PETITIONED PUBLIC HEALTH ASSESSMENT
BURLINGTON NORTHERN LIVINGSTON COMPLEX
(a/k/a BURLINGTON NORTHERN RAIL YARD)
LIVINGSTON, PARK COUNTY, MONTANA
Tables 3-16 in Appendix B list the contaminants detected in each medium on- andoff-site. ATSDR evaluates the contaminants in subsequent sections of the publichealth assessment and determines whether an exposure to them has public healthsignificance. ATSDR selects and discusses the contaminants based upon thefollowing factors:
- concentrations of contaminants on- and off-site;
- field data quality, laboratory data quality, and sample design;
- comparison of on- and off-site concentrations with public health assessment comparison values for (1) noncarcinogenic endpoints and (2) carcinogenic endpoints; and
- community health concerns.
Contaminants listed in the On-site and Off-site Contamination subsections will notnecessarily cause adverse health effects at the levels detected. Instead, the listindicates which contaminants will be evaluated further in the public healthassessment.
ATSDR health comparison values (CVs) are concentrations of contaminants whichare media specific (e.g. water, air, or soil). The CVs are considered to be safeunder default conditions of exposure and are used as screening values in thepreliminary identification of site-specific "contaminants of concern." The"contaminants of concern," listed in the tables in Appendix B, are thosecontaminants that were detected above the screening CVs and contaminantswithout CVs. However, the CVs actually listed in the tables in Appendix B reflectthe most appropriate CV that allows for 'site-specific' conditions of exposure andnot necessarily the screening CV that allows only for 'default' conditions ofexposure. Both CVs, whether allowing for site-specific or default conditions ofexposure, are considered to be protective of public health. The fact that acontaminant is discussed does not mean that site-specific exposure to thesubstance will result in adverse health effects. Rather, the contaminant will beevaluated in subsequent discussions in the document. See Appendix C for adescription of the comparison values used in this public health assessment.
The two principal types of groundwater contaminants at the BNRY are (1) free-floating petroleum hydrocarbons near or on the water table, known as free product,and (2) dissolved volatile organic compounds (VOCs) in the aquifer (1).
The free-product plume and on-site soils are the primary sources of total petroleumhydrocarbons (TPHs) detected above background levels in groundwater beneath theBNRY. Seasonal fluctuations in the water table mobilize TPHs from the residuallycontaminated alluvium (1).
Long-term operations at the BNRY resulted in releases of VOCs to the underlyingLivingston aquifer. Most of those VOCs originated from cleaning and degreasingagents used in the shops. Dissolved VOCs are present in a plume extendingnortheast across the BNRY (1).
Groundwater samples collected from eight on-site monitoring wells at the BNRYrefueling facility on July 29 and 30, 1987, revealed fuel product in one of thewells, (Well L-87-2). Well L-87-2 contained concentrations of TPHs, 1,2-dichloroethene (DCE), trichloroethylene (TCE), and xylene, with DCE and TCEmeasuring well above ATSDR comparison values. Well L-87-2 also contained thesemi-volatile organic compounds (SVOCs) naphthalene, 1-methylnaphthalene, and2-methylnaphthalene, with naphthalene measuring above ATSDR comparisonvalues. Table 8 summarizes the results of the above sampling.
Groundwater samples collected from on-site monitoring wells in June 1988 andanalyzed for VOCs and SVOCs revealed that concentrations of the compounds 2-chlorotoluene and bis(2-ethylhexyl)-phthalate exceeded ATSDR comparison values(10). Concentrations in 21 additional groundwater samples collected from 12monitoring on-site wells between August 17 and August 19, 1988 and analyzed forVOCs, indicated tetrachloroethene (PCE), 1,2-dibromo-3-chloropropane, and 1,4-dichlorobenzene (DCB) exceeded ATSDR comparison values. See Table 8 for sampling results.
On-site groundwater samples were analyzed between May 1989 and May 1992 aspart of an effort to determine the extent of contamination of the Livingston aquifer. Sampling on-site monitoring wells for VOCs, SVOCs, and polychlorinated biphenyls(PCBs)/Pesticides (1,16) revealed that concentrations of DCE exceeded ATSDRcomparison values. No SVOCs or PCBs/pesticides were detected in any of thesegroundwater samples. Table 8 summarizes the sampling results.
Envirocon sampled 14 on-site monitoring wells August 27 through 30, 1990. All samples were analyzed for TPHs and VOCs (7). None of the compounds detected exceeded ATSDR comparison values and were not included in Table 8.
On-site groundwater samples collected from monitoring wells in May 1989 andFebruary 1990 and analyzed for dissolved metals analyses revealed the presence ofarsenic, barium, cadmium, lead, and selenium (1). Of the metals detected, onlylead exceeded the comparison values provided in Table 8. Results are included inTable 8.
Twelve groundwater samples, collected from 11 monitoring wells between June1990 and May 1992 were analyzed for nitrates and nitrites (1,16). Six of themonitoring wells were on-site. Five of six samples collected on-site revealed somelevel of nitrates present; however, none exceeded ATSDR comparison values. Thenitrate levels ranged from 0.17 to 3.87 parts per million (ppm).
On-site groundwater samples were collected during the third and fourth quarters of1994, and the first and second quarters of 1995. The August 1994 samplingevent consisted of 18 primary samples; November 1994 had 21 primary samples;February 1995 had 18 primary samples; and the May 1995 event consisted of 49primary samples. These samples were collected from 15 on-site monitoring wellsand analyzed for PCE, TCE, cis-1,2-DCE, and chlorobenzene. Twelve of the 15 on-site wells contained PCE above ATSDR comparison values; however, thesemeasurements were in much lower concentrations than in previous samplingevents. Eight of the 15 wells monitored contained TCE concentrations aboveATSDR comparison values. Again, these measurements were much lower than inprevious years. One well contained concentrations of cis-1,2-DCE above ATSDRcomparison values and there were no wells with chlorobenzene concentrationsabove ATSDR comparison values.
On-site surficial soil
Envirocon conducted a surficial soil investigation at the BNRY facility during Apriland May 1992 (3). This investigation, part of the site risk assessment, includedareas of potential contamination and potential human exposure. Enviroconseparated the BNRY into nine investigation areas. Surficial soil was defined as anyunconsolidated material extending from the ground surface to a depth of twoinches. Investigators carefully removed layers of ballast, wood chips, or thickvegetation that covered some of the designated sampling locations and sampled theexposed soil at the designated 0 to 2 inch depth. They analyzed samples forVOCs, SVOCs, pesticides, PCBs, and metals. Of the SVOCs detected,benzo(a)pyrene exceeded ATSDR comparison values. The metals detected werebelow the comparison values provided in Table 13. The levels detected aresummarized in Table 13.
On-site subsurface soil
During development of the Interim Remedial Measures Work Plan (IRMWP), theBNRY was divided into 18 investigation areas, where 113 test pits were excavatedand 107 subsurface soil samples were taken. The test pits varied in depth from 1to 15 feet. In the Remedial Investigation (RI) report, the term soil refers to anyunconsolidated material, artificial fill or native material that lies above the watertable of the Livingston aquifer (16). The soil investigations focused on identifyingsubsurface sources of groundwater contamination within and around the BNRY. VOCs, SVOCs, petroleum hydrocarbons, and metals were the compounds analyzed. Of the VOCs detected, TCE and vinyl chloride exceeded the ATSDR comparisonvalues provided in Table 16. Of the SVOCs detected, benzo(a)pyrene exceeded thecomparison values provided in Table 16. PCB-1248 also exceeded comparisonvalues. The metals detected did not exceed the comparison values provided inTable 16. All the results are summarized in Table 16.
Burlington Northern Rail Yard conducted interim remedial actions at all areas wherechlorinated VOCs in vadose zone soils were potentially affecting groundwaterquality. Upon completion of the interim remedial actions, a total of 107confirmation subsurface soil samples were taken from 11 locations. Soil sampleswere analyzed for PCE, TCE, cis-1,2-DCE, chlorotoluene, chlorobenzene, 1,4-dichlorobenzene, and 1,3-dichlorobenzene. PCE was detected in 7 samples in theelectric shop area and TCE was detected in one sample in the electric shop area. Afinal remedial action plan will be implemented in the electric shop area. Results areincluded in Table 16.
On-site subsurface soil/Mission Wye
A waste-oil reclamation plant operated at BNRY from 1955 to 1978. The wasteproducts of this process were reclaimed oil, which was stored and sold to waste-oilrecyclers, and an acid sludge, which was disposed at Mission Wye from 1955 to1978. The on-site soil investigation included sampling the acid sludge disposal areaand the oil reclamation area at BNRY. Soil samples were taken at a depth ofbetween 1.5 to 7 feet from eight test pit areas targeted for sampling. TPHconcentrations were near background concentrations at all eight test pit areas. PCEand several other VOCs were detected at one pit area, although concentrationswere below ATSDR comparison values. Metals were detected at two test pits,although concentrations were below the ATSDR comparison values provided inTable 16. Samples of the test pit area are included in Table 16.
