Formaldehyde Emission Rates From Lumber Liquidators Laminate Flooring Manufactured in China Francis J. Offermann, PE, CIH 1*, 1
Indoor Environmental Engineering, San Francisco, CA Corresponding Email:
[email protected] SUMMARY The Consumer Product Safety Commission (CPSC) tested laminate flooring samples manufactured in China during 2012-2014 and sold at Lumber Liquidators stores. CPSC subsequently requested that the Center for Disease Control and Preventions (CDC) evaluate the test results for possible health effects. CDC reported that while the modeled initial indoor concentrations of formaldehyde from Lumber Liquidators flooring represent significant noncancer health effects, these concentrations may dissipate within several years. This paper reanalyzes the same data and calculates that the non-cancer and cancer health effects will persist for long periods of time (e.g. greater than 78 years), and that cancer risks are more than 12 times higher than those reported by CDC. PRACTICAL IMPLICATIONS The modeled indoor concentrations of formaldehyde from Lumber Liquidators flooring indicate significant non-cancer and cancer health effect that will persist for long periods of time (e.g. greater than 78 years). When considering the health effects of indoor sources of formaldehyde, such as laminate flooring, it is essential to obtain representative data on the long-term decay in emissions. KEYWORDS Cancer, Emission Rates, Formaldehyde, Laminate Flooring. 1 INTRODUCTION A study of indoor air quality and ventilation conducted in 108 new (i.e. < 5 years old) singlefamily residences in California (Offermann, 2009) identified formaldehyde as having the highest risk for cancer and non-cancer risks. In addition, the study concluded that increased ventilation was not a viable solution for controlling the indoor concentrations of formaldehyde. As a result of this and other studies, the California Air Resources Board (CARB) regulated the emissions of formaldehyde from composite wood products sold in California under an Airborne Toxic Control Measure (ATCM, CARB, 2008). On March 1, 2015, the CBS news program 60 Minutes reported that an American company, Lumber Liquidators, was selling a Chinese-produced laminate wood flooring products with medium density fiberboard (MDF) cores that emitted formaldehyde in excess of the CARB ATCM Phase 2 regulations. Because of concerns raised by the 60 Minutes report, the Consumer Product Safety Commission (CPSC) tested laminate flooring samples manufactured in China during 2012-2014 and sold at Lumber Liquidators stores. CPSC subsequently requested that the Center for Disease Control and Prevention (CDC) evaluate the test results for possible health effects. Laminate flooring is typically manufactured as depicted in Figure 1. The source of formaldehyde in laminate flooring is the MDF core, or substrate layer of the flooring, that is typically manufactured with urea-formaldehyde (UF) resins. These resins release formaldehyde from the core as free-formaldehyde that exists in the MDF following
manufacture, as well as formaldehyde created from hydrolyses of the UF resin by water vapor. The free-formaldehyde results in initially higher emission rates following installation, while hydrolyses caused by indoor relative humidity is responsible for the long-term emission rates (Brown, 1999). The top (wear) layer of laminate flooring typically consists of a melamine resin containing aluminium oxide. It is not a significant emitter of formaldehyde, and provides a significant diffusion barrier for formaldehyde emissions from the MDF core into the indoor air.
Figure 1. Depiction of the various construction layers of laminate flooring. Because of the wear layer and the placement of flooring on a solid substrate, the only significant pathways for formaldehyde from the MDF core to enter indoor air, are the clickjoints typically on all four edges of the floorboards and the cut edges at the perimeter of a room (An, 2011). In this paper we examine the CDC report (CDC, 2016) that evaluated the cancer and noncancer health effects associated with the formaldehyde emission tests of Lumber Liquidator’s laminate flooring conducted by the Consumer Product Safety Commission (CPSC). 2 MATERIALS AND METHODS As an initial step, CPSC contracted with three accredited, independent laboratories to conduct small chamber testing to measure the formaldehyde emissions from 33 laminated, uninstalled floorboard manufacturing lots (manufactured 2012-2014) representing eight unique floorboard styles. After the small chamber tests were completed, CPSC selected two of the laboratories to conduct large chamber tests. For these tests, CPSC selected samples from the three floorboard manufacturing lots that emitted the highest amounts of formaldehyde in the small chamber tests and samples from the two floorboard manufacturing lots that emitted lower amounts of formaldehyde, to serve as comparison samples. Emission Rate Measurements ASTM Standard Method D6007-14 was used for the small chamber testing. These were not deconstruction tests to measure formaldehyde emissions from the MDF cores. Rather, the finished products were tested with no click-joints and with the perimeter edges sealed. Since the primary pathway for emissions of formaldehyde from the MDF core into indoor air are the unlaminated click-joints and perimeter edges, the small
chamber testing is expected to produce formaldehyde emission rates significantly less than those from an installation in a home. A modified ASTM Standard Method E1333-14 was used for the large chamber testing. The large chamber testing included unlaminated click-joints and perimeter edges, and as such, better represents formaldehyde emissions for installed flooring. Modeled Concentrations. The CDC calculated the indoor concentrations resulting from the installation of the laminate flooring using a well-mixed single-zone mass balance model according to the following equation:
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(!"#∗!)
