Current Status of Measurement Techniques and Concentrations of

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Current Status of Measurement Techniques and Concentrations of Formaldehyde in Residences RICHARD B. G A M M A G E and A L A N R. H A W T H O R N E Health and Safety Research Division, Oak Ridge National Laboratory, Oak Ridge, T N 37831 For measuring concentrations of formaldehyde in residences, scientists are making increasing use of passive integrating monitors that can provide time-weighted average concentrations down to slightly more than 0.01 ppm if the periods of exposure are extended to a few days. The more traditional modified NIOSH method with a 1-2-h sampling time lacks the sensitivity to make accurate measurements at the frequently encountered concentrations of 0.1 ppm or lower. More rigorous intercomparisons of various monitoring systems are required. Marked dependence of formaldehyde concentration on age is observed for different classes of dwellings. As building and furnishing materials that contain urea-formaldehyde resins age, they emit formaldehyde less strongly. Limited studies have revealed diurnal and seasonal within-house fluctuations of two- and tenfold, respectively. Occasional excursions to 0.1 ppm seem to occur in the majority of houses. H U M A N H E A L T H P R O B L E M S R E L A T E D T O F O R M A L D E H Y D E E X P O S U R E in residences became an increasingly active issue throughout the 1970s. The sectors of the public expressing the most concern were residents of mobile homes and houses insulated with urea-formaldehyde foam insulation (UFFI). For all types of dwellings, the formaldehyde exposure appears to be the highest in mobile homes with a recently reported mean concentration of 0.38 ppm (J). The mean indoor concentration of formaldehyde for several hundred U.S. homes with UFFI, including complaint and noncomplaint homes, has been reported to be 0.12 ppm. Inside UFFI homes in Canada, the mean concentration of formaldehyde was reported recently to be only slightly above 0.05 ppm (2). In about 10% of these homes, however, the formaldehyde concentrations were 0.1 ppm or greater. For comparison, the mean concentrations of formaldehyde inside older conven0065-2393/85/0210/0117$06.00/0 © 1985 American Chemical Society

In Formaldehyde; Turoski, V.; Advances in Chemistry; American Chemical Society: Washington, DC, 1985.


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FORMALDEHYDE: A N A L Y T I C A L CHEMISTRY A N D TOXICOLOGY

tional homes are usually less than 0.05 ppm, and only a few exceed 0.1 ppm (J, 2, 3). The formaldehyde ceiling concentration for personal comfort es tablished by the American Society of Heating, Refrigeration, and Air Con ditioning Engineers (ASHRAE) is 0.1 ppm (4). The primary sources of the airborne formaldehyde are urea-formal dehyde (UF) resins used in pressed-wood products such as particle board, fiberboard, plywood, insulation, and other building material such as deco rative paneling. Degradation of the U F polymeric structure by moistureinduced reactions leads to a chronic release of formaldehyde (5). Usually lesser amounts of formaldehyde can also be emitted by combustion sources and tobacco smokers. To place some perspective on the scale of formaldehyde production, approximately 6 billion lb was produced in 1984 (6). Resins made with urea or phenol account for half of the total formaldehyde consumption in the United States, and most of these resins go into housing materials. It should, therefore, be of little surprise that formaldehyde is ubiquitous to modern living environments. This review is intended to be read with two important questions in mind: How well are the available monitoring devices able to cope with current and future demands? What is satisfactory, lacking, or amiss in our current state of knowledge about the levels and behavior of formaldehyde in residences? Commonly Used Monitors Most of the methods that have been used for measuring formaldehyde lev els in air have recently been reviewed by Β aim at (7) for the Formaldehyde Institute. Only those monitoring techniques that have seen or are seeing extensive use in residential monitoring will be considered here. Modified NIOSH Method (8). The monitoring technique used with the greatest frequency has been the midget impinger sampler containing 1 % sodium bisulfite solution instead of the previously advocated pure wa ter. Subsequent colorimetric analysis is limited to the chromotropic acid method. Sampling is usually conducted for 1 or 2 h at an air flow rate of approximately 1 L/min. Lower limits of detection of 0.04 and 0.1 ppm have been published for the method (9, JO). More recently a minimum de tectable concentration of 0.1 ppm in field work has been quoted by Dally (11) for a 1-h sampling time. The sensitivity could, of course, be improved by increasing the time of air sampling. In most instances this option is unat tractive because a technician usually attends the sampler during operation, and expenses escalate with longer sampling times. Losses of formaldehyde via evaporation can introduce additional difficulties. The NIOSH method was developed with the monitoring of the work place atmosphere in mind, as the name of the parent organization implies. The OSHA standard for the workplace is 3 ppm of formaldehyde averaged



