                                     5,000
                                    10,000
3,000 (typical)
                                      300
                                     1,500
                                     3,000
500 (worst case)
                                      50
                                      250
                                      500
  Source: USEPA 1991a
  cfm = cubic feet per minute

Range of Values for Emitting Surface Area
The emitting surface area of composite wood products in CWP fabrication sites is the most uncertain of the three parameters of the mathematical model.  In CWP fabrication sites, CWP panels can be stacked, in which case the emitting surface area of the stack would be the top surface of the top panel plus the summation of the surface area of the edges of each panel in the stack.  It is uncertain how many hours per day any given panel is expected to remain within a stack and how a stack of panels may grow or shrink throughout the day.  Additionally, panels are handled by workers as they process the panels, which can include sawing, sanding, routing, and assembling (OSHA 2009a; see Appendix F for a categorization of the worker activities identified in the obtained OSHA IMIS data).  During processing activities, all sides of the panel can be exposed to the air as workers handle, transfer, and process the panels.  Therefore, the emitting surface area of a panel can be equal to all surfaces and edges of the panel for some part of a single day of operation.  Finally, when the panels are assembled into a finished fabricated product, some panel surfaces can be covered due to stacking or overlapping the panels with other materials.  There is uncertainty as to the emitting surface area of panels incorporated into a final fabricated product.  Additionally, panels can be covered with decorative finishes or overlays.  However, the effect of barriers due to decorative finishes or overlays is to reduce the emission rate of the panel but not the emitting surface area (CPA 2003a).  The principle is that a finished or overlayed surface is still available for emission, but the actual emission rate is reduced due to the overlay.
Due to data gaps in information on the range of possible values for emitting surface area and due to the expected high variation in the value for this model parameter based on the above discussion, a range for this model parameter is estimated as follows.  The estimate of the emitting surface area is based on the aggregate average throughput of CWP panels per site.  Throughput is estimated from the estimated domestic consumption of CWP at baseline, the total number of CWP fabrication sites at baseline, and an estimate of the sites' operating days per year.  The baseline U.S. consumed volume of CWP for the three CWP types combined, which accounts for domestic production less exports and plus imports, is 18,045,282 m[3] (USEPA 2010a) with a total surface area of 1,895 million m[2] (assuming each CWP has a thickness of (3/4) inch and that both sides of the panel are exposed to air).  This quantity of material was divided by the total number of assessed CWP fabrication sites, 33,737 sites (USEPA 2010a), and the number of operating days (which was not determined but was assumed to be equal to the assessed frequency of exposure of 250 days per year) to obtain 224.6 m[2] per site per day, which is an estimate of the daily throughput, or amount processed daily, of all three CWP types combined (the number of sites and the frequency of exposure are given in Section 4.2.2).
This intermediate estimate of emitting surface area is predicated on the aggregate average site-specific throughput of CWP panels (assuming a (3/4) inch thickness) and that both sides of the panel throughput are available for emission.  As discussed above, it is recognized that panels processed in a single day can have less than their full two sides available for emission for part of the day.  It is additionally recognized that inventoried panels that are not processed in a given day can also contribute to formaldehyde emissions (such as from a stack of panels).  The effect of these uncertainties on the intermediate estimate cannot be quantified.  Since the estimation method of emitting surface area is highly uncertain, a range of values for emitting surface area was adopted by assuming that the low-end and high-end values are equal to 10% and 1,000%, respectively, of the intermediate estimate of emitting surface area based on throughput.  The 10% and 1,000% values of this intermediate estimate are hereinafter referred to as the low-end and high-end estimates, respectively.  The adopted range for emitting surface area including the intermediate value is given in Table 3-4.
Range of Values for Emission Rate
The emission rate is the only parameter of the mass balance equation that will be affected by the FSCWPA; therefore, values for this parameter were obtained for the baseline and for each of the analytical options.  Emission levels for the baseline and for the analytical options were obtained from the EPA market profile (USEPA 2010a) and the EPA draft exposure assessment (USEPA 2009b), respectively, and are presented in Appendix D.  Uncertainty in the values of these emission levels and their applicability to the estimation of average indoor air concentration in a CWP fabrication site is discussed below.
Representativeness of Emission Levels Reported in the EPA Market Profile
The emission level estimates for domestic and Canadian CWPs at baseline were obtained from an EPA survey of domestic CWP manufacturers.  The survey received the following response rates from the manufacturing facilities (mills) that received the survey: 85% of the 39 HWPW mills surveyed; 100% of the 20 MDF mills surveyed; and 97% of the 31 PB mills surveyed.  The mills surveyed only included mills subject to FSCWPA and did not include mills that only produce products exempted or not otherwise covered by FSCWPA.  Therefore, the survey results for domestic CWPs are likely representative of all U.S. CWP manufacturing mills subject to FSCWPA.  However, the EPA market profile notes that some survey responders only provided information about the compliance standards being achieved but not specific emission levels (USEPA 2010a).  Therefore, the surveyed population of mills is likely representative of U.S. mills subject to FSCWPA.  The emission level estimates for non-Canadian imported CWPs at baseline were estimated from data from a 2009 presentation by Professional Service Industries (PSI), a CARB third-party certifier (TPC) that mainly certifies mills located in Asia.  The mills certified by PSI are major sources of CWPs imported into the U.S. (USEPA 2010a).  The EPA market profile discusses the method in which data were obtained from the presentation and used to estimate imported CWP emission levels at baseline (USEPA 2010a).  The representativeness of the emission level values for non-Canadian imported CWP is uncertain.