(1)
C is the indoor air formaldehyde concentration (µg/m3) EF is the emission factor (µg/m2-hr) AER is outdoor air exchange rate (h-1) H is the height of the ceiling (m). For this modeling the CDC assumes that the entire floor area of the home is covered with the laminate flooring.
Probabilistic Analysis. A probabilistic analysis was conduced by CDC using Equation 1 to model a range of formaldehyde concentrations in indoor air using a Monte Carlo simulation with 100,000 realizations utilizing random combinations of the input parameters. The following are the input parameters used for the Monte Carlo analyses: - Emission Factor (EF - µg/m2-h): log normal distribution, meanlog = 5.62, sdlog = 0.59 - Air Exchange Rate (AER – h-1): uniform distribution, min = 0.10, max =1.21 - Ceiling Height (H – m): constant, 2.44 m (8 ft) In this paper, we consider only the CDCs modeling that utilized the large chamber emission rate tests, as only these tests include unlaminated click-joints and perimeter edges, and thus better represent the formaldehyde emission rates in actual home installations. Emission Rate Decay. The emission rate of formaldehyde from laminate flooring is expected to decrease with time as the source is depleted. Knowing this decay rate is essential for calculating the long-term health effects such as cancer. For calculating the cancer risk, the CDC assumed that the emission rate of formaldehyde was constant for the first two years and zero after two years. This assumption was based on the CDC’s review of several studies of formaldehyde concentrations in homes over time. Three of the studies prominently cited are Park (2006), Wolkoff (1991), and Brown (2002). Of these three studies only the Brown study reported the presence of laminate flooring. Park and Ikeda (2006) report formaldehyde concentrations declining in new Japanese homes over a three-year period. - 1st year (134 µg/m3 mean, ± 93 stdev, n=292) - 2nd year (112 µg/m3 mean, ± 105 stdev, n=108) - 3rd year (85 µg/m3 mean, ± 58 stdev, n=60) In this study, there is no evidence that any of the homes had laminate MDF flooring. Plus, there are many other materials in residences that emit formaldehyde with different emission decay rates. Thus, the study may not be relevant for drawing any conclusions regarding the impacts of Lumber Liquidators laminate flooring. Secondly, the number of homes (n) changed drastically as the study advanced from year to year, which undermines the group conclusions
regarding the formaldehyde decay rate from whatever sources were present. Finally, while there was some decrease in the mean formaldehyde concentrations over the three-year period, the indoor concentrations still remained elevated at the 3rd year. The mean concentrations were reduced by only 37% (i.e., 134 µg/m3 to 85 µg/m3). Wolkoff et.al. (1991) reported results for the Danish twin apartment study (one vacant and one occupied). The floor covering in these two apartments was lacquered beech parquet flooring and particleboard with glued linoleum. There was no reported laminate MDF flooring making them irrelevant with respect to the assessment of impacts of the Lumber Liquidators flooring. In both apartments, the formaldehyde concentration decreased from 200-300 µg/m3 to approximately 80 µg/m3 in 35 days. Then over the ensuing 300 days, formaldehyde concentrations ranged from 80 to 400 µg/m3 in the unoccupied apartment and 80-125 µg/m3 in the occupied apartment. The increased concentrations were attributed to elevated indoor air temperatures from solar radiation and no window usage. The Brown (2002) study included a Case A; New Dwelling, which was a new two-story house located in Melbourne, Australia. It was designed to be a "healthy house” with a mechanical supply of outdoor air (0.35 air changes per hour). This house included “laminated high density fiberboard” and "full lamination of wood-based kitchen cupboards”. Brown used a double exponential curve fit for the decay rate. The fast decay time constant of 0.0014 h-1 represents a half-life of just 21 days and is believed to be associated with the release of residual free-formaldehyde from the manufacturing process. The slow decay time constant of 0.0000011 h-1 represents a half-life of 71.9 years and is believed to be the result of formaldehyde released by hydrolysis of the urea-formaldehyde resin in the composite woods caused by normal exposure to water vapor in the indoor air. For our analyses in this paper we have adopted the Brown (2002) double exponential decay rate as being the most representative of the formaldehyde emission decay rate from laminate flooring. 3 RESULTS Table 1 summarizes the formaldehyde emission rate measurements commissioned by the CPSC for five different laminate flooring manufacturing lots measured by two labs in small and large test chambers. Table 1. Formaldehyde emission rates of five different laminate flooring manufacturing lots measured by two labs in small and large test chambers (CDC, 2016).
