Distribution of volatile organic chemicals in

outdoor and indoor air A national VOCs data base

A

Jitendra J. Shah G2 Environmental, Inc.

Portland, OR 97201 Hanwant B. Si@

NASA Ames Research Center Moffen Field, CA 9403.5

The release of many volatile organic chemicals (VOCs) into the ambient en- vironment is a necessary outcome of their use. Many of these chemicals are implicated in the depletion of the stra- tospheric ozone layer and threaten to alter the climate of the earth ( I ) . Others are suspected of causing human cancer. The association between human cancer

5). A Surgeon General's report states, "Toxic chemicals are adding to the dis- ease burden of the United States in a significant although as yet not precisely defined way" (6).

Determining human exposure to a complex array of chemicals is a key factor in quantifying the relationship between environmental factors and hu- man disease. Because people may spend as much as 8040% of their time indoors (7). and because new energy conservation methods could lead to a deterioration of indoor air quality, we need to characterize both outdoor and indoor air environments.

Monitoring activities have intensified over the last two decades in the United States. in an befause of the oublic

and exposure to synthetic chemicals is a matter of active debate and concern (2-

awareness h d fear of cancer. Th&e ac- tivities have generated a significant

0 0 1 3 ~ ~ 0 9 2 2 - 1 3 8 l W l . 5 0 1 0 0 1988Arnerican Chemical Society

body of VOC data widely scattered in scientific journals and reports. Critics charge that too few chemicals are moni- tored, the data generated are of varying and often questionable quality, and the results are not readily available to users. At least part of the problem stems from the complexity of the air mixture and the sophistication that is requid for ultratrace analysis of or- ganic chemicals.

In 1980, EPA recognized the need to organize the available data into a sin- gle, cohesive format so their quantity, quality, and significance could be as- sessed. A VOC national ambient data base was first prepared in the early 1980s and published by EPA (8). In 1986, when the data base needed to be expanded to include the large amount of ambient VOC data published since

Environ. Sci.Technol., MI. 22. No. 12. 1988 1381

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CAS numbers and names for chemlcak, in VOC Uata base

D.h b o a e m s 1Iyltlb.rMllllb.r chalnhdnm

7e-Ot-2 Tmeett~yWumbane 78751 1,ZDibfwmfaWue

1980, EPA contracted to upgrade and expand the earlier study (9). Concur- rently, powerful personal computers (PCs) that could be conveniently used for such data bases became available. As a result of this study, outdoor as well as indoor data are now available in a unified form for FCs and can be used to screen for many environmental prob- lems, including exposure to VOCs.

Here we present a first look at this com- prehensive national VOC data base and construct a picture of VOC distribution in the environment.

Data base and AU available outdoor and indoor data

from both residential and commercial environments were gathered in a wm- prehensive search. This included litera-

ture searches, direct contacts with indi- viduals and organizations measuring VOC, questionnajres, and meetings of experts to assess the internal consist- ency of the data. Industrial indoor spaces were not a part of this study.

Data were accepted from sources in all forms, including reports, journal BT- tides, computer tapes, and direct elec- tronic transfers. Not surprisingly, there

1382 Envimn Scl Technol.. Vol. 22, No 12. 1888

were inconsistencies, duplications, un- supported validation procedures, un- published methods, and, often, numeri- cal errors. Every effort was made to resolve the obvious inconsistencies prior to inclusion in the data base.

The !inal data base includes a total of 320 VOCs, with 261 VOCs measured in the outdoor air and 66 measured in- doors. Some chemicals are identified

but no measurements are provided. In addition to the mixing ratios (in units of parts per billion by volume; ppbv = lW9 v h ) , all pertinent information on locations, dates, sampling methods, and analytical techniques is provided. A l i t of VOCs for which data are avail- able is shown in Table 1.

The entire data base contains about 175,000 records occupying about 19

megabytes of storage. The data are available on lBM-PC-compatible disk- ettes in dBASE III+ format, a com- mercially available information man- agement program by Ashton-Tate. The diskettes include software utilities de- signed to facilitate searching, sorting, editing, and analysis. Information re- garding chemical names, common names, formulas, molecular weights,

Environ. Sci.Technol..Vol. 22. No. 12. lgsS 1383

and conversion factors are also in- cluded in supporting files.