On-site soil gas
Twenty-four soil gas samples were collected during soil investigation activitiesalong on-site drainlines that run from the BNRY shop complex to the WastewaterTreatment Plant (WWTP). The investigation focused on active drainlines or thosethat received heaviest use (1). Of the six compounds detected, TCE, PCE, and cis-1,2-DCE had levels above ATSDR comparison values. Table 3, Appendix B, contains results for this soil gas sampling.
On-site ambient air
The site-wide ambient air monitoring program at the BNRY site measuredparticulate matter with diameters of less than 10 micronsa (PM10), total suspendedparticulates (TSP), and PAHs. The monitoring system comprises one upwind andone downwind air monitoring station. Both stations collect PM10 samples and thedownwind station also collects TSP and PAH samples (1). The system beganoperating in November 1990 and continued through March 1991. See Figure 5 for ambient air monitoring locations.
PAH analyses conducted on samples collected at the downwind station for a 24 hour period on 6 separate days during November and December 1990 detected a total of twelve compounds. None of the compounds were at concentrations above ATSDR comparison values. Table 5, Appendix B, reports the results of the analyses.
Upwind and downwind PM10 filters were analyzed for 34 metals. Six total samples were collected at both stations on the same days during the first 6 sampling rounds(1). Arsenic and cadmium were the only metals detected that exceeded ATSDRcomparison values. Table 7, Appendix B, reports the results of the analyses.
Twenty-three samples for PM10 analyses were collected from November 10, 1990to March 31, 1991. The upwind and downwind samples showed PM10 means of18 and 16 micrograms per cubic meter (ug/m3) and peaks of 56 and 34 ug/m3,respectively. Total suspended particulates were also collected but only at thedownwind station. The mean value was 34 ug/m3 and the peak was 62 ug/m3.
Work-zone ambient air sampling events occurred between November 1989 andJune 1991 (16). Envirocon collected air samples during remedial activities that hadthe potential to generate emissions including sludge handling, test pit excavations,and monitoring well drilling. Several ambient air samples were collected on sixdifferent days from each one of six on-site locations (5). Monitoring results atseveral of the locations, including one station designated as background, werebelow detection limits. However, substances were detected at locations wheresludge was being pumped or monitoring wells were being installed. This suggeststhat the identified pumping and well installation activities may have contributed tothe release of the detected substances from the soil to the surrounding air. Particulate matter was detected at 0.5 - 2.1 mg/m3. Naphthalene andphenanthrene were detected, with naphthalene measuring below comparisonvalues. Table 5, Appendix B, reports the results of the analyses.
Envirocon collected one on-site ambient air sample during February 1992 as part ofan indoor air quality study of residences nearest to the site. The sample wasanalyzed for PCE, TCE, cis-1,2-DCE, and trans-1,2-DCE (4). Analyses of thesample revealed the presence of PCE; however, its concentration did not exceedany comparison values. TCE, cis-1,2-DCE, and trans-1,2-DCE remained below theircorresponding detection limits of 0.22 ug/m3. See Table 5, Appendix B, for thesampling results.
This section involves discussion of off-site monitoring wells sampled from June1988 until May 1995. Monitoring wells were located off-site to the northeast,east, south and southwest areas of BNRY and three wells were located to the eastof the Yellowstone River in an effort to characterize off-site groundwatercontamination. Contaminants detected most often include PCE, TCE, DCE, toluene,arsenic, barium, cadmium and lead. PCE, TCE, cis-1,2-DCE, arsenic, and lead wereabove ATSDR comparison values. However, concentrations of these contaminantshave continued a long-term decline over the last six years. Almost all detectableconcentrations of VOCs extend from the shop area at BNRY eastward to theYellowstone River. All metal concentrations are likewise concentrated in an eastarea toward the river. It is safe to assume this data reflects conclusions that VOCcontamination in groundwater has migrated off-site and that there is a need for fullevaluation of the public health significance of the contaminants.
Groundwater samples obtained from off-site monitoring wells near BNRY in June1988 were analyzed for VOCs and SVOCs (10). Analyses revealed PCE in six off-site wells and TCE, cis-1,2-DCE, and trans-1,2-DCE in no more than one well each. The trans-1,2-DCE, TCE, and the highest PCE levels were detected in the samewell. TCE and PCE were above ATSDR comparison values. See Table 9 for sampling results.
Between August 17 and August 19, 1988, nine off-site monitoring wells wereanalyzed for VOCs (9). None of the compounds were detected at concentrationsthat exceeded comparison values. Table 9 summarizes the results of the sampling.
Off-site monitoring wells were analyzed for dissolved metals in May 1989 andFebruary 1990. The May 1989 results revealed arsenic, barium, cadmium, andlead. Arsenic exceeded ATSDR comparison values. Lead exceeded theEnvironmental Protection Agency's (EPA) action level. February 1990 resultsrevealed arsenic, cadmium, and lead. Again, arsenic exceeded ATSDR comparisonvalues and lead was above EPA's action level. See Table 9 for sampling results.
Envirocon conducted off-site groundwater sampling at twenty off-site wells fromAugust 27-30, 1990 (7). These wells included 13 monitoring wells, 5 privatewells, and 2 municipal wells. This paragraph will report data from monitoring wellsonly. Data on the private and municipal wells appear in later sections. All sampleswere analyzed for TPHs and VOCs. Available data analyses indicate that TPH in allsamples appeared at less than 1 ppm. VOCs detected were DCE, TCE, and PCE. DCE was detected in 2 of 13 monitoring wells, with concentrations of 26 and 3.2micrograms per liter (µg/l). Neither exceeded ATSDR comparison values. TCE wasdetected in 2 of 13 monitoring well samples at levels of 12 and 3.6 µg/l. Both ofthe sample concentrations exceed the 3.0 µg/l cancer risk evaluation guide (CREG)screening value. PCE was detected in 4 of 13 monitoring well samples atconcentrations of 158, 40, 15, and 4.6 µg/l. All four sample concentrations aregreater than the 0.7 µg/l CREG screening value.
Groundwater samples collected from six off-site monitoring wells between June1990 and May 1992 were analyzed for nitrates and nitrites. Nitrates weredetected in all six wells with concentrations ranging from 0.36 to 2.72 ppm. Noneexceeded ATSDR comparison values (1).
Groundwater sampling from off-site monitoring wells was performed duringJanuary, February and March 1992 (11). January 1992 sampling of two wells forVOCs detected 1,1,1-trichloroethane (1,1,1-TCA) at 0.5 parts per billion (ppb) inone of the samples. This was the first detection of 1,1,1-TCA in any monitoringwell; however, a monitoring well sampled during February 1992 indicated 1,1,1-TCA at 0.72 ppb.
In February 1992, a groundwater sampling program collected samples at 11 off-sitemonitoring wells (11). Samples showed PCE in 10 wells, TCE in 2 wells, and DCEin 2 wells. Levels were above ATSDR comparison values for all threecontaminants. See Table 9 for summary results.
In March 1992, samples were collected from three off-site monitoring wells andanalyzed for VOCs. None of the target analytes and no other compounds weredetected (11).
A groundwater sample collected in May 1992 from Monitoring Well 92-2 on theeast side of the Yellowstone River indicated PCE at 15 ppb and TCE at 1.5 ppb. Evidence does not indicate whether underflow beneath the river or VOC sourceseast of the river were responsible for the presence of the PCE and TCE.
Twenty two off-site monitoring wells and one municipal well (Well B) were sampledduring the third and fourth quarters of 1994 and first and second quarters of 1995. A total of 106 samples were analyzed for PCE, TCE, cis-DCE, and chlorobenzene. Thirteen of the 22 off-site monitoring wells (including one well east of theYellowstone River) contained PCE above ATSDR comparison values, though atmuch lower concentrations than in the previous six years. TCE was found aboveATSDR comparison values in 4 of 22 wells; however, neither of the wells east ofthe river indicated TCE contamination. Cis-DCE and chlorobenzene were not foundin any of the well samples.
The 1997 Annual Ground Water Sampling Report for the BNRY site stated that 43samples from 28 monitoring and private wells were collected by Envirocon in May1997. The report summarized data from bi-annual sampling events betweenAugust 1995 to May 1997. The referenced concentrations are all below historicalmaximums.
The municipal water supply system was installed in the 1960s and 1970s. In1988, six wells served the system, including the B Street, D Street, L Street, QStreet, Clarence, and Werner wells. In April 1988, DHES sampling revealed thepresence of PCE in the L Street, Q Street, and Werner wells, at concentrations of0.45, 0.86, and 0.01 parts per billion (ppb), respectively. The PCE concentrationsare below the drinking water standard for PCE (5 ppb). The PCE concentrationmeasured in the Q Street well (0.86 ppb) did exceed ATSDR's cancer riskevaluation guide (CREG) screening value of 0.7 ppb.
As a precaution, however, the City of Livingston took the L and Q street wells outof service. These wells were replaced with two new wells (Clinic and BillmanCreek), located more than 3,000 feet south of BNRY and upgradient of the plume(i.e., in the opposite direction from which the contamination is moving).
