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This appendix contains both the comments received during the public commentperiod for the Burlington Northern Rail Yard site and ATSDR's response to thosecomments. The comments have been numbered and are in italic with the responsedirectly below each comment. Comments were received by the MontanaDepartment of Environmental Quality (DEQ), the Park County Environmental Council(PCEC), the City of Livingston, Envirocon, HSI GeoTrans, and private citizens. Insome cases, comments received from different individuals on the same topic havebeen re-worded and combined to avoid needless repetition. The first severalcomments are "General Comments" on the public health assessment (PHA). Theremaining comments reference specific sections and subsections of the PHA.

1         General Comment: In the beginning of the document it would be helpful for the reader to clarify that in 1995 the Montana Department of Environmental Sciences (DHES) changed its name to the Department of Environmental Quality (DEQ).

Please refer to the Summary section of the document for this clarification.

2         General Comment: It should be mentioned that the data available for the study was limited.

The data are "limited" to the last 10 years. However, since levels of environmentalcontamination at Livingston have been declining for the last 6 years, there is noreason to think that the maximum concentrations of contaminants detected duringthe last 10 years do not form a sufficiently conservative basis for the assessmentof potential, exposure-related, adverse health effects for both the present and theforeseeable future. The data are also "limited" in the sense that their quality andinterpretation are, of necessity, based on the current state of knowledge in therelevant fields of science. However, ATSDR considers that the available data andthe current state of the art is more than adequate to support the conclusions thatthe Agency has drawn in the public health assessment for Livingston, Montana.

3          General Comment: It should be mentioned that the lead role for this project passed among several individuals during preparation of the assessment which may have effected the quality of the study.

ATSDR regrets that it has taken so long for this public health assessment to bebrought this close to completion. However, the resulting input from a larger-than-usual number of public health professionals on a growing environmental databasecan only improve, rather than detract from, the quality of the final product.

4          General Comment: It is unclear if the public health assessment is the result of the LIFE petition or because the site was placed on the EPA proposed NPL.

ATSDR determined that there was a reasonable basis to justify conducting a publichealth assessment in response to the LIFE petition.

5          General Comment: The Baseline Risk Assessment used to define clean-up levels used specific data in the analyses. Is the data used in this study comparable to the health assessment data?

ATSDR reviewed and compared the data used in the Baseline Risk Assessment(BRA) to those used in this Public Health Assessment (PHA). The site RemedialInvestigation (RI) report is the primary source of the data used in both the BRA andthe PHA. Overall the data are comparable, although ATSDR observed someinconsistencies in the maximum concentrations reported for certain contaminants. A comparison of private well data used for each assessment was not possiblebecause the BRA combined the data sets for private wells and monitoring wells. Inaddition, a comparison of contaminant concentrations for off-site soils was not possible because the BRA combines on- and off-site soil data sets.

Observed discrepancies are summarized in the tables below. None of the observed differences change the conclusions of ATSDR's public health assessment.

On-site Groundwater Samples

Contaminant BRA
Highest Reported
Highest Reported

The on-site groundwater concentrations used by ATSDR in the public healthassessment were obtained from pre-RI investigations performed by RemediationTechnologies and are more conservative than those used in the BRA.

On-site Surface Soils

Contaminant BRA
Maximum Reported
Maximum Reported
Benzo(a) anthracene262.7
Selenium (total)0.698

The PHA presents on-site surface soil data from Envirocon's surface soilinvestigation in April and May, 1992. These data were originally presented inEnvirocon's Surficial-Soil Investigation Report, Livingston Rail Yard in July, 1992. The same data were subsequently presented in the RI. The BRA presents on-sitesurface soil data which are a composite of Envirocon's data and data collected byEcology and Environment in 1991 for EPA's Listing Site Inspection. Therefore,where maximum reported concentrations for contaminants in surface soils arehigher in the BRA than in the PHA, the concentrations reported in the BRA aretaken from the 1991 Ecology and Environment sampling data.

Yellowstone River Water Samples (September 20, 1989 and March 23, 1990)
Contaminant BRA
Maximum Reported
Maximum Reported
Tetrachloroethylene1.6 0.91

Overall, the surface water data used in the BRA and PHA are comparable. Asstated previously, the observed differences in maximum concentrations do not alterthe conclusions of ATSDR's public health assessment.

6          General Comment: The document should distinguish the difference between the conclusions made in DEQ's Baseline Risk Assessment (BRA) and ATSDR's public health assessment (PHA). The reason for the different conclusion in the two documents should be clarified. The BRA identified a potential 1 in 10,000 chance of cancer based on exposure to contaminated drinking water. The PHA concludes there is currently no apparent health risk from contaminants at the site. The conclusions of the BRA are based on potential exposure pathways in the future while the conclusions made in the PHA are based on current exposure pathways.

The public health assessment evaluated past, current, and future exposurepathways. The difference between the public health assessment and DEQ'sbaseline risk assessment does not have to do with the consideration or lack ofconsideration of potential future exposures. It merely reflects the fact that theState performed a conventional statistical estimate of carcinogenic "risk", based onavailable cancer slope factors, and treated the results as if they were actuallypredictive of "potential" adverse health effects. ATSDR's assessment of cancer"risk" was, of necessity, qualitative rather than quantitative, since it was based onthe scientific interpretation of a sizable toxicological database rather than on rigidpolicy assumptions and model estimates of one-in-a-million risk levels . ATSDR usesthe latter, in the form of its cancer risk evaluation guide (CREG), solely as screeningtools and NOT as the primary basis for health calls. Unfortunately, many peoplesystematically ignore EPA's own caveat to the effect that a quantitative cancer riskassessment "does not necessarily give a realistic prediction of risk" because "thetrue value of the risk is unknown and may be as low as zero." ATSDR's conclusionthat future exposure pathways pose no apparent health hazard assumes that thecurrent monitoring programs continue in the future as planned.

7          General Comment: It may be appropriate to put an introduction section in the beginning of the document. The Forward discusses all health assessments stating: "Generally, ATSDR does not collect its own environmental sampling data but...". An introduction should state this health assessment does not collect any new data, but analyzes data previously collected by the DHES/DEQ and the PLP's consultants.

This change is not appropriate. In both the Note of Explanation and Forward,ATSDR mentions that currently available data is utilized for public healthassessments. Further, in the Environmental Contamination and Other Hazardssection of this public health assessment there are many specific references madeconcerning the data collected.

8         General Comment: Have institutional controls been implemented concerning the installation of public and private wells in the area? If not, are institutional controls being considered?

Each proposed site clean-up option presented in the Draft Feasibility Study includesa provision to implement institutional controls, with the exception of the "noaction" alternative. Institutional controls, which may include covenants or deedrestrictions, will prevent drilling water wells for domestic use on-site and in theadjacent areas where VOCs are at levels greater than MCLs. The final site plan isexpected to be released in the fall of 1997.

9         General Comment: Several areas of the health assessment reference the Draft Remedial Investigation (RI) Report. A Final RI has been released. Is the information the same?

ATSDR performed a comparison check between the references of the final and draft Remedial Investigation (RI) reports. The final RI contains information that was obtained subsequent to the release of the Draft RI. In checking the data tables in the public health assessment, there are several references to the draft RI. ATSDR compared these values against data tables in the Final RI. The data appears to be consistent.

10         General Comment: This study must discuss the degradation products of PCE and the public health risk.

Under anaerobic conditions, tetrachloroethylene (PCE) can be transformed byreductive dehalogenation to trichloroethylene (TCE), dichloroethylene and vinylchloride (VC). This public health assessment already contains a completediscussion of the levels of TCE, DCE and VC in groundwater at Livingston.

11          SUMMARY, fourth paragraph: Arsenic and cadmium have been detected as dissolved compounds in the groundwater; however, the distribution of these metals shows no relationship to the BNRY, indeed, arsenic is clearly related to the Yellowstone River water. This paragraph gives the impression that these metals are groundwater contaminants from sources within the BNRY.

This paragraph is discussing the contaminants most often identified in on- and off-site media as well as worker and resident exposures. No reference is made tosources.

12          SUMMARY, fifth paragraph: To clarify the last sentence of this paragraph it may be helpful to explain that even though "the VOCs detected so far are not present at levels that may cause adverse health effects"; however, VOC levels exceed MCLs in some private wells that are not currently being used for drinking water.

This change would be inappropriate for the Summary section of the document.

13         SUMMARY, sixth paragraph: It would be helpful to the reader to explain in this paragraph that although ATSDR assumes there is no likely pathway for exposure to on-site groundwater and soil, the final remedy will insure no future completed exposure pathways by implementing institutional controls and other clean-up actions.

Change noted.

14         BACKGROUND, first paragraph: The Burlington Northern Rail Yard in Livingston was proposed for listing on the EPA's National Priorities List (NPL) in August 1994; however, the site has not actually been added to the NPL. Considering the advanced stage of remediation and the minimal health risks, it is very unlikely that the EPA will formally add the rail yard to the NPL.

