Research Project Summary

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Conrad Curtis
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1 Environmentl Assessment nd Risk Anlysis Element Reserch Project Summry June 11,2002 A SCREENING MODEL FOR PREDICTING CONCENTRATIONS OF VOLATILE ORGANIC CHEMICALS IN SHOWER STALL AIR Pul F. Snders, Ph.D. 1 Abstrct A simple equilibrium model ws developed to predict mximum possible concentrtions of voltile orgnic chemicls tht my occur in shower stll ir from the use of contminted during showering event. The only site-specific prmeter tht must be known to use the model is the contminnt concentrtion in the influent. Dt ws compiled from four previous studies for which vpor concentrtions of contminnts in experimentl shower stlls were mesured. Pek concentrtions reported in these experiments were compred to model-predicted concentrtions. Experimentl pek concentrtions were typiclly within n order mgnitude of concentrtions predicted from the model (used under stndrd conditions), with the predicted vlue lmost lwys being the higher of the two concentrtions. When the model-predicted vlues were djusted for experimentlly reported vlues for temperture, ir exchnge rtes, nd flow rtes, greement between experimentl nd predicted vlues improved; predicted vlues usully were in the rnge of 1 to 3 times the experimentl pek concentrtions. The behvior of the model suggests tht it would be useful s screening tool for estimting mximum concentrtions of voltile orgnic chemicls in shower stll ir, rising from the use of contminted during showering event. Exmple clcultions of shower criteri to protect ginst uncceptble inhltion exposures indicted tht t times these criteri were lower thn drinking Mximum Contminnt Levels or other criteri bsed on ingestion of the. This reserch ws supported through the New Jersey A-280 Drinking Wter Reserch Fund. Introduction During the pst decde, incresing ttention hs been given to the potentil for significnt inhltion exposures to voltile orgnic chemicls (VOCs) during showering (Moy et l., 1999; Keting et l., 1997; Girdino nd Andelmn, 1996; Weisel nd Jo, 1996; Tncrede et l., 1992). Requests for ssessments of this exposure pthwy hve become more frequent t the NJDEP s wreness of its potentil importnce hs incresed. While residents of dwellings with VOC-contminted my be instructed to drink bottled until tretment system is instlled, it hs lso been necessry to mke rpid decisions s to whether or not contminted my be used in the mentime for other purposes, such s for showering. This decision usully must be mde when only one piece of informtion is known: the concentrtion of the VOC in the influent shower. Models tht evlute the potentil inhltion of VOCs during showering hve been evolving s the kinetics of contminnt voltiliztion from shower systems hs become better understood (Moy et l., 1999; Little, 1992; McKone, 1987; Wilkes et l., 1996). While some of these pproches my be recommended for more dvnced nlysis, they re too complex for routine use s screening tool. For screening purposes, rpid, simple ssessment of mximum contminnt concentrtions tht my be encountered in shower stll ir is desired. In this study, simple equilibrium model hs been developed to clculte conservtive estimte of the mximum concentrtion of VOC tht might be observed in shower stll ir s function of its concentrtion in the influent. Screening Model Methods The screening model ws derived from the expression for the dimensionless form of the Henry s lw constnt, nd clcultes the equilibrium contminnt concentrtion in ir (C ir ) from of known concentrtion in influent shower (C ): HV C ir =C HV ir + V Wter (1) where V ir is the volume of the shower stll, with the option of including the totl volume of ir exchnged from the stll during the shower event is the totl volume of used during showering event, nd H is the dimensionless Henry s lw constnt t the temperture of the shower. This model simply clcultes the equilibrium prtitioning