Sample ID 1
Small Test Chamber (µg/m3-h) Lab A Lab B 290 50
Large Test Chamber (µg/m3-h) Lab A Lab B 588 472
4 5
40 170
20 70
229 272
154 231
6
350
80
629
367
10
20
20
157
115
For the small test chamber, the differences between Lab A and Lab B emission rates are significant, with an average relative standard deviation (RSD) of 0.54, and with Lab A results consistently higher than those of Lab B. For the large test chamber measurements, the
differences between the two labs are less, with an average RSD of 0.23 (i.e. 2.6 times lower than the small test chamber tests). The larger variation observed in the small test chamber tests can be partially attributed to the lower test chamber concentrations and higher analytical detection limits for these tests. Both ASTM D6607 (small chamber tests) and ASTM E1333 (large chamber tests) specify a modified NIOSH 3500 (NIOSH, 2015) as the primary analytical method. This method has a lower measurement range of 2 µg. Since E1333 requires a minimum of a 60 L air sample and D6007 requires a minimum of 30 L, this translates into minimum measurable emission rates of 57 µg/m3-h, for the small test chamber tests and 29 µg/m3-h for the large chamber tests using the NIOSH 3500 primary analytical method. Five of the ten small chamber tests and none of the large chamber tests were below the minimum measurable emission rate, thus a higher variation in the small chamber tests is expected. The significantly higher emission rates observed in the large test chamber measurements can be attributed to the presence of the unlaminated click joints and perimeter edges in these tests. The regulatory CARB ATCM Phase 2 formaldehyde concentration requirement for unfinished MDF is 0.11 ppm as determined by ASTM E-1333 (large test chamber) or D-6007 (small test chamber). This concentration corresponds to an emission rate of 159 µg/m2-h, at the specified test conditions. The emission rates from the CPSC large chamber tests ranged from 115 to 629 µg/m2-h, with 7 of the 10 tests exceeding the CARB Phase 2 159 µg/m2-h maximum allowable emission rate. As these tests were conducted with finished MDF boards with a top wear layer of melamine resin, which in itself is not a significant emitter of formaldehyde and which provides a significant diffusion barrier for formaldehyde emissions from the MDF cores, it is presumed that these products had MDF cores with formaldehyde emissions well above the Phase 2 limit. Figure 2 compares indoor formaldehyde concentrations over a 78-year period as modeled by the CDC and as modeled using a double exponential emission decay rate as described by Brown (2002) for laminated wood products. The 78-year average indoor concentration is 12.1 times higher for the concentrations modeled using the double exponential emission decay rate. Table 2 summarizes the indoor formaldehyde concentrations calculated by the probabilistic analyses and utilizing the large test chamber emission rates for six population percentiles (i.e. 5 to 95). The percentiles represent the percentage of homes at or below the modeled concentrations and exposures (e.g. the initial indoor concentration is less than 352 µg/m3 for 75 percent of the homes, or conversely, the indoor concentration is greater than 352 µg/m3 for 25% of the homes). C (initial) represents the initial indoor concentration utilizing the emission rates from the large test chamber tests. As the samples were conditioned for a seven-day period prior to testing, the C (initial) concentrations represent those at seven days following installation. The C (78 yr average) is the average indoor concentration calculated using the double exponential emission decay rate. C (78 yrs) represents the indoor concentration 78 years following installation. The hazard quotients (HQ) in Table 2 are the ratios of the calculated indoor concentrations or cancer risks to the health exposure guidelines. Hazard quotients in excess of 1.0 indicate a health risk. For non-cancer health effects, we used the California Office of Environmental Health Hazard Assessment, OEHHA (2014), Chronic Reference Exposure Levels (CRELs) and Acute Reference Exposure Levels (ARELs). The CRELs are for chronic 24-hour/day exposure and the ARELs are for one-hour exposures. These exposure guidelines are designed
to be protective for the general population including sensitive individuals. The formaldehyde CREL is 9 µg/m3 and the AREL is 55 µg/m3.