ATSDR cannot comment on whether or not the EPA will list the BNRY site on thefinal NPL. The health assessment has been modified to state that the BNRY is'proposed for listing.'

15         BACKGROUND, Site Description and History, seventh paragraph: Breakdown products are mentioned as being identified at the rail yard but are not addressed as contaminants of concern for future analysis. I am particularly concerned about vinyl chloride. As bacterial decomposition continues of the diesel contamination, vinyl chloride will be emitted and should be monitored to prevent worker exposure and public exposures to levels potentially causing adverse health effects. Also, what are other breakdown products? Have any been identified in media on-site or off-site?

ATSDR's conclusions were based on the maximum concentrations of contaminants(including vinyl chloride) detected over the entire period for which data wereavailable (approximately 10 years). Considering the age of the Burlington NorthernRail Yard (100 years), the abatement of on-site pollution during the last 10-27years, and the fact that levels of contaminants have been decreasing steadily duringthe last six years, there is no reason to expect that levels of contaminants(including vinyl chloride) are likely to increase in the future. Continued groundwatermonitoring is planned. This monitoring will identify any contaminants that couldpotentially cause adverse health effects in the future.

16         BACKGROUND, Site Description and History, seventh paragraph: The use of the word "may' implies that there is a question as to what caused the release of VOCs. Clearly the rail yard operations resulted in contamination of the soil and groundwater and the following statements are more definitive.

Change noted.

17         BACKGROUND, Site Description and History, eighth paragraph: The Remedial Investigation states chlorinated solvents are present in groundwater from BNRY activities.

Change noted.

18          BACKGROUND, Site Description and History, eighth paragraph: The replacement of the city municipal wells and limit of the use of contaminated private well water for drinking needs to be mentioned here also to complete the discussion of what actions were taken to protect public health upon determination of contamination.

This change is not appropriate. The paragraph is specifically addressing clean-up ofon-site contamination. Please see the Pathways Analyses section titled 'Off-sitegroundwater' for clarification on municipal and private water wells.

19          BACKGROUND, Site Description and History, eighth paragraph: The current status of the site should be further detailed in this paragraph. The FS and ROD status need to be referenced to clearly indicate that the final remedy to meet the clean-up requirements has not yet been determined and that interim clean-up efforts were implemented to protect public health.

Please refer to changes in the main text. BNRY is developing a final site clean-upplan, expected to be completed in the fall of 1997. Once approved by DEQ, theplan will be presented in the site ROD.

20         BACKGROUND, Site Description and History, Mission Wye: Discussion of Mission Wye's potential contribution to groundwater contamination and thus residences living within the plume also needs to be addressed.

Mission Wye is located 5.5 miles northeast of Livingston. A groundwatermonitoring plan for this area was initiated in 1992. The semi-annual groundwatermonitoring network includes 18 monitoring wells. Four wells are located downgradient from the Mission Wye contaminant plume; three wells monitor waterquality at the leading edge of the plume. The general flow of groundwater at theMission Wye area is northeasterly. The following table summarizes April 1997sampling results:

Contaminant ranges found at the Mission Wye site during April 1997 Sampling (in ppb) 1
TCE PCE cis-1,2-DCE
1.3 - 172.9 - 171.0 - 20

1 April 1997 Groundwater Monitoring Report, Mission Wye. RETEC, June 6, 1997

TCE, PCE, and cis-1,2-DCE were detected in the same four monitoring wells (MW-3, MW-5, MW-14, and MW-18). In addition, 1,1,1-trichloroethane was detected inMW-14 at 1.6 ug/L. Additional groundwater sampling reportedly occurred in July1997, but results are not yet available. For this public health assessment, theMission Wye area is considered to be a part of the BNRY site and therefore, thedata is combined with the on-site data.

21          BACKGROUND, Site Description and History, Site history time line: Additional events that could be added to the time line are: 1993-Burlington Northern submits Draft Primary Hydrocarbon Feasibility Study Report, and 1994-Burlington Northern submits Draft Feasibility Study Report.

Change noted.

22          BACKGROUND, Site Visit, second paragraph: The sentence, "the site is unfenced but visitors are required to sign...," implies that there is control on entrance to the site. Access to the cinder pile or other areas of the site are not well controlled. A period at the end of "the site is unfenced" would make the statement better represent what is happening at the site.

Change noted.

23         BACKGROUND, Land Use: This paragraph should also state that a municipal incinerator operates in the same location, roughly as the rail yard and describe the existing rail yard operations to delineate exposure to contaminants from current operations vs. existing operations. Also, there are residential areas surrounding the rail yard to the extent that current operations are conducted just across the street or track from an occupied residential block.

Please refer to changes in the main text of this subsection. ATSDR is unaware ofany municipal incinerator operating in the same location as BNRY. Past rail yardoperations as well as current operations are described in the Background section,Site Description and History subsection, of the public health assessment.

24         BACKGROUND, Natural Resource Use, Groundwater, first paragraph: The location of the municipal wells on a map should be provided to clearly indicate the past, current, and potential exposure pathways to groundwater as the City of Livingston is concerned about future contamination of municipal water from leaks in the pipes located within the contaminant plume.

Please refer to Figure Two for the location of municipal wells. ATSDR was not ableto obtain information on the location of the municipal pipe lines; however, undernormal circumstances, the water pressure would force water out of the pipe linesand not allow contamination to leak into the pipe lines.

25         BACKGROUND, Natural Resource Use, Private Wells, first paragraph: In the fourth sentence, after the word notified add, "by DEQ."

Change noted.

26          BACKGROUND, Natural Resource Use, Private Wells, first paragraph: All of the private well owners within Livingston south and east of the rail yard have for many years been connected to the Livingston municipal water system for drinking water. The last line in this paragraph indicates that well owners switched to the municipal water system after contamination was discovered. This is not true. All of them were originally connected to the municipal system but still had wells that they used for irrigation, etc.

ATSDR has not received any additional information to contradict the statementsmade in the public health assessment concerning the time frame that well ownersswitched to the municipal system for drinking water purposes. Therefore, ATSDRmade no changes to the main text concerning this issue.

27          BACKGROUND, Natural Resource Use, Private Wells, second paragraph: The private well section implies that only 14 of the 63 wells were sampled for VOCs, that only those wells south and east of the rail yard were suspected of being contaminated, and of the 14 wells sampled randomly only 6 had VOCs identified in the wells. Were all 63 private well owners with wells in the vicinity told not to drink their water? What about those wells north of the site that tested positive for VOCs? Please clarify.

The discussion of the number and location of private wells relative to the sitecontamination plume can be clarified as follows:

The contaminant plume extends east/northeast from the BNRY site. Approximately30 private wells are located northeast of BNRY and at least 12 wells are locatedeast of the site, all down gradient of BNRY (53). Fourteen private wells located inthe vicinity of BNRY were sampled by Envirocon in 1989 as part of the RI; sixcontained detectable levels of VOCs. In addition, the former O'Connor well(reportedly purchased by BNRY prior to 1989) and the publicly owned treatmentwell (POTW) had detectable levels of VOCs. According to information collectedduring Envirocon's well survey, none of the affected wells were used for drinkingwater purposes, although some were/are used for irrigation.

The POTW well was reportedly used for car washing, dish washing, andpreparation of de-ionized water for an in-house laboratory, until it was connected tothe municipal water supply in 1992. The POTW well was formerly used fordrinking and showering, but the time and duration of use for these purposes is notdocumented (53).

According to Envirocon, all sampling results were provided to well owners. Residents were encouraged to call the Montana Department of EnvironmentalQuality (DEQ) for further information.

28         BACKGROUND, Natural Resource Use, Municipal Wells: There is a need for a clearer definition of what data was used to evaluate prior exposures to contaminants in drinking water from municipal wells. The wells taken out of service were found to be contaminated with VOCs. Please indicate what the sampling results were and why, from a health perspective, they were taken out of service (e.g. the samples exceeded state drinking water limits or if not, the action to take the wells out of service was strictly precautionary).

Please refer to changes in the main text of this subsection as well as the text in theEnvironmental Contamination and Other Hazards, Off-site contamination, municipalwell subsection.

29          COMMUNITY HEALTH CONCERNS: This section needs to add the fact that the LIFE committee is no longer involved in oversight and has been replaced by the Park County Environmental Council with a Technical Assistance Grant from EPA. This section needs to address how the data on health concerns were collected. Change noted. ATSDR received health concerns during a meeting with the petitioning environmental group.

30         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, first paragraph: Enumerate tables showing contaminants, e.g. Tables 3-?. Explain what you mean by "medium."

Change noted. The term "medium" refers to a substance (water, air, soil) throughwhich contamination is transferred.

