Environ. Sci. Technol. 1984, 18, 682-686
Formaldehyde Release from Selected Consumer Products: I nfhence of Chamber Loading, Multiple Products, Relative Humidity, and Temperature John A. Plckrell,' Larry C. Grifflslt Brian V. Mokier,z George M. Kanapiliy,l and C. H. Hobbs Inhalation Toxicology Research Institute, Lovelace Biomedical and Environmental Research Institute, Albuquerque, New Mexico 87 185
rn Formaldehyde release rates were measured for one sample each of a variety of consumer products under various conditions of temperature, humidity, and mass loading in a ventilated chamber. The rate of formaldehyde released from pressed wood products was much greater than from insulation material or carpeting, whether measured in a dynamic (ventilated) or static (nonventilated) chamber. Formaldehyde was released from wood products at a more rapid rate when chamber loadings (product surface area/chamber volume) and chamber concentrations of formaldehydewere reduced. Formaldehyde release from particle board and plywood was not substantially affected by the different temperatures (25-35 "C) and humidities (40-90%) tested. When particle board was paired with plywood, insulation, or carpet, the formaldehyde released was less than the sum of that released when each product was tested alone. These data suggest that these samples of plywood, insulation, or carpet (slow releasers of formaldehyde) absorbed formaldehyde released from the higher emitting particle board. Consequently, the surface area of carpet, insulation, and/or wood in a ventilated room relative to that of pressed wood products may be an important determinant of formaldehyde concentrations in the air of that room. Many consumer products containing formaldehydebased resins release formaldehyde, leading to consumer annoyance and health-related complaints (1). This release has led to various symptoms, most commonly irritation of the eyes and of the upper respiratory tract (2-5). Formaldehyde also produced nasal carcinomas in mice and rats after exposure to 14.1 and 5.6 ppm of formaldehyde, respectively, for long periods of time (2-6). These findings have led to an intensified interest in formaldehyde release from various consumer products into the indoor environment. Little systematic information is available concerning formaldehyde release by various consumer products. Such information is essential for valid health risk predictions. Formaldehyde release rate coefficientshave been measured for a variety of consumer products by using a small static chamber with no ventilation, a modification of the Japanese Industrial Standard (JIS) desiccator procedure (1, 7-14). Sample conditioning (degree of equilibration with the test environment), sample loading (sample surface area/chamber volume), and water content influence the formaldehyde released from pressed wood products (9-14). Formaldehyde release from wood products in ventilated (dynamic) chambers is a function of air flow and sample loading (8,15)as well. Control of these variables is necessary in measuring relative formaldehyde release rates. A chamber with ventilation rates similar to those in houses more closely mimics actual product use by consumers than do chambers with no ventilation. Moreover, t Present address: Chevron Environmental Health Center, Inc., Richmond, CA 94804. *Presentaddress: Small Particle Technology, Albuquerque, NM 87111. Deceased.
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Envlron. Sci. Technol., Vol. 18, No. 9, 1984
it provides an opportunity to vary temperature, humidity, and chamber loading. The products discussed here were initially tested in static chambers by using a modified JIS test (1,14). Selected products were then tested in ventilated chambers. In this report we present measurements of formaldehyde release rates at different loadings, temperatures, and humidities in a dynamic chamber. In addition, the effect of the presence of a second product on chamber formaldehyde concentrations is presented.
