Document 93wQz94m7pEqxajMzazvgNk4V

MANUFACTURING CHEMISTS ASSOCIATION 1825 CONNECTICUT AVENUE, N W WASHINGTON, D. C. 20009 (202) 483-6126 September 3, 1974 To: Technical Task Group on Vinyl Chloride Research Technical Panel on Fluorocarbon Research Subject: EPA Paper Exposure to Halogenated Hydrocarbons in the Indoor Environment Gentlemen: Distributed herewith are copies of a draft of the subject paper, which was presented at a recent conference on public health implications of components of plastics manufacture. Sincerely, Kenneth D. Johnson, Ph.D. Assistant Technical Director Air Quality KDj/mb Enclosure cc: D. P. Duffield, M.D. Mr. A. W. Barnes Dr. Tiziano Garlanda Mr. Klaus-Peter Methfessel CUSAROSS 01981 COPIED BY MCA DRAFT 00 NOT QUOTE OR CITE Exposure to Halogenated Hydrocarbons In the Indoor Environment ----------------------------------------------------------------------------------------- Prepared by Kenneth Bridbord Paul Brubaker Bruce Gay Jean G. French National Environmental Research Center Environmental Protection Agency Research Triangle Park, North Carolina 27711- ! j ' SECOND DRAFT For Presentation at ;. Conference on Public Health Implications of Componentsof Plastic Manufacture Pinehurst, North Carolina July 31, 1974 1I . `''I ! ! Jt CUSAROSS 01982 INTRODUCTION i i * y * * ' " \JT\h.\ . DO MOT QUOTE OR CITE The indoor environment has often been Ignored as 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 4 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 = Coe^ y * ^ . 0) where; C = concentration at time, t o a in>itial concentration2 at time, 0. Q = air supply rate In ftVmin 3 V room volume, ft t= time; minutes v = a mncb^ tn adiust for imDerfect mixing CUSAROSS 01983 2 DO NOT QUOTE OK CITE "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 is also 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 simplified 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 (shownf in equation (1)) is 1/2. Under these circumstances equation (1) becomes: C = 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 80% of its initial value whereas at 6 CUSAROSS 0198- TABLE 1 DRAFT 00 MOT QUOTE Of! CITE 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 (Q/v=l/60) Co 0.88 Co 0.78 Co (T.69 Co 0.61 Co 0.47 Co 0.37 Co 0.29 Co 0.22 Co Twice Per Hour (Q/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 0.11 Co ..... 0.05 Co 0.01 Co <0.01 Co : -. Jt CUSAROSS 01985 Figure 1. Indoor concentration as a function of air exchange rate and time. _ _. . Jt I CUSAROSS 01986 5 DRAFT do not quote or cite 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 (CQ), but at 6 air exchanges per hour the concentration has fallen below 1% of its initial va'lue. Given a functional dependence of concentration with time 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'hairspray in a 29,000 liter room. The propellants measured are vinyl chloride and Freon-12. The rate of decay of vinyl chloride parellels 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 not 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 the7room containing a washer and dryer, sink, clothes and 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 Mo. 4, taken 150 CUSAROSS 01987 : TABLE 2 ' 1 DRAFT DO NOT QUOTE OR CITE , Sixty-Second Release of Hairspray in 29,300 Liter Room Sample Time Column I Column II Vinyl Chloride Freon-12 Vinyl Chloride Freon-12 No. 1 No. 2 No. 3 No.- 4 Collected at Breathing Zone During Spray ,10 minutes 30 minutes 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 CUSAROSS 01988 Sample I TABLE 3 UK,Hi' 1 DO NOT QUOTE OR CITE Thirty-Second Release of Insect Spray in 21,400 Liter Room r Time Column I Column II Vinyl Chloride Freon-12 Vinyl Chloride Freon-12 1 2 3 4 5 Collected one minute after spray 30 minutes later * 60 minutes later 150 minutes later Collected in adjacent hall at 151 minutes 380.1 ppm 466.4ppm 52.1 24.6 ' 10.3 0.83* 54.45 26.40 11.55 0.94 'v 383.6ppm 457.6ppm 48.7 22.5 9.3 0.65 55.65 25.85 1.2.10 0.83 '- .