2 between shower stll ir nd shower nd ignores contminnt exiting the system vi the shower drin or ir exchnge. Clcultion of equilibrium ir concentrtions Using Eqution 1 nd reported influent contminnt concentrtions from experimentl studies, equilibrium ir concentrtions were clculted for chloroform, trichloroethene, ethylbenzene, toluene, cyclohexne, ethyl cette, nd cetone. Concentrtions were clculted in two wys: 1) using stndrd vlues for ll input prmeters except for the influent VOC concentrtion in, nd 2) dditionlly djusting V ir nd H for the totl ir exchnged, totl consumed, nd the ctul tempertures reported by the investigtors. The stndrd vlues for the model prmeters were s follows: shower stll volume, 1.5 m 3, no ir exchnge; shower volume, 0.1 m 3 (10 minute shower durtion with 10 L/minute shower flow rte); shower temperture for clculting the Henry s lw constnt, 40 C. Reltive to the reported studies, the shower stll volume ws typicl, the temperture ws equl to or bove most tempertures, nd the flow rte ws typicl mximum vlue. Henry s lw constnts were clculted using temperture-dependnt reltionships for this prmeter reported in recent reserch. The U. S. Geologicl Survey hs conveniently summrized experimentlly determined temperture-dependnt reltionships for the Henry s lw constnt for mny VOCs (Rthbun, 1998). Experimentl Shower Systems Dt ws extrcted from four recent studies employing experimentl shower systems for which contminnt concentrtions in the shower stll ir were directly mesured (Moy et l., 1999; Keting et l., 1997; Girdino nd Andelmn, 1996; Jo et l., 1990). Pek contminnt concentrtions were used for comprison to the screening model (except for results from Jo et l. (1990), who reported time-verged ir concentrtions). The experimentl conditions for these studies vried widely with regrd to shower stll ir exchnge rtes (0-379 L/min), shower tempertures (19-46 C) nd contminnt concentrtions in the influent shower (Tble 1). Vlues for V ir nd V were clculted from reported shower stll volumes, ir exchnge rtes, flow rtes, nd shower durtion times. Results Experimentlly mesured contminnt concentrtions in shower ir were compred to predicted concentrtions for eighty-nine reported experiments from four investigtors, subset of which re listed here (Tble 1). Differences between the clculted nd mesured concentrtions re reported s the rtio of the two vlues for convenience. A sttisticl summry of the rtio vlues ws lso prepred (Tble 2). The experimentl concentrtions of Jo et l. were time-verged, rther thn pek vlues. The sttisticl summry ws therefore clculted both with nd without those experiments. The most striking observtion tht cn be mde is the reltively close greement between concentrtions predicted with the screening model nd the experimentlly determined pek concentrtions. When screening model clcultions were djusted for experimentlly reported vlues for V ir nd temperture, the verge rtio of predicted concentrtions to mesured pek concentrtions ws less thn three (Tble 2). This rtio ws reduced to less thn two when the time-verged dt of Jo et l. ws removed from the dt set. When the rtios were determined using stndrd shower conditions, the men rtio ws pproximtely seven either with or without the dt set of Jo et l. (Tble 2). Predicted concentrtions were generlly higher thn mesured results; the reson for this lies in the formultion of the screening model s simple equilibrium system. The model does not ccount for the kinetics of contminnt voltiliztion or its loss from the shower system vi ir exchnge nd exiting the shower drin. The entire mss of contminnt entering the system during the shower run is simply prtitioned between the ir nd phse under equilibrium conditions. Thus, conservtive (high) prediction of contminnt concentrtions would be expected. Such conservtive prediction is desirble in screening model, s long s the prediction is not unresonbly high. A commonly employed stndrd for screening model is tht it should give n order-of-mgnitude estimte of ctul contminnt concentrtions. This condition ws lwys met when the clcultion ws djusted for experimentl V ir nd temperture vlues. Even when run under stndrd conditions, this order of mgnitude greement ws chieved more thn 80% of the time, nd the highest rtios were still not excessively high (between 20 nd 30 for some of the cyclohexne experiments). Another desirble feture of screening model is tht it should not under predict experimentl concentrtions. When run under stndrd conditions, the model under predicted experimentlly mesured concentrtions only 4 times out of 89 experiments, nd in those four cses the under prediction ws less thn fctor of two. Use of the model with experimentlly djusted vlues for V ir nd temperture yielded predictions for 6 of 89 experiments tht were between 58 nd 80% of the mesured vlues. An dditionl 12 predictions were only mrginlly low (between 80% nd 100% of the mesured vlues). While the under prediction ws gin less thn fctor of two in ll cses, it would be somewht more prudent to clculte concentrtions using stndrd conditions. This is lso recommended for nother reson: vlues for V ir nd temperture re not known for ctul cses without site-specific investigtion. The somewht greter over prediction of pek shower concentrtion tht results is not excessive ( fctor of seven, on verge). Discussion A simple rerrngement of Eqution 1 my be used to predict cceptble influent concentrtions from n llowed ir concentrtion in the shower stll. The ltter concentrtion is clculted from the inhltion toxicity endpoint selected by the user nd the inhltion exposure time ssumed, nd it is substituted for the estimted pek ir concentrtion, C ir, from Eqution (1). For noncrcinogens, the cceptble concentrtion is C = RfC 1440 HV + V ir 10 HV (2) 2