The data base and the user report is in the public domain and is available from the authors or the National Tech- nical Information Service (10). De- tailed descriptions of the two data bases and six supporting files, as well as a user guide to the utility programs, are provided. The data base can be ac- cessed either by chemical number or

name (Table 1). The supporting title containing names (including synonyms) and numbers should be searched prior to accessing the data base.

Rating and ranking of the data for quality were based on a complete anal- ysis of measurement methodologies, factors involved in quantification of data, and level of documentation avail- able. Data are compiled for the resolu- tion of daily average concentrations.

n n r a__l

1384 Environ. Sci. Technol.,Vol. 22. No. 12, 1988

Because many measurements were performed for only a few daytime hours, they do not accurately represent a daily average. This factor has been considered in the quality rating of data and must be taken into account by the user. Ratings and rankings depended heavily on the availability of published documentation and consensus among a group of experts. Every effort was made to achieve internal consistency. None of the studies received the highest rating possible because of h o w n defi- ciencies in sampling and analytical techniques.

We recognize that assignment of quality codes to such a diverse body of data cannot be done without subjective judgments. Although subject to refine- ment, the process is a necessary step in establishing checks on the quality of ex- isting data. A user has the option to select all data or data within certain quality codes.

The outdoor data are characterized as urban, tud, suburban, remote, or near source. The remote data represent the midlatitude atmosphere and are in- cluded to provide the minimum level to which the U.S. population is exposed. The distinctions between urban and suburban characterizations may be am- biguous and should be treated in con- text.

The indoor data are principally from residential and workplace environ- ments. Where possible, personal levels are also provided. These data are based on the exposure that an individual faces and are a function of a person’s life- style. Details of methodology and the structure of the data base are provided by Shah and Heyerdahl(9). The indoor and outdoor data bases have a common structure and can be processed and ana- lyzed in a virtually identical fashion.

The studies that have contributed data have a wide variety of objectives, sampling times, sampling methods, and analytical techniques. Though the data were assigned quality codes, unusual or questionable data were included with- out modifications. These inherent limi- tations must be accounted for when drawing any conclusions. In general, this data base is best used as a screening tool.

Results and discussion A glimpse of the information con-

tained in the data base follows. The availability and accessibility of these data do not guarantee that sufficient and satisfactory information is available. They do, however, provide a useful starting point for exploratory analysis and many other applications, including chemical concentration distributions; trend analysis; assessment of inter-site concentration variations; location of

“hot spots”; use with census data for preliminary risk assessment; input for dispersion and receptor modeling; es- tablishment of monitoring priorities; review of detection limits and analysis methods in use and their appropriate- ness; and identification of active re- searchers.

The 122,820 records of outdoor air data for 261 VOCs represent 300 cities from 42 states. Although California, New Jersey, and Texas dominate, nearly 20 of the 42 states have sizable data (more than lo00 records). The temporal distribution of the data re- cords is not uniform: 57% of all data records are from 1981, 1984, and 1985 whereas 90% of all data are from 1975 to 1985. Sampling periods also varied dramatically. Nearly 48% of the data records had a sampling period of less than 1 hour; 16%, 1 to 24 hours; 30%, 24 hours; and 5%, greater than 24 hours.

The indoor data base is much smaller than the outdoor base at 52,810 re- cords; it represents 30 cities from 16 states. Nearly 90% of the indoor data are from California and New Jersey. About 98% of the data are from 1981 to 1984. More than 95% of the indoor data are collected using a 1- to 24-hour sampling period.

Figure 1 provides the distributions of the median concentrations of the VOCs

contained in the data base for both out- door and indoor environments. It is evi- dent that we are dealing with very low concentrations; nearly 50% of the chemicals present fall in the 0.01-1.0 ppbv concentration range. A sizable fraction of chemicals had median con- centrations that were below detectable levels ( ~ 0 . 0 0 1 ppbv). In only 10% of the cases for outdoor air and 25 % of the cases for indoor air did the median con- centration exceed 1 ppbv.