\ ! CUSAROSS 01989 8 UK/Vrl DO NOT QUOTE OR Cl l E minutes after aerosol release, had a concentration of 10.3 ppm vinyl chloride. j` ` ' ' A sample taken in the hallway adjacent to the laundry room at 151 minutes contained 0.83 ppm vinyl chloride, indicating spread of vinyl chloride * to'other areas of the house despite the closed door. Assuming 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-IH concentrations were about one-half those of the vinyl chloride, Freon-12 levels in the insect spray experiment were 10-20% greater than the vinyl - chloride concentrations. Given the frequent sequential use of aerosol products containing Freons such as hairsprays and deoderants, peak exposures to Freon mixtures in excess of 1,000 ppm might'result following combined use of such aerosol products in the indoor environment. This raises the possibility that peak exposures to a mixture of'Freons following use of aerosol products could exceed the peak exposure recommended 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 r be permitted for occupationally exposed individuals(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. Strewn in Table 4 is a breakdown of propellant use in aerosol t products as a function of product category. It is apparent from this table that a > CUSAROSS 01990 DO. NOT QUOTE OR CITE Table 4. USE OF PROPELLANTS IN AEROSOL PRODUCTS BY PRODUCT CATEGORY 1 Product Classification Inhalants Containing Bronchodi1ator 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 (Trichlorofluoro methane) Freon 12 (Dichlorofluoromethane) Freon 114 (Dichlorotetrafluoro ethar e) Freon 12 ! Freon 114 Freon 1426 (Monochlorodifluoroethane ) 5/11 11/11 9/11 5/6 5/6 1/6 i ! Freon 11 Freon 12 Trichloroethane 2/2 2/2 1/2 : Freon 11 Freon 12 Freon 114 Freon 152a (Difluoroethane) Methylene chloride Vinyl chloride Propane Isobutane Freon 11 " Freon 12 Freon "114 Isobutane Freon 11 Freon 12 Freon 114 Freon 142b Propane Isobutane * ryfOiAjC \ f ^^ .. 53/62 54/62 4/62 5/62 8/62 1/62 3/62 32/62 5/22 20/22 6/22 2/22 1 j | ! J ! ' 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 15/13 3/18 2/18 .. 2/18 CUSAROSS 01991 10 DRAFT DO NOT QUOTE OR CITE number of halogenated hydrocarbons are employed as aerosol 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 commonly 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 confirm the presence of measurable quantities of these pollutants in the-indoor air (6). Levels of1Freon-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 (6). 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 CUSAROSS 01992 . DRAFT DO MOT QUOTE OR C1T" Table 5. OVERALL USE OF PROPELLANTS IN 168.'AEROSOL PRODUCTS Propellant Frequency of Use ' Percent Freon 11 Freon 12 Freon 114 Freon 1426 Freon 152 a * * >**. - Isobutane i Methylene chloride Propane Trichloroethane Vinyl chloride 93/168 153/168 . 36/168 2/168 5/168 37/168 8/168 V. 6/168 1/168 55.4 91.1 21.4 . ! .2 3.0 22.0 ' 4.8 3.6 0.6 0.6 t^ G\ CO i CUSAROSS 01993 12 DRAFT DO NOT QUOTt CR CITE Tables 2 and 3. It is noteworthy that the TLV for perchloroethylene is i! 100 ppm with excursions recommended not to exceed 150.ppm (5). Accordingly, aerosol products containing perchloroethylene may, under certain circumstances, t# 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 used for a variety of purposes, in dry cleaning, as a degreasing agent, and as an anesthetic. At 12C (54F) TCE has a vapor pressure of 40 mm Hg and at 20C (68F) TCE has a vapo'r pressure of 60 mm 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 0.1% 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 concentration only 0.1% of their saturation level in the air. In this regard it is noteworthy that carbon CUSAROSS 0J994 I DO MOT, QUOTE OR CITE Table 6. PREDICTED INDOOR CONCENTRATIONS OF HALOGENATED HYDROCARBON SOLVENTS ASSUMING THAT THEY REACH O.'lX'.'of SATURATION LEVELS Solvent Temperature (QC) .......... Predicted Indoor Air Concentration (ppm) Trichloroethylene Tetrachloroethy1ene Trichloroethane (1,1,2) Trichloroethane (1,1,1) 20 i : bo 26 ; t ti 26 21 ! i 26 20 130 Carbon tetrachloride 23 130 Methylene chloride 24 . 