Envirocon conducted additional sampling of the municipal wells (excluding Clinicand Billman Creek wells, but including the out of service wells) between May 1989and May 1992 (16). PCE was consistently detected in only the Q Street well, atlevels ranging from 0.50 to 0.95 ppb. No volatile organic compounds (VOCs) weredetected in the B Street, D Street, L Street, Clarence, or Werner municipal wells.
Dissolved metals analyses of groundwater samples obtained in February 1990revealed arsenic, cadmium, and lead in municipal well water at concentrations of0.009, 0.001, and 0.01 ppm, respectively (16). However, the arsenic wasdetected in the L Street Well, which was not in service. Cadmium detected in theB Street Well was below the ATSDR chronic environmental media evaluation guide(EMEG) of 0.007 ppm. The B Street Well continues to be sampled on a semi-annual basis. Lead did not exceed EPA's action level.
Water samples were collected on September 20, 1989, from five points along themunicipal water distribution system and from the one-million gallon storage tank onthe town's west end (1). No detectable concentrations of chlorinated ethenes werereported in any samples (1).
Additional municipal well sampling for PCE, TCE, and DCE August 27-30, 1990 didnot detect any of these contaminants.
Dissolved petroleum hydrocarbons are present in the Livingston aquifer. Groundwater samples were collected from the B, D, L, and Q street wells and fromthe Clarence and Werner wells between August 1989 and May 1991. Results ofthe analyses for TPHs were all below detection limits (less than 0.1 ppm) exceptfor one sample in November 1989 detected at 0.1 ppm (1).
The D Street, Clarence, and Werner Wells are being sampled every three years. Quarterly sampling of the B Street well was performed from August 1994 throughMay 1995. Samples collected were analyzed for PCE, TCE, cis-DCE, andchlorobenzene. No detectable concentrations of these contaminants were reportedin any of these samples. Currently, semi-annual groundwater sampling events ofthe B street well are part of the ongoing site investigation because of it's proximityto the site (approximately 3 blocks upgradient). Sampling results included in the1997 Annual Ground Water Sampling Report (Envirocon, August 1997) show thatno VOCs were detected in the B Street Well during sampling events in November1996 and May 1997.
Fourteen private water wells were randomly sampled for VOCs during July andAugust 1989. None of the wells north of BNRY contained detectableconcentrations of VOCs. People are continuing to use these wells for drinkingwater. VOC contaminants were identified in six of the wells located south ofBNRY. Of the contaminants detected, PCE, TCE, and cis-1,2-DCE exceededATSDR comparison values. None of the private water wells containing these VOCsare currently used for drinking water. Before the 1989 sampling, four of the sixwells furnished water for either drinking or domestic use (1). After the 1989sampling, well owners were notified of possible contamination and provided withmunicipal water. See Table 11 for the results.
In February 1990, arsenic was detected at a level that exceeded ATSDRcomparison values in a private well located south of BNRY near the Yellowstoneriver. This well is currently used for drinking water and domestic purposes. Overall, dissolved metals have not shown correlation with other groundwatercontaminants and occur at concentrations consistent with naturally occurring metalconcentrations in the Yellowstone River (16). Specifically, arsenic is considered tobe a naturally occurring metal in the river (1). Additionally, the generalgroundwater flow is either east or north; this well is south of BNRY near the river. These circumstances suggest that the arsenic detected in this well originates fromnatural sources and not from BNRY. See Table 11 for the level detected.
Three private wells were sampled August 27-30, 1990 for VOCs and two otherprivate wells were sampled for dissolved metals. At the time of sampling, none ofthe wells were used for drinking water. PCE, TCE, and DCE were found in two ofthree wells above ATSDR comparison values. The wells with these contaminantsare southeast of BNRY but are in close proximity to BNRY. Metals were all belowdetectable limits. Table 11 presents the results.
Off-site surficial soil investigation
Envirocon conducted a surficial soil investigation at BNRY during April and May1992 (12). Five off-site background surface soil samples were collected. For thisinvestigation, surficial soil was defined as any unconsolidated material extendingfrom the ground surface to a depth of two inches. Envirocon removed layers ofballast, wood chips, or thick vegetation that covered some of the designatedsampling locations and sampled the exposed soil at the designated 0 to 2 inchdepth. Samples were analyzed for VOCs, pesticides and PCBs, metals and PAHs. All of the contaminants detected were below the comparison values provided inTable 14. See Table 14 for the levels detected.
Off-site soil gas
Remediation Technologies, Inc. (ReTec) performed a soil gas survey at and in the vicinity of the BNRY facility during August 1988 in an effort to correlate migrationof off-site soil gas with that of on-site gas. ReTec collected 168 soil gas samples. The survey detected PCE, TCE, DCE, TCA, benzene, toluene, xylene, andethylbenzene in varying concentrations in the collected soil gas samples. The VOCconcentrations were largest above the source areas. Contour plotsb of the detectedVOCs reveal that PCE and, to a lesser degree, TCE have apparently migrated off-site at BNRY (9). The migration patterns are much less apparent for the otherdetected compounds. In several of the soil gas plots, there are contours that revealoff-site areas of soil gas contamination appearing to be disconnected from the on-site areas. These off-site soil gas contamination areas may or may not be relatedto the BNRY site. Based on the August 1988 soil gas sampling results, it appears,in general, that it is possible to generate qualitative approximations of soil gascontamination based on detected groundwater contaminants.
The contaminant levels in off-site soil gas appear to correlate poorly with the levelsof indoor air contaminants detected in residences located in the general area of soilgas contamination. For example, PCE is thought to be the soil gas contaminantthat has most noticeably migrated from the BNRY site (9); however, air samplesobtained at houses located in the general area of soil gas contamination (east andwest of the site) did not reveal the presence of PCE. However, it must be notedthat some of the detection limits of the 1989 and 1990 indoor air sampling roundswere higher than the detection limits used in the soil gas samples.
Indoor residential air
The Montana Department of Health and Environmental Sciences (MDHES)performed indoor air monitoring for four residences during August and October1989. MDHES also sampled the indoor air of two of the previous four residencesplus an additional four residences in November 1989 (1,15,16). The August 1989analyses by MDHES revealed the presence of 1,1,1-TCA in each house sampled. InOctober 1989, 1,1,1-TCA was detected in two houses at levels thousands of timeslower than the August 1989 detection levels. There was no detection in theremaining two residences. In November 1989, with detection limits lower than inthe August monitoring period but higher than in October, 1,1,1-TCA was notdetected in any of the six houses sampled. Detection limits for the Novembersampling ranged from 200 to 450 ug/m3.
TCE was not detected in the MDHES analyses for August, October, and November1989. Analyses of TCE were not requested in two residences during the August1989 sampling rounds. However in October 1989, the two residences wereanalyzed and TCE remained below detection limits. PCE was not detected in any ofthe MDHES analyses (1,15). Trans-1,2-DCE was detected in the October 1989sampling round but was not detected in any other sample. Toluene was detectedin two residences during the August 1989 sampling round. The same tworesidences showed no toluene in the October 1989 sampling. See Table 12,Appendix B, for the levels detected.
Envirocon performed air sampling of two residential basements during November1990 (1). These analyses revealed the presence of ethylbenzene, xylene, and TCE. Only TCE exceeded ATSDR comparison values. All of the analyses for PCE,benzene, 1,2-DCE, and toluene remained below detection limits (1). Detectionlimits during the November 1990 indoor air sampling round ranged from 50 to 90ug/m3. See Table 12, Appendix B, for the levels detected.
Envirocon performed additional sampling of indoor air in February 1992, in thebasements and upstairs of 17 residences. The 17 homes were distributed overthree study areas. Samples were analyzed for PCE, TCE, cis-1,2-DCE, and trans-1,2-DCE. PCE and TCE were the only contaminants detected, and both exceededATSDR comparison values. PCE was detected both upstairs and in the basementsin all residences. TCE was found upstairs and in the basements in 13 of thehomes. Detections of both contaminants were greater in the upstairs of homes than in the basements. One outdoor ambient air sample was also collected from each study area.
A follow-up investigation was performed in March 1992 at selected residences. Analyses were performed for vinyl chloride as well as for the previous targetcompounds (4). During these sampling rounds, PCE and TCE were detected. Thecis-1,2-DCE isomer was detected in four residences, the trans-1,2-DCE isomer wasdetected in two residences, and vinyl chloride was detected in two residences. Theresidences containing the vinyl chloride detection overlie an uneven part of thegroundwater plume and are across the street from a petroleum storage facility. Those circumstances suggest that vinyl chloride does not originate from BNRY. Table 12, Appendix B, summarizes results for these sampling rounds.
Envirocon collected 68 indoor air samples, including 6 duplicates, at 36 houses and1 school during January and February 1993 to evaluate the possible contribution ofPCE migrating from the BNRY in groundwater or soil gas (6,16). Nine of the 36residences sampled had detectable levels of PCE in the air and concentrations wereabove ATSDR comparison values. Review and determinations made throughsampling log books indicated that the PCE originated from sources unrelated toBNRY. Table 12, Appendix B, summarizes results for these sampling rounds.
