SCHOFIELD BARRACKS
WAHIAWA, HONOLULU COUNTY, HAWAII
APPENDIX A: GLOSSARY
Analyte:
A chemical component of a sample to be determined or measured. For example, if the analyte is mercury, the laboratory test will determine the amount of mercury in the sample.
Background level:
A typical or average level of a chemical in the environment. Background often refers to naturally occurring or uncontaminated levels.
Carcinogen:
Any substance that may produce cancer.
CERCLA:
The Comprehensive Environmental Response, Compensation, and Liability Act of 1980,
also known as Superfund. This is the legislation that created ATSDR.
Comparison Values:
Estimated contaminant concentrations in specific media that are not likely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. The comparison values are calculated from the scientific literature available on exposure and health effects.
Concentration:
The amount of one substance dissolved or contained in a given amount of another. For
example, sea water contains a higher concentration of salt than fresh water.
Contaminant:
Any substance or material that enters a system (the environment, human body, food, etc.) where it is not normally found.
Dermal:
Referring to the skin. Dermal absorption means absorption through the skin.
Dose:
The amount of substance to which a person is exposed. Dose often takes body weight into account.
Environmental contamination:
The presence of hazardous substances in the environment. From the public health
perspective, environmental contamination is addressed when it potentially affects the health and quality of life of people living and working near the contamination.
Exposure:
Contact with a chemical by swallowing, by breathing, or by direct contact (such as through the skin or eyes). Exposure may be short term (acute) or long term (chronic).
Hazard:
A source of risk that does not necessarily imply potential for occurrence. A hazard produces risk only if an exposure pathway exists and if exposures create the possibility of adverse consequences.
Ingestion:
Swallowing (such as eating or drinking). Chemicals can get in or on food, drink, utensils, cigarettes, or hands where they can be ingested. After ingestion, chemicals can be absorbed into the blood and distributed throughout the body.
Inhalation:
Breathing. Exposure may occur from inhaling contaminants because they can be deposited in the lungs, taken into the blood, or both.
Media:
Soil, water, air, plants, animals, or any other parts of the environment that can contain contaminants.
Minimal Risk Level (MRL):
An MRL is defined as an estimate of daily human exposure to a substance that is likely to be without an appreciable risk of adverse effects (noncancer) over a specified duration of exposure. MRLs are derived when reliable and sufficient data exist to identify the target organ(s) of effect or the most sensitive health effects(s) for a specific duration via a given route of exposure. MRLs are based on noncancer health effects only. MRLs can be derived for acute, intermediate, and chronic duration exposures by the inhalation and oral routes.
National Priorities List (NPL):
The Environmental Protection Agency (EPA) list of sites that have undergone preliminary assessment and site inspection to determine which locations pose immediate threat to persons living or working near the release. These sites are most in need of cleanup.
No Apparent Public Health Hazard:
Sites where human exposure to contaminated media is occurring or has occurred in the
past, but the exposure is below a level of health hazard.
Plume:
An area of chemicals in a particular medium, such as air or groundwater, moving away
from its source in a long band or column. A plume can be a column of smoke from a chimney or chemicals moving with groundwater.
Potentially Exposed:
The condition where valid information, usually analytical environmental data, indicates the presence of contaminant(s) of a public health concern in one or more environmental media contacting humans (i.e., air, drinking water, soil, food chain, surface water), and there is evidence that some of those persons may have an identified route(s) of exposure (i.e., drinking contaminated water, breathing contaminated air, having contact with contaminated soil, or eating contaminated food).
Public Health Assessment:
The evaluation of data and information on the release of hazardous substances into the environment in order to assess any current or future impact on public health, develop health advisories or other recommendations, and identify studies or action needed to evaluate and mitigate or prevent human health effects; also the document resulting from that evaluation.
Public Health Hazard:
Sites that pose a public health hazard as the result of long-term exposures to hazardous substances.
Risk:
In risk assessment, the probability that something will cause injury, combined with the potential severity of that injury.
Route of Exposure:
The way in which a person may contact a chemical substance. For example, drinking
(ingestion) and bathing (skin contact) are two different routes of exposure to contaminants that may be found in water.
