PUBLIC HEALTH ASSESSMENT

MCCLELLAN AIR FORCE BASE
SACRAMENTO, SACRAMENTO COUNTY, CALIFORNIA


APPENDIX D: HEALTH CONSULTATION ON OU B1 PCBS

Appendix D was not available in electronic format for conversion to HTML at the time of preparation of this document. To obtain a hard copy of the document, please contact:

Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Attn: Chief, Program Evaluation, Records, and Information Services Branch E-56
1600 Clifton Road NE, Atlanta, Georgia 30333


APPENDIX E: HEALTH CONSULTATION ON PRIVATE WELL SAMPLING

Appendix E was not available in electronic format for conversion to HTML at the time of preparation of this document. To obtain a hard copy of the document, please contact:

Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Attn: Chief, Program Evaluation, Records, and Information Services Branch E-56
1600 Clifton Road NE, Atlanta, Georgia 30333


APPENDIX F: CLINICAL DESCRIPTIONS

The following are clinical descriptions of diseases about which the community had questions.

Gout

Gout is a rare metabolic disease that may develop for a variety of reasons. In most of the western world the overall prevalence is 0.13 to 0.37 percent of the population (1). It is characterized by high levels of uric acid in the blood and recurrent attacks of acute arthritis, usually affecting one joint (1-4). It may be accompanied by the deposit of urate crystals in subcutaneous tissue called tophi, especially around joints, leading to deformities and crippling. The joint most frequently affected is the metatarsal phalangeal joint of the big toe; other joints include those of the feet (tarsal and metatarsal) and the ankles, and knees. The arthritis is a result of deposits of monosodium monohydrate urate crystals in a joint, followed by infiltration of white blood cells that engulf these crystals. Because these white cells are unable to digest these crystals, it results in the death of the cells releasing irritating lysosomal enzymes into the joint causing inflammation, swelling, and pain. The kidney is affected in varying degrees; kidney stone may develop as a result of the excretion of high concentration of uric acid. Sometimes kidney damage is the most prominent feature of gout.

Gout is classified as primary or secondary, according to the origin of increased blood concentrations of uric acid (2-4). Primary gout is an inheritable disease characterized by overproduction and/or underexcretion, resulting in high levels of uric acid in the blood (hyperuricemia). Secondary gout is related to acquired causes of hyperuricemia such as diuretic use, myeloproliferative (unusual bone marrow growth) disorders, multiple myeloma, chronic hemolytic anemia, chronic kidney disease, and lead poisoning (2).

Graves' Disease

Graves' disease is characterized by an enlarged thyroid gland which produces an excess amount of thyroid hormone. As a result of the increase in thyroid hormone, patients may have the following symptoms : weakness, weight loss, nervousness, heat intolerance, heart disturbances, tremors, and exophthalmos (bugging eyes). Not all of those symptoms need be present, however, for the diagnosis of Graves' disease to be made (4-6). Graves' disease occurs in about 2.7 % of women, and 0.23 of men (5). The disease seen more frequently in people with a family history of people with the disease than those with no such history. It has a familial tendency, and histocompatibility studies have shown an association with halotype groups HLA-B8 and DW3 (DRW3) in caucasians, HLA-Bw36 in Japanese, and HLA-Bw46 in Chinese (1,4). In addition, among family members of patients with Graves' disease, a clinical and immunologic overlap exists with respect to Hashimoto's disease, primary thyropprivic hypothyroidism, pernicious anemia, myasthenia gravis and diabetes (1,4). It is believed to be an autoimmune disease, meaning that the body's immune system produces antibodies against itself (6). In this case, antibodies are produced against the Thyroid Stimulating Hormone receptors of the thyroid gland (4,6). For unknown reasons, the immune system recognizes them as foreign and begins to produce antibodies against them. The antibodies typically either damage the thyroid gland or bind to it stimulating the thyroid gland to produce more hormone (4-6).

Major Depression

Major depression is diagnosed when an individual experiences a disturbance in mood resulting in a loss of interest in all or almost all usual activities and pastimes. Major Depression is associated with at least four of the following symptoms, which are continuous over two weeks: poor appetite or significant weight loss without dieting, or significant weight gain; insomnia or sleeping too much; agitation or slowed movement; loss of interest or pleasure in usual activities or decrease in sexual drive; loss of energy or fatigue; feelings of worthlessness, self-reproach, or excessive or inappropriate guilt, diminished ability to think or concentrate, slowed thinking, indecisiveness not associated with marked loosening of association or incoherence; or recurrent thoughts of death or suicide, wishes to be dead or suicide (7).

  1. Wilson J D et al. eds. Harrison's Principles of Internal Medicine. 12th ed. New York: McGraw-Hill, Inc. 1991.


  2. Kelly WN, Fox IH, Palella TD. Gout and Related Disorders of Purine Metabolism. In: Kelly WN, Harris ED, Ruddy S, Sledge CB. eds. Textbook of Rheumatology. 3rd ed. Philadelphia: WB Saunders, 1989:1395-1435.


  3. Talbott JH. Gout. 3rd ed. New York: Grune & Stratton, 1967.


  4. Schroeder SA, Krupp MA, Tierney LM, McPhee SJ. eds. Current Medical Diagnosis and Treatment 1990. Norwalk: Connecticut, 1990.


  5. DeGroot L et al. eds. Graves' Disease and the Manifestations of Thyrotoxicosis. In: The Thyroid and Its Diseases. 5th ed. New York: John Wiley and Sons, 1984.