Materials and Methods Samples Tested. One sample each of particle board (E-820-0963),plywood (E-810-3906),insulation material (E-860-6228), and carpet (E-810-4585) was tested. All samples were obtained for us, and the identifying number was affixed by the US.Consumer Product Safety Commission, Bethesda, MD. Dynamic (Ventilated) Chamber System. A 27-in. Laskin-type chamber with a volume of 0.45 m3 was used (Figure 1). Humidified air was introduced at the top through a 3/e-in. tube. Air was withdrawn through the bottom exhaust port. A small upward facing fan was located under the steel support rack in the back left corner of the chamber and blew upward to continuously mix the air in the chamber. A 250-W heat lamp provided heat to maintain the temperature at either -25 or -35 "C. Incoming air was humidified before entering the chamber by passing through two pairs of 250-mL gas-washing bottles (bubblers) connected in series and each filled with -200 mL of water. The four gas-washing bottles were kept partially submerged in a constant temperature bath (Brinkmann Lauda RC20). To maintain the chamber at -25 "C and -90% relative humidity (RH) required a 25 "C water bath temperature, while -35 "C and 90% RH in the chamber required a 45 "C water bath temperature, and -35 "C and -40-50% RH required a 22 "C water bath temperature. Tygon tubing was used to connect the air to the bottles, the bottles to each other, and the bottles to the chamber. The single Tygon tube carrying the air from the bottles to the chamber was surrounded by an -1/2 in. thick foam insulating tube to minimize temperature changes in the air before it reached the chamber. The total air flow was 0.076 m3/min, or one volume change per hour. Temperature and RH within the chamber were monitored with a General Eastern Instrument (Watertown, MA; Model 400). The probe was positioned over the mixing fan so that moving air passed over the sensor (Figure 1). The General Eastern Instrument was calibrated in chamber-humidified atmospheres obtained by using saturated solutions of MgClz (33% RH) and NH4H2P04(93% RH). Formaldehyde Measurement. To determine formaldehyde concentration, an air sample was drawn through two fritted glass midget 25-mL impingers in series at 0.26 L/min. The first impinger contained 20 mL and the second 10 mL of deionized water. Less than 5% of the total formaldehyde collected from any sampling was present in the second impinger (average 0.4%). Sampling time ranged from 17 to 300 min. Formaldehyde was
0013-936X/84/0918-0682$01.50/0
0 1984 American Chemical Society
DYNAMIC CHAMBER 0.45
Table 1. Equilibrium and Measurement Conditions for the Dynamic (Ventilated) Chamber
m3
-Humidified Air 7.6 Ilmin RH-Temp. Sensor
time, day
equilibration test I test I1 equilibration test I11
d
Mixing Fan
testing cycle
-
110 2.5 2.5 2.5 2.5
airflow, volumes/h
temp,
RH,
"C
%
0
-25 -25 -35 -35 -35
1 1 1 1 Test
Support Grate
._
80-90 80-90 80-90 40-50 40-50 Test
Exhaust
1 Air C h a n g d h r .
Flgure 1. Dlagram of dynamic test chamber. A typical example of sample placement is shown.
measured spectrophotometrically with p-rosaniline (13,16, 17). Formaldehyde concentrations in air were expressed as micrograms per liter. The release rate coefficient (pug of formaldehyde released (g of product)-l day-' or pg of formaldehyde released (m2of product surface area)-' day-') was calculated (using the sum of formaldehyde in both impingers) for that product under the test conditions. Product surface area was calculated by using both sides and the edges. Total formaldehyde extracted into toluene was measured by the perforator procedure (7). Equilibration of Material with Chamber Atmosphere and Sequence of Measurement Conditions. Materials were equilibrated with the initial chamber atmosphere to bring product humidity to near that of the test atmosphere. A pan containing 2 L of a saturated Na2C03solution was placed in each separate chamber with no air flow to obtain the specified equilibrium RH -90%. This RH was verified periodically by the General Eastern Instrument, and the chambers were used to condition eight pieces of particle board and 11 pieces of plywood for several days before testing in the dynamic (ventilated) chamber at the conditions used in test I, but with no airflow (Table I). Total surface area was 4.1-5.3 m2to give chamber loadings of 8.6 and 11 m2/m3chamber volume. Between test I1 and test 111, a second equilibration was performed and the weight gain recorded. The sample was run at the conditions of test I11 for 2.5 days to cause it to be nearer equilibrium with this test condition (Table I). We did not equilibrate plywood or particle board for longer periods of time at either condition. The volume of wood products tested was 512% of the chamber volume. Other products tested occupied volumes which displaced 512 ?% of the chamber air. No correction was made for the displaced volumes. A complete cycle in the dynamic chamber was about 20 days for the three tests conducted on each sample (Table I). Formaldehyde Release from Multiple Products. In a second study, the effect of multiple products on formaldehyde release was measured. Particle board, plywood, insulation, and carpet samples were equilibrated for 2 weeks at test I conditions (Table I). Formaldehyde release from these single samples was individually measured in a ventilated chamber (one volume change per hour) at test I conditions for temperature and RH. Sample loadings were 1.4-2.8 m2 of sample surface area/m3 of chamber volume (surface area = 0.7-1.3 m2). The effect of different sample loadings was not investigated. After testing of each of the four individual products, three pairs of products were tested in the chamber ventilated at one air change per hour. The three pairs were particle board/plywood, particle board/insulation, and particle board/carpet.
