Formaldehyde Emissions From Laminate Flooring.
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 product with medium density fiberboard (MDF) cores that emitted amounts of formaldehyde that were more than 13 times the maximum allowed by CARB ATCM Phase 2 regulations.
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 ureaformaldehyde (UF) resins.
Because of concerns raised by the "60 Minutes" report, the Consumer Product Safety Commission (CPSC) tested laminate flooring samples manufactured in China during 2012 to 2014 and sold at Lumber Liquidators stores. CPSC subsequently requested that the Centers for Disease Control and Prevention (CDC) evaluate the test results for possible health effects. (3)
The CDC report initially contained an error in the modeling of the potential exposures and health risks, where they assumed that the residential ceiling height was 8 m instead of 8 ft, which resulted in the model underpredicting formaldehyde exposures by a factor of 3.28 (i.e., 1 m = 3.28 ft). While the CDC corrected this error, the CDC also erroneously assumed that the emissions of formaldehyde remained constant for the first two years following installation and then became zero after two years, an error that has never been corrected.
The MDF core of Lumber Liquidators' laminate flooring is 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 hydrolysis of the UF resin by water vapor. The free formaldehyde results in initially higher emission rates following installation, while hydrolysis caused by indoor relative humidity is responsible for the long-term emission rates. (4)
The top (wear) layer of laminate flooring typically consists of a melamine resin, which is not a significant emitter of formaldehyde and provides an effective diffusion barrier for formaldehyde emissions from the MDF core into the indoor air. Because of the wear layer and the placement of flooring on a solid substrate, the pathways for formaldehyde from the MDF core to enter indoor air are the many click-joints, typically on all four edges of the floorboards, and the cut edges at the perimeter of a room.
At Indoor Air 2016 I presented a paper, (5) which reanalyzed the same data in the CDC report with the formaldehyde emissions decay rate corrected as described by Brown (6) for laminate flooring. The initial decay rate has a half-life of just 21 days, and the long-term decay rate resulting from hydrolyses has a half-life of 71.9 years. Emission rate measurements made of actual Lumber Liquidators' laminate flooring over a four-month period confirm an almost constant long-term formaldehyde emission rate.
Using the corrected formaldehyde emission rate decay rates described above, I used the same probabilistic modeling analysis and input parameters that the CDC used to recalculate a range of formaldehyde concentrations in residential indoor air using a Monte Carlo simulation with 100,000 realizations using random combinations of the input parameters. The following are the input parameters used for this analysis:
* Emission Factor (EF: [micro]g/[m.sup.2] x h): log normal distribution, mean log = 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);
* Laminate floor coverage (% of total floor area): 100.
The results of these calculations are summarized in Figure 2, along with the relevant noncancer exposure guidelines.7,8 The initial formaldehyde concentrations range from a median of 189 [micro]g/ [m.sup.3] (i.e., 50th percentile; 50% of the homes have higher concentrations) to 929 [micro]g/[m.sup.3] for the highest 5% of the homes (i.e., the 95th percentile). Note that 1 [micro]g/[m.sup.3] equals 0.8 parts per billion or 0.0008 parts per million. These are very high indoor formaldehyde concentrations. By comparison, the median indoor concentration in the 108 new homes of CNHS is just 36 [micro]g/[m.sup.3], with a 95th percentile of 100 [micro]g/[m.sup.3] and a maximum of 136 [micro]g/[m.sup.3].
The formaldehyde concentrations from Lumber Liquidators' laminate flooring substantially exceed the recommended noncancer exposure guidelines as summarized by the hazard quotients in Table 1.
Hazard quotients are the ratio of the exposure to the exposure guideline-ratios greater than 1.0 indicate a health risk.
And the emissions of formaldehyde from laminate flooring persist for a long time (e.g., more than 100 years), such that the indoor concentrations ten years after installation remain quite high, ranging from a median concentration of 76 [micro]g/[m.sup.3] to a 95th percentile concentration of 372 [micro]g/[m.sup.3]. (5)
These projected indoor concentrations also represent significant cancer health risks. Both the CDC's and our cancer risk calculations use the EPAs inhalation unit risk (IUR) for formaldehyde, which is 1.3 x [10.sup.-5] [(ug/[m.sup.3]).sup.-1].
The calculated cancer risks in our analyses using the correct formaldehyde emissions decay rate for laminate flooring are more than 12 times higher than those reported by the CDC. The CDC reports an excess cancer risk of 30 per 100,000 for the 95th percentile, while our analysis indicates a cancer risk of 376 per 100,000, which is 376 times the no significant risk level (NSRL) of one excess cancer case per population of 100,000. (9)
All of the exposure calculations (CDC and herein) assume that the entire floor of the home is covered with the Lumber Liquidators' laminate flooring and has continuous occupancy 24 hours/day. If the installed flooring does not cover the entire floor, the noncancer and cancer hazard quotients will be correspondingly lower (e.g., if only 50% of the total floor area is covered, the modeled concentrations will be one half of those presented). Similarly, if the average time of exposure in the home is less than 24 hours/day the cancer risks will be correspondingly lower.
In conclusion, exposure to the formaldehyde released by Lumber Liquidators laminate flooring manufactured in China represents significant noncancer and cancer health effects. In addition, the emissions of formaldehyde persist for much longer than the two years that the CDC estimates, (3) lasting for more than 100 years.