Table 2 summarizes outdoor daily mean, median, lower quartile, and up- per quartile concentrations (in units of ppbv), as well as number of observa- tions, for a select group of 66 VOCs. Many of these chemicals are known for their mutagenic and toxic properties, albeit at significantly higher concentra- tions (11). Table 2 presents a summary of data from all outdoor types, includ- ing highly polluted environments as well as clean remote environments. This causes a few high values to influ- ence the means so that they are almost always greater than the medians. This skewedness is sometimes so pro- nounced that the mean is larger than even the upper quartile.

Extremely high values for chlorin- ated hydrocarbons from one reference with a questionable quality rating were excluded when we calculated averages, A value of zero in the median or upper

quartile column implies that much of the data were below detection levels. Table 2 shows instantly the abundance and variability of many VOCs in the outdoor air. Similar data for a select group of 35 VOCs in the indoor envi- ronment are presented in Table 3.

Comparing the data from Tables 2 and 3 quickly shows that upper quartile, concentrations of VOCs such as for- maldehyde; chloroform; 1 , 1 , l-trichlo- roethane; and tetrachloroethene are higher in the indoor environment than in the outdoor air. It should be realized, however, that chemicals like formalde- hyde are often measured in those in- door spaces where a problem has al- ready been inferred based on either complaints or knowledge of the materi- als used.

Bursts of high chloroform levels may be encountered in homes immediately after someone showers because of the high concentration of trihalomethanes in tap water. As a general rule, the am- bient outdoor air provides the toxic background that a typical indoor space could add to or subtract from. The ma- jor indoor sources of VOCs are build- ing materials (including adhesives), consumer products, and indoor com- bustion. Indoor problems are exacer- bated by the emission of pollutants as well as by poor ventilation.

Table 4 summarizes the median con-

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Environ. Sci. Technol., Vol. 22, No. 12, 1988 1385

ABLE 2 )ally outdoor concentmtbns tc chernlcals Data base VOGAMBI) for ell w1aoor site types’

Ntlnba CiUIlllW 0fd.p

umbu Name @m 5 Formaldehyde 629 7 Carbon tetrachloride 4913

10 Dimethylnitrosamine 42 11 Formic acid 29 13 Acetone 17 14 Chloroform 3658

8.293 4 060 1 900 0.188 0 122 0.070 0.583 0 014 0 006 4 069 4 000 2 000 6 927 0 930 0 000 0.630 0 058 0 010

16 Benzene 541 1 2 . m 17 l,l,l-Mchlomethen# 2982 19 Bromomethane a58 23 Chloromethane 706 24 lodomethane 167 25 D i b m m t h a n e 21

29 Chloroethane 142 30 Vinyl chloride 574 31 Acetonitrile 4 32 Acetaldehyde 175 33 Methylene chloride 798 35 Thiobismethane 360

I

1.665 0.162 0.179 0.652 0.003 0.000 0.045 0.000 0.000 1.300 ... 0.774 0.995

0.630 0.129 0.046 0.807 0.002 0.WQ 0.017 0.000 0.000 0.000 0.314 0.467

. - uppr 9.800 0.130 0.085 6.000 2.827 0.180

3.343 0.610

5.440 1.809 2.334

10 0,030 0.m 0.346

Jo7 BK) 184 0.W 0.330 638 0.m 0.628 714 0.w 0.065

42 45

Y i l o P 46

I@

255 272 280 282 289 315

0

I ,2,3,4TetrameIhyU 1,3-Diihlorobsnzen

886 1.103 0.000 0 000 0.026 3021 0.495 0 158 0 010 0.470 1011 0.101 OOOO 0 000 0.008 1032 0.484 0 103 0 023 0.264

72 0.036 0003 0 001 0.006 67

35 ^^^

310 947

1980 629 .~. 49

4074 1491

48 7

111- 18 31 31

.-. 451 646

Undecane 529 PAN 481 Nitrooxopropylperoxide 132 Methylmethylethenylcyclohexene 61 Trichlorobenzene 144 Benzoyl nitro peroxide 6

