PUBLIC HEALTH ASSESSMENT
BOOMSNUB/AIRCO SUPERFUND SITE
(a/k/a BOOMSNUB/AIRCO)
VANCOUVER, CLARK COUNTY, WASHINGTON
APPENDIX A: CONTAMINANTS OF CONCERN
The criteria for listing a chemical as a contaminant of concern include: exceedance or lack of media specific health comparison values, community health concerns, and data quality. Also, any contaminant of concern detected in one medium will be by default listed in all other media in which it is detected.
Media-specific health comparison values are contaminant concentrations in specific media (i.e., soil, water and air) used to select contaminants of concern for further evaluation. If the concentration of a chemical exceeds the health comparison value, it does not mean that a public health threat exists but rather signifies that the chemical be further evaluated.
The health comparison values used in this public health assessment include environmental media evaluation guidelines (EMEGs), reference dose media evaluation guidelines (RMEGs), cancer risk evaluation guidelines (CREGs), and lifetime health advisories (LTHA). Ecology Model Toxic Control Act (MTCA) cleanup levels were also used when no other comparison values were available.20, 21 For metals in soil, Ecology natural background values are also used as comparison values since metals occur naturally in the environment.
EMEGs are media-specific health comparison values derived from minimal risk levels (MRLs) presented in ATSDR Toxicological Profiles. RMEGs are media-specific health comparison values derived from EPA's reference dose (RfD) that are used when EMEGs are not available. MRLs and RfDs are estimates of daily exposure of a human to a chemical that is likely to be without an appreciable non-cancer risk over a specified duration of exposure. CREGs are estimated media specific contaminant concentrations that are anticipated to result in one excess cancer risk in one million persons exposed over a lifetime. CREGs are derived from EPA's cancer slope factors (CSFs), also known as cancer potency factors. CSFs are cancer potency estimates derived for chemicals shown to be carcinogenic in animals or humans. LTHAs are guidelines derived for a lifetime ingestion exposure to a contaminant in drinking water. They are derived for non-carcinogenic compounds from Drinking Water Equivalent Levels (DWELs) which are based on oral RfDs. Ecology MTCA cleanup levels are derived for carcinogenic and non-carcinogenic compounds using CSFs and RfDs, respectively.
APPENDIX B: EXPOSURE ASSUMPTIONS
To obtain conservative daily exposure doses to evaluate non-cancer health effects and cancer risk associated with the ingestion and dermal contact with site soil contaminants, a site worker exposure was used. An ingestion and dermal exposure dose were calculated using the following formulae:
Ingestion Exposure Dose = C x CF x IR x EF x ED)/ BW x AT.
Dermal Exposure Dose = C x CF x A x ABS x EF x ED)/ BW x AT
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C =
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Concentration of tetrachloroethene in water (mg/l) |
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CF=
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Conversion Factor (10 -6) |
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IR =
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Ingestion Rate (liters per day) Child (0 - 5 years): 1 liter per day Young adult (6-15 years): 2 liters per day Adult (>= 16 years): 2 liters per day |
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EF =
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Exposure Frequency (day/year) It was assumed that people were exposed 350 days per year. |
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ED =
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Exposure Duration (years) It was assumed that residents were exposed to contamination for 30 years. Thirty years represents the average time that a person spends at one residence. |
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BW =
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Body Weight (kg) Child (0 - 5 years): 16 kg Young adult (6-15 years): 40 kg Adult (>= 16 years): 70 kg |
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AT =
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Averaging Time (days) For exposure to carcinogens the averaging time is assumed to be 70 years x 365 days/year. For non-carcinogens, the averaging time is the actual length of the exposure period. |
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A =
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Total Soil Adhered (mg) The total soil adhering to the dermal surface is estimated as the product of the exposed dermal area and the soil adherence concentration. |
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ABS=
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Absorption Factor (unitless) Absorption factors are used to reflect the desorption of the chemical from soil and the absorption of the chemical across the skin and into the bloodstream. |
APPENDIX C: NON-CANCER ADVERSE HEALTH EFFECTS AND CANCER RISK EVALUATION
Evaluating Non-Cancer Adverse Health Effects
In order to evaluate the potential for non-cancer adverse health effects from exposure to contaminated media (i.e., soil, water, and air), a dose is estimated for each contaminant of concern. The doses are calculated for situations in which people might come into contact with the contaminated media. The estimated dose for each contaminant of concern under each situation is then compared to ATSDR's minimal risk level (MRL) or EPA's oral reference dose (RfD) to determine if there is a potential for non-cancer adverse health effects. MRLs and RfDs are derived from toxic effects levels obtained from human and animal laboratory studies. The toxic effects levels are expressed as either the lowest adverse effect level (LOAEL) or the no-observed adverse effect level (NOAEL). In human or animal studies, the LOAEL is the lowest dose at which an adverse effect is seen; the NOAEL is the highest dose that did not result in any adverse human health effect.