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GAMMAGE AND HAWTHORNE

Concentrations in Residences

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over 8 h. In residences, however, one is usually concerned with measuring much smaller concentrations of formaldehyde. Nevertheless, during the latter 1970s, the modified NIOSH method, probably because it was the best available at the time, became the standard method for measuring formaldehyde in residences. Very recently an error analysis has been reported (2) for results obtained in large-scale residential studies in Canada. The aim of an absolute, total error limit (sampling plus analysis) of 15% at the 90% confidence level was not achieved. The observed uncertainty at a concentration of 0.1 ppm was 38% . The magnitude of this uncertainty increased dramatically for concentrations below 0.1 ppm and was caused largely by an increase in the coefficient of variation associated with the sample analysis. Because of the large uncertainties in results at the formaldehyde concentrations commonly encountered in residences ( 0.1 ppm)

0.12 0.38 0.036 0.054

1 1 2 2

17

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0.025

27

-600 several hundred 50

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0.050 0.12 0.047

27 27 28

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0.06 0.07 0.06

29 30 30

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0.86 0.25 0.06 0.08 0.04 0.03

33 33 34 34 34 34

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a class, only a modest elevation of formaldehyde concentrations compared to non-UFFI houses. This statement, however, needs to be counterbalanced by the circumstance that a considerably higher percentage of UFFI houses, as opposed to non-UFFI houses, have formaldehyde concentrations at or exceeding 0.1 ppm. As a class, mobile homes are the dwellings with the apparently highest concentrations of formaldehyde; the mean concentrations are close to 0.4 ppm in most of the studies listed in Table IV, and concentrations for individual mobile homes have been recorded as high as 4 ppm. Individual Houses: Temporal Considerations. Individuals are usu-


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0.14

i

MEAN FORMALDEHYDE CONCENTRATION

(ppm)

EN

LIVING ROOM

AGE OF HOUSE (yr)

Figure 2. Mean concentrations of formaldehyde in 40 homes in east Tennessee measured biweekly with passive formaldehyde monitors during the warmer seasons of the year; a more complete set of data is provided in Ref. 34. (Reproduced with permission from Ref. 38. Copyright 1984 CRC.) ally more concerned with the current levels of formaldehyde inside their homes than with average concentrations of formaldehyde for any group of housing. The first question to answer is what is the most appropriate type(s) of formaldehyde measurement to make? This decision depends on whether one's aim is trying to determine an individual's short-term or longer term exposure profile. The passive formaldehyde monitor provides a time-weighted average concentration. The monitor is exposed for a period of time that is usually between 1 day and 1 week. Such measurements of integrated exposure must be made during the different seasons of the year to provide an adequate profile of the homeowner's potential exposure. A rather extreme example of seasonal fluctuations of formaldehyde levels inside a prefit UFFI home (36) is shown in Figure 3. This home was one of 40 houses that were studied, most of which showed more moderate seasonal fluctuations in formaldehyde levels (34). Most of the individual measurements were made


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OCT

NOV

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MAR

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MAY

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Figure 3. Seasonal fluctuations of formaldehyde concentrations inside the small, south-facing study of a 3-year-old UFFI-prefit house. Key: • , study; O , living room; and A, kitchen. (Reproduced with permission from Ref. 38. Copyright 1984 CRC.) over 24-h periods with passive formaldehyde monitors (21 ). The suggested reasons for the marked fluctuations in concentration of formaldehyde va por are given in Reference 36. The marked increase in formaldehyde con centration in October was, for example, speculatively attributed to the on set of the heating season; heated and low-humidity air issuing from floor vents located by the interior walls was possibly causing evaporation of formaldehyde-bearing pools of moisture within the walls. Temperature and humidity both can have strong influences on the emission rates of formaldehyde (I, 37). Another important finding of the east Tennessee 40-home study (34) was that in a majority of the homes, the formaldehyde concentration ex ceeded 0.1 ppm on 1 or more days of the year. Unfortunately, very few measurements of seasonal variability in formaldehyde levels have been made in other studies (38). A profile offluctuationsin formaldehyde concentration may be needed within a time frame shorter than 24 h. Short-term peak exposures might, for example, be a triggering event for asthma (39). The passive integrating formaldehyde monitor is unsuitable for such a task. The modified NIOSH method (8) is generally too insensitive for making accurate measurements of diurnal fluctuations in formaldehyde levels. Consequently, little informa tion is available about diurnal or other short-term fluctuations. One example of a study of short-term variations made by the Oak Ridge group (36) is shown in Figure 4; diurnal fluctuations observed re-


128

F O R M A L D E H Y D E : A N A L Y T I C A L CHEMISTRY A N D TOXICOLOGY

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Figure 4. Diurnal fluctuations in formaldehyde concentrations inside a 3-year-old UFFI-prefit house and a 10-year-old non-UFFI house; the out door temperatures are indicated. Key: w, UFFI-prefit house; and • , nonUFFI house. (Reproduced with permission from Ref. 38. Copyright 1984 CRC.)