  6. Mckenzie J, Zakarija M, Hyperthyroidism. In Endocrinology, 2nd ed. Vol 1. Philadelphia: WB Saunders, 1989.


  7. Weisman M et al. Affective Disorders. In: Psychiatric Disorder in America: The Epidemiologic Catchment Area Study. New York: The Free Press, 1991.

APPENDIX G: COMMENTS ON THE MCCLELLAN AFB PHA

The following comments were received by ATSDR in response to the public comment period for the McClellan Air Force Base PHA. This list of comments does not include editorial comments concerning word spellings, sentence syntax, etc. It does not include comments on the accuracy of stated facts. If the accuracy of a statement was questioned, the statement was verified or corrected. Some comments were paraphrased by ATSDR for brevity or clarity. If the same comments were received from more than one source, only one comment and response is listed. ATSDR's response (in bold) follows each comment.

  1. Base well # 18 is a well used for drinking water that has been shown to be contaminated with VOCs, and located in an area where three major groundwater flow directions converge underneath the McAFB site. Describe the "activated carbon treatment system" used to treat water coming from BW 18; show data on water quality for BW-18 before and after the treatment system; specify when the system was installed.

    2. This information has been added to the text.

  2. Briefly describe the groundwater extraction treatment system near building 655, as well as the groundwater extraction system operation at Operable Unit (OU) C that treats simultaneously water from OU D. What is the use of the water after treatment? What type of extraction and treatment do they use? Describe the method of disposal of the extracted contaminants, i.e., thermal destruction, absorbed in carbon filters, or emissions from a stripper? Show efficiency of decontamination, and the nature and concentration of contaminants. The Report should briefly describe the efficiency of contaminant removal. Mention if the groundwater extraction and treatment program has been approved by the Regional Water Quality Control Board.

    3. Additional available information has been added to the text.

  3. A groundwater plume on OU D identified in 1979 is mentioned on page 5. Define exactly the identity of this plume by referring to the aquifer in which it is present. It is unclear what is the nature, magnitude or extent of the contamination.

    4. Although the groundwater system under McClellan Air Force Base functions more as a single unit than as separate hydrostratigraphic units, the groundwater subsurface has been divided into five distinct monitoring zones based primarily on geophysical logs between pilot borings. The zones and approximate thicknesses are: Zone A - 25 to 45 feet thick; Zone B - 50 to 65 feet thick (except in Operable Unit B where it ranges in depth from 1900 to 2100 feet); Zone 3 - 65 to 75 feet thick; Zone D - 65 feet thick, and Zone E -70 feet thick. Trichloroethene (TCE) appears to be the major groundwater contaminant in Operable Unit D. TCE concentrations are greatest in Monitoring Zone A and decrease in Monitoring Zones B and C. Groundwater extraction wells in Operable Unit D appear to be limiting the downward migration of contamination (Installation Restoration Program , McClellan Air Force Base Comprehensive CERCLA Workplan, Radian Corporation, July, 1991). Contaminant concentrations of concern for monitoring wells in Operable Unit D are presented in Table 2 of the Environmental Contamination section.

  4. The PHA describes that soil boring analyses have shown that solvents and metals have migrated down to 80 feet below ground surface from building 666, located on OU B, site 47. Show in a map, the exact location of building 666. These results suggest that the water table at McAFB, located at 80-110 feet below ground surface, may have been contaminated with solvents and metals migrating from building 666. Although building 666 is described as having been an electroplating shop and later a hazardous waste storage area, the Report describes the site as "a probable source of a TCE/PCE in the groundwater migrating southwest from the area." The ATSDR report should describe the type and level of contaminants other than TCE/PCE, including heavy metals. Nowhere in the ATSDR report is the contamination from this hot spot described.

    5. The contaminants detected around building 666 are discussed in the Environmental Contamination section of the public health assessment.

  5. The PHA mentions an "earthen cap" constructed over the OU D area. That area is actually covered by a formal capping system. An earthen cap is equivalent to stating that the area was covered with dirt. Briefly describe the actual capping of the area.

    6. This information has been added to the text.

  6. The PHA site description maps should show a wind rose with prevalent wind direction. This information would help in understanding the direction of migration of contaminants, whether they are off of or on to the McAFB site. That information would clarify that although all on-base housing and recreation areas are upgradient from groundwater plumes, they seem to be downwind or marginally downwind from on-site originating atmospheric contaminants.

    7. A wind rose has been added as Fig. 8. The wind rose is discussed in the Completed Off-site Ambient Air Pathway portion of the Pathways Evaluation section.

  7. The PHA states that on-site production wells are about 145-400 feet deep, and that they are locally hydrologically interconnected, allowing vertical movement of water and contaminants. At what depth is production well 18 screened? Describe the relative location of the various aquifers existing in the McAFB area.

    8. Base well 18 (BW-18) is 408 feet deep and has four screen intervals occurring from 169-185, 210 to 260, 304 to 349, and 378 to 387 feet below ground surface. Although the groundwater system under McClellan Air Force Base functions more as a single unit than as separate hydrostratigraphic units, the groundwater subsurface has been divided into five distinct monitoring zones based primarily on geophysical logs between pilot borings. The zones and approximate thicknesses are: Zone A - 25 to 45 feet thick; Zone B - 50 to 65 feet thick (except in Operable Unit B where it ranges in depth from 1900 to 2100 feet); Zone 3 - 65 to 75 feet thick; Zone D - 65 feet thick, and Zone E -70 feet thick. This monitoring zone approach was necessary to apply groundwater investigation tools such as numerical modeling and contouring of aquifer parameters. Most of the pumped water from base well 18 is drawn from the deeper, less contaminated D and E zones (Preliminary Groundwater Operable Unit Remedial Investigation, Final Report, Radian Corporation, September, 1992).