31         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, first paragraph: I don't know what you mean when you say ATSDR "selects" contaminants based on concentrations, etc. This implies judgement on the part of ATSDR. Is it conservative and protective of public health?

ATSDR has determined levels of chemicals that can reasonably (and conservatively)be regarded as harmless, based on the scientific data the Agency has collected inits Toxicological Profiles. This information is used to identify contaminants ofconcern that are included and discussed throughout the public health assessment. The high degree of conservatism in ATSDR's selection of contaminants of concernis further detailed in the Toxicological Evaluation section.

32         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, first paragraph: It appears only the highest values of various contaminants gathered from a large body of results are combined into tables in Appendix B, and subsequently used for hazard analysis. The reader might better understand the process if this was mentioned in an introductory paragraph for this section, and also in each table in Appendix B. Some of the tables in Appendix B do not reference the source of their data. Data incorporated into Appendix B should be consistently referenced as to its source.

Some tables in Appendix B list only the highest level of each contaminant in a givenmedium while other tables list a range of values. Please refer to the ToxicologicalEvaluation section of the public health assessment for a complete discussion ofATSDR's analysis methods, including the use of the highest concentration of acontaminant. All of the tables in Appendix B reference the source of the data,either within the table as a separate column or at the bottom of the table in afootnote.

33          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, subsections: Introductory paragraphs in the various subsections of B. Off-Site Contamination are good summaries of the data to follow. Similar introductions to subsections A. On-Site Contamination would assist the reader to understand the data.

Both subsections currently contain information that details the sampling of eachenvironmental medium in order to assist the reader to understand the contaminantdata. Further information is not thought to be necessary.

34          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, third paragraph: Please explain what "safe under default conditions of exposure" means. This whole paragraph is confusing. Please clarify the explanation of CV's relative to site-specific conditions of exposure vs. default and what is meant by the discussion of contaminants vs. site-specific exposure vs. adverse health effects. I suggest explaining the screening process in simpler terms and that the substances listed in the following sections represent those that ATSDR 'screened' as being at those concentrations that needed a more thorough analysis to determine if there were adverse health effects.

"Default conditions of exposure" refers to exposure estimates based on standardassumptions, e.g., a daily adult intake of 2 liters of drinking water (1 liter forchildren), 20 cubic meters of air (15 m3 for children), and 100 mg of soil (200 forchildren). "Site-specific exposure" refers to somewhat more accurate estimatesbased on conditions at the site that are expected to influence the degree ofexposure. For example, the default estimates for daily soil ingestion would beinaccurate (i.e., too high) for a small industrial facility that had been fenced and abandoned for years. Similarly, default estimates of daily consumption of drinkingwater would be useless if no one were actually drinking the water from the sourcein question. Exposure estimates that try to take site-specific conditions intoaccount are still just estimates, of course, but they tend to be much more realisticthan those based on default assumptions alone.

35         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, On-Site Contamination, On-Site subsurface soil/MIssion Wye: It is unclear if the On-site subsurface soil/Mission Wye subsection is discussing data collected from the BNRY site or the Mission Wye site.

The subsection referenced in this comment is referring to sampling at the MissionWye area.

36         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, On-Site Contamination, On-site ambient air: This section does not accurately describe the variety of air monitoring conducted at the rail yard. It confuses the site-wide ambient air monitoring with work-zone specific air monitoring for VOCs. Site-wide ambient air monitoring consisted of PM10, TSP, and PAH sampling at permanent sampling locations and began on November 1990 and continued through March 1992. Work zone air monitoring was conducted during remedial activities that had the potential to generate emissions.

The correct dates for the "Site-Wide Ambient Air Monitoring" program at BNRY areNovember 1990 to March 1991 as indicated on page 6-5 of the Final RemedialInvestigation report. The work-zone ambient air sampling events occurred betweenNovember 1989 and June 1991 as indicated on pages 6-3 through 6-5 of the FinalRemedial Investigation report. The main text of the public health assessment hasbeen updated to reflect this information.

37          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Off-site groundwater, Monitoring wells, first paragraph: The last two sentences appear to imply metal contamination has migrated off-site eastward toward the river. The data may or may not show metal concentrations result from off-site migration or whether they are occurring naturally.

Please refer to changes made to the sentence in question. ATSDR reexaminedavailable metals data for groundwater. Only dissolved metals data are provided inthe Remedial Investigation. Based on these data, low levels (i.e., less than drinkingwater standards) of arsenic, cadmium, and lead were sporadically detected. Asstated in the public health assessment, only arsenic and lead exceeded availablecomparison values. The maximum detected concentrations of arsenic (7 ppb) andlead (20 ppb) were only slightly above comparison values (ATSDR's arsenic chronicEMEG (child) of 3 ppb and EPA's Action Level of 15 ppb for lead). In addition, thepublic health assessment does indicate that the arsenic in the Yellowstone Riverappears to be naturally occurring in the discussion of private well contamination.

38          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Off-site groundwater, Monitoring Wells, first paragraph: Why was the evaluation in the last sentence made as there are other such evaluations that could have been made in the prior section were left to the later section.

The discussion concerning the migration of contamination in groundwater isthought to be both useful and appropriate in this paragraph.

39         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Off-site groundwater, Monitoring Wells, fifth paragraph: Was TPH at 1 ppm above CVs?

ATSDR does not have a CV for total petroleum hydrocarbons. However, mostpetroleum distillate products are poorly absorbed by the gastrointestinal tract,greatly reducing the potential for any systemic toxicity via the oral route. This isone reason why the ingestion of less than 1 to 2 milliliters of petroleum distillatesper kg body weight does not generally result in any systemic toxicity. It followsthat ingestion of water containing 1 part per million total petroleum hydrocarbonswould be even less toxic. The greatest health threat is chemical pneumonitisfollowing aspiration of swallowed gasoline, kerosine, furniture polish, etc. Theonly toxicologically-meaningful way to treat exposures of this sort is by theindividual components. This has already been done in the public healthassessment.

40         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Off-site groundwater, Monitoring Wells, seventh paragraph: Was 1,1,1-TCA above CVs?

No, the maximum concentration of 1,1,1-TCA of 0.72 parts per billion (ppb) wasbelow the Maximum Contaminant Level (MCL) of 200 ppb.

41          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Off-site groundwater, Monitoring Wells, tenth paragraph: Were PCE and TCE detected east of the river above CVs?

The maximum level of PCE (15 ppb) detected east of the river was above the MCLof 5 ppb. The maximum level of TCE detected east of the river was belowcomparison values.

42         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Off-site groundwater, Municipal Wells, first paragraph: Discuss the municipal well system and if the Q street well water intermingles with the rest of the systems water or does it supply a group of residences with little or no mixing (dilution). Were the L street and Werner well levels above CVs?

According to Clint Tinsley, Director of Public Works, Town of Livingston, mixing ofwater from the individual municipal wells occurs. The municipal water systemconsists of interconnected water mains that pump water from the individual wellsup to one reservoir. Water is then distributed to residences from the reservoir.

PCE levels detected in the L street and Werner wells were below comparisonvalues.

43          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Off-site groundwater, Municipal Wells, second paragraph: Please explain in discussion of CV's what it means when you reference an EPA value like the EPA action level for Lead.

When no ATSDR comparison value is available for a particular substance, guidelinesfrom other agencies are used to put the concentration of that substance intoperspective. ATSDR has no comparison value for lead (Pb). EPA's action level of15 ppb in drinking water is the only numerical guideline currently available.

44         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Off-site groundwater, Private Wells, first paragraph: Please update the data to reflect conversations held with the state and John Mills on private well sampling Feb. 26 during the site visit.

According to the 1997 Annual Ground Water Sampling Report for the LivingstonRail Yard, 43 samples from 28 monitoring and private wells were collected byEnvirocon in May 1997. The report summarized data from bi-annual samplingevents between August 1995 to May 1997. The following table summarizes theseresults. The referenced concentrations are all below historical maximums. Thehighest concentrations reported below were detected in on-site monitoring wells.

Range of Contaminant Concentrations (in ppb), 1995-19971
Contaminant Sampling Event
August 1995 November 1995 May 1996 November 1996 May 1997
PCE ND2-186ND-199ND-205ND-172ND-163
cis-1,2-DCE ND-523ND-88ND-23ND-54ND-21

1 1997 Annual Ground Water Sampling Report, Envirocon, August 15, 1997.
2 ND <0.5 ug/L
3 value is from a duplicate sample. Original sample detection limit was too high due to foaming in sample bottle.

45          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Off-site soil gas: If soil gas is not a valid pathway of exposure there is no need to go into the detail on this page as it just confuses the reader. The soil gas data is useful for remediation purposes only.

ATSDR considers the discussion in question to be both useful and appropriate. Thelimitations of soil gas data vis à vis the evaluation of public health implications arediscussed in the appropriate sections.

46         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Off-site soil gas, second paragraph: The last sentence is confusing. Please clarify.