s
D A Y S OF TRIAL
Figure 2. Weight during equilibration and measurement of formaldehyde release, shown as a function of time. (Initial equilibration -25 O C , 90% RH; test I -25 O C , 80-90% RH; test I1 -35 O C , 80-90% RH; equllibratlon -35 O C , 40-50% RH; test 111 -35 O C , 40-50% RH.) At the end of test condition I, plywood has two data points. The line (continuous) is an average of them. In every other case, the continuous line connects the data points. The dashed line connects two points. However, no data were collected in the intervening periods.
Loadings were 3.0-4.2 m2/m3(surface area = 1.4-2.0 m2). Release rate coefficients for particle board and plywood measured in a ventilated chamber were compared to those released in a desiccator (1). Although the desiccator is unventilated, it involves a water sink for formaldehyde. Calculation of Equilibrium Concentrations of Formaldehyde. To better understand formaldehyde release in ventilated chambers, the calculated equilibrium concentration of formaldehyde in the atmospheres of static chambers was compared to levels measured in the ventilated chamber under test I conditions. The equilibrium concentration of formaldehyde in a static chamber was calculated, considering the vapor pressure of formaldehyde (7) and assuming that -20% by weight of the wood product was water (18),that the formaldehyde was in the water (lo),and that the formaldehyde in air and water had reached equilibrium. Equilibrium formaldehyde concentrations of insulation and carpet were not calculated because water/mass figures were unavailable and these products released much less formaldehyde.
Results Water Gain. Weight gain of particle board and plywood was measured for each material at each different condition of equilibration and measurement (Table I and Figure 2). Plywood and particle board weight gain during analysis at test condition I suggested the plywood approached but did not achieve equilibrium with the chamber RH. A small loss of board weight noted during analysis a t condition I11 indicated that the plywood boards were near equilibrium with the RH of the test chambers (Figure 2). Effect of Temperature and Humidity on Formaldehyde Release Rate Coefficients. Table I1 and Figure 3 summarize the formaldehyde release rate coefficients for particle board and plywood measured under Environ. Sci. Technoi., Vol. 18, No. 9, 1984
883
Table 11. Formaldehyde Offgassing and Related Parameters in a Dynamic Chamber
condition particle board I I1 I11 plywood I I1 I11
RH,
temp,
%
"C
85 85 45
25 35 35
85 85 40
25 35 35
formaldehyde release rate coefficient, pg m-2
net weight gain,b %
chamber loading, m2/m3
38 000 36 000 52 000
NDd ND ND
11 11 11
31 000 31 000 33 000
+0.5 +1.8 -0.4
8.6 8.6 8.6
aCalculated as (pg/L)(L/day)(l/m2)when m2 = surface area of wood products and pg = formaldehyde released. bNet weight gain relative to initial weight before equilibration. m2 of product surface area/m3 of chamber volume. Airflow was one air change per hour. ND = not determined. Table 111. Loading Effect of Plywood and Particle Board at -25 "C and -90% RH
extractable formaldehyde, mg/100 g particle board
55
loading, m2/ma0
formaldehyde release rate coefficient,b,e pg m-2 day-l
calcd loading effectd
weight change, %
38 000
11
NDe 4.4
plywood
22
1.4 8.6
168000 31 000
+1.8
+0.5 2.2
1.6
+2.4
68 000
am*of product surface area/m3 of chamber volume. bpg of formaldehyde released (m2of surface area of product)-' day-'. cOffgassing strengths of formaldehyde extrapolated to a loading of 21 m2/ms were 21 000 (particle board) and 16000 pg m-2 day-' (plywood). dIncreased offgassing resulting from reduction from high to low loading. One air change Der hour was the flow rate. "D = not determined.