  8. If the source for drinking water changes, or levels of production from supply wells changes, the groundwater flow could be locally affected. Then a potential exists for more rapid movement of contaminants off-site.

    9. Changes in pumping rates from supply wells may indeed affect the direction and flow rate of contaminated groundwater. However, the Air Force has installed a groundwater extraction system in Operable Units B, C, and D to limit offbase migration of groundwater contamination. The Air Force also has a network of monitoring wells in place to evaluate the nature of groundwater contamination as well as the extent and movement of groundwater contamination. The Air Force monitors drinking water supplies to make sure that they are in compliance with Safe Drinking Water Act requirements and thus safe to use.

  9. The community health concerns in the PHA-Public Comment Release are identical to those found in the previously-released "red cover" PHA. If additional community health concerns were raised during the March and May public meetings, they should be incorporated into the final PHA.

    10. ATSDR has incorporated the community concerns raised during the March and May public meetings and has responded to them accordingly.

  10. The health concerns expressed by the local community deserve forthright answers based on good science. Most of these concerns could be more appropriately addressed by conducting a detailed health risk assessment on this site. The starting point is a thorough site characterization, describing the nature, severity and extent of the contamination. A sound response can only be attempted once all data generated from the McAFB site becomes available for evaluation and analysis.

    11. ATSDR agrees that community health concerns deserve forthright answers based on good science. ATSDR approaches the health issues at McClellan AFB from a public health perspective instead of a regulatory or engineering perspective. A public health assessment is the review of available data and information on hazardous substance releases into the environment in order to determine any studies or actions needed to evaluate and mitigate or prevent health effects resulting from exposures to hazardous substance releases. Although all of the information characterizing the nature, severity, and extent of contamination is not available for McClellan Air Force Base, and will likely not be available for several years, ATSDR believes that it is appropriate to review the available data to determine if exposures are currently occurring that need to be stopped, if additional sampling data are needed to fully evaluate a potential exposure, or if a health study or health education are indicated. To delay such public health actions for several years until a site is fully characterized is not prudent public health practice.

  11. Little information is given with regard to the critical assumptions, formulas, and experimental data utilized for the calculation of ATSDR's various health comparison values (e.g., environmental media evaluation guides (EMEGs), cancer risk evaluation guides (CREGs), and minimum risk levels (MRLs). Viewing the critical importance of these health comparison values, it is imperative that all pertinent information be provided, so that the scientific credibility of the derivation of these values can be independently assessed. Please include the calculations of exposure values using the EMEGs, MRLs, and CREGs for the contaminants in an appendix to the PHA.

    12. A public health assessment is not the appropriate forum to present the logic, algorithms, and research data needed to develop Minimal Risk Levels (MRL), Environmental Media Evaluation Guides (EMEGs), and Cancer Risk Evaluation Guides (CREGs). (The Endangerment Assessments prepared by the Air Force under the IRP also do not include this type of information.) The derivation and use of EMEGs and CREGs is discussed in the ATSDR Public Health Assessment Guidance Manual (Public Health Assessment Guidance Manual, U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry, Atlanta, Georgia 30333, 1992). General guidelines for developing MRLs has been added in Appendix D. The Toxicological Profiles developed by ATSDR for hazardous substances found at waste sites discuss the specific assumptions used to derive specific MRLs. To ensure the scientific credibility of the Toxicological Profiles, ATSDR submits the Toxicological Profiles to independent scientific peer review before final release. Other health guidelines such as Cancer Slope Factors, Reference Doses, etc that may be used in public health assessments are developed by other agencies such as the U.S. Environmental Protection Agency. These guidelines are available on the EPA's IRIS database and they are the same guidelines used by the Air Force when performing Endangerment Assessments.

  12. It should be clarified that the chronic RfD is an estimate of the lifetime average daily exposure to a contaminant that is unlikely to result in adverse health effects. As shown, the statement reads that a single daily exposure does not result in adverse health effects.

    13. The RfD definition has been corrected in the text (Environmental Contamination and Other Hazards) to reflect that the value represents a lifetime exposure that is unlikely to result in adverse health effects.

  13. Explain whether the expression "indicator chemical" means that TCE is one of many contaminants found in groundwater, or if it means that TCE is used as a surrogate for all other contaminants. The approach of using TCE as a surrogate indicator chemical for contamination in groundwater production wells is not acceptable. Health risks, as defined by ATSDR, are the result of multiple-contaminant, multiple-pathway components, and NOT the result of a single toxicant.

    14. Since TCE was present at higher concentrations and/or occurred as a contaminant more frequently than other VOCs, it was the chemical discussed in most early 1980s groundwater reports. Other chemicals, present at lower levels in the groundwater were not reported in the summary documents reviewed by ATSDR for the public comment release of the PHA. However, more complete information on other VOC contaminants has been provided to our agency and those data are included in the final version of the PHA.

  14. Results shown in table 1-A for TCE in on-site production wells are useful but insufficient. Expand with data between '81-'92 on TCE and other contaminants. Can you explain why some base wells shown in Table 1-A were "monitored" at up to 2000 ug/L while others were taken off line at trace levels of TCE? Describe which production wells are still in use, and what are the current contaminant levels.