PCE may have been detected in the air samples if lower detection limits were used.

47         ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Indoor residential air, sixth paragraph: Please explain where ATSDR obtained copies of sampling log books from the basement gas investigation.

The log books referenced in the public health assessment are contained within Appendix A of the Phase IV Indoor Air Quality Investigation report. Specifically, theappendix contains Field-Activity Documents, including "building structure surveys"and "house activity forms" for the locations sampled. The surveys/forms documenthome use of PCE-containing materials, such as glue, paint, and furniture stripper.

48          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Off-Site Contamination, Yellowstone stream sediment and river gravel analyses, first paragraph: Please check the statement that oily waste material was released from the WWTP into the Yellowstone in 1990. It is my understanding that waste went into a drain line that discharged into the Yellowstone but that was in the 50s?

The Draft and Final Remedial Investigation (RI) reports and the Baseline RiskAssessment refer to an oily waste discharge that occurred in January 1990. Whenremediated in March of 1990, the extent of the stained gravel area was found to belarger than expected. The Final RI report refers to 1942 aerial photographs thatdepicted oily water discharged from the pre-1943 relic slough accumulating in thestained gravel area, possibly explaining why the area was larger than expected.

49          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Quality Assurance and Quality Control, first paragraph: It is somewhat disturbing that ATSDR "assumes that adequate quality control methods were followed...". Because data used in this assessment originates from so many sources, the QA/QC could be a significant issue. I believe that it would be appropriate for ATSDR to, at least, review QA/QC and data validation presented with each source of data and incorporate that review in the assessment.

ATSDR did review QA/QC and data validation with each source of data beforeincorporating the data in the public health assessment. Each source was checkedfor inadequacies, insufficiencies, and discrepancies in the data and in the samplingand analytical techniques used to obtain the data. If ATSDR had found a significantissue, the issue would have been detailed in this Quality Assurance and QualityControl section of the public health assessment. No significant issues werediscovered.

50          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Quality Assurance and Quality Control, second paragraph: Please clarify. The implication is that the QA/QC of these samples is suspect.

The QA/QC of soil gas and air samples are NOT suspect. This paragraph has beendeleted from the QA/QC section.

51          ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS, Physical and Other Hazards: There was and is exposure to noise from the operation of the diesel engines. The lack of physical site control allows residents to have access to the cinder pile which still contains asbestos and heavy metals and is evidenced by the tire marks in the pile.

According to DEQ, the cinder pile still remains at the site and is accessible. Accessto this material will be addressed in the final site plan. Based on sampling of thecontents of this pile, asbestos was identified. Please refer to changes in the maintext of this subsection.

52         PATHWAYS ANALYSES, Completed Exposure Pathways, Off-site groundwater, first paragraph: This paragraph lists arsenic and lead as contaminants of concern and then states that this contamination is due to spillage of diesel fuel and cleaning solvents. Arsenic and lead concentrations in groundwater do not show any correlation with other contaminants from the rail yard. The metals appear to be naturally occurring compounds in the Livingston Aquifer.

Change noted.

53         PATHWAYS ANALYSES, Completed Exposure Pathways, Off-site groundwater, first paragraph: The volume of diesel fuel on the water table was estimated at 300,000 gallons in 1989. Since this time, recovery and, more importantly, biodegradation have reduced the apparent product thickness substantially. Therefore, there is now much less than 300,000 gallons of diesel fuel.

Change noted. According to the 1997 Annual Ground Water Sampling Report,recovery and biodegradation have significantly reduced the volume of free producton the water table. The Draft Primary-Hydrocarbon Feasibility Study Report(Envirocon, 1993) estimated the corrected volume of the free product plume to be150,000 gallons. This was determined to be a result of biodegradation, freeproduct recovery, the disruption of free product from recovery operations, anduncertainties associated with calculating volumes of free product from free-productthickness measurements in monitoring wells. Calculating the current free productvolume from free-product thickness measurements obtained during 1997 samplingresults may yield an even lower free product volume.

54          PATHWAYS ANALYSES, Completed Exposure Pathways, Off-site groundwater, first paragraph: Please refer to the March 1994 RI for a description of dates of use and sources of contaminants for the BNRY site which will more clearly bound the potential exposure dates.

Please refer to the Background section of the document which contains a SiteHistory Time Line for clarification of event dates and sources of contamination. Please refer to Table Two for a description of the time frames associated withcompleted and potential exposures.

55          PATHWAYS ANALYSES, Completed Exposure Pathways, Off-site groundwater, second paragraph: The last two sentences seem to indicate that groundwater from east of the Yellowstone River is the source of Livingston municipal drinking water. This is not true.

Change noted.

56         PATHWAYS ANALYSES, Completed Exposure Pathways, Off-site groundwater, third paragraph: The current groundwater monitoring schedule is semi-annual, not quarterly as indicated in this paragraph.

Change noted.

57         PATHWAYS ANALYSES, Completed Exposure Pathways, Off-site ambient air, second paragraph: In the final sentence it states that since the rail yard continues to operate, residents who live in the vicinity of the rail yard will continue to be exposed to PCE in air. This is not true. The present operators of the rail yard do not use chlorinated cleaners of any type. Therefore there should be virtually no emissions from current operations.

Refueling by means of a tanker truck and railcar maintenance currently occur on-site. One operator temporarily stores used oil in an above ground tank. Currentoperations will necessarily result in (unspecified) "exposures", though notnecessarily in exposures of public health concern. Chlorinated cleaners/solventsare reportedly not used on-site. Please refer to changes in the last sentence of thisparagraph in the main text.

58         PATHWAYS ANALYSES, Completed Exposure Pathways, Off-site ambient air, second paragraph: This paragraph incorrectly states that refueling continues on-site; it does not.

Also, current fueling activities are limited to the use of above ground tanks withregs in place to immediately address fuel spills. Residential exposure to dieselemissions is a current concern but not associated with BNRY remediation.

As stated previously, refueling by means of a tanker truck and railcar maintenancecurrently occur on-site. One operator temporarily stores used oil in an aboveground tank.

59         PATHWAYS ANALYSES, Completed Exposure Pathways, On-site ambient air, first paragraph: "On-site operations, cleaning operations, and maintenance" should not result in present and future exposures.

As stated previously, on-site operations will necessarily result in (unspecified)"exposures", though not necessarily in exposures of public health concern. However, the purpose of the pathways section is to identify pathways of exposure,not to evaluate their potential impact, if any, on public health.

60          PATHWAYS ANALYSES, Potential Exposure Pathways, Off-site soil gas, second paragraph: This paragraph recommends additional soil gas sampling, but the toxicological discussion eliminates this as a viable exposure pathway. Please clarify.

Soil gas measurements per se do not represent a hazard to public health, since theyare not representative of concentrations in the breathing zone. More relevantmeasurements, e.g., those taken of air in basement crawl spaces, were judged tobe of no public health concern. Nevertheless, in the absence of more completedata, ATSDR considers it prudent to continue monitoring soil gas in closed,subterranean spaces such as basements, and to sample other areas during futureexcavation activities.

61          PATHWAYS ANALYSES, Potential Exposure Pathways, Off-site soil gas, second paragraph: Is the only source of VOCs in off-site soil gas the volatilization from the VOC plume? Would this be a health concern since the VOC concentrations are in the ppb range? It is very difficult to believe that there is a potential health concern caused by soil gas volatilized from this dissolved plume and then liberated by off-site soil excavations. This potential health concern should be eliminated based on existing data.

ATSDR did not mean to imply that the primary source of soil gas is thegroundwater plume. Clearly, both soil gas and groundwater contamination share acommon source, i.e., cumulative contamination of subsurface soil. However,regardless of the original source of this contamination, soil gas measurements perse do not represent a hazard to public health, since they are not representative ofconcentrations in the breathing zone. More relevant measurements, e.g., thosetaken of air in basement crawl spaces, were judged to be of no public healthconcern. Nevertheless, in the absence of more complete data, ATSDR considers itprudent to continue monitoring soil gas in closed, subterranean spaces such asbasements, and to sample other areas during future excavation activities.

62         PATHWAYS ANALYSES, Eliminated Exposure Pathways, On-site groundwater: It would be helpful to clarify that the final clean-up remedy will insure on-site groundwater will not be used for human consumption.

Change noted. As stated previously, each of the clean-up options described in theDraft Feasibility Study includes a plan for implementing institutional controls, withthe exception of the "no action" alternative. Institutional controls, which mayinclude covenants or deed restrictions, will prevent drilling water wells for domesticuse on-site and in the adjacent areas where VOCs are at levels greater than MCLs. The final site plan is anticipated to be released in the fall of 1997.

