PUBLIC HEALTH ASSESSMENT
ANDERSEN AIR FORCE BASE
YIGO, GUAM
APPENDIX C: ATSDR'S EXPOSURE EVALUATION PROCESS
Estimates of Human Exposure Doses and Determination of Health Effects
Deriving Exposures Doses
After identifying contaminants in site media above comparison values, ATSDR further evaluates exposures to these contaminants considering information about exposures combined with scientific information from the toxicological and epidemiological literature. If necessary, ATSDR estimates exposure doses, which are estimates of how much contaminant a person is exposed to on a daily basis. Variables considered when estimating exposure doses include the contaminant concentration, the exposure amount (how much), the exposure frequency (how often), and the exposure duration (how long).
The estimated exposure doses can be used to evaluate potential noncancer and cancer effects associated with contaminants detected in site media. When evaluating noncancer effects, ATSDR compares the estimated exposure dose to standard toxicity values, including ATSDR's minimal risk levels (MRLs) and the U.S. Environmental Protection Agency's reference doses (RfDs), to evaluate whether adverse effects may occur. The chronic MRLs and RfDs are estimates of daily human exposure to a substance that is likely to be without appreciable risk of adverse noncancer effects over a specified duration. The chronic MRLs and RfDs are conservative values, based on the levels of exposure reported in the literature that represent no-observed-adverse-effects levels (NOAEL) or lowest-observed-adverse-effects-levels (LOAEL) for the most sensitive outcome for a given route of exposure (e.g., dermal contact, ingestion). Uncertainty (safety) factors are applied to NOAELs or LOAELs to account for variation in the human population and uncertainty involved in extrapolating human health effects from animal studies. ATSDR also reviews the toxicological literature and epidemiology studies to evaluate the weight of evidence for adverse effects.
When evaluating the potential for cancer , ATSDR uses a weight of evidence approach to determine whether cancer effects are likely or not from an exposure to a toxic agent. In it's evaluation, ATSDR considers toxicologic and epidemiologic literature as well as cancer slope factors (CSF) that define the relationship between exposure doses and the likelihood of an increased risk of developing cancer over a lifetime. The CSFs are developed using data from animal or human studies and often require extrapolation from high exposure doses administered in animal studies to lower exposure levels typical of human exposure to environmental contaminants. The CSF represents a theoretical, 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 extrapolation. ATSDR also considers the cancer effect levels (CELs) reported in the literature. The CEL is the lowest dose of a chemical in a study, or group of studies, that was found to produce increased incidences of cancer (or tumors) in animals.
Estimating Exposure Doses from Ingesting Drinking Water from Base Wells
VOCs have been detected in Andersen AFB water supply wells MW-1, MW-2, and the Tumon-Maui well at concentrations greater than ATSDR comparison values and EPA's maximum contaminant levels for drinking water. To determine whether exposure to these contaminants in the well water is related to adverse health effects ATSDR estimated exposure doses for people consuming water containing the highest measured concentrations in the wells (39 ppb of TCE and 10 ppb of PCE). The estimated exposure doses were then used to estimate potential noncancer outcomes.
In estimating to what extent people might be exposed to contaminants, ATSDR used "conservative" or safe assumptions about possible human exposure and any associated health effects. ATSDR assumed that a person drank the most contaminated well water. ATSDR also used conservative assumptions about how often people drink water and how much they drink. For example, ATSDR assumed that a typical adult drank 2 liters of water each day and weighed 70 kilograms (kg) and that a child drank 1 liter of water each day and weighed 10 kg. Because ATSDR does not know with certainty how long exposure may have occurred, ATSDR estimated an exposure period of 30 years for an adult and 6 years for a child to calculate maximum exposure doses. These assumptions likely overestimate actual exposure because water from the wells was blended with other water in the distribution system and military employees drinking the TCE- and PCE-contaminated water were unlikely to be exposed for more than a year or two due to the relatively short duration of military duty stations. Furthermore, the actual exposure period was likely much shorter than 30 or 6 years, because the contaminated well was taken off line once the contamination was detected. The conservative assumptions, however, allow ATSDR to estimate the highest possible exposure dose and determine the corresponding health effects. Although ATSDR expects that few individuals, if any, were exposed to the highest levels of contamination, the "conservative" estimates are used to protect public health. Also, as a reminder, Guam residents and the general public did not use drinking water from the military supply system.