0.074 0.000 0.204 0.090 0.020 0.996 0.042 0,000 0.323 0.OW 0.000 0.807 0.318 0.152 6.318 6.000 3.700

0.500 0 290 0 200 0.010

0.166 0.055 0.055 1.198 3.200 1.176 5.210 0.310

18.735 0.093 0.200

22.900

3.m 0.040 0.870 0.113 0.054 0.200 0.618 1.403 0.119 0.054 0.012 n ran

1388 Environ. Sci. Technol., Vol. 22, No. 12. 1988

1-

7 1 +(Dioxane) 170 Decane 173 Teirachloroeihene 1 97 Decamethylcyclopentil~xane

1,Mkhloroben; TideCarm Twadecane pentadecane

,164

585 1 .OB 71 0 0.775

2195 3.056 25 0.206

255 Undecane 289 Trichlorobenzene 297 Dichlorobenzene

212 12 11 11

706 0.746 2 0.065 3 0.900

0.282 0.100 0.065 0.050 0.110 0.090

centration in ppbv and the number of obsexvations by site types for 20 cbemi- cals. It also compares these with indoor and personal data where available. Blanks indicate the absence of available data. For consistency, data are reported to three significant digits; however, not all data are accurate to le3 ppbv levels.

Bend analysis for VOCS is also pos- sible by sorting data for a chemical by years, although often data variability is so much larger than the expected trends that no defnitive conclusions can be drawn. Based on these data, Singh and coUeagues (12) have suggested that, over the Last two decades, the concen- trations of aromatic hydrocarbons have declined significantly in southern Cali- fornia. Some of the other applications of the data base include site-specific re-

ceptor modeling for San Jose (9) and an interurban comparison of VOC concen- nations in various US. cities.

Lookingahead It is evident from this study that both

indoor and outdoor air environments are contaminated with many synthetic organic chemicals. In most cases, the concentrations are quite low, with a majority of chemicals at subppbv lev- els. Although the quantity of available data is substantial, it is probably inade- quate to accurately assess human expe sure and to establish long-term trends. In their present state, the data are most useful in providing comparisons of air quality in urban, rural, sourcedomi- nated. and indoor environments; in highlighting areas of unavailable infor-

mation; and in studying atmospheric composition and chemishy.

Althmgh many ambient VOC mea- surements have been made, little infor- mation is available to relate them to their sources. The present data should both facilitate and encourage the devel- opment and evaluation of source recep tor models. It is a valuable resource and provides a national perspective for state and local agencies grappling with the potentially deleterious impacts from ex- isting and new VOC sources. At this time, the data base. can be used as a reliable screen for risk analysis and en- vironmental management.

However, it is the user’s responsibil- ity to ascertain the suitability of these data for any specific application. The data have come from a wide range of

Envimn. Sci.Technol..Mi. 22, NO. 12, 1988 1387

TABLE 4 Daily median concentrations and number of samples by site types for 20 chemicals I