63         PATHWAYS ANALYSES, Eliminated Exposure Pathways, On-site subsurface soil: "The implication that exposure to on-site subsurface soil is highly unlikely" should be removed. Excavation and construction activities occur often at the site and workers may be exposed to subsurface soil; however DEQ, through a screening analysis, evaluated and eliminated this exposure pathway as a health risk in the baseline risk assessment.

Significant exposure to subsurface soil is unlikely under normal circumstances. Thepossibility of exposure during future excavation activities is acknowledged in thisdocument and is specifically addressed in recommendations 3 and 4. Suchexposures, if and when they occur, will be of limited duration. Furthermore, themagnitude of such exposures will not be predicted by conventional soil gasmeasurements. ATSDR does not anticipate that soil gas will necessarily be aproblem in the future, even during excavation activities. As stated in the PHA,"Soil vapor extraction wells were included as a part of a MDHES interimremediation plan. The well system has minimized and/or eliminated the soil gascontaminant pathway for workers at BNRY."

64          PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, General: Explain why chemicals are listed without any CV's and what that means to the reader. How are they evaluated? How do you explain health effects from exposure to those substances with known toxicity (e.g. chlorobenzene, see Table 3, or fluorene, see Table 5) but no CV?

It is part of ATSDR's conservative screening policy to list as "contaminants ofconcern" not only those chemicals whose maximum concentrations exceed one ormore of ATSDR's comparison values, but also any contaminants for which ATSDRhas no comparison value. (See Appendix C for an explanation of the potentially-misleading term "contaminants of concern".) ATSDR only develops comparisonvalues for those chemicals for which there are data to suggest that they could,under certain circumstances, pose a hazard to human health, as a result of theirtoxicity, or the opportunity for widespread exposure, or both. When ATSDR has nocomparison value for a particular "chemical of concern", comparison valuesdeveloped by other agencies such as EPA, NIOSH, FDA and the ACGIH are used inthe preliminary evaluation process. When no comparison values at all are available,the scientific literature is searched for relevant experimental or epidemiologicalstudies before a conclusion is made on its public health relevance. Substanceswithout CVs usually pose little or no threat to public health and, therefore, may notbe discussed in the Toxicological Evaluation.

65         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, General: If an individual with a chronic health problem is exposed to a contaminant, how is that reflected in the consideration of the most "sensitive population." Those individuals with lupus, MS, etc. want to know if they are more sensitive to exposure and therefore not protected by the concentration referenced.

Most of ATSDR's comparison values are based on animal data and are set at levelstypically 100 to 1000 times lower than the lowest no-effect level in animals. Whenenough human data are available to establish a human no-effect level, smallersafety factors are still applied to protect "sensitive" individuals. As used here, theterm "sensitive" does not apply to people with allergies. Since allergic reactions arenot dose-related, they cannot be used as the basis for useful comparison values. Although the causes of lupus and MS are still unknown, both appear to involve agenetic predisposition toward abnormal immune responses that may be triggered bya variety of (immunogenic) environmental stimuli, including viral infections andcertain therapeutic drugs. Lupus has even been triggered by sunlight and beestings. Occupational exposures to highly reactive compounds (e.g., isocyanates)may also induce autoimmune reactions. However, ATSDR has concluded that thetypes and concentrations of contaminants detected at Livingston are notimmunogenic in the conventional sense; nor is there currently any evidence of acausative relationship between these exposures and either Lupus or MS.

66         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, General: If a "sensitive" population is exposed to a possible/probable carcinogen (e.g., children and the elderly), is their risk increased if they also have an existing health problem?

As a general rule, if an organ's functional capacity is underdeveloped (e.g., due toimmaturity) or compromised (e.g., due to disease), then that organ may becomemore susceptible to those substances that normally induce toxic effects in thatparticular organ. However, it does not necessarily follow that the underdevelopedor impaired organ (or other, healthy organs) will become unusually sensitive to allsubstances, including those which do not normally have any effect on thoseorgans. Based on current toxicological and biomedical knowledge concerning theeffects of specific environmental pollutants, there appears to be no plausible linkbetween the type or concentration of contaminants at BNRY and the specific healthproblems identified at Livingston, including MS and lupus. This conclusion is basedon the absence of any known causal relationship between the identified exposuresand the health effects of interest, and has nothing to do with the issue of relativesensitivities.

67          PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, General: There is no discussion of potential health effects from diesel fuel, TPH, hydrocarbons. Please explain why not.

Please see answer to comment number 39.

68         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, PCE: Please indicate what a town the size of Livingston could expect as far as "background" PCE concentrations in ambient air.

EPA's 1995 Urban Air Toxics Monitoring Program Report includes ambient airconcentrations of PCE for three rural towns in Vermont: Rutland, Underhill, andWinooski. Based on 88 valid samples, these data indicate that the highest reportedPCE concentration was 0.53 parts per billion volume (ppbv) and the medianconcentration was 0.02 ppbv.

69         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, PCE: There is no discussion of the additive effects on a person working at a the rail yard, living in a house with PCE present in the wells and indoor air, and eating fish from the Yellowstone. Please comment on this scenario.

In the discussion of "Combined Effects" in the Toxicological Evaluation section ofthis document, it was concluded that all of the detected chemicals combined wouldnot be expected to produce any adverse effects, because the estimated exposuredoses for each of the individual substances was far below established no-effectlevels for those substances. The studies on which this conclusion was based arecited in the text. The same argument would apply equally well to the hypotheticalexposure scenario described above. Although the definitive study on the effect ofmixtures at environmental levels has not yet been performed, research in this areaprogresses almost daily. Meanwhile, ATSDR considers that the studies cited in theToxicological Evaluation under the subheading "Combined Effects" provide anadequate basis for the professional judgements expressed.

70         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, PCE, third paragraph: Does the statement "that the relevance of animal data to humans is questionable", apply to PCE or all chemicals?

In the present case, this statement applies specifically to PCE and TCE.

71         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, PCE, third paragraph: Please provide a more definitive opinion of the likely cancer risk from inhalation or ingestion of PCE as this is the contaminant the Livingston public has been exposed to and is most concerned about. Please provide a more definitive opinion for TCE too.

Site-specific, quantitative risk assessments, if what the comment means by "amore definitive opinion", are useful for setting risk management priorities, but theydo not represent accurate predictions of the "true" risk which, according to EPA, "may be as low as zero". ATSDR public health assessments are a qualitative,narrative interpretation of the relevant scientific data as opposed to a policy-drivennumerical (i.e., statistical) approach. In its newly-revised cancer guidelines, EPAalso emphasizes the value of this narrative approach, adopting it in place of the oldalphanumeric classification system that has been used since 1984. Thus, ATSDRis not able to offer a more definitive opinion relative to the potential carcinogenicityof PCE and TCE than it has already provided in the Toxicological Evaluation sectionand in Appendix D.

72         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, PCE, Off-site groundwater: Please define past exposure risk.

ATSDR can only provide informed opinions about probable health risks during andafter periods for which environmental data are available. Since ATSDR'sconclusions were based on the maximum concentrations detected over the entireperiod for which data were available (approximately 10 years), those conclusionsshould be applicable over that entire period and for the foreseeable future as well. The identified maximum concentrations are not likely to be superseded in the futureby even higher values because contaminant concentrations have actually beendeclining for the last 6 years.

73          PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, PCE, Off-site groundwater: Please identify which private wells are used for drinking water.

The Department of Public Works reported all property within the Livingston citylimits are presently connected to the municipal water supply system. For thepurpose of this public health assessment, ATSDR conservatively assumed residentsutilized their private wells for drinking water. Contaminants were evaluatedassuming the residents were drinking water with the levels reported in Table 11.

74          PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, TCE, fourth paragraph: The ATSDR states that cancer appeared in animals treated with TCE and supports this with reference 20. (Reference 20 is an ATSDR report.) The ATSDR goes on to state "the positive animal studies are plagued by a number of problems." In the end, the reader is left to interpret the ATSDR position regarding the carcinogenicity of TCE. In the next section, private well water, the ATSDR states exceeding the MCL and CREG by three to five times respectively is not likely to produce acute or chronic health effects, implying the ATSDR does not consider TCE a carcinogen. Is this consistent with reference 20, the ATSDR report on TCE? Isn't this inconsistent with the statement made at the bottom of page 90, in the absence of compelling data to the contrary, the ATSDR policy considers it prudent to presume that a substance which causes cancer in animals may also pose a potential carcinogenic risk to humans, and that exposure to the substance should be minimized?

As stated in the Toxicological Evaluation, the animal studies of TCE are of dubiousrelevance to the evaluation of cancer risk in humans because excessively high, toxicdoses were employed and the observed tumors appear to have been the result ofspecies-specific mechanisms that are operative in rodents, but not in humans. Ifvery low levels of a substance were, in fact, carcinogenic in humans, then onewould expect elevated cancer rates to be readily detectable in large populationsexposed to high levels of that substance. However, studies in TCE-exposedworkers have been largely negative. Thus, neither the animal nor the human dataprovide convincing evidence that TCE causes cancer in humans. However, on theassumption that TCE (or PCE) can cause cancer in humans at a rate consistent withthat indicated by public health benchmarks (typically, one-in-a-million risk levels),the magnitude and duration of estimated exposures and the size of the potentiallyaffected population (less than 10,000) at Livingston would be insufficient toproduce a single excess case of cancer.