Figure 2. Indoor formaldehyde concentrations as modeled by the CDC (2016) and as modeled using a double exponential emission decay rate from Brown (2002). Table 2. Modeled indoor formaldehyde concentrations, cancer risks and hazard quotients. 5 25 50 75 90 95 Percentile a 54 110 189 352 649 929 C (initial) b - µg/m3 C (78 yr avg) c - µg/m3 17 23 59 110 202 290 d 3 C (at 78 yrs) - µg/m 11 34 39 73 135 194 HQ-CREL (initial) e 6 12 21 39 72 103 HQ-CREL (at 78 yrs) f 1.2 2.6 4.3 8.1 15.0 21.6 HQ-AREL (initial) g 1.0 2.0 3.4 6.4 11.8 16.9 HQ-AREL (at 78 yrs) h 0.2 0.4 0.7 1.3 2.5 3.5 Cancer Risk and HQ i 22 44 77 142 263 376 a.) Percentage of homes at or below the modeled concentrations and exposures. b.) Initial concentration (µg/m3), seven days after installation. c.) 78 year average concentration d.) Concentration at 78 years e.) Initial CREL Hazard Quotient – Initial concentration divided by formaldehyde OEHHA CREL (9 µg/m3) f.) CREL Hazard Quotient at 78 years – Concentration at 78 years divided by formaldehyde OEHHA CREL (9 µg/m3) g) Initial AREL Hazard Quotient – Initial concentration divided by formaldehyde OEHHA AREL (55 µg/m3) h.) AREL Hazard Quotient at 78 years – Concentration at 78 years divided by formaldehyde OEHHA AREL (55 µg/m3) i.) Cancer Risk (excess cases per 100,000). Using EPA Inhalation unit risk (IUR) for formaldehyde: 1.3 E-5 (µg/m3)-1, and continuous exposure. This is also the Cancer Hazard Quotient (HQ) - excess cases per 100,000 divided by 1 excess case per 100,000 - California OEHHA, No Significant Risk Levels (NSRL) for carcinogenic health effects.
We calculated the cancer risks from the modeled 78-year average indoor concentrations and the EPA inhalation unit risk (IUR) of 1.3E-5 (µg/m3)-1 for formaldehyde and assuming continuous 24-hour/day exposure. For an acceptable cancer risk, we used the California Office of Environmental Health Hazard Assessment, OEHHA (2013), No Significant Risk Level (NSRL) of 1 excess cancer case per population of 100,000. 4 DISCUSSION With respect to non-cancer health effects (e.g. eye, nose and throat irritation), the modeled indoor formaldehyde concentrations indicate significant health risks that persist for a long time (e.g. 78 years). The hazard quotients for the initial long-term 24-hour exposures (HQCREL), are >6 for 95% of the homes and >21 for half the homes (i.e. 50th percentile, median). The hazard quotients for the initial short-term 1-hour exposures (HQ-AREL) are >2.0 for 75% of the homes and >3.4 for half the homes. These non-cancer hazard quotients persist, with hazard quotients for the long-term 24-hour exposures (HQ-CREL) at 78 years of >1.2 for 95% of the homes and >4.3 for half the homes. The hazard quotients for short-term 1-hour exposures (HQ-AREL) at 78-years is >1.3 for 25% of the homes. With respect to cancer health effects, the modeled indoor formaldehyde concentrations also indicate significant health risks. The cancer risks (excess cases per 100,000) and the hazard quotients are >22 for 95% of the homes, >77 for half the homes, and >376 for 5% of the homes. The calculated cancer risks in our analyses using a double exponential emission decay rate are more than 12 times higher than those reported by the CDC using an assumed initial emission rate that is constant for two years and then zero after two years. The CDC reports an excess cancer risk of 30 per 100,000 for the 95th percentile (i.e. 5% of the homes), while our analysis indicates a cancer risk more than 12 times higher (i.e. 376 per 100,000). All of the exposure calculations (CDC and herein) assume that the entire floor of the home is covered with the laminate flooring and 24-hour/day occupancy. If the installed flooring does not cover the entire floor, the non-cancer and cancer hazard quotients will be correspondingly lower (e.g., if only 50% of the total floor area is covered the modeled concentrations and hazard quotients will be one half of those presented in Table 2). Similarly, if the average time of exposure in the home is less than 24-hours/day then the cancer risks will be correspondingly lower. Additionally, neither analysis considers other factors needed for a full risk assessment, such as product replacement cycle and fraction of lifetime spent in a singlefamily residence. 5 CONCLUSIONS The modeled indoor concentrations of formaldehyde from Lumber Liquidators flooring indicate significant non-cancer and cancer health effects will persist for long periods of time (e.g., greater than 78 years). The cancer risks calculated in this paper are more than 12 times higher than those reported by CDC when analyzing the same data set. Our re-analysis emphasizes the importance of measuring the long-term decay of sources of formaldehyde and other volatile organic chemical emissions when conducting exposure and risk assessments. 6 REFERENCES An J, Kim S, and Kim H, Formaldehyde and TVOC emission behavior of laminate flooring by structure of laminate flooring and heating condition. Journal of Hazardous Materials, 197, 44-51.
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