Off-site ambient air
Envirocon collected four off-site ambient air samples on January 27, 1993 (6). Three of the four sampling stations were located upwind of the site. PCE wasdetected at two of the upwind stations, with both concentrations exceedingATSDR comparison values. PCE was also detected at the downwind samplinglocation, but at a concentration less than ATSDR comparison values. The datasuggest that the BNRY facility contributions of PCE to the ambient air during theperiod sampled may have been smaller than the contributions of sources in theLivingston business district. See Table 6, Appendix B, for results of the sampling.
Envirocon took two off-site ambient (outdoor) air samples during February 1992. The samples were analyzed for PCE, TCE, cis-1,2-DCE, and trans-1,2-DCE (4). Analyses of these off-site ambient samples revealed the presence of PCE, althoughno comparison values were exceeded. TCE, cis-1,2-DCE, and trans-1,2-DCEremained below their corresponding detection limits, which ranged from 0.17 to0.18 ug/m3. See Table 6, Appendix B, for the results from the sampling described above.
Yellowstone River water samples
One Yellowstone River water sample was collected on September 20, 1989 from apoint 50 feet upstream from the 9th Street Bridge. This sample was analyzed forVOCs, TPHs, and dissolved metals. Only TPH, at 0.1 ppm, was detected in thissample.
On March 23, 1990, during a period of low water flow, six Yellowstone Riverwater samples were collected at five locations upstream and downstream of theBNRY. These samples were analyzed for VOCs, SVOCs, PCBs/pesticides, TPHs,and total metals. No SVOCs or PCBs/pesticides were detected in any of theseYellowstone River water samples. One sample taken immediately downstream ofthe Livingston treatment works plant revealed PCE, 2-chlorotoluene, and TPH. Arsenic was detected in all of the samples, and cadmium was detected in onesample (1). Of the contaminants detected, none exceeded the comparison valuesprovided in Table 15. Arsenic is thought to be naturally occurring and probablyoriginates from warm springs that enter the river in Yellowstone Park. See Table 15, Appendix B, for the levels detected.
Yellowstone stream sediment and river gravel analyses
Oily waste material was released during January 1990 from the wastewatertreatment plant (WWTP) discharge line into the gravel river bed lining within theYellowstone River. Remedial activities included removal of the oily material fromthe in-line sumps and removal of a portion of the drainline (1).
Stream sediment and gravel were sampled from the Yellowstone River on March 7and March 21, 1990 at 0.0 and 0.2 ft. depths (See Figure 4 in Appendix A forRiver sediment sampling locations). Gravel was sampled at the outfall of theabandoned WWTP discharge line, and sediment samples were collected from thebanks of the Yellowstone River, Sacajawea slough outfall. Sample locationsincluded areas downstream from the WWTP's discharge line and one locationupstream (1). All of the contaminants detected were below the comparison valuesprovided in Table 10. See Table 10 for the results.
Fish tissue samples from the Yellowstone River
Sixteen fish were collected from the Yellowstone River on October 4, 1988. Liverand muscle tissue samples from these fish were submitted to the Montana StateUniversity for VOC and SVOC analyses. Results revealed all of the targetcompounds remained below detection limits. The detection limits were 15 ppm formost of the VOCs and 1 ppm for the SVOCs of interest (13).
Bird tissue samples
Samples of bird tissue were submitted to the Montana State University for VOCand SVOC analyses. Results revealed that all of the target compounds remainedbelow detection limits. The detection limits were 15 ppm for most of the VOCsand 1 ppm for the SVOCs of interest (14).
ATSDR staff relied on the information provided in the referenced documents toprepare this public health assessment. The Agency assumes that adequate qualityassurance and quality control measures were followed with regard tochain-of-custody, laboratory procedures, and data reporting. The validity of theanalyses and conclusions drawn for this public health assessment depends upon the reliability of the referenced information.
The entire BNRY property is unfenced. Most hazards at the site are related tonormal train yard activities. Train movements within and through the yard occur ona daily basis. A large pile was observed by ATSDR on an earlier site visit. According to DEQ, the cinder pile still remains at the site and is accessible. Basedon sampling of the contents of this pile, asbestos was identified. Access to this material will be addressed in the final site plan.
To determine whether nearby residents are exposed to contaminants migrating fromthe site, ATSDR evaluates the environmental and human components that lead tohuman exposure. The pathways analysis consists of five elements: a source ofcontamination, transport through an environmental medium, a point of exposure, aroute of human exposure, and an exposed population.
ATSDR categorizes an exposure pathway as a completed, potential, or eliminatedexposure pathway. Completed pathways require that the five elements exist andindicate that exposure to the contaminant has occurred, is occurring, or may occur. Potential pathways are those in which one of the five elements is missing, butcould exist. Potential pathways indicate that exposure to a contaminant could haveoccurred, could be occurring, or could occur in the future. In an eliminatedexposure pathway, at least one of the five elements is missing and will never bepresent. The discussion that follows describes only those pathways that arerelevant to the site. It also includes information on eliminated exposure pathways. Table 2 presents the completed and potential pathways, and their elements.
Groundwater monitoring data indicate that chlorinated solvents (VOCs), metals, andtotal petroleum hydrocarbons have been identified in the groundwater. Contaminants of concern include trichloroethylene (TCE) and tetrachloroethene(PCE). This contamination originates from spillage of diesel fuel during refuelingoperations that began in 1947 at BNRY. The volume of diesel fuel on the watertable was estimated at 300,000 gallons in 1989. Currently, the volume of dieselfloating on the water table is estimated to be 150,000 gallons. Maintenance andcleansing operations also contributed heavily to the contamination. Chlorinatedsolvents have been identified from wastewater treatment sumps, oil and waterseparator ponds, and overflow ponds.
Monitoring data indicate that contamination from BNRY has probably migrated off-site. Contaminants can migrate through the groundwater, which flows either eastor north toward the Yellowstone River depending on the water table level and theseason. Contaminants may also flow beneath the river, although it is inconclusiveas to whether VOC detections east of the river originate from BNRY at this time. This groundwater is a source of drinking water.
A past completed exposure pathway was identified for municipal wells which theresidents of Livingston utilized for drinking water and other domestic purposes. The two municipal wells with PCE contamination have since been taken off line andreplaced with two municipal wells located south of BNRY. Past exposures occurredamong residents of Livingston who drank water obtained from the municipal wellswhere PCE was detected. Of the municipal wells currently in use, five are sampledevery three years while one well (B Street) is monitored semi-annually.
A past completed exposure pathway to VOCs was identified for private wells usedby residents for drinking water. Past exposures occurred among residents ofLivingston who drank from the private wells in which contamination was confirmed. None of the wells where VOC contamination was detected currently providedrinking water. Owners of private wells south and east of BNRY were notified ofpotential VOC contamination. Well owners who received such notification nowuse the wells for irrigation and other domestic purposes but not for drinking water.
A past, current, and future exposure pathway exists for residents who use theprivate well where arsenic was detected. This well is located south of BNRY nearthe Yellowstone river and is currently used for drinking water and other domesticpurposes. To date, dissolved metals have not shown correlation with othergroundwater contaminants. The general groundwater flow in the area is either eastor north; this well is south of BNRY near the river. Additionally, the Yellowstoneriver contains arsenic that is thought to be naturally occurring. Thesecircumstances suggest that the arsenic detected in this well originates from naturalsources and not from BNRY.
Exposure routes other than drinking water would include dermal absorption andingestion of foods that have been irrigated or washed with contaminatedgroundwater. Exposed populations would include residents of Livingston who gettheir drinking water from this groundwater source.
Off-site ambient air
The source of contamination to the residents of Livingston could be from twoorigins, BNRY and the Livingston business district. The sampling data availablesuggest that the business district of Livingston may be a contributor to the airquality of BNRY. However, a completed past, present and future exposurepathway exists from contamination of the air in the vicinity of BNRY.
Contaminants released to the ambient air are dispersed by the winds. Anycontaminants emitting from BNRY and the city of Livingston will mix and dispersethroughout the area. Off-site sample data indicated the presence of PCE at a higherconcentration upwind of BNRY than what was recorded downwind of BNRY. Datacollected from off-site ambient air sampling indicated past exposures to personswho live, work, and play in the areas where sampling occurred. Because BNRYcontinues to operate as a rail yard with refueling by means of a tanker truck andrailcar maintenance operations, present and future completed pathways also existfor residents who live within the vicinity of BNRY.
Exposed populations would include residents within the areas where prevailing winds mix the air from BNRY and surrounding area.
Indoor residential air
A past, present, and future completed exposure pathway was identified forresidential homes. Various indoor air contaminants, most noticeably PCE; TCE;1,1,1-trichloroethane (TCA); vinyl chloride; and toluene, were detected duringsampling of residences in the city of Livingston. Persons who resided or worked inthese homes experienced past exposures from these contaminants. It is notcertain, however, that the contaminants detected in indoor residential air areassociated with emissions from BNRY. The possibility exists that some of thecontaminants detected may have sources originating inside the residences.