75         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, TCE, Private Well Water: How should the general public relate the MCL for TCE, which is 5 ppb, to the statement, "ATSDR considers that 15 ppb TCE in drinking water is not likely to produce acute or chronic adverse health effects."

The MCL is a level that incorporates technical feasibility, economics, and health. Itshould not be confused with a toxicity threshold, i.e., a strict demarcation betweenlevels that are safe and levels that are not. The MCL attempts to address, withinthe limits of technical feasibility, the potential for (hypothetical) cancerous effectsas well as (less-hypothetical) non-cancer effects. Based on an analysis ofepidemiological studies in occupationally-exposed populations, cancer studies inlaboratory animals, the mechanisms of action presumptively involved in each, andthe estimated magnitude and duration of site-specific exposures, ATSDR concludesthat, regardless of whether or not the CREG is exceeded, TCE (and PCE)contamination at Livingston does not represent a plausible cancer risk to localresidents.

76         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, Other Contaminants: Why was a discussion of friable asbestos exposed on the surface of the cinder pile omitted from this study?

Asbestos was not detected during any surficial soil or ambient air sampling reportedin the Final Remedial Investigation or Baseline Risk Assessment. A sample obtainedby DEQ from the surface of the cinder pile contained asbestos based on laboratoryanalysis. ATSDR was not able to obtain the sampling results from DEQ. However,this on-site cinder pile is not likely to represent a source oftoxicologically-significant exposures.

77          PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, Other Contaminants, third paragraph: Should lead be a constant that is monitored for on a regular basis as additional sources of lead contamination from older residential drinking water systems may increase exposure?

Lead has been detected sporadically in private, municipal, and monitoring wells atconcentrations ranging from not detected to 20 ppb. The EPA "Action Level" forlead is 15 ppb. The Montana Department of Public Works is required by EPA totest for lead in the municipal water supply once every 5 years. The City ofLivingston's municipal water supply has never been found to contain elevatedconcentrations of lead. No information on the age of the distribution system (pipes,etc.) is documented in available sources. As stated in the main text of the publichealth assessment, ATSDR does not consider that the few elevated readings fromoff-site monitoring wells reflect a current or future hazard to public health.

78         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, Other Contaminants, fifth paragraph: The statement regarding the supposed continued decline of contaminants needs to be followed by the stated assumption that monitoring will continue to verify the decline.

Change noted.

79         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, Combined Effects: ATSDR discusses the risks of concurrent exposure to contaminants at BNRY, specifically if these risks should be additive or not. Five studies are cited as evidence that risks of concurrent exposures are not additive. Two identical references (but included as separate references) evaluate the additive risks of exposure to compounds which target the same organ. Two of the studies focus on acute exposure (24 hrs) and two focus on intermediate exposure (14 days to 1 year). Only one study might address chronic exposure, but this study is not concerned with the suite of compounds present at the site. It is our understanding that chronic exposure is the concern at BNRY. Please explain why these references are relevant to the evaluation of additive effects of risks from chronic exposures and the BNRY site? Have there been any studies that would indicate risks from concurrent chronic exposures are additive?

No. ATSDR is not aware of any studies reported in the literature demonstratingadditivity of "risks" from chronic exposures to chemical mixtures at low,environmental levels. For the purpose of assuring conservatism in formal riskassessments, however, it is commonly assumed that such risks are additive - EPA'sHazard Index approach is an excellent example - even though less than additiveeffects are likely to predominate in the environment. Although the definitive studyon the effect of chronic, low-level exposure to mixtures has yet to be performed,ATSDR considers the studies cited in the Toxicological Evaluation to be of relevance to chronic exposures for three reasons: First, ATSDR's comparison valuesare typically 100-1,000 times lower than the relevant NOAELs, regardless of thedesignated exposure duration, acute, intermediate, or chronic. Second, only thoseenvironmental contaminants that share similar mechanisms of action might beexpected to exhibit genuine additivity of effect, and many of those may exhibitcompetitive inhibition (a less, than additive interaction), instead. Finally,conservative default estimates of exposure on which ATSDR's comparison valuesare based are likely to be higher than actual intake rates under site-specificconditions of exposure. (Please see the answer to comment number 34.)

80         PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, Combined Effects: Did all the contaminants considered in the health assessment have concentrations below the NOAELs? Does the correlation between NOAELs and potential carcinogenic effects hold?

Yes. All contaminants detected at Livingston were present at concentrations thatwere lower (usually by 1-3 orders of magnitude) than established NOAELs. ATSDRbelieves that all of the potentially carcinogenic contaminants detected at Livingstonwould present no threat of cancerous health effects, either individually orcumulatively, at the maximum levels detected. Prudent public health policy (notthe consensus of scientific opinion) currently states that carcinogens have nothreshold, and therefore no NOAEL, other than zero. However, this zero-thresholdpolicy for carcinogens is, of necessity, a conservative assumption rather than ascientific fact. (According to EPA's 1986 cancer risk assessment guidelines, "thetrue value of the risk is unknown and may be as low as zero".) Since it isimpossible to prove a negative, the general absence of a threshold for carcinogenshas not been and never will be established in the laboratory. On the other hand,there is a growing body of evidence suggesting that most, if not all, non-genotoxiccarcinogens (such as PCE, TCE, and arsenic), and at least some genotoxic ones,actually do exhibit thresholds. At the present time, however, the assumption thatall carcinogens exhibit non-zero thresholds is no more provable than the assumptionthat none do.

Fortunately, it is not necessary to resolve the zero-threshold controversy in order toanswer the present question regarding the additivity of carcinogenic risks atLivingston. If one accepts at face value both the assumption of zero-threshold forcarcinogens and the numerical conclusions of quantitative cancer risk assessments, then the chronic intake of a potential carcinogen at a level equivalent to its CREGwould, by definition, be associated with an increased cancer risk of one in a million. Similarly, a concentration 100 times the CREG would be associated with a risk ofone in 10,000. Since the population of Livingston within one mile of BurlingtonNorthern Rail Yard is only about 7,000, a site-specific practical threshold or "NOAEL" for carcinogens at Livingston would be at least 100 times the respectiveCREGs. In other words, not even one excess case of cancer would be expected in7,000 people exposed over their entire lifetimes. The average concentrations of allpotentially carcinogenic substances identified in completed pathways of exposure atLivingston, both on-site and off-site, were below this practical threshold. In privatewells, only the maximum detected concentrations of PCE (96 ppb) and arsenic (15ppb), exceeded the site-specific, practical threshold for cancer, and neither of thesemaximum concentrations was representative of probable lifetime exposure levels. (Cancer-based comparison values are based on the assumption of lifetimeexposure.) However, it must be re-emphasized that, based on the availableevidence from animal and human studies, it is not clear that even lifetime exposureto PCE and arsenic at these levels would pose a credible risk of cancer in humans. (For the basis of the latter conclusion, please see the relevant discussions in theToxicological Evaluation and Appendix D, "PCE Carcinogenicity".)

81          PUBLIC HEALTH IMPLICATIONS, Toxicological Evaluation, Combined Effects: The section on combined effects of individual contaminants does not instill much confidence in your conclusions. Unsubstantiated inferences are made because it sounds like there is a lot you really don't know. The explanation by the toxicologist at the Livingston meeting didn't quell any of my questions or doubts either. Most of the ATSDR's conclusions are derived from studies of what people have died from, and not the effects on growing children and living adults. What about the effects on a developing fetus? I don't see this addressed.

None of ATSDR's conclusions are "derived from studies of what people have diedfrom". All health agencies, including ATSDR, give precedence to studies of effectsin "growing children and living adults", whenever such data are available. Whenuseful human data are available, they are usually derived from populationsexperiencing unusually high levels of exposure, either occupationally or as a resultof serious environmental accidents. However, since relatively unambiguous data ondose-response relationships in human populations are usually unavailable - forethical reasons, conditions of exposure cannot be controlled and manipulated inpeople the way they can be in laboratory animals - the majority of all health-basedbenchmarks, regardless of source (ATSDR, EPA, FDA, NIEHS, etc), are derivedfrom studies in laboratory animals. Whether animal or human data are used,ATSDR comparison values are based on the estimated no-adverse-effect level(NOAEL) or lowest-adverse-effect level (LOAEL) for less serious effects, as opposedto serious or even lethal effects. This is yet another way that ATSDR attempts toassure that its conclusions are conservatively protective of public health.