the three test conditions of temperature and humidity. Formaldehyde chamber concentrations under the three conditions are illustrated for particle board and plywood (Figure 3). Background formaldehyde measurements were considered to be acceptably low (0.06-0.34 pg/L). The average coefficient of variation for concentrations of formaldehyde released at each of the three test conditions was 13%. Changing temperature and humidity as described in Table I led to no significant change in chamber concentration and formaldehyde release rate coefficient except for the particle board at condition I11 relative to that from the first analysis condition (p I0.05; Mann Whitney U Statistic). Sample weights were relatively stable (0.4-1.8% change) during the measurements at test conditions I, 11, and 111 of formaldehyde release from plywood (Figure 2). Effect of Chamber Loading on Formaldehyde Release Rate Coefficients. Release rate coefficients were increased by a factor of 4.4 for particle board and 2.2 for plywood at loadings of 1.4-1.6 m2/m3 over values at loadings of 9-11 m2/m3 (Table 111). To assess whether increased pressure of formaldehyde in the chamber was associated with reduced release of formaldehyde from wood products, chamber concentrations were compared to equilibrium concentrations of formaldehyde. Equilibrium concentrations of formaldehyde in the chambers at room temperature were calculated for particle board (35 pg/L) and plywood (14 pg/L) by using the vapor pressure of formaldehyde and assuming that the water of the product contained all the free formaldehyde (IO). At sample loadings of -9-11 m2/m3 and one air change per hour, chamber concentrations were 50-81 % calculated equilibrium concentrations. At sample loadings of 1.4-1.6 m2 of product surface area/m3 of chamber volume, chamber concentrations of formaldehyde were 40-55% of those at the higher loading and were 28-32% of calculated equilibrium concentrations. 884
Environ. Scl. Technol., Vol. 18, No. 9, 1984
Test -
T e s t I1 -
I
T e s t Ill -
Equilibration
Mean= 24 3 p g i L
,
P~
II
I
,
,
I
I
!
/
,
/
/
,
Table IV. Release Rate Coefficients from Product Combinations in Dynamic Chambers
sample particle board plywood particle board and plywood insulation particle board and insulation carpet particle board and carpet
loading, m2/mSa 1.4 1.6 3.0
formaldehyde release rate coefficient, pg m-2 day-' 168000 68000 71 000
total formaldehyde release rate, pg day-' m-3C 235 000 109 000 213 000
total extractable formaldehyde, mg/100 g 55 22 NDd
1.7 3.1
3 000 55 000
5 000 171 000
1.6 ND
2.8 4.2
1500 31 000
4 000 129000
0.5 ND
'm2 of surface area/m3 of chamber volume. bpg of formaldehyde released (m2surface area product)-l day-'. coefficient)(loadine). ND = not determined.
(Formaldehyde release rate
Table V. Comparison of Formaldehyde Release Rate Coefficients in Ventilated Chambers and Nonventilated Desiccators loading, m2/ms' ventilated nonventilated desiccator chamber particle board plywood particle board plywood particle board
+ plywood
21 21 1.4 1.6 3.0
21 21 1.8 1.5 3.4
ventilated chamber
release rate coefficient, pg m-z dag' nonventilated desiccator
21 OOOb 16 OOOb 168000 68000 71 000
24 000 14000 121000 71 000 65000
difference, %
13 13 33 4 14
'Chamber loading in m2 of Droduct surface area/m3 of chamber volume. bCorrected to a loading of 21 m2/m3by using data in Table 111.
V). A good correlation was noted between release rate coefficients (pg of formaldehyde released (m2of product surface area)-l day-l) at loadings of 1.4-2.8 m2 of product surface area/m3 of chamber volume and formaldehyde extractable into toluene (Table V; r2 = 0.999; p < 0.001). Total extractable formaldehyde was quite low in both carpet and fiberglass insulation (0.5-1.6 mg/100 g of material) relative to that in plywood or particle board (22-55 mg/100 g of material). Comparison of Formaldehyde Release Rate Coefficients in Ventilated (Dynamic) Chambers and Nonventilated Desiccators at Different Chamber Loadings for Particle Board and Plywood. Release rate coefficients measured in ventilated chambers at 9-11 m2/m3 differed by 13% from release rate coefficients analyzed under modified JIS desiccator conditions (nonventilated) for the same products when extrapolated to a loading of 21 m2/m3(Table V) (7). On the basis of a mean of high and low values, release rate coefficients for particle board or plywood measured in a ventilated chamber at a loading of 1.4-1.6 m2/m3were 4-33% different from those measured in a desiccator a t similar loadings (1.4-1.8 m2/m3). A similar comparison indicated that release rate coefficients for particle board plus plywood measured in the ventilated chamber were 14% higher than those measured in the desiccator a t loadings of 3.0-3.4 m2/m3 (Table V). These data indicate that there are no consistent differences between release rates measured in ventilated chambers and nonventilated desiccators between loadings of 1.4 and 21 m2/ma.