    15. McAFB determined when to take a BW off line (removal as a drinking water production well). All were removed when levels of TCE were high enough to affect TCE levels at the distribution point except BW #2. Why that well was removed with "trace levels" is unknown to ATSDR. However, later sampling did indicate higher contamination in that well. Further data has been provided to ATSDR on analyses results for BWs between '81 and '93; data included closure wells and those currently in use. Those data were reviewed and included, as appropriate, within the document.

  15. Further information on current testing of production wells, both on and off base, would be helpful. Some people still are concerned that their health may be currently affected by contaminants in the drinking water.

    16. Testing of active base production wells occurs for VOCs every two weeks, except BW #18 which is sampled weekly (and has the filter treatment system). Distribution points are sampled monthly. The base also samples each BW and the beginning point in the distribution system annually for metals, inorganics and a wide range of synthetic organic compounds. The frequency of testing is much more often than required by the Safe Drinking Water Act. The base has undertaken such a testing program to assure that the drinking water supply today is not affected by the environmental contamination.

    City production wells are sampled on schedules established by the state for safe drinking water. Further protection is offered to the residential community by the McAFB monitoring well system off base. The detection of any contaminants moving toward the city wells would be determined by quarterly MW sampling at wells near the city wells. All data from the MW sampling are reviewed carefully by the agencies involved with the NPL site.

  16. The following comments were received concerning filtered versus unfiltered groundwater samples:

    17. The PHA states that water analysis was conducted on filtered water. Since on-site and off-site McAFB personnel and residents have used or are still drinking unfiltered water, the health assessment should only be made based on analytical data from unfiltered water. Heavy metals absorbed to particles in suspension are mostly removed by filtration, which would lead to an underestimation of the actual total concentration of metals in water. The use of upgradient water samples and other local sources for background contamination is recommended.

    For plume migration and utilizing groundwater monitor wells, filtered samples will give adequate results. Migration of metals will be primarily in the dissolved form. Colloidal particles greater than 0.45 microns that are removed in the filtration process would likely not be moving in the aquifers at McClellan. If one is concerned with what someone is being exposed to in a water production well, then unfiltered samples are warranted. However, if the well has concentration of metals greater than concentrations of concern, tracking those metals back to its origin would be extremely difficult at McClellan. Concentration of metals in a water production well can be the result of formation materials entering the well, the varying formation materials that the well is screened in, construction materials used to construct the well, sediment accumulation within the well, well design, and other similar mechanisms, along with the dissolved metal concentrations.

    McAFB has performed limited groundwater sampling using unfiltered samples, and that data should be incorporated into this PHA report. Background concentrations for total metal concentrations will likely be a function of the metals within the formation materials that the well is screened.

    All the comments above are important. Filtered samples, in monitoring wells where water samples may be cloudy, are acceptable. This topic is discussed in the PHA section on monitoring well data. However, for comparison to drinking water standards, the agency agrees with the first comment above, that such water samples should be unfiltered. Also, ATSDR does use background levels of groundwater contaminants, such as metals, whenever the data are available. The only unfiltered water sample data ATSDR reviewed was connected with the sampling of residential wells for the health consultation. Other data were not received for our agency review.

  17. With the exception of the SA 12 lot, heavily contaminated with PCBs, surface soil on the McAFB site has not been analyzed for contaminants; in spite of the extensive evidence for past disposal, burning, spills, and mismanagement of hazardous materials. This is a major data gap in this study, and it is an important limitation of this public health assessment document. Surface soil analyses should include location of hot spots, a list of contaminants (mainly metals and semivolatiles), with measured concentrations and detection limits, and the extent of the migration both horizontally and vertically.

    18. ATSDR agrees with this comment. Since surface soils sampling is not completed, and will not be for several years for all the OUs on McAFB, that does, indeed, define a data gap. However, in the interest of public health, ATSDR must respond with a public health evaluation using the available information. Should more data be presented which has public health significance, such as a completed human exposure pathway with contaminants at levels of health concern, ATSDR would issue a health consultation, addendum to the PHA, or other appropriate public health actions.

  18. The PHA reports PCB concentrations as high as 10% near Building 700, as recent as early 1992. Describe the results of dioxin and furan analyses conducted at this location, which should be available by now.

    19. Dioxins and furan results were reviewed during the preparation of the final PHA. Those data are discussed in the surface soils section as related to the PCB contaminations near building 700. The concentrations of dioxins and furans detected in those soils are not of public health concern.

  19. Air analyses for PCB used a method with a detection limit of 0.005 mg/m3. The method is inappropriate, since the detection limit is 5 times higher than the NIOSH REL of 0.001 mg/m3. The NIOSH REL in turn, is an inadequate health comparison value, since it is not based on an air concentration associated with a cancer risk level considered safe, but it is an occupational exposure standard. The inhalation cancer potency slope developed by Cal/EPA is 7.7 [mg/kg.day]-1, and hence, a CREG for air should be available.

    20. CREGs are used in circumstances where chronic, 70 year exposures may occur. Such exposures are not expected to occur at the DRMO yard. Thus ATSDR has not derived a CREG for air using the California EPA's cancer slope factor. Although ambient environmental air data are not available for the DRMO, the McClellan Air Force Base Bioenvironmental Engineering shop did collect monitoring data from personal air monitors worn by DRMO yard workers. The detection limit for the method was 0.005 mg/m3. No PCBs were detected. The NIOSH REL guideline for air for PCBs is 0.001 mg/m3 which is less that the detection limit by a factor of five. The OSHA PEL of 0.5 mg/m3 of PCBs in air is for dermal absorption, not inhalation exposure. ATSDR considers the DRMO to be of public health concern because of exposures to PCB contaminated soil and has recommended that workers in the area use proper protective equipment and that additional samples be collected.