82          PUBLIC HEALTH IMPLICATIONS, Health Outcome Data, first paragraph: Please comment on the availability of health data to determine morbidity prevalence rates for Lupus, multiple sclerosis, and liver disease.

At this time, ATSDR has not identified any health data concerning the prevalencerates for Lupus, multiple sclerosis, and liver disease.

83         PUBLIC HEALTH IMPLICATIONS, Health Outcome Data, first paragraph: It would be helpful to provide additional statistics on disease prevalence for towns the size of Livingston with a similar industrial base if such statistics exist.

At this time, ATSDR has not identified any additional statistics on diseaseprevalence for towns the size of Livingston.

84         PUBLIC HEALTH IMPLICATIONS, Community Health Concerns Evaluation, first paragraph: The statement that the B street well is on the edge of the contaminant plume is misleading. It is actually located about 3 blocks south of the plume.

Also, the B street municipal water well is not on the edge of the chlorinated VOCplume as is indicated by the last sentence. The B street well is up gradient fromthe entire chlorinated VOC plume.

Change noted. ATSDR agrees that the B Street well is not located directly on theedge of the plume but is located approximately 3 blocks south/southwest (and upgradient) of the contaminant plume.

85         PUBLIC HEALTH IMPLICATIONS, Community Health Concerns Evaluation: This study was requested to specifically address community health concerns. This discussion appears to summarily minimize these concerns and does not go into the detail the community expected.

ATSDR has attempted to objectively address as fully as possible all of thecommunity health concerns it has received from the residents of Livingston, makingfull use of existing environmental and health data. ATSDR cannot guarantee thatthe conclusions of the public health assessment will necessarily support or confirmthe beliefs and opinions of local residents. It is even (though not likely) thatcurrently unavailable data would provide the basis for a different conclusion. ATSDR may perform limited, targeted exposure investigations and/or health studiesdesigned to generate new data when there is a plausible association between site-related contaminants and known or potential adverse health effects at the site. However, this criterion was not satisfied at Livingston. In cases where the publichealth issues or problems at a site do not fall within the purview of ATSDR, theAgency refers those issues/problems to other appropriate federal, state or localgovernmental entities.

86         PUBLIC HEALTH IMPLICATIONS, Community Health Concerns Evaluation, third paragraph: I feel that the ATSDR has glossed over the longstanding concerns of the community that lupus, MS, and other disorders with an auto immune component have a higher incidence in Livingston. In spite of repeated requests, and several health studies conducted in Livingston looking at other disorders, this concern remains unanswered. Why? Just because there are no registries for these disorders, does that mean it is impossible to study them? The toxicologist's conclusion that if there were increased incidence of these disorders in Livingston, it could simply be attributed to a cluster of genetically-predisposed individuals is ludicrous. What is this conclusion based on? The report states on page 46: 'Data on specific incidence of lupus and MS in Livingston were not available for review.' That is because it has never been investigated. Can this issue be studied once and for all?

Also, why was pancreatic cancer chosen? Why were there no disease andsymptom prevalence studies, other than pancreatic cancer, preformed to addresscommunity health concerns regarding the excessive number of such healthconcerns as multiple sclerosis, miscarriages/birth defects, lupus, etc., prior todetermining there was no apparent health affect?

As stated previously, ATSDR has made full use of existing environmental andhealth data in an attempt to address fully and objectively all of the communityhealth concerns expressed by the residents of Livingston. However, it is not withinATSDR's purview to study the incidence of lupus and MS in Livingston in theabsence of a plausible connection between these diseases and site-relatedcontamination. (See the answer to comment number 85.)

ATSDR was notified by the state concerning a possible pancreatic cancer cluster. ATSDR decided it should be looked into because of the potential chemicalcontamination which is the reason ATSDR was created; ie., investigate possiblehealth effects of environmental chemical contamination.

87          CONCLUSIONS: In the conclusions, ATSDR makes many statements concerning the source of observed contamination. However, in the Foreword of this document ATSDR states, "the aim of these evaluations is to find out if people are being exposed to hazardous substances and, if so, whether that exposure is harmful and should be stopped." We believe that in providing opinions as to the source contamination the ATSDR has inappropriately gone beyond the scope of a public health assessment. These statements exist in conclusions 3, 4, and 5.

Actually, throughout the document ATSDR provides statements concerning thesuspected sources of observed contamination. In the Pathways Analyses section, anecessary part of defining 'exposure' is determining the suspected source ofcontamination as it is one of the five pathway elements. Without knowing wherethe contamination is originating from, ATSDR cannot make recommendations toreduce or eliminate the exposure.

88          CONCLUSIONS, Conclusion 1: Please define better for the citizens of Livingston why exposure does not equal health problems and relate past, present, and future exposures to the success of the on-going remediation of the rail yard contamination.

Exposure does not necessarily result in toxicity for the same reason that eatingdoes not always result in satisfaction. In both cases, the mere fact of "intake" is aprerequisite, but the determining factors will be "what" and "how much". Pleasesee the introductory remarks of the Toxicological Evaluation and Appendix C for anexplanation of this point, as well as descriptions of the various comparison values,their use and limitations, and a clarification of the term, "contaminants of concern". As stated in the public health assessment, the maximum environmentalconcentrations of the "contaminants of concern" detected most often and at thehighest levels at Livingston (i.e., PCE, TCE, DCE, toluene, arsenic, and cadmium)translate into exposure doses that are too low to represent a probable hazard tohuman health either now or in the future. Concentrations of these contaminantshave continued a long-term decline over the last six years, and there is no reason tobelieve that this trend will reverse itself in the foreseeable future.

89          CONCLUSIONS, Conclusion 2: The past completed exposure pathway needs to be better bound by dates and information as available.

A past completed exposure to groundwater (contaminants) has occurred forresidents drinking water from private wells with VOC contamination. There are nodetailed data that would allow ATSDR to further characterize these past exposures. BNRY has been around for a hundred years. Only the residents know how long andto what extent they have been using their private wells as a source of drinkingwater. However, the detected concentrations of contaminants are below levelsthat might cause adverse health effects.

90         CONCLUSION, Conclusion 4: The comment regarding known exposure to PCE not expected to be of health concern needs to be restated as the concern is still there especially since the contaminant will continue in the environment. Please make a more definitive statement on health conclusions. The statement regarding worker exposure to cadmium and arsenic raises the question of PCE and other VOC exposures to workers as was brought up at the public meeting.

As used by the ATSDR, the term "contaminants of concern" has a very specificmeaning that has nothing to do with "concern" in the conventional sense of theword. (See the opening comments of Appendix C "Comparison Values".) Currentlevels of exposure at Livingston do not represent a hazard to public health. Nor arethey likely to in the future, since the concentrations of contaminants are continuinga 6-year decline. ATSDR can make no more definitive a statement than this, basedon the data currently available. If by "a more definitive statement" the respondentmeans a quantitative cancer risk assessment, it should be noted that theseinstruments were initially designed for numerically ranking sites for clean-up andthat they do not provide realistic estimates of the "true" risk of excess cancer,which may actually be as low as zero (EPA's 1986 Cancer Risk AssessmentGuidelines).

91          CONCLUSIONS, Conclusion 6. Although soil gas is not representative of breathing zone exposures, EPA does use direct reading instruments, e.g. photo-ionization detectors (PIDS), to establish non-chemical specific quantities to indicate when personnel protective equipment should be changed. This indicates a rationale on that Agency's part to attempt a correlation between emissions and ground level to the potential for worker inhalation. Why isn't that a valid approach for estimating worker exposures in this case?

Such non-chemical-specific measurements are of practical value in the conservativemanagement of worker exposures in "real time". However, no one, includingATSDR and EPA, would (or could) use such measurements for "estimating workerexposures". Meaningful exposure assessment requires more data of a morespecific nature. It would be up to EPA to decide whether the potential health risksof the activity in question warranted the collection of additional data of higherquality. ATSDR's recommendations do not force EPA to do anything that it mightconsider unwarranted under a given set of circumstances.

92          CONCLUSIONS, Conclusion 7: Is there a risk of additive effects for workers potentially exposed to soil gases at the rail yard who then go home to a house where off-site soil gas studies indicate an elevated level of VOC's?

No. Soil gas measurements per se do not represent a hazard to public health, sincethey are not representative of concentrations in the breathing zone. More relevantmeasurements, e.g., those taken of air in basement crawl spaces, were judged tobe of no public health concern. Regarding the potential for additivity, see thesubsection entitled "Combined effects" in the Toxicological Evaluation.

93          RECOMMENDATIONS, General: All of the statements in this section recommend continued sampling and avoiding exposure to contaminated groundwater, etc. This implies that there are in fact potential health issues associated with such exposure in fact the Appendix on PCE carcinogenicity states that ATSDR policy is to recommend that exposure be minimized to potential carcinogens. Please elaborate why minimizing exposure to contaminants is a generic good health practice even though it is unlikely that past, future or continued exposure has or will cause health problems, including cancer.