2.700 2 720 6.500 9.150 44.000 80.000

7

3

8

104

106

114

133

135

I 137

Carbon tetrachbnda 0.124 1134

Chloroform 0.020 15

Benzene 0.160 221

1,1,1 T‘ichloroethane 0.132 1064

chloromethane 0.713 5

Vinyl chloride 0.000 3

2

7

Acetaldehyde 3.115

Methylene chlo 0.052

Dichlorodifluoromethane 0.332 (F-12) 664

Hexachlomcyclopentadiene 0.021 7

0.013 14

0.350 7

1,2-DichbmLmnzene 0.WO 1

1,4-Dichlorobanzene

1,2-Dibromoethane

1.2CIichlomethane 0.000

Toluene 0.049

Chlorobenzene 0.000

Phenol 0.WO

4

225

1

1

86 0.000

82 0.467 246

0.074 8

0.923 2

0.000 45

0.WO 13 0.054

1 0.231

4 0.023

3 0.010

84 0.025 239 0.000

20 0.WO 20

0.000 75

O.OO0 44

0.350 248

0.035 80

0.WO 1

0.091 791

0.010 739

1.800 980

0.587 659

0.641 599

0.WO 88

2.050 8

0.604 136

0.598 130

0.318 67

0.057 739

0.645 937

0.000 530

0.048 545

0.oW 318

0.000 600

0.195 958

0.WO 647

0.110 2754 0.060 2696 1.612 3812 0.396 1118 0.810 100

0.000 500

1.550 140

0.840 590

0.726 86

0.133 107

0.205 2056 0.800 2297 0.020 424 0.050 369

0.000 1518 0.012 17iA . 2.883 2519 0.220 R79 -. -

0.015 2

0.125 I d A ...

0.507 122

1.474 148

0.330 133

0.17 65

0.179 12

0.568 64

0.090 1 24

1.196 98

0 048 77

O.Oo0 1.1

0.253 58

0.255

6.314 104

0.009 88

6.683 44

182

I NOW The chemical numbers repr-entlhe numben used in the original VOC data basa Blanks indicae no data.

sources with different methods of mea- surement and analysis, sampling times, site type definitions, and quality con- trol. We hope that this VOC data base, though widely applicable now, will be periodically updated so that exposure t o chemicals can be assessed over years and decades.

Acknowlegment This project was sponsored by EPA under Contract No. 68-02-4190 to Nero and As- sociates, Inc. We are grateful to Larry Cu- pin of EPAs Atmospheric Sciences Re- search Laboratory and Emily Heyerdahl of Nero and Associates, Inc. for their techni- cal assistance, and to the many researchers who generously contributed time and data to this project.

References (I) “Atmospheric ozone 1985”; report No,

16; World Meterological Organization, Global Ozone Research and Monitoring Project; 1985.

(2) Fed. Regisr. 1985,50, 10374-442. (3) Fed. Regisr. 1986.51, 33993-4014. (4) Wilkinson, C. E Environ. Sci. Technol.

(5) Slovic, I! Science 1987,236, 280-85. 1987.21, 843-47.

“Health Effects of Toxic Pollutants: A Report from the Surgeon General”; re- port to US. Senate, serial no. 96-15; Dept. of Health and Human Services. US. Government Printing Office: Wash- ington, DC, 1980. Proceedings of the Firsf hlernafiOM/ In- doDr~Climare Symposium; Fanger, P. 0.; Valbjoan, O., Us.; Copenhagen, Den- mark, 1979. Brcdzinsky, R.; Singh, H. B. Volatile Or- ganic chemicals in rhe Armosphere: An Assessmenr of Available Darn; Environ- mental Sciences Research Laboratory. US. Environmental Protection Agency. US. Government Printing Office: Re- search Mangle Park, NC, 1983; EPA- 600/3-83-027(a). Shah, 1. J. Presented at the APCA Spe- cialty Conference on Receplor Models in Air Resources Management, San Fran- cisco, CA, February 1988. Shah, J . 1.; He erdahi, E. K. N n t i o ~ l Ambienr VolariL Organic Compounds (VOCs) Dora Base Updare; U S . Envi- ronmental Protection Agency. US. Gov- ernment Printing Office: Research Trian- gle Park, NC. 1988; EPA 600/3- 88/010(a). (b); NTIS No. PB 88-195 631/ AS, PB88-I89 OZZIAS, 1988. “Monographs on Organic Air Pollu- tants;’ final report to the National Can- cer Institute on contract NCI NOI-CP- 2Mw)4, SRI-International: Menlo Park, CA. 1983. Singh, H. B. et al. Armos. Emiron. 1985, 19, 1911-19.

n ._.

Jacndm 1. Shoh (I) is president of C2&: vironmenral, Inc. in Portland, OR, afirm rhar provides monitoring analysis and in- terpretation of environmental problems. Prior lo forming rhis company, he was vice president of the environmenral group ar Nero and Associares, Inc. in Porrlond and senior scienrisr at Environmental Research & Technology in Concord, MA. He spe- cializes in air moniroring and evaiuaring visibility impairmenr.

Hmwanl B. Singh (r) leads the trace gas measurements and analysis group and is acting branch chief at rhe NASA A m s Re- search Center ar Mofferr Field, CA. He was direcror of the atmospheric chemisrry pro- gram at SRI-Internarional in Menlo Park, CA, and has been involved infield experi- ments and theorerical studies involving rhe disrriburion and fate of chemicals in rhe armosphere.

1388 Environ. si. Technol., MI. 22. NO. 12. 1988