Contamination may occur as a result of chemicals inside the home and/or emissionsfrom BNRY. Air currents and wind dispersion may bring contaminantconcentrations into any given area, including residences. Residential buildingsthemselves would help keep chemical vapors from any chemicals stored in thehome in a defined area. Sample data suggest that present and future exposures toindoor contaminants are likely to occur when residents of these homes breathe theindoor air directly. Exposed populations include adults and children who reside inthese homes.
On-site ambient air
Various ambient air contaminants, most noticeably PCE, arsenic, and cadmium,were detected during on-site ambient air sampling at the BNRY. Some of thecontaminants may have been introduced into the breathing zone by activities whichdisturbed the soil. Other contaminants may have resulted from outside emissionsunaffiliated with BNRY. Regardless of the sources, measurements of the air flowthrough BNRY indicate that workers and on-site personnel have been exposed toon-site contamination in the past. Contaminants emitting from on-site operations,cleaning operations, and maintenance, could result in present and future exposureto on-site contamination.
Points of exposure would include workers and others who entered the area of theBNRY or visitors who had direct contact with windblown dust or with contaminantsthat volatilized from disturbances of the soil.
Routes of exposure include inhalation of ambient air in the surrounding areas ofBNRY. Exposure may occur through inhalation of contaminants in airborne dustfrom contaminated soil or in emission of contaminants from the facility itself. Workers and visitors to BNRY are the receptor populations.
A future potential pathway exists for persons north of BNRY who currently useprivate wells for drinking water. Residents who are currently consuming waterfrom private wells north of BNRY could experience exposure if the groundwaterplume area expands. Currently there are monitoring wells located just northeast ofBNRY. Quarterly monitoring of these wells indicate contaminant levels that do notpresent a threat to human health. Private wells will be sampled should anymonitoring wells in the north area reveal contamination levels that may be of health concern.
Yellowstone River fish
Fishermen use the Yellowstone River extensively. It is therefore very likely thatpeople have consumed fish caught in the Yellowstone River. Sampling data fromfish tissue, however, revealed that VOCs and SVOCs were below laboratorydetection limits. The detection limits were 15 ppm and 1 ppm, respectively. However, the detection limits for this particular sampling exercise were well aboveATSDR comparison values. This would indicate that a past, current, and future exposure pathway may exist from the ingestion of fish. Potential exposures for individuals periodically consuming such fish are not expected to be of health concern.
On-site soil gas
Twenty-four soil gas samples were collected during soil investigation activitiesalong on-site drainlines that run from the BNRY shop complex to the WastewaterTreatment Plan (WWTP). It is reasonable to assume that a given gaseouscontaminant released from the soil into the air would be diluted to a lowerconcentration in the air space above the soil. Samples taken between January 21,1990, and March 4, 1990, revealed airborne substances at stations where sludgewas being pumped or monitoring wells were being installed. The levels detectedwere orders of magnitude higher than the levels detected during the ambient airsampling program. This finding suggests that the mentioned site activities mayhave contributed to the release of the detected substances from the soil to thesurrounding air. The data thus appear to represent a transient or temporarysituation.
The contaminants detected could have resulted in a past exposure pathway forworkers to on-site soil gas. However, sampling data indicate that contaminationmay be temporary. No basement sampling of the buildings on-site was performed.A present or future exposure pathway could result if soil gas contaminants arefound to be stationary as a result of on-site activities. Soil vapor extraction wellswere included as a part of a MDHES interim remediation plan. The well system has minimized and/or eliminated the soil gas contaminant pathway for workers at BNRY.
Off-site soil gas
Soil gas surveys in 1988 revealed that various VOCs have apparently migrated off-site. PCE and TCE, which slightly exceeded ATSDR comparison values, are mostprominent among those VOCs. Contour plots performed during the survey suggestthat migration patterns are strongest in areas where groundwater contamination isknown to exist. However, the contour plots fail to show that off-site soil gasoriginated at BNRY. Data from samples also fail to show a connection between off-site soil gas and on-site gas, indicating off-site gas in these particular homes maybe of other origins.
Residents and workers of homes in the sampled area could have experienced past exposures from elevated levels of VOCs. Present and future exposures for residents and workers could exist because of such soil-disturbing activities as drilling, building, or excavation of basements. Additional sampling during these soil-disturbing activities is advised.
On-site groundwater was not used for human consumption in the past. The finalclean up remedy will insure on-site groundwater is not used for human consumptionin the future. Exposure to this medium is not likely, and this pathway is eliminated.
On-site subsurface soil
Subsurface soil pits varied in depth from 1 to 15 feet. Exposure to contaminatedsoils found at depths of 1 to 15 feet is highly unlikely; therefore, ATSDR concludesthis is an incomplete exposure pathway.
Yellowstone River sediment
It is unlikely that recreational users may have ingested sediments in quantities ofconcern from the Yellowstone River. ATSDR has thus eliminated this exposurepathway.
Montana State University staff analyzed bird tissue for volatile organic compounds(VOCs) and semivolatile organic compounds (SVOCs). All of the target compoundsremained below detection limits. The species of bird analyzed, the circumstancesunder which bird samples were obtained, and the relationship the bird may havehad to the site under evaluation are not known. The bird species is not thought tobe part of the human food chain; therefore, ATSDR has classified bird tissue as aneliminated pathway.
Yellowstone River water
Recreational users of the Yellowstone River would be unlikely to ingest water inquantities large enough to be of health concern. Sampling data indicated smallamounts of contaminants upstream of BNRY, thus suggesting these contaminantsare of other origin or naturally occurring. ATSDR has thus eliminated this exposure pathway.
On-site surficial soil
Sampling data indicate levels of contaminants that are not thought likely to produceillness. It is unlikely that workers would have direct contact with on-site soil inquantities large enough to produce illness. ATSDR has thus eliminated thisexposure pathway.
Off-site surficial soil
Low concentrations of VOCs, SVOCs, and metals were detected in off-site soils atlevels that were not thought sufficient to cause illness. ATSDR has thus eliminatedthis exposure pathway.
|Pathway name||Pathway elements||Time|
|Source||Media||Point of exposure||Route of exposure||Exposed |
|Off-site groundwater||BNRY||MUNICIPAL WELL WATER||RESIDENTIAL WATER USE||INGESTION, INHALATION, DERMAL||MUNICIPAL WELL WATER CONSUMERS||PAST|
|Off-site groundwater||BNRY/ NATURALLY OCCURRING (METALS)||PRIVATE WELL WATER||RESIDENTIAL WATER USE||INGESTION, INHALATION, DERMAL||PRIVATE WELL WATER CONSUMERS||PAST |
|Off-site ambient air||BNRY/ LIVINGSTON BUSINESS DISTRICT||AIR||RESIDENTIAL AREAS||INHALATION||RESIDENTS OF LIVINGSTON||PAST |
|Indoor air||BNRY/ RESIDENCES||AIR||RESIDENCES (INDOOR)||INHALATION||RESIDENTS OF LIVINGSTON||PAST |
|On-site ambient air||BNRY||AIR||ON-SITE||INHALATION||WORKERS AND CLIENTS||PAST |
|Off-site ground- water||BNRY||PRIVATE WELL WATER||RESIDENTIAL USE||INGESTION||RESIDENTS||FUTURE|
|Yellowstone River fish||BNRY||BIOTA||FISH CONSUMPTION||INGESTION||FISH CONSUMERS||PAST |
|Off-site soil gas||BNRY||AIR||OFF-SITE||INHALATION||RESIDENTS, |
|On-site soil gas||BNRY||AIR||ON-SITE||INHALATION||WORKERS||PAST |
This section contains discussions of health effects that could plausibly result fromexposures to site contaminants. While the relative toxicity of a chemical isimportant, the response of the human body to a chemical exposure is determinedby several additional factors, including the concentration (how much), the durationof exposure (how long), and the route of exposure (breathing, eating, drinking, orskin contact). Lifestyle factors (e.g., occupation and personal habits) have a majorimpact on the likelihood, magnitude, and duration of exposure. Individualcharacteristics such as age, sex, nutritional status, overall health, and geneticconstitution affect how a contaminant is absorbed, distributed, metabolized, andeliminated from the body. A unique combination of all these factors will determinethe individual's physiological response to chemical contaminants and any adversehealth effects the individual may suffer as a result of the chemical exposure.
ATSDR has determined levels of chemicals that can reasonably (and conservatively)be regarded as harmless, based on the scientific data the agency has collected in itsToxicological Profiles. The resulting comparison values and health guidelines(which include ample safety factors to ensure protection of sensitive populations)are used for screening contaminant concentrations at a site, and to selectsubstances that warrant closer scrutiny by agency health assessors andtoxicologists. (See Appendix C for a more complete description of ATSDR'scomparison values, health guidelines, and other values ATSDR uses to screen sitecontaminants.)