  20. Discuss the cap installed over the polychlorinated biphenyl (PCB) hot spots (at the DRMO yard) to prevent contaminated rain run-off from discharging into the drainage ditches and to prevent potential surface soil exposure. McAFB completed installation of a synthetic liner over the PCB "hot spots" (>100 ppm) before February 1, 1993. The "capped" area is no longer used by DRMO for storage.

    21. Information on the various exposure preventive measures, including the capping of the "hot spots" has been added to the section on contaminants in the DRMO yard.

  21. The PHA states that in stream sediments on-base, no metals were present above health comparison values for soils and that the results of sediment sampling should be considered preliminary data. How is it that in the summary it is stated that there is a potential risk to children by incidental ingestion or contact with stream sediments that contain metals?

    22. Metals were detected in sediments collected off base in residential areas. The PHA summary refers to those results, not to the preliminary data from on base sampling.

  22. In the section discussing surface water sampling on-base it is stated that surface water was sampled only once and that the resulting data may not adequately document the extent of contamination. A later comment states that creek effluent sampling has occurred monthly since 1984. This appears to be a contradiction; please clarify.

    23. Monthly creek effluent sampling may not be representative of discharges into the base drainage system in industrial areas; such releases could result in contaminants being deposited in drainage sediments prior to the effluent sampling. However, CRWQCB has stated that additional sampling will be occurring at industrial discharge points during rain events and dry events to provide such information.

  23. The Aerojet facility, located south-southeast of McAFB, was used for background air contaminant levels. This may not be an appropriate choice for background air samples, since the urban areas surrounding McAFB and Aerojet sites are very different.

    24. Selection of background air emission data was based upon several criteria. Air monitoring stations in areas nearer McAFB did not include testing for the VOCs that were of concern to ATSDR. Since Aerojet, also an NPL site, did have the type data needed for comparisons, and had many sampling events, those data were used.

  24. Environmental Media Evaluation Guide (EMEG) is inappropriately used as a standard comparison to occupational exposure data. The appropriate standard comparison value is the OSHA PEL for mercury, 0.05 mg/m3.

    25. Because mercury was released from Building 252 into the environment, the EMEG for mercury was used instead of a workplace comparison value such as the OSHA PEL. Comparison values (such as EMEGs) used in the Environmental Contamination section of the public health assessment are for the purpose of selecting contaminants that need to be further evaluated in the public health assessment. The health consequences associated with the presence of chemicals in environmental media are discussed in the Toxicological Implications section, not the Environmental Contamination section.

  25. Groundwater samples for inorganic (metals) should be compared to up gradient background sampling results prior to direct comparison to "health comparison values." It is possible that the groundwater in the area does contain naturally elevated levels of some metals. That information is necessary to determine if McClellan has caused an adverse impact to groundwater quality in the off-Base groundwater.

    26. When background data are available, ATSDR does use the information. However, at the time the PHA was prepared, the base did not yet have the sampling plan completed and results for such groundwater background metal levels.

  26. The PHA does not address past pollution into Magpie and Second Creeks. Testing of the creeks began in 1984, but the real contamination occurred before that time; base employees historically disposed of waste chemicals, such as TCE into the creeks, or onto the ground and ditch system leading into the creeks. Adverse health effects could be occurring to people exposed to the creek waters and sediment, even if you do not have "laboratory data" to support the exposures. The exposures could have been to high levels of contaminants and for longer periods in the time before testing (pre 1979).

    27. ATSDR agrees with this comment: past contamination of the creeks could cause adverse health effects, which would be a potential pathway. However, without the data to support such exposures, evaluations of health effects cannot be completed. The PHA toxicological evaluation section does discuss potential adverse health effects from chemicals, such as TCE, where environmental data in the pathways are available.

  27. Table 18 lists a completed exposure pathway for the ingestion of water from private wells for the past, present and future. Private residences were hooked up to the municipal wells for potable purposes. Since there is currently no information that any nearby residents are using such water for potable purposes, should this pathway be listed as a "completed pathway," for either the present or future? Since this situation is only a possibility, shouldn't the pathway be listed only as a "potential pathway?" Maybe this pathway should be shown as a potential pathway for the present and future.

    28. The private well pathway has been changed to indicate a completed past exposure pathway. It is now considered potential for present and future exposures until data from a well use survey indicates current usage of private wells.

  28. It is shown in the table 20 that 16,000 workers on base are affected by two completed exposure pathways and two potential exposure pathways. However, the assessment doesn't discuss the basis to support this estimate. In addition, is the assessment really saying that for each pathway the exposed population would be 16,000? Whenever feasible, separate estimate should be presented for the various exposed populations under the subheadings of past exposure, present exposure, completed pathways, and potential pathways, etc.

    29. Table 20 is meant to provide summary information on estimated populations for completed and potential pathways. More detailed discussions on the pathways follows in that section of the PHA. To present all information through subheadings within the table would be confusing. When a pathway is known to only affect a subset of the worker population, such as with the mercury exposures in building 252, that is indicated in the table. The assumption is made that all workers would be using the drinking water and breathing air, thus subsets are not represented.

  29. With regard to mercury contamination in off-base surface soil, the only detected concentration (out of 14 analyses) was 1.1 mg/kg (Table 11, page 34) which is above the health comparison value of 0.6 mg/kg. However, the health comparison value was developed by ATSDR for pica children who are assumed to ingest 5000 mg of soil per day (see footnote *, Table 11). This daily soil consumption rate is more than an order of magnitude higher than the reasonable maximum exposure. Why was this value used?