suited in a near doubling of formaldehyde concentrations. The sampling technique uses molecular sieve sorbent (24) and a 15-min collection time and has a detection limit of 0.025 ppm. An empirical equation has been developed to predict breakthrough as a function of sampling rate, relative humidity, and sorbent mass. The formaldehyde collections in this instance were labor intensive and required round-the-clock involvement of a techni cian. An automated sampling system of the type developed by Dietz (40) would be much better for short-term repetitive sampling. Available methods are not altogether suitable for measuring, in a costeffective manner, changes in formaldehyde levels over the short term (hour by hour). This situation, together with the sparsity of reported field stud ies, led the exposure panel of the "Consensus Workshop on Formaldehyde" (26) to conclude that data were inadequate to characterize the frequency or magnitude of short-term peak (acute) exposures of various groups within the population.


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Acknowledgments Oak Ridge National Laboratory is operated by Martin Marietta Energy Systems, Inc., for the U.S. Department of Energy under Contract No. DE-AC05-840R21400.


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21. Matthews, T. G.; Hawthorne, A . R.; Howell, T. C . ; Metcalfe, C. E . ; Gam mage, R. B. Environ. Int. 1982, 8, 143-51. 22. de Planque, G.; Gesell, T. F. Health Phys. 1979, 36, 221-34. 23. Matthews, T. G . Am. Ind. Hyg. Assoc. J. 1982, 43, 547-52. 24. Matthews, T. G.; Howell, T. C. Anal. Chem. 1982, 54, 1495-98. 25. Brown, R. H.; Harvey, R. P.; Purnell, C. J.; Saunders, K. J. Am. Ind. Hyg. Assoc. J. 1984, 45, 67-75. 26. “Exposure Panel Consensus Report”; Consensus Workshop on Formaldehyde, Little Rock, Ark., October 1983. 27. Orheim, R. M., letter to the editor Chem. Eng. News 1982, 60, 2; also per sonal communication. 28. Everrett, L . H., presented at the Consensus Workshop on Formaldehyde, Lit tle Rock, Ark., October 1983. 29. Godish, T. J. Environ. Health 1981, 44, 116-21. 30. Frank, C. Fed. Reg. 1982, 47, 14386-87. 31. Calvert, J. G . “Formaldehyde and Other Aldehydes”; NAS: Washington, D . C . , 1981; Chap. 5. 32. Garry, V . F.; Oatman, L.; Plens, R.; Gray, D . Minn. Med. 1980, 63, 107-11. 33. Clayton Environmental Consultants Fed. Reg. 1983, 48, 37139. 34. Hawthorne, A . R.; Gammage, R. B.; Dudney, C. S.; Hingerty, Β. E . ; Schuresko, D . D.; Parzyck, D . C.; Womack, D . R.; Morris, S. Α.; Westley, R. R.; White, D . Α.; Schrimsher, J. M . “An Indoor Air Quality Study of Forty East Tennessee Homes,”Oak Ridge National Laboratory Report, ORNL-5965, 1985. 35. Nero, Α. V . ; Grimsrud, D . T. “The Dependence of Indoor Pollutant Concen trations on Sources, Ventilation Rates, and Other Removal Factors,”Law rence Berkeley Laboratory Report, LBL-16525, 1983. 36. Gammage, R. B.; Hingerty, Β. E . ; Matthews, T. G.; Hawthorne, A. R.; Wo mack, D . R.; Westley, R. R.; Gupta, Κ. C. Proc. Spec. Conf. Meas. Monit. Non-Criter. (Toxic) Contam. Air 1983, 453-62. 37. Matthews, T. G . ; Hawthorne, A. R.; Daffron, C. R.; Reed, T. J.; Corey, M . D . “Proceedings of the 17th International Washington State Uni versity Particle Board-Composite Materials Symposium,”Pullman, Wash. 1983. 38. Gammage, R. B.; Gupta, K. C . ”Formaldehyde”; Walsh, P. J.; Dud ney, C. S.; Copenhaver, E. D . , Eds.; C R C : Boca Raton, Fla., 1984; pp. 109-42. 39. Hendrick, D . J.; Lane, D . J. Br. J. Ind. Med. 1977, 34, 11. 40. Dietz, R. N . “Brookhaven Air Infiltration Measurement System (BNL-AIMS) Manual for Field Deployment,”Brookhaven National Laboratory Report, BNL-31544, 1984. RECEIVED

for review September 28, 1984.

ACCEPTED

January 10, 1985.


Current Status of Measurement Techniques and Concentrations of

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