Noncancer: The resulting adult and child exposure doses for PCE are lower than its ATSDR MRL of 0.01 mg/kg/day. No chronic oral MRL or RfD is currently available for TCE. ATSDR recently withdrew the intermediate MRL and no chronic MRL or RfD exists for TCE. The study on which the intermediate MRL was based has been questioned because it contains certain flaws and limitations (e.g., the exact amount of TCE-contaminated water consumed by laboratory animals in the study is uncertain). For comparison, ATSDR reviewed the available toxicologic literature to determine possible adverse effects associated with exposure at doses estimated for this pathway. On the basis of this review, the exposure doses estimated for TCE by ATSDR are several orders of magnitude lower than the lowest doses reported in the toxicologic literature capable of producing noncancer effects in experimental animals administered oral doses of TCE (ATSDR 1997). Therefore, drinking water containing the highest detected levels of TCE and PCE reported in the wells is not likely to result in adverse noncancer effect.
Cancer: TCE and PCE have been shown to cause cancer in laboratory animals given large doses. The link between TCE or PCE and cancer in humans drinking water is controversial, however. Available studies are inconclusive and the data are inadequate to establish a link. EPA is currently reviewing the scientific literature pertaining to the carcinogenicity of TCE and PCE to determine its cancer classification. Some studies have shown that individuals drinking TCE-contaminated water with up to 220 ppb (a concentration over 24 times greater than the maximum level detected at Andersen AFB) suffered no increased incidence of cancer (Vartianinen et al. 1993; ATSDR 1997a, b).
ATSDR concludes that there is no apparent public health hazard associated with drinking water in the past from MW-1, MW-2, and the Tumon-Maui well.
Estimating Exposure Doses from Ingesting of Local Biota
Metals, pesticides, and SVOCs were measured in samples of crops grown or game grazing at Andersen AFB. People regularly consume papaya fruit and other edible fruit grown on and off base. Some Guam residents recreationally hunt game around Andersen AFB. ATSDR evaluated potential human health hazards associated with ingesting contaminated biota. Chemical exposure doses were estimated using conservative consumption rates for a 70 kg adult (2 grams per day of Sambar deer and monitor lizard; 20 grams per day of wild pig; and 340 grams per day of papaya) and exposure frequencies (365 days per year for a 30-year period).
Of all the chemicals analyzed, only arsenic (0.00044 mg/kg/day) exceeded its respective MRL (0.0003 mg/kg/day). No MRL or RfD exists for aluminum, an essential human nutrient. Aluminum concentrations in Guam biota, however, appeared elevated compared to normal background concentrations. Aluminum concentrations in on-base deer and pig tissue were slightly above normal background concentrations in mammals (1 to 5 ppm) as reported by Puls (1989), but detected concentrations in off-base deer and pig tissue were within normal background levels. ATSDR further examined the toxicologic literature to evaluate whether health effects were likely to occur at the detec ted levels of arsenic and aluminum.
Arsenic
ATSDR found that the estimated exposure doses for consumption of on-base produce were approximately 30 to 100 times lower than the lowest observed effect levels for chronic, oral doses of arsenic in humans (ATSDR 1993). Additionally, several epidemiologic studies of chronic, oral arsenic exposure report no health effects at average chronic doses of 0.0004-0.01 mg/kg/day (Mazumder et al. 1988; Valentine et al. 1985; Cebrian et al. 1983; Southwick et al. 1981; Harrington et al. 1978). It should be noted that estimated exposure doses and excess cancer risk were evaluated assuming that all produce (fruits and vegetables) consumed by Guam residents contained arsenic levels equal to the maximum arsenic level detected in on-base papaya. This assumption likely overestimates actual exposure. Access to Andersen AFB is restricted and no on-base areas are commercially farmed. Most residents, therefore, probably obtain their fruits and vegetables from areas not grown on Andersen AFB property. No off-base papaya samples had detectable levels of arsenic in their edible parts. The consumption of produce grown off-base, therefore, would not pose a public health threat. The estimated exposure dose from ingesting arsenic in on-base produce (0.00044 mg/kg/day) only slightly exceeds ATSDR's chronic oral MRL of 0.0003 mg/kg/day.
Aluminum
Aluminum non- and off-base papaya slightly exceeded background concentrations in unprocessed produce (0.1 to 7.16 ppm) as determined by Schenck et al. (1989). All monitor lizard aluminum concentrations were elevated. Over three-fourths of exposure to aluminum in local biota results from the ingestion of monitor lizard tissue. No island residents claimed, however, to eat monitor lizard when asked during the Guam diet survey (EA Engineering 1995). Therefore, exposure from the consumption of monitor lizard tissue appears unlikely, and, if it occurs at all, limited.