    30. The default values from the EPA guidance document Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation Manual: Part A (December 1989) were used to derive health comparison values. The default values are as follows: 100 mg/day for adults; 200 mg/day for children; and 5000 mg/day for pica children.

    The off-base surface soil contamination was detected in a residential area. The health comparison value for a pica-child scenario is the value that is most protective of public health in a residential exposure scenario.

  30. It should be noted that the old Magpie Creek drainage was cutoff from flow from Magpie Creek sometime in the 1950's. Sediments in the upper soil column of the old Magpie Creek channel are likely derived from runoff from the surrounding area and not drainage associated with McClellan AFB.

    31. Information on when Magpie Creek had been re-channeled is important. If that occurred prior to any McAFB industrial activities, then the old channel would not be of concern.

  31. In discussions of the on-base air emissions pathway, it should be noted that the majority of workers had been removed from the building when "The mercury levels were reported throughout building 252 in the breathing zone."

    32. That information has been emphasized within the pathways discussion in the PHA.

  32. ATSDR has no health comparison value for PCB levels in air, yet it is mentioned that the sampling methodology used did not have adequate detection limits for ATSDR to compare health values. It should be noted that the detection limit of 0.005 mg/m3 is 100 times less than the OSHA PEL of 0.5 mg/m3 for airborne PCBs.

    33. The OSHA PEL of 0.5 mg/m3 of PCBs in air is for dermal absorption, not inhalation exposure. Also, see response to question 19.

  33. The attempt has been made to explain the difficult nature of interpreting toxicological information and the impact of mixtures of compounds on public health. However, the impact of the exposure to specific chemicals plus the added exposure to other unnamed compounds would be a public health concern. These conflicting statements may lead to a misunderstanding by the potentially impacted community over the true nature and extent of the potential health effects.

    34. Data are very limited on the health effects from environmental exposure to multiple chemicals. Due to the lack of toxicologic information, it is often unacceptable to interpret exposures to mixtures of compounds. However, multiple chemical exposure does not imply that exposure is a public health concern. Toxicity from exposure to two or more chemicals may be additive (equal to the sum of the toxicity from individual chemicals), synergistic (greater than the sum of the toxicity from the individual chemicals), or antagonistic (less than the sum of the toxicity from the individual chemicals). However, an attempt to interpret the toxicity from multiple chemical exposure without the appropriate scientific data is inappropriate.

    When multiple chemical exposure information is available, such interactions are stated in the public health assessment document. Often this information is of a clinical nature, such as interactions with medicinal drugs or disease states, because information is available concerning these types of interactions. To be protective of possible synergistic interactions, ATSDR uses conservative exposure estimates and conservative health comparison values.

    To provide clarification, the paragraph has been edited in the text of the Toxicologic Evaluation section.

  34. Since ATSDR is a public health agency established to protect the general public's health, the PHA should discuss more about the effects of multiple chemical exposure. Even if there are a number of unknowns at this time, the "error" should be in favor of the public's health.

    35. See response to Comment #33.

  35. It is stated that people are being exposed to contaminants cadmium, lead, chromium, and arsenic in the sediments in Magpie Creek. Exposure to contaminants is not of concern. (However,) exposure to unacceptably high concentrations of contaminants is a concern. It is not clear in this paragraph if the exposure is a problem.

    36. ATSDR discusses the completed and potential exposure pathways in the Pathways Analyses section of a public health assessment. The Pathways Analyses section identified past and current exposures to cadmium and lead: the one sample with arsenic results was considered a localized result and not part of the pathway; the recent chromium VI testing indicated that chromium was not of health concern. The potential health implications associated with the exposures to the concentrations of cadmium and lead found in sediments from Magpie Creek are discussed in the Public Health Implications section.

  36. Information on inhalation exposures to TCE and methylene chloride appear to be contradictory: concentrations are listed as higher than health comparison values, but the exposures are then stated not to be a public health concern.

    37. A contaminant concentration may be greater than the health comparison value and be determined not to be of public health concern. Health comparison values are used as a screen to select contaminants of concern for further evaluation in the public health assessment. Selection of a contaminant as one of concern does not mean the exposure scenario at the site will be of public health concern. Health comparison values are based on daily exposure over a specified duration (often lifetime) and are compared to the maximum concentration detected at the site. Often the site specific exposures are less frequent, have shorter durations, and the exposure concentrations change over time. These factors are considered in the final evaluation to make the determination if the exposure is of public health concern. Therefore, a contaminant may be selected as a contaminant of concern, but after evaluation of the site specific scenario, the exposure is determined not to be of public health concern.

  37. According to the potency slope (46)factor described by CAPCOA (1992), a concentration of MC of 96.2 ug/L is associated with an extra lifetime cancer risk of 9.6x10-6. This may represent a level of concern.

    38. An extra lifetime cancer risk of 9.6 x 10-6 is one additional cancer per 100,000 persons. About one in four persons are expected to have some type of cancer in their lifetime (25,000 per 100,000 persons). An increased risk of 1 cancer per 100,000 persons would result in 25,001 cancers per 100,000 persons. In addition, the 1 in 100,000 additional risk is based on the maximum concentration detected in a private residential well and an average lifetime exposure. Average exposure concentrations are unlikely to be equal to the maximum concentration detected at the site.

    More importantly, an alternate water source has been provided to the area eliminating the exposure. In addition, VOCs were not detected at levels of concern in all of the wells in the area. About 20 of 240 private wells in the area were contaminated with VOCs above health comparison values. Therefore, it is unlikely that people would be exposed to the maximum concentration over a lifetime. In conclusion, the site specific exposures are not expected to increase the number of cancers in the exposed population.

