Document 3JJQjKqYwK5V53LBvq86nYEZO
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MANUFACTURING CHEMISTS ASSOCIATION
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1825 CONNECTICUT AVENUE, N.W. WASHINGTON, D.C. 20009 (202) 483-5126
SEP 10 1974
September 3, 1974
To:
Technical Task Group on Vinyl Chloride Research Technical Panel on Fluorocarbon Research
Subject: EPA Paper Exposure to Halooenated Hydrocarbons in the Indoor Environment
Gentlemens Distributed herewith are copies of a draft of the
subject paper, which was presented at a recent conference on public health implicatimoief components of plastics '* manufacture.
Sincerely,
'Kenneth D. Johnson, Fh.D. Assistant Technical Director Air Quality
KDJ/mb Enclosure
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cc: D. P. Duffield, m.D.
Hr. A. W. Barnes Dr. Tiziano Garland*
Mr. Klaus-Peter Methfessel
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COPIED BY MCA
Exposure to Halogenated Hydrocarbons In the Indoor Environment
Prepared by Kenneth Bridbord
Paul Brubaker Bruce Gy
Jean G. French
National Environmental Research Center Environmental Protection Agency
Research Triangle Park, North Carolina 27711*
SECOND DRAFT
For Presentation at Conference on
Public Health Implications of Components of Plastic Manufacture Pinehurst, North Carolina July 31, 1974
*
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The Indoor environment has often been Ignored os a significant source of exposure to air pollution despite the fact that levels of pollutants In the Indoor air can frequently exceed those concentrations which commonly occur In the outdoor environment. The Indoor environment Includes that present In a number of circumstances Including occupational situations, public buildings, hospitals and the home. The discussion to follow stresses, but is not limited to, consideration of exposures In the home situation. The present paper endeavors to review those Instances where Indoor air pollutants and particularly halogenated hydrocarbons, may reach concentrations of potential public health significance. In the past there has been considerable attention given to the potential health hazards of chlorinated aromatic compounds such as PCB's and pesticides. To date, however, there has been relatively little attention given to the halogenated aliphatic compounds which are the primary focus of the present paper.
Behavior of Pollutants In the Indoor Environment
Assuming that a given pollutant Is chemically stable In the Indoor
air and that It is present as a result of being generated from an indoor
source than Its concentration as a function of time may be described by the
following equation (1): C *
7^
0)
where;
C * concentration at time, t co In*itial concentration3 at time, 0. Q ** air supply rate In ft /min
Y room volume, ft3
t time, minutes v x mnctant* trt adiust for imoerfect mixinq
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This equation assumes that after time zero the source is turned off
and that the air supply Into the room is not contaminated by the pollutant
In question. If a continuous source for a given pollutant 1$ also I
present then the problem becomes more complex. Even a small continuous
source can greatly affect Indoor pollution levels which under certain cir
cumstances may build up considerably (2,3). In the discussion to follow
only the mplifled situation without a constant source of pollution will be
considered* recognizing that this may underestimate exposure in those
Instances when a constant emission source is present.
In practice, under best mixing conditions, the highest achievable value
for k, the mixing constant (shown In equation (1))*1s 1/2. Under these
circumstances equation (1) becomes: C
(2)
It Is apparent from this equation that'an important parameter affecting concentration Is the turnover rate of air In the room per minute, Q/V. If there Is no exchange of fresh air then the equation reduces to a con dition In which the concentration at any time Is equal to the concentration at time zero. The more frequent Is the exchange for fresh air, the more rapid Is the concentration of the pollutant decreased.
Let us examine, for example, the decrease In concentration with time predicted by equation (2) under various rates of fresh air exchange. These calculations are shown.In Table 1 and In Figure 1. The strong dependence of outdoor concentration upon air exchange rate is illustrated in this Table and Figure. For example, with but one air exchange per hour, at 30 minutes the concentration Is nearly 80S of Its initial value whereas at 6
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TABLE 1
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Dependence of Indoor Concentration Upon Air Exchange Rates in a Room
Air Exchange Rate
Time (minutes)
0 15 30 - 45--
60
. 90 120 150 `
180
Once Per Hour tq/v-l/60) Co 0.88 Co 0.78 CO 0.69 Co 0.61 Co 0.47 Co 0.37 Co 0.29 Co 0.22 Co
Twice Per Hour (t)/v*2/60) Co 0.78 Co 0.61 Co 0.47 Co
0.37 Co . 0.22 Co 0.14 Co 0.08 Co 0.05 Co
Six Times Per Hour (Q/v 6/60) Co 0.47 Co 0.22 Co -
o.n co v. . 0.05 Co 0.01 Co <0.01 Co
: -.