Accuracy of Emission Level Values Reported in the EPA Market Profile
As discussed above, some survey responders only stated the compliance standard they would achieve and not the specific emission levels of their products; in such case, the actual emission level may be lower than the compliance standard.  All survey data were assumed to represent actual emission levels of products, and therefore these data may be an overestimate of emission level.  CARB ATCM emission standards are based on the ASTM E1333 chamber test method (ASTM 2002a).  Therefore, it is assumed that emission levels reported in the survey and provided from PSI are based on the ASTM E1333 chamber test method (see Appendix E for a description of ASTM E1333).  The emission levels from the survey and the PSI presentation are converted to emission rates in units of flux for use in the indoor air concentration mathematical model according to the equations described in ASTM E1333 (see Appendix E).  Another consideration with respect to the accuracy of the emission levels reported in the EPA market profile is the accuracy associated with the measurements made to obtain these values.  ASTM E1333 discusses the precision and bias of the large chamber test method in general.  However, ASTM E1333 does not discuss the accuracy and precision of the analytical test method recommended in ASTM E1333 for measuring formaldehyde levels in the chamber air samples: NIOSH 3500 chromotropic acid test procedure.  The accuracy and precision of this procedure is discussed in NIOSH 3500 (NIOSH 1994a).  ASTM E1333 does not discuss the overall accuracy of the test chamber method for determining accurate formaldehyde off-gassing emission rates.  Additionally, it is uncertain if chamber test results from ASTM E1333 accurately represent actual off-gassing rates in real world industrial settings, including CWP fabrication mills.  For ASTM E1333 chamber test results to accurately represent off-gassing rates in actual CWP fabrication mills, the ASTM E1333 parameters should be consistent with the actual conditions in the fabrication sites.  However, adequate data to perform this comparison were not available.  This assessment did not consider how ASTM E1333 uncertainties would impact the overall uncertainty of the assessment results.  However, it is likely that ASTM E1333 uncertainties are of small impact to the assessment results compared to the uncertainties of other mathematical model parameters.  It is also uncertain as to what extent manufacturers will actually obtain their predicted emission levels in 2013.
Applicability of Emission Level Values Reported in the EPA Market Profile to the Estimation of Average Indoor Air Concentration in a CWP Fabrication Site
An additional consideration is the decay with time of CWP formaldehyde emission levels.  Various literature sources have discussed the decay of formaldehyde emission levels with time, such as Groah 2005a, Zinn 1990a, and Gammage 1988a.  A wide range of values for the formaldehyde emission level half life for PB, MDF, and HWPW were reported in these articles.  The studies, which span a period of approximately 20 years, cite CWP emission level half lives ranging from less than three months to less than two years.  Not all tests used the same test method for determining emission level half life.  Additionally, the test method conditions may not be similar to the conditions of storage and transport between CWP manufacture and fabrication.  Therefore, the test results may not be applicable for the emission level decay experienced during storage and transport.  The initial emission level has a moderately strong influence on half life (Groah 2005a).  A higher initial emission level will result in a more rapid decay (Groah 2005a).  Therefore, half lives from older studies may not be applicable for newer or future CWPs with lower initial emission levels, which would have less rapid decays.
The available literature on formaldehyde emission level decay indicate that CWPs at CWP fabrication sites could have emission levels less than their emission levels at the time of their manufacture if the time for distribution from manufacturer to fabricator is considerable and depending on the conditions of storage and transport prior to delivery to the fabricator.  However, the residence time of CWPs at CWP fabrication sites is small and would likely not result in significant further emission level decay while the CWPs are at the fabrication site.  Formaldehyde emission level decay is not accounted for in this assessment due to data gaps in decay rates for CWPs manufactured at the baseline or under any of the analytical options.  In this assessment, formaldehyde concentration modeling at CWP fabrication sites assumes the emission levels from the EPA market profile (USEPA 2010a) are for newly-manufactured CWPs, which may overestimate the actual emission levels at CWP fabrication sites.
The range of emission levels and corresponding emission rates, including weighted-average values for the baseline and analytical options, is given in Table 3-4.  These values account for both domestically manufactured and imported CWPs.  See Appendix D for a complete list of the emission levels for baseline and each analytical option.  It is important to note that CWPs will continue to emit formaldehyde as they are overlayed and after they are overlayed.  However, emissions from overlayed panels at CWP fabrication sites were not accounted for in the estimation of indoor air concentration.  Many overlay materials serve as a barrier and reduce formaldehyde emissions from 50% to as much as 95% or higher (CPA 2003a).  Therefore, emissions from overlayed products have a diminished effect on indoor air concentrations compared to non-overlayed products at CWP fabrication sites.
Value for Ambient Air Formaldehyde Concentration
Limited statistics of ambient air formaldehyde concentrations are available in the EPA draft report Formaldehyde from Pressed Wood Products: Exposure Assessment (USEPA 2009b).  Table 3-1 of the draft exposure assessment provides ambient air formaldehyde concentrations for various land use categories.  The CWP fabrication indoor air concentration mathematical model uses the average value of the ambient formaldehyde concentration for industrial land use areas.  The average value is chosen for use in this mathematical model since the low standard deviation indicates limited variation in this parameter and the average value is representative.  This average value of 6.28 ug/m[3] is kept constant throughout the what-if calculations.
Table 3-4. Estimated Values for Parameters in the Mathematical Model for Average Indoor Air Concentration at a CWP Fabrication Site for the Baseline and the Analytical Options
                                Parameter Name
                                   Scenario
                              (Analytical Option)
                              Value of Parameter