Superfund:
Another name for the Comprehensive Environmental Response, Compensation, and
Liability Act of 1980 (CERCLA), which created ATSDR.
Superfund Amendments and Reauthorization Act (SARA):
The 1986 legislation that broadened ATSDR's responsibilities in the areas of public health assessments, establishment and maintenance of toxicologic databases, information dissemination, and medical education.
Vadose Zone:
The zone of aeration (also referred to as the unsaturated zone) in the earth's crust above the groundwater level.
Volatile organic compounds (VOCs):
Substances containing carbon and different proportions of other elements such as hydrogen, oxygen, fluorine, chlorine, bromine, sulfur, or nitrogen; these substances easily become vapors or gases. A significant number of the VOCs are commonly used as solvents (paint thinners, lacquer thinner, degreasers, and dry-cleaning fluids).
APPENDIX B: COMPARISON VALUES
The conclusion that a contaminant exceeds the comparison value does not mean that it will cause
adverse health effects. Comparison values represent media-specific contaminant concentrations
that are used to select contaminants for further evaluation to determine the possibility of adverse
public health effects.
Cancer Risk Evaluation Guides (CREGs)
CREGs are estimated contaminant concentrations that would be expected to cause no more than
one excess cancer in a million (10-6) persons exposed over lifetime. ATSDR's CREGs are
calculated from EPA's cancer potency factors.
Environmental Media Evaluation Guides (EMEGs)
EMEGs are based on ATSDR minimal risk levels (MRLs) and factors in body weight and
ingestion rates. An EMEG is an estimate of daily human exposure to a chemical (in mg/kg/day)
that is likely to be without noncarcinogenic health effects over a specified duration of exposure.
Maximum Contaminant Level (MCL)
The MCL is the drinking water standard established by EPA. It is the maximum permissible level
of a contaminant in water that is delivered to the free-flowing outlet. MCLs are considered
protective of public health over a lifetime (70 years) for people consuming 2 liters of water per
day.
Reference Media Evaluation Guides (RMEGs)
ATSDR derives RMEGs from EPA's oral reference doses. The RMEG represents the
concentration in water or soil at which daily human exposure is unlikely to result in adverse noncarcinogenic effects.
APPENDIX C: ESTIMATES OF HUMAN EXPOSURE DOSE AND DETERMINATION OF HEALTH EFFECTS FROM PAST CONSUMPTION OF TCE-CONTAMINATED GROUNDWATER
ATSDR estimated the human exposure dose for past ingestion of Schofield drinking well water.
The estimated exposure dose was used to determine whether noncancer and cancer effects are a
concern for this pathway.
Noncancer Effects
When evaluating noncancer effects, ATSDR uses standard toxicity values, such as ATSDR's
minimal risk levels (MRLs), to determine whether adverse effects will occur. An MRL is defined
as an estimate of daily human exposure to a chemical that is likely to be without an appreciable
risk of deleterious effects (noncarcinogenic) over a specified duration of exposure. In the ATSDR
toxicological profiles, MRLs are developed for acute, intermediate, and chronic exposure
intervals. Currently, the only MRLs for TCE are the Intermediate Oral MRL and the Acute Oral
MRL.
The intermediate MRL is a conservative value because it is based on the levels of exposure
reported in the literature that represent no-observed-adverse-effect levels (NOAELs) or lowest-adverse-effect-levels (LOAELs) for the most sensitive outcome for a given route of exposure
(e.g., dermal contact, ingestion). In addition, uncertainty (safety) factors are applied to the
NOAELs or LOAELS to account for variation in the human population and uncertainty involved
in extrapolating from animal studies to the human experience.
Hazard is an estimate of the potential that a noncancer effect will occur at the estimate exposure
dose for a contaminant. It is calculated as the ratio of the estimated exposure dose (for the
contaminant) divided by the MRL. The hazard index (HI) is the sum of the contaminant-specific
hazards for an exposure pathway. Total HI is the sum of the HIs for several pathways, assuming
that simultaneous exposure is occurring via various pathways.