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Figure 1. Indoor concentration as a function of air exchange rate and time.
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air exchanges per hour the concentration has dropped to about 20% of the Initial value. After 2 hours, at one air exchange per hour the concen tration Is still better than one-third the initial concentration (C0)v but at $ air exchanges per hour the concentration has fallen below IS of Its initial value.
Given a functional dependence of concentration with tine as shown in equation (2) let us examine some real world measurements of indoor pollution levels (4) to see If they obey this type of relationship. Shown in Table 2 are measurements of propellant concentrations following a 60 second release of a halrspray In a 29,000 liter room. The propellants measured are vinyl chloride and Freon-12. The rate of decay of vinyl chloride parallels that of Freon *12 (shown in Figure 2) suggesting that the vinyl chloride was chemically Inert over the time frame examined and under the existing experimental conditions. The effect of air exchange upon concentration In this experiment is similar to that predicted by equation (2) assuming an air exchange rate of 6 times each hour, and considering that the initial high measurements In the breathing zone at time 0 do hot reflect complete mixing of the propellants in the room.
Shown In Table 3 are the results of a 30-second aerosol insect spray released In a home laundry room of 21,000 liter volume. The spray was released along the baseboards of the'room containing a washer and dryer, sink, clothes end other miscellanceous items. The room has two doors, one leading to a hallway in the house proper and the other leading to the outside. During the experiment, the door to the hall was Closed and samples were taken by entering the door to the outside of the 'house; Sample No. 1, collected one minute after the aerosol was released, showed a concentration of 380 ppm vinyl chloride. Sample No. 4, taken 150
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TABLE 2
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Sixty-Second Release of Hairspray in 29,300 Liter Room
Sample
Time
Column 1
Column II
Vinyl Chloride Freon-12 Vinyl Chloride Freon-12
No. 1
Collected at
Breathing Zone During Spray
No. 2 ,10 minutes
No. 3 30 minutes
No.* 4^. 60 minutes
122.7 ppm 62.15ppm
25.8 5.56 0.13
11.0 2.53 0.06
124.4ppm
25.1 5.2 0.12
58.30ppm
11.0 2.26 0.05
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Thirty-Second Release of Insect Spray In 21.400 Liter Room
Sample
Time
Column I
Column II
Vinyl Chloride Freon-12 Vinyl Chloride Freon-12
1 Collected one minute after spray
2 30 minutes later
3 60 minutes later
4 150 minutes later .
5 Collected In adjacent hall at 151 minutes
380.1ppm 466.4ppa
52.1 24.6 10.3
0.83*
54.45 26.40 11.55
0.94
383.6ppa 457.6ppm
48.7 22.5
9.3 0.65
55.65 25.85 12.10
0.83
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minutes after aerosol release, had a concentration of 10.3 ppm vinyl chloride.
A sample taken In the hallway adjacent to the laundry room at 151 minutes
contained 0.83 ppm vinyl chloride, Indicatlng'spreadof v1riyt'chloride
to other areas of the house despite the^losell~dodrr""AssumThg~that the
initial measurement was not made at a time when there was equal mixing
throughout the room, the rate of decay-of concentration;with time was similar
to that which would be expected at an air turnover of twice per hour accord
ing to equation (2).
.
In contrast to the experiment with the hairspray, In which Freon-12
concentrations were about one-half those of the vinyl chloride, Freon-12
levels in the insect spray experiment were 10-201 greater than the vinyl
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chloride concentrations. Given the frequent sequential use of aerosol
products containing Freons such as halrsprays and deoderants, peak exposures
to Freon mixtures in excess.ot^1,000_ppm_mw ight`result following combined use of such aerosol products In the indoor environment. This raises the
possibility that peak exposures to a mixture of iFreons following use of
aerosol products could exceed the peak exposure recofimended for such a mixture
in the work environment. The current TLV for Freon-12 is, for example,
1,000 ppm, suggesting that excursions In excess of 1,250 ppm should not
be permitted for occupationally exposed 1nd1vidua1$(5). Naturally, exposures
of the general population should be kept well below those permitted for the
occupational population since the general population frequently includes
potentially high risk groups not usually found in the work forces.