  38. How DCA causes both inhibition and induction, which may lead to an increase in toxicity, may be confusing. A more detailed explanation, or one that omits the description of induction, is needed for the public to understand the potential adverse health impacts from DCA.

    39. ATSDR has determined that a detailed explanation of enzyme function and alterations is not essential to the discussion. The section has been revised to give a more direct explanation.

  39. Persons who were potentially, occupationally exposed to mercury at McClellan AFB may associate the list of clinically defined symptoms in the document with what was actually observed in workers at the installation. This difference should be clarified.

    40. The paragraph in the Toxicologic Evaluation has been changed to reflect that the described clinically defined symptoms are those documented in scientific studies. The symptoms may not be representative of those actually observed in workers at the installation.

  40. In discussions on benzene, it is difficult to determine from the presentation of the data what impact the 1992 sampling had on evaluating potential exposures that were described by the 1987 monitoring at stations #2 and #5. If the levels at station 5 in 1987 (2.0 parts per billion in volume) were of concern off-site, then the 1992 data should lead to a wording change that "benzene exposures in the PAST at McAFB are of public health concern, however, current sampling information indicates no elevated levels of concern. The conclusions as written may cause elevated levels of public concern that are not warranted. Please clarify whether there is a current exposure to benzene or whether it was due to past exposure only.

    41. The benzene evaluation section in the Toxicologic Evaluation has been edited to clearly reflect the conclusions. The exposures to benzene (present and past) via inhalation at McAFB are not of public health concern for noncancerous adverse health effects. The exposures (past and present) may result in an increased risk of developing cancer. However, the levels detected at McAFB are similar to those reported in a national study of 300 cities and rural areas.

  41. The estimated exposure dose of PCBs by occasional visitors to the DRMO yard appears to be based on the assumption that the visitors may ingest and/or inhale the maximum concentration (100,000 mg/kg) found on the site. This assumption doesn't seem reasonable because of the isolated nature of the "hot spots," the surface cover on the most highly contaminated sections of soil, and the selected locations visited by off-base personnel. Also, if no contamination has been found in air sampling, please explain how can incidental ingestion exist.

    42. Recent environmental sampling data have detected concentrations of PCBs as high a 240,000 ppm. The discussion in the text of the Toxicologic Evaluation section has been changed to reflect this additional data. The evaluation does consider past exposure to the most elevated "hot spot" for occasional visitors to the DRMO. An exposure to the less contaminated "hot spots" has also been considered. The area is considered of public health concern for visitors in the area because it was possible that the one exposure was to the most elevated concentrations. A statement has been added that it is most likely that exposure was to the less concentrated areas of contamination.

    Incidental ingestion is unintentional ingestion of a substance. A person may get contaminated soil/dust on their hands/clothes from activities performed in the contaminated area. Such activities may include: handling objects which have contaminated soil on them or by walking in the area and getting soil/dust on their shoes. This contaminated soil/dust can then be inadvertently ingested by the person from activities such as: eating with unwashed hands, placing fingers in the mouth following tying of shoe laces or handling of equipment.

  42. The evaluation of appropriate and community-specific health outcome data is central to the success of any health assessment. Unfortunately, ATSDR did not have the opportunity to evaluate any of the available health outcome data sources at the state level. This is a critical missing element in the report which raises questions concerning ATSDR's recommendation for conducting comprehensive epidemiological studies.

    43. No additional information has been obtained at this time.

  43. The discussion on the study of worker exposures to mercury in building 252 lists 50% "incidence" of symptoms was tied to the questionnaire that could be associated with mercury exposures. The certainty of association should be clarified. The health assessment document may have inaccurately portrayed the adverse health effects to the potentially exposed personnel. In addition, comments within the PHA on the physical exams performed on workers exposed to mercury is unclear; please explain the statement that a thorough physical exam should have been completed.

    44. Questionnaires completed by employees were reviewed to identify symptom patterns. Employees were asked if they had experienced the following: recent pain with chewing within the last 60 days, bleeding gums, prolonged bouts of diarrhea, unexplained loss of appetite, unexplained weight loss, personality changes, changes in sleep pattern, muscle tremors, skin changes, recent respiratory difficulties, history of kidney disease, seasonal allergies, family history of Parkinsonism/kidney disease/hyperthyroidism. Thirty four employees underwent medical evaluations; twenty-nine employees' questionnaires were reviewed, and five employee medical records did not include a questionnaire. Nine individuals reported seasonal allergies, 6 reported changes in sleep pattern, 6 reported personality changes, 5 reported skin changes, 5 reported muscle tremors, and 4 reported bleeding gums. The significance of the frequency of reported symptoms is unknown without additional information in regards to the duration or severity of symptoms, the time of onset in relation to work exposures or other work history information. The above symptoms are non specific and could be related to many diseases including mercury toxicity. Further medical information is needed to adequately interpret the symptom findings. Urine mercury levels drawn on all 34 employees were below 6 mcg/l (Normal 0-20). Normal physical examinations and urine mercury levels reported at the time of the questionnaire suggest that no significant health effects from mercury exposure were observed; however, the date of last exposure would be necessary to make any judgement about the validity of the urine test and examination.

  44. Based on the environmental sampling data presented in the assessment, it appears the only unique feature associated with Building 252, as compared to other McClellan AFB facilities, is the potential past cases of mercury exposure. Since the assessment already concluded that "mercury has never been associated with gout," a more definitive answer to this particular community health concern is merited.