ATSDR's comparison values and health guidelines do not represent thresholds oftoxicity. They are screening values used to facilitate the initial selection of site-specific chemical substances (known as "contaminants of concern") for furtherevaluation of potential health effects. After the contaminants of concern at a sitehave been identified, they must be individually scrutinized in more detail (includingconsideration of all the various factors mentioned in the first paragraph of thissection) to determine whether or not, under site-specific conditions, they representa realistic threat to human health. Although concentrations at or below ATSDR'scomparison values may reasonably be considered safe, it does not automaticallyfollow that any concentration above a comparison value will necessarily producetoxic effects. Comparison values are intentionally designed to be lower, oftenorders of magnitude lower, than the corresponding no-effect levels determined inlaboratory experiments.
Solely for the purpose of screening individual contaminants, ATSDR typicallycompares the lowest comparison value available (i.e., CREGs or other chronicexposure values) for the most sensitive, potentially exposed individuals (usuallychildren or pica children) to the highest single concentration of a contaminantdetected. This high degree of conservatism results in the selection of manycontaminants as "chemicals of concern" that will not, upon closer scrutiny, bejudged to pose any hazard to human health. However, ATSDR judges it prudent touse a screen that "lets through" many harmless contaminants rather than one thatoverlooks even a single potential hazard to public health. Even those contaminantsof concern that are ultimately labeled in the toxicological evaluation as potentialpublic health hazards are so identified solely on the basis of the maximumconcentration detected. The reader should keep in mind the protectiveness of thisapproach when considering the potential health implications of ATSDR'stoxicological evaluations.
In this section, only those contaminants that have been detected at concentrationsexceeding the relevant comparison values will be discussed in any detail. Note thatall contaminants at BNRY were initially screened by comparing their maximumdetected concentrations to the lowest available comparison values, as describedabove. However, the data tables in the Appendix generally list only the morerelevant, site-specific comparison values, where available, in order to provide amore useful perspective.
Since a contaminant must first enter the body before it can produce any effect,adverse or otherwise, on the body, this evaluation will further focus on thosecontaminants associated with completed pathways of exposure. Soil-gas, forexample, is not discussed in this toxicological evaluation because soil-gasmeasurements are not representative of levels in the breathing zone (i.e., do notreflect a completed exposure pathway) and are therefore not directly relevant tohuman exposure. The only completed pathways at BNRY were on- and off-site air,indoor air, and off-site groundwater. (See Parts B and C of the Pathways Analysissection for discussions of potential and eliminated pathways.)
PCE, TCE, arsenic, and cadmium were detected in completed pathways atconcentrations that exceeded relevant comparison values. Each of these 4contaminants is discussed separately below. Toluene, lead, cis-1,2-DCE, and1,1,1-TCA were detected less frequently and/or at generally lower levels when theywere detected, but their maximum concentrations did exceed some of ATSDR'scomparison values. These four contaminants are discussed together under the last subsection entitled "Other Contaminants".
PCE (perchloroethylene, tetrachloroethylene, or tetrachloroethene) was detected atelevated levels in off-site groundwater, and indoor air. However, ATSDR considersthat current levels of exposure are unlikely to produce any adverse health effects.
PCE is a chlorinated hydrocarbon used primarily as a dry-cleaning solvent, a vapor-degreasing solvent, and a drying agent for metals; it is also used in the manufactureof fluorocarbons (17). Not known to occur naturally, PCE enters the environmentfrom sources such as vaporization losses from dry cleaning and metal degreasingindustries, and leachate from vinyl liners in asbestos-cement water pipelines usedfor water distribution. The general population can be exposed to PCE throughinhalation of contaminated ambient air and ingestion of contaminated drinkingwater, especially from polluted groundwater sources. Most absorbed PCE is slowlyeliminated unchanged (half-life = 65 hours) in the breath.
PCE is slightly to moderately toxic in laboratory animals (17). In humans, ingestionof small amounts of PCE is unlikely to cause permanent injury. In fact, PCE wasformerly used as a remedy for intestinal worms, until that use was discontinuedbecause of inebriating side effects. The known human health effects of PCE haveusually been the result of occupational exposure to high concentrations, primarilyby inhalation. The threshold limit value (TLV) for PCE in air is 25 ppm or 170ug/m3. In excess of 100 parts per million (ppm), PCE is irritating to mucousmembranes and the respiratory tract and may produce largely reversible effects inthe liver. At 200 to 500 ppm, PCE causes symptoms of central nervous systemdepression, e.g., dizziness, headache, vertigo, inebriation and unconsciousness. However, in men or women repeatedly exposed to 100 ppm for 7 hours per day, noadverse neurological effects were identified by a battery of behavioral andneurological tests. PCE has been declared a probable/ possible (B2-C) humancarcinogen by the Environmental Protection Agency (EPA), based on sufficientevidence in animals and inadequate evidence in humans. However, the relevance ofthe animal data to humans is now being questioned because the induction ofcancers in rodents required such high doses and involved elements of rodentbiology not shared by humans. Therefore, ATSDR considers that cancer effects arenot the most appropriate basis for an assessment of this chemical's potentialimpact on public health at Livingston. (See Appendix D for a discussion of the carcinogenicity of PCE.)
Because the city regularly monitors the public water supply, municipal well water isnot now, nor is it likely to become, a significant source of PCE exposure for thegeneral public. Although the maximum level of PCE in private well water (96 ppbor 0.096 ppm) was significantly higher than the maximum contaminant level (MCL)of 5 ppb, it was still much too low to produce any noncancerous adverse healtheffects in persons using this water as their sole source of drinking water. Themaximum level of PCE detected in off-site groundwater (530 ppb) was measured inMonitor Well 89-4 near the northeast edge of the facility, in May 1990. PCE in thiswater, which is not used for drinking, only marginally exceeded EPA's drinkingwater equivalent level (DWEL). The DWEL is a lifetime exposure level specific fordrinking water (assuming that all exposure is from that medium) at whichnoncarcinogenic adverse health effects would not be expected to occur (34). TheDWEL for PCE is 500 micrograms per liter (µg/L) and includes an uncertainty factorof 1,000, i.e., the DWEL was set at a level 1,000 times lower than the No AdverseEffect Level (NOAEL) observed in animal studies.
The levels of PCE in off-site ambient air were too low to be a health concern. MorePCE was detected upwind than downwind of the site, which suggests theexistence of sources for the PCE in the air other than BNRY.
The highest concentration detected in indoor air at Livingston (82.1 micrograms percubic meter (µg/m3) or 12 ppb in a basement) marginally exceeded ATSDR'sintermediate environmental media evaluation guide (EMEG) of 9 ppb, which is alevel to which one could be exposed for 2 weeks to a year without deleteriouseffects. However, real exposures (in this case, in a basement) are likely to beintermittent and of much shorter duration. For comparison, 12 ppb is at least2,000 times lower than the American Conference of Governmental IndustrialHygienists (ACGIH's) threshold limit value of 25 ppm PCE, a level considered safeto work in for 8 hours per day, 40 hours per week. Since the first draft of thisassessment was written, the intermediate EMEG for PCE has been replaced with achronic EMEG of 40 ppb or 270 ug/m3, which is not exceeded by anyconcentration of PCE measured in off-site air.
Inhalation exposure may also occur during bathing. However, based on a worst-case scenario (assuming 500 µg PCE/L domestic water), ATSDR has estimated thatpeak transitory levels of volatilized PCE that might occur while bathing orshowering in PCE-contaminated water would be too low to produce any acutehealth effects such as drowsiness. Neither would intermittent exposure to suchlow levels for relatively short periods of time be expected to have any adversechronic effects.
The levels found in fish were all below the detection limits of the assay methodsused. That means that we do not really know how much, if any, of thesecompounds was present. The detection limit that applied to most VOCs was 15ppm. This detection limit is much higher than EPA Region III's Risk-BasedConcentration (RBC) of 0.061 ppm PCE in fish. However, the latter limit is basedon 2 assumptions that may not apply at BNRY and the surrounding communities. The first is the assumption that PCE may cause cancer in humans. A number ofepidemiological studies of occupationally exposed men and women have notidentified an increased risk of cancer attributable to PCE, and the cancers inducedin laboratory animals at very high doses of PCE by species-specific mechanismshave little or no relevance for human risk evaluation at environmental levels ofexposure many orders of magnitude lower. Secondly, the RBC is based on theassumption of a default fish ingestion rate of 54 grams or about 2 ounces/day. When one considers that local patterns of consumption of fish from theYellowstone River are likely to be intermittent in nature, and that the concentrationsof any solvents in the fish would be greatly reduced during cooking, it is highlyunlikely that the undetectable levels of PCE that may exist in fish would represent apotential health hazard to individuals periodically consuming such fish.
Arsenic was present in some air and water samples at levels that exceededATSDR's lowest comparison value for this metal. However, ATSDR considers thatcurrent levels of exposure are unlikely to produce any adverse health effects.