To account for uncertainty, the toxic effect levels are divided by safety factors (10, 100, or 1,000) to provide the more protective MRL or RfD. If a dose exceeds the MRL or RfD, the potential exists for adverse health effects. Therefore, a dose only slightly exceeding the MRL or the RfD would fall well below the toxic effect level. The higher the estimated dose is above the MRL or RfD, the closer it will be to the toxic effect level.
Evaluating Cancer Risk
By calculating a dose similar to that described above and multiplying the dose by the EPA cancer slope factor, the increased cancer risk can be estimated. An exposure to a contaminant which results in an estimated increased cancer risk of one additional cancer in a population of one million people exposed, averaged over a 70 year lifetime, is considered an acceptable risk, and is used as the screening value. In a population of one million men in the U.S., 333,000 (one in three) are expected to develop cancer from all causes in the lifetime (through 79 years of age). For U.S. women, the figure is 200,000.22 The additional estimated cancer risk means that if those one million men are exposed for 30 years to this level of chemical, 333,001 would be expected to develop cancer. For the one million women exposed, 200,001 would be expected to develop cancer.
APPENDIX D: RESPONSE TO PUBLIC COMMENTS
Comment 1: Page 2, paragraph 4. There is no mention of the surface soil on the BOC property. BOC has investigated their site and analyzed many surface soil samples as part of their site characterization efforts. No significant concentrations of organic compounds have been detected in the surface soil at BOC.
The data for site surface soil contamination are limited. Please refer to Section C, paragraph 2.
Comment 2: Page 3, last paragraph. The equivalent of a door-to-door survey was conducted several years ago when Ecology was the lead agency. This would include the efforts of Clark Public Utilities, Ecology, and Belle Fuchs at the Department of Health.
DOH has talked with utility and agency representatives regarding this informal door-to-door survey. Unfortunately, no documentation could be located on the methods, results, and conclusions of the survey.
Comments 3: Page 5, first paragraph, line 5. The dry well on the BOC property where water and sediment containing organic compounds was found was used for waste water and storm water infiltration.
Comment noted.
Comment 4: Page 5, first paragraph, line 6. Replace the word "most" with "some." Most of the dry well contents were removed in March 1994.
Comment noted.
Comment 5: Page 7, first bullet, line 6 and 7. Replace "whether" with "that" and insert "not" between "had migrated." The soil vapor survey did not find significant concentrations of VOCs on adjacent properties.
This paragraph merely states what was done in the way of environmental investigation. Results of the soil vapor survey are presented in Section C.
Comment 6: Page 14, last paragraph, last two lines. Replace "A portion" with "Most," replace "Surface sediments" with "Sediments remaining in the dry well."
Comment noted.
Comment 7: Page 15, first two lines. Replace "at the surface of the "with "in the." After the sediment removal was completed a sample of the residual sediment in the bottom of dry well was collected and analyzed. The sample was not at the surface of the dry well.
Comment noted.
Comment 8: Page 15, Conclusions, first line. Replace Boomsnub with BOC.
Comment noted.
Comment 9: Page 16, paragraph 3, line 3. After "4,400 feet in length and "add "up to."
The distances are already qualified with the word "approximately."
Comment 10: Page 16, paragraph 3, last line. After "plume extends" insert "to."
Comment noted.
Comment 11: Page 17, first full paragraph. Has DOH contacted the two residents they identified that may be using well water for household purposes? If not, please provide the names of the potential users to EPA.
The water well locations of the potential users have been provided to EPA.
Comment 12: Page 17, paragraph 2. There are no City of Vancouver wells identified on Figure 1. Identify the City well locations on Figure 1 or delete the reference to City wells.
Comment noted.
Comment 13: Page 18, Recommendation No. 2. Clark Public Utilities currently uses wells near the Site to meet peak water demand only. This practice should be continued.
Recommendations for this health assessment pertain to reducing or eliminated potential human exposures to environmental contaminants. DOH can not make any specific recommendation on how Clark Public Utilities should meet peak water demand.
Comment 14: Page 20, Actions Proposed No. 4. After "EPA" insert "and BOC."
EPA is the lead regulatory agency for the site. DOH will work directly with EPA on groundwater contamination issues as they relate to public health. BOC is welcome to be involved in these discussions.
Comment 15: Page 21, Actions Proposed. Add "BOC will reduce or eliminate groundwater and soil contamination on their property to levels protective of human health."
Please see response to Comment 14. EPA will be working with BOC gases to further define, contain, and reduce levels of groundwater contamination on the site.
This Public Health Assessment was prepared by the Washington State Department of Health under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health assessment was begun.
Debra Gable
Technical Project Officer,
SPS, SSAB, DHAC
ATSDR
The Division of Health Assessment and Consultation, ATSDR, has reviewed this
Public Health Assessment and concurs with the findings.
Richard Gillig
Branch Chief,
SSAB, DHAC
ATSDR