Shewn In Table 4 is a breakdown of propellant use in aerosol,products
as a function of product category. It Is apparent from this table that a
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Table 4. USE OF PROPELLANTS IN AEROSOL PRODUCTS BY PRODUCT CATEGORY
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Product Classification Inhalants Containing Bronchodilator drugs (11 products) Mouth Products (6 products)
Vaporizers (2 products)
Hair products (62 products)
, Women's personal hygiene products (22 products)
Deoderants and antiperspirants (38 products)
Foot products (9 products)
Miscellaneous products for personal use (18 products)
Propellants Used
Frequency Usi
Freon 11 Trlchlorofluoro methane) Freon 12 D1chiorof1uoromethane) Freon 114 [Dlchlorotetrafluoro ethai )
Freon 12
;
Freon 114
Freon 1426 (Monochlorodlfluoroetham )
5/11 11/11 9/11
5/6 5/6 1/6
Freon 11 Freon 12 Tvichloroethane
*
2/2 2/2
1/2
Freon 11
Freon 12
Freon 114
Freon 152a (Dlfluoroethahe)
Methylene chloride
Vinyl chloride
Propane
Isobutane
53/62
54/62
4/62 5/62 8/62 1/62
3/62 32/62
,
1
1 I 1
Freon 11 Freon 12 Freon 114 Isobutane
5/22
20/22 6/22
2/22
Freon 11
Freon 12 Freon 114 Freon 142b
Propane Isobutane
13/38 37/38
8/38 1/38
1/38 1/38
Freon 11
Freon 12 Freon 114
8/9 9/9
1/9
Freon 11 Freon 12 Freon 114 Isobutane
Propane ....
7/18 15/18 3/18
2/18 ... 2/18
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number of halogenated hydrocarbons are employed'as aeroYdr propellants. Depending upon the frequency and patterns of use of-aerosol-products among the population, a substantial number of individuals may be^repeatedly exposed to these compounds. By far the most conmonly used propellants as illustrated in Table 5 are Freon-11 and Freon-12.
Recently published studies of instantaneous.Freon-11 and Freon-12 concentrations in the indoor environment taken at random, conflrm the presence of measurable quantities of these pollutants in the*indoor air (6). Levels of*Freon-12 in homes, for example, exceeded 500 ppb and were generally much greater than simultaneous outdoor'concentrations which usually measured 1 ppb or less. In one study, a measurement of Freon 12 in a beauty shop Indicated a concentration of 370 ppb (15). A study of Freon-12 levels in a beauty shop conducted by the Environmental Protection Agency found a concentration of 3,000 ppb or 3 ppm averaged over a 15 minute period. In this experiment no vinyl chloride was identified.
Apart from aerosol propellants, another important source of exposure to halogenated hydrocarbons in the indoor environment may be from the active Ingredients contained In aerosol products. For example, aerosol spot re movers used for clothing, carpets, upholstery and wallpaper may frequently contain perchloroethylene as the active ingredient. Though the concentration of perchloroethylene in such products often is not identified on the label, it is conceivable that the proportion of active ingredients could be similar to the quantity of propellant in these products. Under these circumstances, peak concentrations of perchloroethylene well in excess of 100 ppm might occur during and immediately following spraying as judged from the data in
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Table 5. OVERALL USE OF PROPELLANTS IN 158 AEROSOL.PROOUCTS
Propellant
Frequency of'Use i
Percent
Freon 11 Freon 12 Freon 114 Freon 1426 Freon 152 a . Isobutane Hethylene chloride Propane Trlchloroethane Vinyl chloride
93/168
153/168
. 36/168
2/168
5/168
37/168
V.
8/168 6/168 -
1/168
1/168 * .........
. 55.4 91.1 21.4 . 1.2 3.0 22.0* 4.8 3.6 0.6 0.6
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Tables 2 and 3.
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It Is noteworthy that the TLV for perchloroethylene Is
100 ppm with excursions recommended not to exceed 150:ppm (5). Accordingly,
aerosol products containing perchloroethylene may, under certain circumstances,
result in exposures among the general population which exceed established
exposure limits for Industry.
Another Important source of Indoor exposure to halogenated hydrocarbons
may be from solvents. Such products contain volatile components which could
build up to high concentrations in the indoor air. Consider a substance
such as trichloroethylene, a structural analogue to vinyl chloride, which Is t
used for a variety of purposes. In dry cleaning, as a degreasing agent,
and as an anesthetic. At 12C (54F) ICE has a vapor pressure of 40 m Hg
and at 20C (68F) TCE has a vapor pressure of 60 run Hg. In contrast,
water at 12C has a vapor pressure of 11 mm Hg and at 20C a vapor pressure
of 18 mm Hg. Consequently the tendency for trichloroethylene to vaporize
is greater than that of water, which does not attain a vapor-pressure of
60 mm Hg until 42C (108F). Should the atmosphere above trichloroethylene
reach only 0.13C of saturation then at 20C the concentration of trich
loroethylene would be nearly 80 ppm. The threshold limit value for TCE
is currently set at 100 ppm{5). Naturally with good ventilation TCE would -
never reach 80 ppm but under certain situations, air exchange may be low
and TCE used In a closed space could build up to appreciable airborne con
centrations.