Arsenic, which may be either trivalent or pentavalent, is a metalloid element that iswidely distributed in the earth's crust, with an abundance of about 5 microgramsper gram (µg/g or ppm) (18). The manufacture of arsenical pesticides representsthe major source of occupational exposure, mainly through the inhalation of fumesand dusts. Arsenic compounds are also used in some pharmaceutical preparations. The threshold limit value/time-weighted average (TLV-TWA) for arsenic and itssoluble compounds in the workplace is 0.01 milligrams per cubic meter (mg/m3). Cigarette smokers incur an additional exposure to arsenic as shown by the fact thatthey have mean blood arsenic levels approximately 50% higher than nonsmokers. The primary route of nonoccupational exposure is by ingestion of food and water;the daily dietary intake of arsenic in the U.S. ranges from <0.04 to 0.2 mg/day,depending on the amount of seafood in the diet. Organic forms of arsenic, whichare less toxic and more rapidly excreted, predominate in fish and seafood. There issome evidence that arsenic acts as an essential nutrient with anticancer value. Nutritional essentiality has been demonstrated in at least three different species(rats, goats, and minipigs), but not yet in humans.
Occupational exposure to airborne arsenic is associated with lung cancer, andchronic exposure to high levels in drinking water has been associated with a uniqueform of skin cancer. In contrast to most human carcinogens, however, arsenicdoes not cause cancer in laboratory animals when administered orally. At lowlevels of exposure, toxic inorganic arsenic compounds are effectively detoxified bymethylation and excreted in the urine. Only after the methylation capacity of theliver is exceeded do blood arsenic levels increase and adverse health effects occur. Saturation of this detoxification mechanism may provide an explanation for theobservation that both the cancerous and noncancerous effects of arsenic exhibit athreshold somewhere between 250 and 500 µg/day (45,46).
Current cancer-based limits on arsenic in drinking water are based on a largeTaiwanese study in which consumption of arsenic-contaminated well water (170 to800 ppb) was associated with increased skin cancer. However, in the U.S., wherelevels of arsenic in drinking water are much lower (average 5 µg/L), no excess skincancer incidence has been observed in people consuming relatively high levels ofarsenic in drinking water (18). It now appears that arsenic exposure wasunderestimated in the Taiwan study, leading to an overestimation of risk. It is alsopossible that the protein- and methionine-deficient population studied in Taiwanwas more sensitive than typical U.S. populations, due to a compromised ability todetoxify (i.e., methylate) ingested arsenic (45,46).
Arsenic was below the MCL of 50 ppb in all water samples analyzed, including on-site (7 ppb) and off-site groundwater (5 ppb), and Yellowstone river water. Inparticular, the maximum level of arsenic in private well water (15 ppb) was wellbelow the MCL. Although the latter concentration does exceed ATSDR's cancerrisk evaluation guide (CREG) and ATSDR's chronic EMEGs/RMEGs, ATSDR'scomparison values are not predictive of adverse health effects (see the discussionon arsenic and cancer in the preceding section). The daily arsenic intake (30 µg/day) from drinking 2 liters of this water every day is an order of magnitudebelow the apparent threshold for the adverse effects (carcinogenic or non-carcinogenic) of arsenic (approx. 400 µg/day). The daily arsenic dose for a 70kilogram per day (kg) adult consuming 2 L/day of water containing 15 ppb arsenicwould be 0.4 µg/kg/day which is within the range of currently recommendedreference dose (RfD) values, i.e., 0.1 to 0.8 µg/kg/day (34). Thus, ATSDRconsiders that no adverse health effects, including cancer, are likely to result fromdrinking water containing arsenic at the levels detected in private wells inLivingston, Montana.
The mean levels of arsenic detected in on-site ambient air, i.e., 0.001 µg/m3upwind and 0.006 µg/m3 downwind (Table 7), exceed ATSDR's CREG of 0.0002µg/m3 by factors of 5 and 30, respectively. However, ATSDR's CREGs are basedon EPA cancer risk assessments which are in turn based on a risk model (i.e., theLinear Multistage Model) that does not take into account the existence ofthresholds for promoters like arsenic. In such cases, linear extrapolation from highoccupational exposures will significantly overestimate risk for the generalpopulation.
The maximum level of arsenic detected in air at BNRY (0.0146 ug/m3) was 75times lower than EPA's risk-based concentration (1.1 µg/m3) for noncancer effects,and the corresponding maximal dose of 0.292 ug/day (assuming inhalation of 20m3 air/day and 100% absorption) would be over 1,000 times lower than apresumed 400 µg/day threshold for cancer effects as well. Thus, based on theavailable data, ATSDR considers that the levels of arsenic in on-site ambient air atBNRY are too low to produce adverse health effects of any kind.
Cadmium was present in some air samples at levels that exceeded ATSDR's lowestcomparison value. However, ATSDR considers that current levels of exposure areunlikely to produce any adverse health effects.
The concentration of cadmium in U.S. topsoil ranges from 0.1 to 1.0 ppm with anaverage value of 0.26 ppm (19). The major use of cadmium is electroplatingmetals to inhibit corrosion. Cadmium and its compounds are also used in pigments,plastic heat stabilizers, fungicides, and nickel-cadmium batteries. The principalroute of occupational exposure is inhalation. The TLV-TWA for cadmium dusts andsalts, as cadmium, in the workplace is 0.01 mg/m3 (TLVs, 1993-1994). Nonoccupational exposure is primarily via ingestion of food and drink and cigarettesmoking. The body burden of cadmium can be twice as high in smokers as innonsmokers. Typical concentrations in ambient air are 0.001 to 0.005 µg/m3 inrural areas and up to 0.05 or 0.06 µg/m3 in urban areas. Absorption of cadmium is15-30% from the respiratory tract, but only 5 to 8% from the gastrointestinal tract.
Chronic occupational exposure to cadmium can lead to renal dysfunction with proteinuria (19). High, prolonged, cadmium exposures have produced bone disease(e.g., osteomalacia and itai itai disease) in a few industrial workers and in somewomen who resided in cadmium-contaminated areas of Japan for 50 years. Exposed individuals with deficient intakes of calcium or vitamin D are at increasedrisk for itai itai disease. Cadmium is classified as a "probable human (B2)carcinogen" based on limited occupational epidemiological studies and sufficientevidence of carcinogenicity in rodents exposed by inhalation. Administered orally,however, cadmium has not caused cancer in laboratory animals. Epidemiologicalstudies suggest that long-term occupational exposure to cadmium may contributeto the risk of lung cancer. However, because of confounding exposures to othermetals and cigarette smoke, the observed risk cannot be conclusively attributed tocadmium at this time (19).
Cadmium was detected in on-site air at levels that exceeded ATSDR's CREG. However, epidemiological studies provide only weak evidence that prolongedinhalation exposure to cadmium is associated with an increased risk of lung cancerin occupational cohorts. Such data do not provide a reasonable basis for predictingcancer effects in nonoccupational populations exposed to much lowerenvironmental levels of cadmium. A comparison value based on establishednoncancer effects would, therefore, be more appropriate for use under the site-specific conditions that prevail in Livingston. Taking this approach, it is found thatmean cadmium levels downwind from BNRY were more than 8 times lower thanATSDR's chronic EMEG of 0.2 µg/m3 and were within the range of concentrationstypical of urban areas. The fact that cadmium was not elevated in either on- or off-site soils suggests that long-term deposition of cadmium from air has beeninsignificant at this site. Therefore, based on the available data, it is concluded thatthe levels of cadmium in on-site air at BNRY do not represent a public health hazard to exposed residents.
Trichloroethylene, also called trichloroethene or TCE, was detected at elevatedlevels in some samples of groundwater and indoor air. However, the generally lowconcentrations to which residents might actually be exposed are not likely toproduce any adverse health effects.
The primary use of TCE is as a solvent for degreasing metals (4). High levels ofexposure are expected for workers in degreasing plants due to inhalation of vaporsor adsorption through the skin. The TLV is 50 ppm in air or 269 mg/m3 (31). Thegeneral public is exposed to low levels of TCE, primarily from ambient air anddrinking water. Additional low-level exposure may be incurred by persons livingnear degreasing plants or spill sites (4).
TCE is an effective central nervous system depressant at high doses (severalhundred to 1,000 ppm) and was formerly used as an anesthetic. Chronic exposureto lower doses (27 ppm) may irritate mucous membranes and cause somedrowsiness. However, there are no reliable reports of adverse health effects atenvironmental levels of exposure (i.e., the low parts per billion range).
Various types of cancer have appeared in animals treated with TCE orally and by inhalation (20). However, the positive animal studies are plagued by a number of problems, including high rates of mortality due to high dose toxicity; the use of TCE containing epoxide stabilizers that may themselves cause cancer; high, strain-specific, background rates of specific cancers; and species-specific mechanisms (peroxisome proliferation, alpha-2µ-globulin accumulation, activation of TCE-glutathione conjugates) that do not occur in humans and, hence, have no relevance to human risk assessment. The findings from epidemiological studies of workers exposed by inhalation have been largely negative and provide no clear evidence that TCE causes cancer in humans. Some controversial studies suggest a weak association between TCE in drinking water and cancer (mostly leukemia) in humans. However, because these studies fail to establish a link between actual TCE exposure and the incidence of health effects, their findings have been repeatedly challenged in the scientific literature. Based on this conflicting evidence, International Agency for Research Cancer (IARC) has recently upgraded TCE from Group 3 ("not classifiable") to Group 2A ("probably" carcinogenic to humans). EPA, on the other hand, has downgraded TCE from a B2 ("probable") to a B2-C ("probable/possible") human carcinogen, while the ACGIH designates TCE as an "A5" substance, i.e., an agent "not suspected to be a human carcinogen on the basis of properly conducted epidemiological studies" (31). Therefore, ATSDR considers that cancer effects are not the most appropriate basis for an assessment of this chemical's potential impact on public health at Livingston.