Discussion Formaldehyde release rate coefficients measured previously in desiccators were similar to those from the dynamic chamber at similar loadings. Initial formaldehyde release rate coefficients for one sample each of particle board and plywood measured a t 11.4 and 8.6 m2/m3 in these chambers at one volume change per hour were
-2-fold higher than those measured in desiccators at higher loadings (1). However, when the release rate coefficients were adjusted for differences in loading, the calculated release rate coefficients were similar to those measured in desiccators ( I ) . These extrapolations extend beyond the data collected in dynamic chambers and were for only one sample each. Thus, they must be used cautiously. The agreement between different samples of particle board and of plywood has been investigated previously by using a modification of the Japanese desiccator procedure (1,14). Particle board and plywood released sufficient formaldehyde to attain air concentrations that approached calculated equilibrium air concentration values. At 9-1 1 m2/m3 loadings, concentrations of formaldehyde were >50% of calculated equilibrium concentrations, probably because airflow was low relative to the mass of the product. The high chamber concentration of formaldehyde may have limited formaldehyde release in the dynamic chamber. Reduced sample loadings led to decreased formaldehyde concentrations in the chamber as noted or predicted previously by others (7,15,19-22). This resulted in increased release rate coefficients (pg m-2 day-'). Samples analyzed at 1.4 and 1.6 m2 of product surface area/m3 of chamber volume chamber loadings and formaldehyde chamber concentrations of 28-32 % of the calculated equilibrium air concentrations of formaldehyde, suggesting better relative ventilation than that at higher chamber loadings. Increased airflow seemed to lead to an increased release rate coefficient of formaldehyde from pressed wood products because of lower chamber concentrations of formaldehyde. Changes in temperature and humidity did not significantly increase formaldehyde chamber concentrations measured when particle board or plywood was tested at 9-11 m2 of product surface area/m3 of chamber volume. In fact, Figure 3 indicated a small increase in formaldehyde Envlron. Scl. Technol., Vol. 18, No. 9, 1984
685
release with reduced humidity, although no such change was noted in plywood. These data suggest that, at the high loadings used in our experiment, changes in our temperature and humidity did not substantially affect formaldehyde release. This finding differs from those of others (7, 19, 21)) who conducted their experiments at lower formaldehyde concentrations. The reason for these differences is not clear. Our use of a higher loading of wood products in the chamber may have been a factor, since concentrations reached were 250 % of calculated equilibrium concentrations. Future research is needed to define the changes noted in dynamic chambers in relation to temperature and humidity. Such understanding should prove valuable in relating formaldehyde concentrations to loading and airflow measured in dwellings. When particle board was paired with plywood, insulation, or carpet and tested in a dynamic chamber, the formaldehyde released was -60% of the sum of that released when each product was tested alone. Similar results have been observed by others (20). Approximately half of this reduction is related to the increase in chamber loading noted in Table IV (13). In fact, the release of formaldehyde when these products were combined with particle board was less than that released by particle board alone. These results suggest that formaldehyde from the high-emitting particle board moved into the lower emitting product. If this is the case, it is highly likely that the water present in the second product actually absorbed some formaldehyde given off by the particle board, since formaldehyde tends to move into the water phase of the product (10). To confirm this, corroborating measurements will have to be made. An equilibrium of formaldehydebetween the water of the two product might reduce the calculated equilibrium concentration of formaldehyde and, under constant ventilation, the formaldehyde concentrations in a room by as much as -30-50%. Wood contains approximately the same amount of water as pressed wood products and might behave the same way. This factor would become important in houses where surface areas of pressed wood products were small compared to that of other wood. Most houses contain large surface areas of carpet or insulation relative to that of pressed wood products. The former products may account for substantial reductions in total formaldehyde concentrations when used with pressed wood products.