3 where RfC is the inhltion reference concentrtion, nd the rtio of 1440/10 is n djustment mde for the dose tht would normlly be received over 24 hours (1440 minutes) being concentrted into 10 minute shower exposure time period. For crcinogens, the equivlent eqution is C = HV + V ir URF 10 HV where 10-6 is the cceptble risk level nd URF is the inhltion unit risk fctor. It hs been estimted tht derml exposure my be roughly equivlent to inhltion exposure during showering event (Jo et l., 1990). Incorporting this ssumption into the clcultion of n cceptble concentrtion would require dividing the result from Equtions (3) nd (4) by fctor of two. Exmple shower criteri for selected VOCs to protect ginst uncceptble inhltion exposures re listed in Tbles 3 nd 4. Tble 3 lists six noncrcinogens of potentil concern, nd Tble 4 lists five crcinogens. Also shown in these tbles re current New Jersey ground helth criteri, bsed on ingestion of ground, nd Mximum Contminnt Levels (MCLs) for severl of the chemicls in drinking. Henry s lw constnts t 40 C for these clcultions were determined using softwre pckge vilble from the Environmentl Protection Agency (USEPA, 2000). If derml dsorption is ignored, the shower criteri shown for the exmple noncrcinogens re ll higher thn the New Jersey ground criteri nd/or MCLs (Tble 3). When djustment is mde for derml dsorption, the criteri for cis- nd trns-1,2-dichloroethene fll slightly lower thn the criteri bsed on dsorption, but overll the shower inhltion pthwy for these chemicls is not significnt concern reltive to the ingestion pthwy. For the exmple crcinogens, shower criteri were usully lower thn the corresponding MCL vlues nd the ground helth criteri, prticulrly if the criteri were djusted for derml exposure during showering (Tble 4). Of prticulr note is chloroform, which does not hve n MCL but does hve ground criterion of 70 µg/l bsed on ingestion. The shower criteri for chloroform of 0.12 µg/l (0.06 µg/l with djustment for derml exposure) is substntilly lower thn the ground criteri nd suggests tht the showering exposure pthwy my be worthy of further considertion for some chemicls when VOCs re regulted in potble. The results of this study suggest tht the simple model described my serve s useful nd resonbly conservtive screening tool for deciding whether or not potentil inhltion exposures resulting from VOC-contminted shower re significnt reltive to other exposure pthwys such s ingestion. For site-specific cses, the model my suggest whether the inhltion exposure pthwy wrrnts further investigtion. For follow-up site-specific investigtion, either on-site mesurements or lterntively, more sophisticted models, such s the two-film model pproch, described by Little nd Moy et l., re recommended. (3) References Girdino N.J., nd Andelmn J.B. J Exposure Anl. Environ. Epidemiol. 1996: 6: Jo W.K., Weisel C.P., nd Lioy P.J. Risk Anl. 1990: 10: Keting G.A., McKone T.E., nd Gillett J.W. Atmos. Environ. 1997: 31: Little J.C. Sci. Technol. 1992: 26: McKone T.E. Eniron. Sci. Technol. 1987: 12: Moy J., Howrd-Reed C., nd Corsi R.L. Environ. Sci. Technol. 1999: 33: Rthbun R.E. Trnsport, Behvior, nd Fte of Voltile Orgnic Compounds in Strems. U.S. Geologicl Survey Professionl Pper U.S. Government Printing Office: Wshington, DC, Tncrede M., Yngisw Y., nd Wilson R. Atmos. Environ. 1992: 26A: USEPA. User s guide for the Johnson nd Ettinger (1991) model for subsurfce vpor intrusion into buildings (revised). U.S. Environmentl Protection Agency, Office of Emergency nd Remedil Response: Wshington, DC, Weisel, C.P.; Jo, W.K. Environ. Helth Perspec. 1996: 104, Wilkes C.R., Smll M.J., Dvidson C.I., nd Andelmn J.B. J Exposure Anl Environ. Epidemiol. 1996: 6: Prepred By 1 Pul F. Snders, Ph.D. Principl Investigtor 3