    45. Additional information has been included in the Community Health Concerns Evaluation section, question #6 related to gout and mercury exposure.

  45. Who reported the incidence of brain cancer related to employees in building 252?

    46. Perceived cancer clusters are a concern of the community. Anecdotal cases of cancer were described by many concerned community members but no formal data list of names and/or medical records has been compiled. NIOSH reviewed the cancer cluster information available and reported it to be inadequate and recommended that all employees or former employees with cancer complete health forms available in the Military Public Health Office at McAFB.

  46. Judging by the information provided in the assessment, neither one of the two types of bone deterioration appears to be associated with mercury exposure. This lack of association between mercury exposure and bone deterioration is also supported by information presented in Casarett and Doult's Toxicology: The Basis Science of Poisons (third edition, 1986, MacMillan Publishing Company). Thus a more definitive answer to this concern is merited.

    47. Current medical literature has not associated bone deterioration with mercury exposure (this statement has been incorporated into the Community Health Concerns Evaluation section).

  47. Discussions on the exposures to residents west of the base by ground water and stream sediments pathways states that exposed populations in the area are experiencing multiple long-term exposures to multiple compounds, increasing the probability of adverse health effects. However, it appears unclear that an exposed population currently exists.

    48. Exposures are possible today if people are using contaminated private well water for drinking, irrigating lawns and gardens, etc. Also exposures may be occurring if children continue to play in Magpie Creek and incidentally ingest contaminated soils from the creek sediment.

  48. The PCB inhalation exposure for the workers in B624D is 0.038 mg/day assuming the measured PCB air level of 0.005 mg/m3, an inhalation rate of 23 cubic meters/day and eight hours exposure/day. The literature indicates that PCBs are readily absorbed by the lungs. Compare that level to the chronic ingestion MRL of 0.000005 mg/kg/day. For a 70 kg person, the MRL is 0.00035 mg/day. It appears that the absorption rate from inhalation in B624D is high compared to the ingestion MRL.

    49. The ambient air concentrations detected in Building 624D in 1985 were less than 0.005 mg/m3 (the detection limit). Actual concentrations are expected to be less than the detection limit. Therefore, the estimated exposure would be less than 0.038 mg/8-hour day or less than 0.0005 mg/kg/day for 70 kg-adult. The MRL is a health guideline for oral chronic exposure (exposures greater than 1 year). Exposures in Building 624D were over a period of two months. Therefore, it is inappropriate to directly compare inhalation exposures or short-term exposure to this health guideline.

  49. The literature on human PCB, dioxin, and furan exposures is very limited. the increased cancer risk is evident, but the exact extent of the risk is unknown. Obviously, controlled human tests are not ethical. However, the exposures at B624D are the closest thing to a controlled test. The exposure levels are known. The time of exposures is known. Most of the exposed personnel did not work with any other chemicals at their job. The number of exposures, about 200, is relatively large. The medical community can learn from those exposures.

    50. The exposures in Building 624D are not known. The available data only provides information that the exposures are less than 0.005 mg/m3. This can be interpreted that the exposure range is 0.00 - 0.005 mg/m3. The exposures were for a duration of only two months. Therefore, adverse health effects from these exposures are unlikely. The exposed population of 200 would not provide the sensitivity required for detection of adverse health outcomes from this exposure scenario.

  50. A-1 Metals, previously located in the northwest corner of the base, may have contaminated the area with dioxin by burning PCB-laden oils in an unpermitted incinerator. Information concerning this occurrence will be transferred to the property owner for appropriate action. A sampling strategy to characterize contamination should be incorporated into the work plan for OU-F.

    51. The above information has been communicated to McAFB.

  51. People living west of the base want the health study for their community. Will this recommendation from the PHA be implemented (funded)? Persons who live near city well # 150 are particularly concerned about a potential cancer cluster in that area. Will the study provide information on the health status for the community include cancer and noncancer health problems, such as heart disease, lung disease, brain dysfunction, motor or coordination problems, nerve disorder, and birth defects?

    52. ATSDR's Division of Health Studies is currently working with the community to design a study. A community assistance panel (CAP) has been selected and that group of community representatives is working with the health studies staff. Meetings with the CAP are open meetings and residents are encouraged to attend and learn more about what types of information will be collected and evaluated during the health study.

  52. Comments on the recommendations:

    53. McAFB is initiating a background (inorganic) groundwater sampling plan. Use of filtered and unfiltered samples during the background sampling will aid in determining if metals concentrations are naturally occurring. The base will also analyze ground water samples for metals using unfiltered sampling methods when evaluating health exposure pathways. This is part of the Groundwater Sampling and Analysis Plan (GSAP).

    Game fowl will be added to the list of biota which need to be sampled for the presence of contaminants in order to fully characterize potential exposure.

    The "Recommended Surface Soil and Stream Sediment Sampling Program to Define Basewide Background Concentrations", Draft Document, 8 Apr 93, is currently being reviewed by McClellan AFB and the regulatory agencies. Once this document is reviewed and approved, a specific sampling plan will be developed, describing where on and off-base additional samples will be collected. After background concentrations have been established, then the requirement for additional sampling in Magpie Creek will be evaluated. Under the NPDES permit, substantial monitoring of surface water has taken and continues to take place.

    The above comments reflect some of the actions being taken by the McAFB and other agencies involved with the NPL site. ATSDR has reviewed the actions being implemented, or already completed, and that information is incorporated into the PHAP (public health action plan) near the end of the document.

Table of Contents


Error processing SSI file