                                     Units
                    Intermediate / Typical / Average Value
                                 Low-End Value
                                High-End Value
Emitting Surface area
All
                                     m[2]
                                     224.6
                                     22.5
                                     2,246
Ventilation Rate
All
                                      cfm
                                   (m[3]/h)
                                     1,500
                                    (2,549)
                                      50
                                     (85)
                                    10,000
                                   (16,990)
HWPW Emission Level
Baseline
                                      ppm

                                     0.04
                                     0.013
                                     0.163

CARB Phase 1

                                     0.025
                                     0.013
                                     0.058

FSCWPA / CARB Phase 2

                                     0.021
                                     0.013
                                     0.032

NAF

                                     0.013
                                     0.013
                                     0.013
PB  Emission Level
Baseline
                                      ppm

                                     0.06
                                     0.013
                                     0.384

CARB Phase 1

                                     0.05
                                     0.013
                                     0.090

FSCWPA / CARB Phase 2

                                     0.053
                                     0.013
                                     0.057

NAF

                                     0.013
                                     0.013
                                     0.013
MDF Emission Level
Baseline
                                      ppm

                                     0.08
                                     0.024
                                     0.502

CARB Phase 1

                                     0.07
                                     0.024
                                     0.140

FSCWPA / CARB Phase 2

                                     0.073
                                     0.024
                                     0.082

NAF

                                     0.035
                                     0.024
                                     0.035
Ambient (outdoor) Air Concentration of Formaldehyde
All
                                   ug/m[3]
                                     6.28
                                Parameter Name
                                   Scenario
                              (Analytical Option)
                              Value of Parameter

                                     Units
                    Intermediate / Typical / Average Value
                                 Low-End Value
                                High-End Value
HWPW Emission Rate
Baseline
                                  ug/m[2]-h
                                     60.9
                                     18.6
                                     232.9

CARB Phase 1

                                     36.0
                                     18.6
                                     82.9

CARB Phase 2

                                     29.8
                                     18.6
                                     45.7

NAF

                                     18.6
                                     18.6
                                     18.6
PB  Emission Rate
Baseline
                                  ug/m[2]-h
                                     81.7
                                     18.6
                                     548.8

CARB Phase 1

                                     77.1
                                     18.6
                                     128.6

CARB Phase 2

                                     75.8
                                     18.6
                                     81.5

NAF

                                     18.6
                                     18.6
                                     18.6
MDF Emission Rate
Baseline
                                  ug/m[2]-h
                                     180.5
                                     56.7
                                    1186.5

CARB Phase 1

                                     173.6
                                     56.7
                                     330.9

CARB Phase 2

                                     172.5
                                     56.7
                                     193.8

NAF

                                     81.6
                                     56.7
                                     82.7
 Notes:  Table 3-5 indicates the sources of these data.  Emission rates are shown as both emission levels in units of ppm and as emission rates in units of flux in ug/m[2]-h for convenience of the reader.  Emission levels are assumed to represent the measured concentration from ASTM E1333, while emission rates in units of flux represent the emission rate value calculated from the measured concentration and the ASTM E1333 test parameters.  Appendix E describes ASTM E1333 and the conversion between emission levels in units of concentration and emission rates in units of flux.

Table 3-5. Data Sources for the Estimation of Parameters of the Mathematical Model for Average Indoor Air Concentration at a CWP Fabrication Site
                                Parameter Name
                              Intermediate Value
                                 Low-End Value
                                High-End Value
Emitting Surface Area
(see "Range of Values for Emitting Surface Area" in Section <IP_ADDRESS>)
Aggregate average daily throughput estimated as the baseline U.S. consumed volume of CWP divided by the assessed number of fabrication sites and the assessed exposure frequency
10% of aggregate average daily throughput
1,000% of aggregate average daily throughput
Effective Ventilation Rate
(see "Range of Values for Effective Ventilation Rate" and Table 3-3 in Section <IP_ADDRESS>)
Typical ventilation rate multiplied by typical mixing factor.
Worst-case ventilation rate multiplied by worst-case mixing factor
High-end ventilation rate assuming ideal mixing (no mixing factor applied)
HWPW, PB, or MDF Emission Rates
Baseline  Values