4 Experimentl dt Influent Influent Pek Air concentrtions from model Rtio of clculted to Time of concentrtion (mg/m 3 ) experimentl concentrtions Expt. shower V V ir temperture concentrtion in shower ir Adjusted Stndrd Adjusted Stndrd Contminnt Investigtor No. (min) (M 3 ) (M 3 ) ( C) (mg/l) (Mg/M 3 ) conditions b conditions c conditions b conditions c Chloroform Keting et l. (1997) Girdino nd Andelmn (1996) Jo et l. (1990) d d d d d Trichloroethene Girdino nd Andelmn (1996) Cyclohexne Moy et l. (1999) Ethylbenzene Moy et l. (1999) Toluene Moy et l. (1999) Ethyl cette Moy et l. (1999) Acetone Moy et l. (1999) , Experimentl contminnt concentrtions in ir re pek vlues mesured unless otherwise noted. Totl number of experiments = 89. b VWter, V ir, nd Henry s lw constnt djusted for experimentl conditions. c Stndrd conditions s described in text. d Experimentl concentrtions re verge vlues over durtion of shower runs. P. Snders, NJDEP, My

5 Tble 2. Rtio of Clculted to Experimentl Contminnt Concentrtions in Shower Air: Sttisticl Summry Model clcultions djusted for Model clcultions under stndrd experimentl conditions conditions b All experimentl dt All dt except Jo et l. All experimentl dt All dt except Jo et l. (n=89) (n=70) (n=89) (n=70) Averge rtio Std. dev. of rtio Rtio rnge Experimentl vlues for temperture, V ir nd V b Stndrd vlues for temperture, V ir nd V s given in text Tble 3. Acceptble VOC Concentrtions in Shower Stll Wter to Protect Aginst Uncceptble Inhltion Exposures: Noncrcinogens Chemicl Reference Shower Wter Criteri (µg/l) NJDEP Ground Concentrtion No derml With derml Helth Criteri (µg/l) (RfC) in Air (µg/m 3 ) bsorption bsorption Acetone ,400 9, ,1-Dichloroethne b 1,2-Dichloroethene (cis) b 1,2-Dichloroethene (trns) b MTBE b Tertiry buty lcohol (TBA) 61 7,800 3, Current s of My, 2002 b Equls Mximum Contminnt Level Tble 4. Acceptble VOC Concentrtions in Shower Stll Wter to Protect Aginst Uncceptble Inhltion Exposures: Crcinogens Chemicl Shower Wter Criteri (µg/l) Unit Risk No derml With derml NJDEP Mximum Fctor (URF) bsorption bsorption Ground Helth Contminnt in Air (µg/m 3 ) -1 Criteri (µg/l) Level (MCL) (µg/l) Benzene 8.3 x Crbon tetrchloride 1.5 x Chloroform 2.3 x Trichloroethene 1.7 x ,1-Dichloroethene 5.0 x Current s of My,

6 STATE OF NEW JERSEY Jmes E. McGreevey, Governor Deprtment of Environmentl Protection Brdley M. Cmpbell, Commissioner Division of Science, Reserch & Technology Mrtin Rosen, Director Environmentl Assessment & Risk Anlysis Element Dr. Eileen Murphy, Assistnt Director Plese send comments or requests to: Division of Science, Reserch nd Technology P.O.Box 409, Trenton, NJ Phone: Visit the DSRT web RESEARCH PROJECT SUMMARY Division of Science, Reserch & Technology P.O. Box 409 Trenton, NJ Plce Lbel Here

THERMAL EXPANSION COEFFICIENT OF WATER FOR VOLUMETRIC CALIBRATION

XX IMEKO World Congress Metrology for Green Growth September 9,, Busn, Republic of Kore THERMAL EXPANSION COEFFICIENT OF WATER FOR OLUMETRIC CALIBRATION Nieves Medin Hed of Mss Division, CEM, Spin, mnmedin@mityc.es