MRLs, in general, have uncertainty spanning an order of magnitude or more. Uncertainty factors
(UFs) and modifying factors (MFs) are incorporated into the MRL to reflect the uncertainties
about the data and to ensure that the levels are protective of health, even for sensitive
populations. For chemicals with an MRL that has relatively few uncertainties (less than or equal
to a factor of ten), the hazard is typically compared with 1. Conversely, when the MRL for a
chemical is based on less than adequate data, UFs and MFs are incorporated in the MRL to
provide greater certainty that the value is protective of human health. An MRL that has many
UFs and MFs has a large margin of safety built into it; therefore the hazard can be compared with
a less stringent value (greater than 1).
In addition to calculating HI values, ATSDR reviewed the literature-based NOAEL and LOAEL
values to determine possible adverse effects associated with exposure at the doses estimated for
the pathways described above.
Cancer Effects
When evaluating the potential for cancer to occur, ATSDR uses cancer potency factors (CPFs)
that define the relationship between exposure doses and the likelihood of an increased risk of
developing cancer over a lifetime. The CPFs are developed using data from animal or human
studies and often require extrapolation from high exposure doses administered in animal studies
to the lower exposure levels typical of human exposure to environmental contaminants. The CPF
represents the upper-bound estimate of the probability of developing cancer at a defined level of
exposure; therefore, they tend to be very conservative (i.e., overestimate the actual risk) in order
to account for a number of uncertainties in the data used in the extrapolation.
ATSDR estimated the potential for cancer to occur for the exposure pathway from ingestion of
TCE-contaminated groundwater. The method involved estimating the lifetime cancer risk using
the following equation which incorporates the estimated exposure doses and CPF values:
Lifetime Cancer Risk = Estimated exposure dose (mg/kg/day) x CPF (mg/kg/day)-1
Although no risk of cancer is considered acceptable, ATSDR often uses a range of 10-4 to 10-6
estimated lifetime cancer risk (or 1 new case in 10,000 to 1 million exposed persons), based on
conservative assumptions about exposure, to determine whether a concern for cancer effects
exists. A zero cancer risk is not possible to achieve. This range is consistent with values adopted
by EPA for cleaning up hazardous waste sites to a level that does not contribute excess cancer in
a population.
Past Consumption of Schofield Well Water
ATSDR used the following equation to estimate exposure dose for past ingestion of
Schofield's TCE-contaminated water supply:
where:
Conc. =
Maximum concentration in Schofield well water previous to
the closure of the wells = 0.030 mg/L for TCE
IR =
Ingestion Rate: 2 liters/day for adults; 1 liter/day for children
EF =
Exposure frequency or number of exposure events per year of
exposure:
1 event/day x 7 days/week x 52 weeks/year or 365 events/year
ED =
Exposure duration or the duration over which exposure occurs
= 20 years for adults (the longest period of potential contamination at
the supply wells: from the earliest possible year of contamination [1966]
to the installation of the stripper [1986]); 6 years for children
BW =
Body weight (kg): adult = 70 kg; child (1 to 6 years of age)
= 16 kg
AT =
Averaging time or the period over which cumulative exposures
are averaged (20 or 6 years x 365 days/year for noncancer and 70 years x
365 days/year for cancer).
Estimating Human Exposure Dose and Human Health Effects
Using the above equation, ATSDR's estimated past exposure doses for ingestion of
Schofield well water are 0.000857 mg/kg/day and 0.001875 mg/kg/day for adults and
children, respectively.
These estimated exposure doses are less than the intermediate MRL value of 0.002 for oral exposure to TCE; therefore, adverse noncancer effects are not a concern for this pathway.
ATSDR calculated a total lifetime cancer risk for ingesting the maximum level of TCE discovered in 1985. The estimated cancer risk for adults is 2.69 x 10-6; therefore, cancer is not considered a concern for this exposure pathway.
Furthermore, the estimated exposure dose calculated here is a conservative estimate. A
conservative exposure dose may overestimate adverse health effects. Actual exposure dose would be less, based on the following reasons:
The dose is estimated using the maximum contaminant level present before the wells were
shut down. Four water supply wells are located on Schofield, and water is typically
pumped from more than one pump at a time (Fukuda 1997). Depending on demand, water
may be pumped from any combination of the four wells to storage tanks. Due to the
blending of water from the different wells and the volatilization of VOCs that would
naturally occur during pumping and storage, the water that reached the tap would contain a TCE concentration less than the maximum level detected at the wellhead.