Shown in Table 6 are the predicted indoor levels for some commonly
used solvents assuming that these attain a concantration only 0.1X of their
saturation level in the air. In this regard it Is noteworthy that carbon
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Table 6. PREDICTED INDOOR CONCENTRATIONS OF HALOGENATED HYDROCARBON SOLVENTS ASSUMING THAT THEY REACH O.irdf SATURAnON LEVELS
Solvent
Temperature (*C)
......... Predicted Indoor Air Concentration (oom)
Trichloroethylene Tetrachloroethylene
20 i 26 {_
; i 26
Trichloroethane (1,1,2) Trlchloroethane (1,1,1)
21 20
i 26 130
Carbon tetrachloride
23
130
Methylene chloride
24
.520
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tetrachloride, trichloroethylene and tetrachloroethylene (perchloroethylene) have been detected In either the ambient or the indooi; air (6,7).
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For example, one study In Los Angeles County In 1966 estimated that
...
emissions of hydrocarbons Into the atmosphere from organic solvent usage
comprised better than 20% of all hydrocarbon emissions, (8) the majority
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of emissions coming from gasoline-powered motor vehicles. Of the estimated
590 tons emitted per day from organic solvents, 88 tons per day were
attributed to halogenated hydrocarbons. Including trichloroethylene and
tetrachloroethylene. Given the similarity of chemical structure betofeen ' 1 ;
trichloroethylene and vinyl chloride one flould desire to study the health
implications of this substance In much greater depth. (3) In a study of the airborne environment near a solvent recovery plant In
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Maryland (7) levels of carbon techrachloride In the ambient air were
commonly measured In the ppm range. The levels of carbon tetrachloride
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indoors were sometimes 3-4 times greater than those which were measured outdoors. At times concentrations of CCI of 10-45 ppm were measured
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Inside a house when levels outside were 1 ppm. The highest indoor concen
tration of carbon techrachloride recorded was 90 ppm. These large
differences In 1ndoor/outdoor concentration may reflect buildup of Indoor - J
concentrations from an outdoor source measured at a point in time Imnadiately
following dramatic reductions In outdoor concentrations. The possibility,
of course, must also be considered that an indoor source of carbon
tetrachloride also existed.
A potentially important source of indoor exposure to halogenated
hydrocarbons may be from use of such compounds as anesthestlc agents. It
,
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has already been noted that trichloroethylene continues to be used as an anesthetic, particularly In oral surgery. Vinyl chloride, a structural analogue to trichloroethylene and a recently identified carcinogen and liver toxin has similar neurologic action, and once was considered for use as an anesthetic. Ethylene, though not containing chlorine, has also been used as an anesthetic. Under these circumstances, one wonders whether potential for carcinogenic activity and/or liver toxicity exists for unsaturated halogenated compounds with anesthetic activity such as trldi-
a
loroethylene. If so, a possible health risk may exist not only for patients but also for personnel who'day In-day out administer these compounds. A number of other halogenated compounds besides, trichloroethylene are-also frequently used as anesthetics. These confounds Include halothane and methoxyflurane. Though not unsaturated, these latter compounds may require reexamination In terms of their potential for toxic activity, particularly to the liver. Methoxyflurane combines an ether structure with that of-a halogenated aliphatic compound and Its structural similarity to the chloromethyl ethers should not be overlooked. Chlorform, also halogenated. Is yet another anesthetic which is extremely toxic to the liver. It Is noteworthy that divinyl ether, while not a halogenated compound, in some respects is analagous In structure to trichloroethylene and vinyl chloride and also represents an anesthetic with established liver toxicity.
It Is evident from this brief discussion that a number of h&logenated hydrocarbons have been documented and/or are suspected to be present In the airborne environment both indoors and out. What data as are available suggest that indoor levels of these substances are frequently much greater
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than are found outdoors, though the source oi f indoor home contamination may
frequently originate from emissions Into the ambient air.