While increasing the ventilation of the residence (e.g., opening windows) can produce small reductions in the indoor formaldehyde concentrations (e.g., 20% to 30%), depending on the regional climate, the increases in heating and cooling costs can be significant (e.g., hundreds of dollars per year). Air cleaners are also not a solution, as they remove only a fraction of the formaldehyde removed by ventilation. More importantly, neither ventilation nor air cleaning can mitigate the health risks associate with laminate flooring. Only removal of the laminate flooring can achieve complete mitigation.
Does all laminate flooring emit large amounts of formaldehyde? No. Our testing to date has only identified problems with Lumber Liquidators' laminate flooring manufactured in China prior to 2016. (Lumber Liquidators no longer sells this flooring.)
What if you don't know if your laminate flooring is from Lumber Liquidators manufactured in China?
The only way to know if there is a problem with formaldehyde from your laminate flooring is to test it.
The following is a link from Indoor Environmental Engineering called "Laminate Flooring Formaldehyde Fact Sheet," which contains some formaldehyde testing options for homeowners: http://www.iee-sf.com/pdf/ LaminateFlooringFormaldehydeFactSheetrev3.pdf.
Finally, are there resin systems other than ureaformaldehyde (UF) resin that composite wood products such as MDF can be manufactured with that do not emit, or emit much less, formaldehyde? Yes, and one alternative is phenol-formaldehyde (PF) resin, which is a much more stable resin system. And, unlike UF resins, it does not release any significant amounts of formaldehyde from hydrolysis when exposed to water vapor.
For this reason, PF resins are routinely used for exterior products.
So why aren't PF and other alternative resin systems used for interior products such as MDF? I think the answer to this question is the same one I received as a young researcher at an ASHRAE Annual Meeting 35 years ago. At that meeting, I asked an executive of a large wood products manufacturing company why, if PF resins only increase the cost of a sheet of plywood by a few cents, don't you use PF resins for manufacturing interior plywood? He looked me in the eye and said "Son, we manufacture hundreds of millions of panels of interior plywood each year. You do the math."
(1.) Offermann, F. 2009. "Ventilation and Indoor Air Quality in New Homes." California Environmental Protection Agency Air Resources Board and California Energy Commission, PIER Energy-Related Environmental Research Program. Collaborative Report. CEC-500-2009-085. http://tinyurl.com/glv6kur.
(2.) CARB. 2008. 'Airborne Toxic Control Measure to Reduce Formaldehyde Emissions From Composite Wood Products, Final Regulation Order." Section 93120-93120.12, Title 17, California Code of Regulations. California Air Resources Board. http://tinyurl.com/lvbxtdy.
(3.) CDC. 2016. "Possible Health Implications From Exposure to Formaldehyde Emitted From Laminate Flooring Samples Tested by the Consumer Product Safety Commission." Centers for Disease Control and Prevention. http://tinyurl.com/govn2wn.
(4.) Brown, S. 1999. "Chamber assessment of formaldehyde and VOC emissions from wood-based panels." Indoor Air 9(3):209-215.
(5.) Offermann, F. 2016. "Formaldehyde emission rates from lumber liquidators laminate flooring manufactured in China." Indoor Air 2016.
(6.) Brown, S. 2002. "Volatile organic pollutants in new and established buildings in Melbourne, Australia." Indoor Air 12(1):55-63.
(7.) WHO. 2010. WHO Guidelines for Indoor Air Quality: Selected Pollutants. Geneva: World Health Organization. http://tinyurl.com/6d2xxmg.
(8.) OEHHA. 2016. "OEHHA Acute, 8-Hour and Chronic Reference Exposure Level (REL) Summary." Office of Environmental Health Hazard Assessment. http://tinyurl.com/zht7934.
(9.) OEHHA. 2016. "Proposition 65 No Significant Risk Levels (NSRLs) for Carcinogens and Maximum Allowable Dose Levels (MADLs) for Chemicals Causing Reproductive Toxicity." Office of Environmental Health Hazard Assessment. http://tinyurl.com/hv4rltm.
Francis (Bud) J. Offermann, P.E., C.I.H., is president of Indoor Environmental Engineering in San Francisco and the 2016 recipient of the ASHRAE Environmental Health Award.
Caption: FIGURE 1 Depiction of the various construction layers of laminate flooring.
Caption: FIGURE 2 Projected indoor formaldehyde concentrations from Lumber Liquidators laminate flooring manufactured in China and relevant noncancer exposure guidelines.
TABLE 1 Hazard quotients associated with the formaldehyde emissions from Lumber Liquidators' laminate flooring made in China. FORMALDEHYDE HAZARD QUOTIENTS EXPOSURE GUIDELINES 50TH PERCENTILE 95TH (MEDIAN) PERCENTILE 30-Minute Exposure (100 1.9 9.3 [micro]g/[m.sup.3]) (7) 1-Hour Exposure (55 3.4 17 [micro]g/[m.sup.3]) (8) 24-Hour Exposure (9 21 103 [micro]g/[m.sup.3]) (8)
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|Title Annotation:||COLUMN: IEQ APPLICATIONS|
|Author:||Offermann, Francis (Bud) J.|
|Date:||Mar 1, 2017|
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