The exposure frequency and duration are extremely conservative. The dose is estimated
assuming people are exposed every day of the year. This is the maximum exposure that an
individual could have, and it is not likely that one would be exposed every day. For
instance, civilian personnel who work at the installation would typically be exposed only 8 hours per day during a 5-day workweek and not during weekends or on vacation.
Similarly, the exposure duration used for estimating dose was 20 years for adults and 6
years for children.
Although 20 years has been determined to be the longest possible duration of contaminated
drinking water, it may be an overestimation of the exposure duration; for instance, military
personnel and their dependents were typically stationed at the installation for only a few years.
REFERENCE
Fukuda, J. 1997. Correspondence with W. Mark Weber, ATSDR, regarding Schofield drinking water wells. July 3, 1997.
APPENDIX D: RESPONSE TO COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD
The Schofield Army Barracks (Schofield) Public Health Assessment was available for public
review and comment from October 31, 1997, through November 30, 1997. The Public Comment
Period was announced in a press release dated October 29, 1997. Copies of the public health
assessment were made available for review at the U.S. Army Garrison, Hawaii Department of
Health, and the Wahiawa Public Library. The public health assessment was also sent to state and
federal agencies and interested members of the general public.
ATSDR received the following comments/questions for the Schofield Public Health Assessment.
The specific comments that were received either identified new information; questioned specific
sentences or paragraphs in the text or tables; or suggested additions or corrections to improve the
clarity, completeness, or accuracy of a specific sentence or paragraph. Those specific comments
were not repeated by other respondents and are listed separately. This list of specific comments
does not include editorial comments concerning word spelling, sentence syntax, format, etc. If
the accuracy of a statement was questioned, this statement was verified and corrected. Comments
which requested that information be added to the document without providing documented
sources of that information were not addressed here.
Comments/Questions on Groundwater Quality and Contamination
Comment: The drinking water supply and irrigation wells of Del Monte's Fresh Produce
(Hawaii) Inc.'s Oahu Plantation (Kunia wells) are located near the southern border of the
Main Post of Schofield and may have been impacted by groundwater contamination from
Schofield. Due to measurable concentrations of trichloroethylene (TCE), carbon
tetrachloride, and 1,2 dichloroethylene (all below the corresponding Maximum
Contaminant Levels [MCLs]) in these wells in 1986, Del Monte installed an air stripping
tower, which became operational in 1991. In accordance with the Schofield Operable Unit
2 Record of Decision, the Army reimbursed Del Monte for capital costs of the air stripping
tower treatment facility and funds the operation and maintenance of the facility. TCE has
historically been detected below the MCL with the following two exceptions: TCE was
detected at 7.7 parts per billion (ppb) on October 5, 1993, and at 5.2 ppb on May 1, 1997. Both of these detections were in water collected before the air stripper tower.
Response: ATSDR amended the groundwater section in the Community Health Concerns and Potential Pathways of Exposure section to reflect these TCE detections above the MCL and the installation of an air stripper at the Del Monte Kunia wells. Specifically, changes were made to the conclusions, off-site contamination, past exposure, and current and future exposure segments.
Comment: The summary makes reference to the presence of seven contaminants found in groundwater under Schofield. Only TCE and carbon tetrachloride were found more than once and therefore not considered anomalous; only TCE and carbon tetrachloride should be mentioned in the summary.
Comment: On page 12, the public health assessment states that pentachlorophenol was
found in an off-site well in Waipio, which is in the Honolulu-Pearl Harbor Basal Water
Body, yet in the summary on page 1 it is said to be found in the groundwater beneath
Schofield Barracks. This is in error and should be deleted.
Response: Text in the summary was amended. See above comment and response.
Comment: Groundwater at Schofield is monitored on a quarterly basis, not on a continuous basis as stated in the conclusions of the groundwater section.
Response: Text amended.
Comment: Add text to the first conclusion on page 18 to read: Current and future
exposures to contaminants in drinking water are unlikely to occur because air strippers
operating at the wellhead effectively treat the water of the existing wells. Further, any
wells drilled in the vicinity to develop water from the same groundwater source for
drinking purposes in the future will be subjected to federal, state, and county regulations to meet safe drinking water standards (MCL).