520 A, CUSAROSS 01995 14 DO NOT. QUoft' OR CITE tetrachloride, trichloroethylene and tetrachloroethylene (perchloroethylene) have been detected in either the ambient or the indoo^ air (6,7). 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 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 between ' ` trichloroethylene and vinyl chloride one would 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 Maryland (7) levels of carbon techrachloride in the ambient air were commonly measured in the ppm range. The levels of carbon tetrachloride indoors were sometimes 3-4 times greater than those which were measured outdoors. At times concentrations of CCI of 10-45 ppm were measured 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 indoor/outdoor concentration may reflect buildup of indoor concentrations from an outdoor source measured at a point in time immediately 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 anesthestic agents. It CUSAROSS 01996 15 DRAFT DO NOT QUOTE 00 CITE has already been noted that trichleroethylene continues to be used as an anesthetic, particularly in oral surgery. Vinyl chloride, a structural i 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 trich 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 ofother halogenated compounds besides, trichloroethylene are also * frequently used as anesthetics. These compounds 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. CWorform, 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 halogenated 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 CUSAROSS 01997 16 DRAFT 'DO'NOT QUOTE OR CITE than are found outdoors, though the source of indoor home contamination may frequently originate from emissions into the ambient air. Health Implications -I In assessing the risk to health for the general population 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 class would have to be considered as potential health risks for the general population. * in viewing this class of materials it is 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 is 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 CUSAROSS 01998 I DO NOT QUOTE OR CITE 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 ' N2 ;co : Ozone * Peak Indoor Concentration Ambient Air Quality (ppm) . Standard (ppm) 380 466 90 * 0.14 ppm (24-hr. average) 0.05 ppm (annual average) 35.00 ppm (1 hour average) 9.00 ppm (8 hour average) 0.08 ppm (1 hour average) > CUSAROSS 01999 18 DO NOT QUOTE OR CITE concentrations' ^at halogenated hydrocarbons present outdoors may also participate In photochemical reactants yielding other undesirable products. Shown In Tablfi 8 are comparisons of relative atmospheric 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/m ) and as reported to occur in the indoor air (28-144 -ng/m ), This comparison does 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 is 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, commonly used as aerosol propellants', involve consideration of acute, but not chronic effects. Accordingly the carcinogenic'potential for these compounds cannot readily be dismissed.* * ---------------- ------------------ * 1 ` ---- ^ IH 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 arrythmias. 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 CUSAROSS 02000 TABLE 8 DO KOI QUOTE Oft CITE Comparative Atmospheric Loading Between 1 ppm Vinyl Chloride and Benzo(a)pyrene Comparisons : Weight per Volume Comparison VC(lppm)/BaP (10 ng/m3. annual average in ambient air) 260,000/1 VC(lppm)/8aP (28-144 ng/m3. reported indoor concentrations) (18,000-93,000)/l; # -* Molecules per Volume Comparison 1,000,000/1 - (72,000-372,000)/! CUSAROSS 02001 ' DRAFT 20 DO NOT QUOTE OR CITE hydrocarbons should also be examined for their potential effects upon CO metabolism? Home cleaning agents In aerosol form have the potential to t exceed accepted occupational exposure limits for perchloroethylene. Are i 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 lation includes a substantial portion of time spent indoors, the cleanliness of the indoor air becomes an important consideration. CUSAROSS 02002