Acknowledgments The technical assistance of Tina Shifani and other members of the ITRI staff, the editorial assistance of Lynn Byers, the illustrative assistance of Emerson E. Goff, and the scientific and editorial review of A. Dahl, J. Dutcher, T. Marshall, R. Henderson, and other members of the ITRI staff, as well as A. Ulsamer, A. Bathija, and W. Porter of the Consumer Product Safety Commission, are gratefully acknowledged. Registry No. Formaldehyde, 50-00-0.
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Literature Cited (1) Pickrell, J. A.; Griffis, L. C.; Hobbs, C. H. National Technical Information Service, 1982, final report to the Consumer Product Safety Commission, Lovelace Inhalation Toxicology Research Institute, Albuquerque, NM, LMF-93. (2) Blackwell, M.; Kang, H.; Thomas, A.; Infante, P. Am. Ind. Hyg. ASSOC. J . 1981, 42 (7))A34-A46. (3) Albert, R.; Sellakumar, A.; Laskin, S.; Kuschner, M.; Nelson, N.; Snyder, C. A. J . Natl. Cancer. Inst. 1982,68,597-604. (4) Committee on Toxicology “Formaldehyde-An Assessment of Its Health Effects”, prepared for Consumer Product Safety Commission by National Academy Sciences, 1980. (5) Moschondreas, D. J.; Reactor, H. E. National Technical Information Service, 1981, Technical Report LBL 12590, EEB-Vast 81-12. (6) Swenberg, J. A.; Kerns, W. D.; Mitchell, R. I.; Gralla, E. J.; Pavkov, R. L. Cancer Res. 1980, 40, 3398-3401. (7) Meyer, B. “Urea Formaldehyde Resins”; Addison-Wesley: Reading, MA, 1979; p 423. (8) Myers, G. E.; Nagaoka, M. Wood Sci. 1981,13 (3), 140-150. (9) Fujii, S.; Suzuki, T.; Koyagashiro, S. Kenzai Shiken Joho (Transl.) 1973, 9 (3)) 10-14. (10) Johns, W. E.; Jahan-Latiban, A. Wood Fiber 1980, 12, 144-152. (11) Meyer, C. B.; Carson, N. L. Lawerence Berkeley Laboratories, Berkeley, CA, 1982, LBL 14286. (12) Meyer, C. B.; Koshlap, K.; Geisling, K. L.; Miksch, R. R. Lawerence Berkeley Laboratories, Berkeley, CA, 1982, LBL 14259. (13) Griffis, L. C.; Pickrell, J. A. Environ. Int. 1983, 9, 3-7. (14) Pickrell, J. A.; Mokler, B. V.; Griffis, L. C.; Hobbs, C. H.; Bathija, A. Environ. Sci. Technol. 1983, 17, 753-757. (15) Myers, G. E.; Nagoka, M. presented at the Symposium on Wood Adhesives-Research, Applications and Needs, Forest Product Laboratories, Madison, WI, 1980. (16) Miksch, R. R.; Anthon, D. W.; Fanning, L. Z.; Hollowell, C. D.; Revzan, K.; Glanville, J. Anal. Chem. 1981, 53, 2118-2123. (17) Tiffany, T. 0. CRC Crit. Rev. Clin. Lab. Sci. 1974, 5, 129-191. (18) Wood Handbook “Wood as an Engineering Material”; U.S. Department of Agriculture, Forest Products Laboratory, U.S. Government Printing Office: Washington, DC, 1974; Forest Service Agricultural Handbook No. 72. (19) Andersen, I.; Lundquist, G. R.; Molhave, L. Atmos. Environ. 1975, 9, 121-127. (20) Singh, J.; Walcott, R.; St. Pierre, S.; Ferrell, T.; Garrison, S.; Gramp, G.; Groah, W. “Evaluation of the Relationship between Formaldehyde Emissions from Particle Board Mobile Home Decking and Hardwood Plywood Wall Panelling in Experimental Mobile Homes”; prepared for U.S. Department of Housing and Urban Development, Office of Policy Development and Research, Division of Energy, Building Technology, and Standards, 1982, p 36. (21) Myers, G. E.; Nagaska, M. For. Prod. J. 1981,31 (7),39-44. (22) Esmen, N. A. Environ. Sci. Technol. 1978, 12, 337-339.
Received for review September 19, 1983. Accepted March 14, 1984. Research supported by the Consumer Product Safety Commission through Interagency Agreement CPSC IAG 801463 under U.S. Department of Energy Contract DE-ACO476EV01013.