True, the substantial amount of data available to ATSDR does not suggest that anypublic health hazard currently exists or is likely to exist in the future, under presentconditions. However, prudent policy would indicate that sampling be continued tomonitor future conditions of contamination and exposure that may alter theconclusions and recommendations of this public health assessment.

94          RECOMMENDATIONS, Recommendation 1: ATSDR indicates that additional sampling of private water wells is necessary to complete the assessment of health risks (summary section). BNRY and DEQ have conducted several phases of private water well sampling since 1989. There are no private water wells within the VOC plume that are used for drinking water. Moreover, due to many years of groundwater sampling in monitoring wells, the control on the distribution of VOCs in the ground water is quite reliable. The VOC concentration in the VOC plume have declined dramatically since most of the private well samples were collected. Consequently, there is no reason to recommend additional sampling.

Notwithstanding ATSDR's conclusion to the contrary, many residents of Livingstoncontinue to be concerned about the potential for site-related adverse health effectsin Livingston, Montana. The evolving status (whether improving or declining) of apotential public health hazard is ascertainable only if the relevant environmentalmonitoring data are available and up-to-date. (See response to comment number93.)

95         RECOMMENDATIONS, Recommendation 1: Based on sampling results from monitoring wells, there is very good control over the position of the north boundary of the VOC plume. This boundary is south of all of the private wells north of the site. Therefore, there is no need to sample these private wells again. There are no private water wells east of the Yellowstone River for several thousand feet. It is therefore very unlikely that any of these wells are close enough to be impacted. This recommendation should be deleted.

ATSDR agrees that, based on logical assumptions, significant contamination ofprivate drinking water wells North of BNRY or East of the Yellowstone River is"unlikely". However, given the established existence of significant groundwatercontamination and the limited predictability of groundwater movement in fine detail,ATSDR considers it preferable to base an assessment of the safety of a family's drinking water supply on actual data. It should be pointed out, however, that noneof ATSDR's recommendations are mandatory for EPA, or any other Agency, to doanything that it might consider unwarranted under a given set of circumstances. (See response to comment number 93 and 94.)

96          RECOMMENDATIONS, Recommendation 1: This recommendation should include a recommendation for on-site contaminated groundwater.

Change noted.

97         RECOMMENDATIONS, Recommendation 2: Metals such as arsenic and cadmium are not chemicals of concern at the rail yard. They are not elevated in on-site subsurface soils and no remedial actions are anticipated for metals. Both the upwind and downwind ambient air sample locations showed arsenic and cadmium concentrations above CREG values. Therefore, further collection of PM10 samples and analyses for metals is not warranted. On-site air sampling (employee work zone monitoring) for VOCs may be necessary during remedial actions conducted at the electric shop. This is the only area on the rail yard where soil contains VOCs above the soil clean-up levels. This recommendation should be deleted.

ATSDR agrees that airborne arsenic and cadmium do not appear to represent aplausible public health risk at Livingston at this time. Although atmosphericconcentrations of arsenic and cadmium at Livingston exceeded ATSDR's CREG's,the mean levels listed in Table 7 are comparable to levels reported in manyuncontaminated rural areas in the U.S. This is not an uncommon situation withnaturally-occurring metals, tempting one to conclude not that the environmentalconcentrations are too high, but that ATSDR's CREGs (or, rather, the cancer slopefactors on which they are based) are too low. Nevertheless, arsenic and cadmiumwere higher downwind than upwind of BNRY. The difference was even morepronounced with lead and zinc, but ATSDR had no comparison values for these (ormost of the other) metals in air. Additional PM10 sampling and analysis wouldbetter characterize air emissions at BNRY, particularly during remedial activities.

98          RECOMMENDATIONS, Recommendation 3: Nearly all of the homes that have basements overlying the dissolved VOC plume were sampled in the prior investigation. Since that time the concentrations in the dissolved VOC plume have steadily declined. If the results of basement air samples taken in 1991 through 1993 revealed concentrations that are not expected to cause adverse health affects, then the current conditions should have an even lower potential to cause such problems. Therefore, further sampling is not necessary. This recommendation should be deleted.

The described scenario is not an unreasonable one. However, the only way that itcan be verified is through additional monitoring. Furthermore, the emphasis of therecommendation is on "new areas where soil may be disturbed", as well as on"basement areas of existing homes". Neither focus should result in unnecessary orredundant activities, provided that professional judgement is appropriatelyexercised.

99          RECOMMENDATIONS, Recommendation 4: Monitoring employees in underground or confined spaces is the responsibility of the present operators on the rail yard. It should not be a part of the long term monitoring plan described in the final remedy. This recommendation should be deleted.

It is unimportant who does this monitoring, as long as it is done. Therecommendation only specifies what an on-site monitoring program should include,not who it should implement it.

100          RECOMMENDATIONS, HARP Statement: Please explain who HARP is.

The process of recommending follow-up health activities is monitored by the HealthActivities Recommendations Panel (HARP). This panel consists of representativesfrom each Division in the Agency with expertise in environmental health, medicine,epidemiology, health education, and toxicology. Each draft public healthassessment is reviewed to determine if further health activities are indicated.

101          RECOMMENDATIONS, HARP Statement: ATSDR received comments concerning the health education activities the Division of Health Education and Promotion had planned for this site.

At this time, the Division of Health Education and Promotion determined furtherhealth education activities are not warranted.

102          RECOMMENDATIONS, HARP Statement: How will ATSDR become aware of additional data requiring further study or action and how will Livingston be made aware of future information (including additional toxicological or health outcome data) that may be pertinent to this study's conclusions?

ATSDR will receive additional information concerning this site from the MontanaDEQ. If ATSDR receives additional data that is pertinent to the conclusions andrecommendations of this public health assessment, ATSDR will release a reviseddocument which will include the additional data and health determinations. Theresidents of Livingston will be made aware of any revisions through public notice inarea television stations, radio stations, and newspapers. However, because thelevels of contaminants have demonstrated a 6 year decline, ATSDR does notexpect any new data to alter the conclusions and recommendations set forth in thispublic health assessment.

103          Conclusions vs Recommendations: There is an apparent inconsistency between the Conclusions and Recommendations of this report. Conclusion 1 states "future exposures are possible. However, based on the available data, these exposures are not expected to cause adverse health effects." But in the Recommendation 1, ATSDR states "Efforts should be made to prevent human exposure to contaminated groundwater." Why should this effort be made if there is no adverse health effects?

It is true that, based on currently available data, future exposures are not expectedto be hazardous. However, future conditions cannot be projected with certainty. Therefore, it is prudent to remain vigilant and avoid unnecessary exposure todrinking water contaminants in the future.

104          RECOMMENDATIONS, Public Health Action Plan, ACTIONS PLANNED, first, second and third paragraph: Change MDHES to DEQ in the Actions Planned Section.

Change noted.

105          APPENDIX C, Figures: Several comments were received asking ATSDR to provide additional figures and maps.

ATSDR provided figures and maps to assist the reader in understanding the publichealth assessment and believes the figures and maps currently contained inAppendix C are sufficient.

106          APPENDIX C, Figure 6: Figure 6 depicts shading inside site boundaries for 'Females Aged 15-44' and 'Children 6 Years and Younger'. This seems unfeasible.

Shaded areas in demographic distribution maps depict population totals within eachCENSUS block boundary. The different shadings represent amounts within aboundary, not the exact location.

107          APPENDIX D, PCE: The ATSDR states "However, in the absence of compelling data to the contrary, the ATSDR policy considers it prudent to presume that a substance which causes cancer in animals may also pose a potential carcinogenic risk to humans, and that exposure to the substance should be minimized." However, in the discussion of PCE in off-site groundwater, carcinogenic risks are ignored. This seems like a major inconsistency.

Since it is impossible to prove a negative, "compelling data to the contrary" shouldnot be interpreted as a requirement for "proof" of non-carcinogenicity in humans. The current weight of evidence from both human and animal studies fails tosupport the assumption that either PCE or TCE is a human carcinogen underexisting occupational and environmental conditions of exposure. The apparentinconsistency of conclusions between various agencies (e.g., ATSDR, EPA, andIARC) is less the product of radically different interpretations of the scientific datathan it is a reflection of the different administrative policies and procedures of thoseagencies. For additional discussion, please see the answer to the comment number74 as well as Appendix D, PCE Carcinogenicity.

a. One micron is equal to one-millionth of a meter or 0.000001 meter.

b. Contour plots are lines that run through sample collection points that show similar concentrations.

c. All values from reference (16).

d. ND = not detected.

e. All values from reference (16).

f. BDL = below detection limit.

g. All values from reference (16).

h. Detected at the same concentration in duplicate samples.

i. Not analyzed.

j. Below Detection Limit.

k. All values from reference (16).

l. All values from reference (16).

m. All values from reference (16).

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