Private Well Water
The maximum level of TCE detected in off-site private well water was 15 ppb. This levels exceeds both the MCL of 5 ppb and ATSDR's CREG of 3 ppb but is 466times lower than ATSDR's intermediate EMEG (7,000 ppb for children, 20,000 ppbfor adults). ATSDR considers that 15 ppb TCE in drinking water is not likely toproduce acute or chronic adverse health effects.
The maximum levels of TCE detected in indoor air (73 and 567 µg/m3 or 14 and106 ppb) exceeded ATSDR's CREG of 0.6 µg/m3 (0.1 ppb), but were far belowATSDR's intermediate EMEG of 2,000 ppb (10,750 µg/m3). These measurementswere taken in a basement crawlspace and 1.5 feet down a basement well, areaswhich clearly do not represent "living" space or contribute to a person's normalbreathing zone. Thus, the intermediate EMEG is more applicable to thesemeasurements than is a CREG, which assumes lifetime exposure. The maximumlevels detected in upstairs and basement living spaces were 3.33 µg/m3 (0.6 ppb)and 2.71 µg/m3 (0.5 ppb) respectively. These levels would not be expected tocause adverse health effects of any kind.
The maximum levels of toluene in indoor air (8,000 and 45,000 µg/m3 or 2,123and 11,942 ppb) were above ATSDR's chronic and acute EMEGs of 1,000 and3,000 ppb, respectively (21). The latter values are 30 times lower than the Lowest Adverse Effect Levels (LOAEL) for minimally adverse human effects onwhich they are based. Both of the maximum levels were detected in August 1989. However, subsequent measurements in October and November were all belowdetection limits. ATSDR cannot at this time explain the aberrant high readings inAugust 1989 and considers that they should not be used in the assessment of anypotential long-term health effects. Toluene was not detected at levels of concern inany other environmental samples, either on- or off-site. Based on this data, noadverse health effects attributable to toluene exposure would be expected.
Elevated levels of 1,1,1-TCA were detected in indoor air in August 1989, but notduring subsequent sampling events. Nor was there any clear relationship betweenmeasurements of 1,1,1-TCA on-site and the isolated occurrence of elevated levelsin off-site indoor air. Based on this data, no adverse health effects attributable to1,1,1-TCA exposure would be expected.
The maximum level of lead detected in off-site groundwater was 20 ppb, whichmarginally exceeded EPA's Action Level of 15 ppb. However, lead levels werebelow 15 ppb in both municipal and private wells. Considering the length of timethat lead has had to migrate from the site, the levels involved, and the seasonalvariation in the direction of groundwater flow, it is not likely that lead on-site willresult in levels of public health concern off-site in the future. Thus, although it isdesirable to keep lead levels in drinking water below the action level of 15 ppb,ATSDR does not consider that the few elevated readings from off-site monitoringwells reflect a current or future hazard to public health.
Cis-1,2-dichloroethene (DCE), like lead, was detected inconsistently in off-sitegroundwater, and then usually at levels below comparison values. It was notdetected in municipal well water. The maximum level detected off-site (190 ppb)exceeded the MCL and Lifetime Health Advisory (LTHA) of 70 ppb, but not theChild's Longer-Term Health Advisory (CLHA) or child intermediate EMEG of 3,000ppb. The maximum level detected in a private well was 99 ppb. Considering theseasonal variation in the direction of groundwater flow, the inconsistency withwhich DCE was detected, and the levels involved, the CLHA and intermediateEMEG, which are based on exposure durations of 1-7 years, would seem to bemore appropriate than the LTHA and MCL, which are based on daily exposure overan entire lifetime. Thus, although it is desirable to keep DCE levels in drinkingwater below the MCL of 70 ppb, ATSDR does not consider that the few elevatedreadings from off-site wells reflect a current or future hazard to public health.
Finally, it should be noted that the above toxicological evaluations were all basedon historical maximum concentrations, and that the concentrations of thesecontaminants have continued a long-term decline over the last six years, a declinewhich should continue in light of the on-going remediation activities on-site. Monitoring will continue to verify the decline.
Since the individual contaminants detected at this site are present at levels thatwould not be expected to result in adverse health effects, ATSDR considers thatthe combined effect of all these contaminants is not likely to be of public healthconcern either. This conclusion is based on 4 studies which suggest that a mixtureproduces no adverse health effects in dosed animals when the components of thatmixture are present at levels below their respective No Observed Adverse EffectLevels (NOAEL), i.e., at concentrations that would have produced no adverseeffects in animals treated separately with those component chemicals (47-51). Intwo of these experiments (48,49), all of the component chemicals affected thesame target organ, albeit through different mechanisms. In two others (50,51), thechemicals had different target organs and exhibited different modes of action, as domost chemicals in typical environmental mixtures. Considering that ATSDRComparison Values are typically 100-1000 times lower than the correspondingNOAELs, it is reasonable to expect that environmental contaminants will notproduce any combined effects, even if their individual concentrations exceed their respective EMEGs by a significant fraction of the associated safety factor (which ATSDR refers to as a composite "uncertainty factor").
The Montana Department of Health and Environmental Sciences, with technicalassistance from ATSDR Division of Health Studies, completed a cancer clusterstudy for Livingston and Park County, Montana (1992). Data from the MontanaCancer Registry indicated apparent increases in digestive tract cancer in ParkCounty over the years 1980-1989. More detailed examination of the data revealedthat the increase was specifically in cancer of the pancreas. An increase inpancreatic cancer was observed in Livingston in white males, but not in theremainder of Park County, nor in white females (minorities were present in numberstoo low to allow investigation). The mean age of onset is between 70 and 80years which is the third largest age group in Livingston's total population;pancreatic cancer is more prevalent in areas with older populations. No associationwith smoking was observed for these cases.
The association between cancer mortality and contaminant exposure from railroadrefueling facilities was suggested as a possibility. An investigation by the MontanaDepartment of Health and Environmental Services was completed utilizing deathcertificate data for populated areas where refueling facilities are located in Montana(1995). No statistical relationship between residential proximity to the refuelingfacilities and cancer mortality could be identified.
Overall mortality in Park Country was examined using CDC computerizeddatabases. Overall mortality was less than in the State of Montana taken as a whole, on either a crude or an age adjusted basis, over the period 1979-1988.
- Groundwater contamination with diesel fuel and solvents.
On-site and off-site groundwater contained elevated levels of arsenic, TCE, andPCE. People did not consume on-site groundwater. Monitoring data for privatewells revealed elevated levels of PCE and TCE. Owners of private wells withelevated levels of contaminants have been notified. Monitoring wells are in place toallow for detection of any contamination present. The groundwater plume isthought to move in a northeastern direction toward the Yellowstone River. Lowlevels of TCE and PCE that were detected on the east side of the Yellowstone Rivermay be due to underflow beneath the river or may be caused by non-BNRY VOCsources east of the river.
- The occurrence of unusual cancers, such as brain, pancreas, andchildhood cancers. The occurrence of miscarriages and gallstones.
ATSDR and the State of Montana have completed a health study of cancerincidence in the Livingston, Park County, Montana, area. This study revealed anincreased incidence of pancreatic cancers in Livingston that was not associatedwith residential proximity to a railroad facility. Incidence of other cancers appearsto be average. Gallstones are often associated with diet. Miscarriages occurconsiderably more often than is usually acknowledged. Nationally, ten to twentyper hundred pregnancies end in miscarriage. The contamination detected in on-siteand off-site media at BNRY would not be expected to cause miscarriages inLivingston.
- Unusually high incidence of lupus and multiple sclerosis (MS) in theLivingston community.
Data on specific incidences of lupus and MS in Livingston were not available forreview. Lupus and MS are chronic inflammatory diseases of unknown etiology(42,43,44). Although the causes are unknown, both environmental and geneticfactors are clearly implicated. In genetically-predisposed individuals, the onset ofthese autoimmune diseases are often triggered by viral infections or reactions tocertain drugs, or other chemicals. The onset of MS and Systemic LupusErythematosus has been triggered by bee stings and exposure to sunlight. Theenvironmental data available neither implicates nor exonerates chemical exposuresat Livingston as possible triggers of autoimmune disease in genetically-predisposedindividuals. However, since natural, non-specific triggers are ubiquitous in theenvironment, the availability of man-made triggers may not be a determining factorin the incidence of these diseases. In other words, an increased incidence of Lupusand/or MS would most likely reflect a cluster of genetically-predisposed individuals,rather than an increased availability of environmental triggers.
- Perceived high mortality in the area.
ATSDR examined data on overall mortality from all causes in Montana and in Park County. Overall deaths and death rates were slightly less in Park County than in the state of Montana.