Health Impl1catlons
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In assessing the risk to health for the general fjopulatlon from
exposure to a given air pollutant one must consider the Inherent toxicity
of the material in question, the range of concentrations which may be
present in the air, and the probability that members of the population *
may be exposed to these concentrations. If one were to examine the
halogenated hydrocarbons on the basis of the above criteria, many compounds
in this dass would have to be considered as potential health risks for
the general population.
*
In viewing this class of materials It 1$ Instructive to compare the peak
Indoor concentrations for several halogenated hydrocarbons with those of
other air pollutants for which ambient air quality standards have already
been set. In making this comparison it 1$ recognized that the relative
concentrations are by no means Indicative of relative toxicity and that
differences are being accentuated by comparing peaks with concentrations
over longer averaging periods. On the other hand these comparisons are
suggestive of the relative-increased Indoor atmospheric loading with
halogenated hydrocarbons that can occur and of the existence of a potentially
important class of air pollutants.whose health implications have heretofore
not been adequately examined. These contrasts are Illustrated in Table 7.
In assessing these data one must also recognize that halogenated hydrocarbons
present in the ambient air may add to the exposure attributable to indoor
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Table 7. COMPARISON OF PEAK INDOOR AIR MEASUREMENTS FOR HALOGENATED HYDROCARBONS WITH PRESENT AMBIENT AIR QUALITY STANDARDS
Substance Vinyl Chloride :Freon 12 :Carbon Tetrachloride :S02*
NOj ;co
Ozone
Peak Indoor Concentration Ambient Air Quality
(PP)
. Standard (ppm)
380
466
90
* 0.14 ppn (24-hr. average)
0.05 ppn (annual average)
* 35.00 ppn (1 hour average) e 9.00 ppn (8 hour average)
0.08 ppn (1 hour average)
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concentration!'iljd that halogenated hydrocarbons present outdoors may also
participate In p||tochem1cal reactants yielding other undesirable products.
Shown In Talil* 8 are comparisons of relative atmdspherlc loading on a weight per volume basis and on a molecule per volume basis between vinyl chloride at 1 ppm and benzo(a)pyrene as typically found In the ambient air (10 ng/m8) and as reported to occur in the Indoor air (28-144 ng/*8).-
Thls comparison docs not directly reflect relative toxicity between vinyl
chloride at 1 ppm and BaP In the air. On the other hand, the relative In
creased atmospheric loading of 1 ppm vinyl chloride compared to benzo(a)pyrene,.a suspected airborne carcinogen is worthy of note.
Observations such as those discussed In this paper strongly suggest that the general population 1$ currently exposed to substantial quantities of
halogenated hydrocarbons In the Indoor environment. The health Implications
of many of these compounds are not well understood. For example, the
preponderance of studies on Freons, cornnonly used as aerosol propellants'.
Involve consideration of acute, but not chronic effects. Accordingly the
carcinogenic'potential for these compounds cannot readily be dismissed.
Though Freons are considered to be chemically inert in the environment this assumption cannot be extended to biological systems. Available data
suggest that short term exposures to Freons in man may result In cardiac
arrythmlas. The possible effect of such exposures upon Individuals already
prone to arrythmias such as those with atherosclerotic heart disease must
thus be considered. Use of aerosal products containing methylene chloride
combined with Freons may further stress the cardiovascular system by increased endogenous formation of carbon monoxide. How many other halogenated
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TABLE 8
K*
Comparative Atmospheric Loading Between 1 ppm Vinyl Chloride and Bcnzo(a)pyrene
Comparisons
: Weight per Volume Comoarlson
VC(1ppm)/8aP (10 ng/nP,
annual average in ambient air)
260,000/1
VC(lppm)/BaP (28-144 ng/m3.
reported Indoor concentrations)
(18,000-93,000)/1. *
Molecules per Volume Comoarlson
1,000,000/1
. .. '
(72,000*372,000)/1 .
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A.
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hydrocarbons should also be examined for their potential effects upon CO -i
metabolism? Home cleaning agents In aerosol form have the potential to t
exceed accepted occupational exposure limits for perchloroethylene. Are
there additional aerosol products which unknowingly may also have the
potential to exceed exposure limitations established for occupational
situations? Clearly the multitude of aerosol products commercially
available represent an Important source of exposure to halogenated hydro
carbons, as do solvents and anesthetics. Exposure to these substances Is
greatly accentuated in the Indoor environment where there Is less oppor
tunity for dispersion. Since the activity patterns of the general popu-
latlon Includes a substantial portion of time spent indoors,, the
cleanliness of the Indoor air becomes an Important consideration.
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