Due to restricted access to base properties, public exposure to contaminants from local biota is more likely to result from the consumption of off-base food sources. The estimated cumulative exposure to aluminum from analyzed off-base biota sources (0.0036 mg/kg/day) is 10 times lower than exposure from on-base biota.
The toxic potential of aluminum is extremely low compared to many other metals (ATSDR 1997c). If aluminum is chronically ingested, it may interfere with the body's up-take of calcium and phosphorous, however, the retention of aluminum in healthy mammals, specifically those without kidney dysfunction, is minimal. Even when dietary levels are high, aluminum concentrations in tissues do not reflect this increased exposure because most aluminum is excreted in the feces (ATSDR 1997c). Therefore, ATSDR concludes that aluminum is not likely to pose a noncancer public health hazard.
The EPA has not classified aluminum for human carcinogenicity, but ATSDR found no studies regarding cancer in humans after oral exposure to aluminum or aluminum compounds (ATSDR 1997c). Therefore, ATSDR concludes that exposure to aluminum in Guam biota will not pose a carcinogenic public health hazard.
Using current toxicologic information, ATSDR concludes that there are no apparent health hazards (past, current, or future) associated with consumption of local biota.
Evaluation of Radon Exposure
According to EPA, exposure to radon is a national environmental health problem and is not isolated to Guam (EPA 1992). Elevated radon levels have been discovered in virtually every state (Air Chek 1998). The EPA estimates that as many as 8 million homes throughout the country have elevated levels of radon. To date, state surveys show that 1 out of 5 homes in the United States has elevated radon levels (above 4 pCi/L) (Air Chek 1998).
Toxicologic studies report that radon exposure causes no adverse health effects from short term exposure. The primary health concern associated with residential radon exposure is lung cancer, although there is currently no clear evidence that radon exposure causes lung cancer. A recent report from the National Research Council estimates that approximately 1 in 7 of all lung cancer deaths can be attributed to radon exposure, independent of smoking status, though these estimates are uncertain (BEIR VI 1999).
Many factors influence the risk of lung cancer resulting from radon exposure. Among these are the radon level, the duration of exposure, the time since initiation of exposure, the age of an exposed individual, and the individual's smoking habits. The combined effects of cigarette smoking and radon exposure place current and former smokers at particularly high risk for lung cancer.
Epidemiologic studies show that individuals working in certain industries susceptible to radon releases are at greatest risk, because they are often exposed to high levels of radon over an extended period of time. In one study, uranium miners exposed to radon levels of 50 to 150 pCi/L in air for about 10 years have shown an increased frequency of lung cancer (ATSDR 1990), though this study suffers from several weaknesses including lack of control for exposures to other agents that could contribute to lung cancer, such as silica and smoking. In the past, some housing units at Andersen AFB contained radon levels above 50 pCi/L, but the duration of exposure to these levels was probably closer to 2 years (not 10 years), the average tour length on Andersen AFB.
The most effective methods of lung cancer prevention are to reduce radon exposure and to modify other risk factors, such as smoking (ATSDR 1992). Fortunately, the Air Force has been actively mitigating on-base housing levels of radon since 1989. Andersen AFB plans to continue its radon testing and mitigation of residential units in the future, as well as expand its base program to other, lower priority buildings.
ATSDR was unable to fully assess potential health hazards (if any) associated with past radon exposure at Andersen AFB. First, the full extent of past radon exposure at Andersen AFB remains unknown due to limited historical sampling data. Second, ATSDR does not have health-based comparison values for radon and EPA has not identified an inhalation reference concentration for radon. Moreover, EPA's carcinogen assessment summary for radon (formerly determined a human carcinogen) has been withdrawn pending further review. ATSDR found no clear evidence that long-term exposure to radon at levels that are normally present in the environment (1 to 3 pCi/L for average outdoor air levels) is likely to result in harmful health effects.
Table D-1.Chemical Concentrations Detected in Tissue (Muscle and Liver) of Sambar Deer (Cervus unicolor) Collected On-site Andersen AFB, Guam
| Contaminant | Number of Samples | Detection Frequency | Concentration Range (ppm) | Mean* Concentration (ppm) |
| Muscle | ||||
| Aluminum | 7 | 85.7% | 1.1-16.3 | 6.02 |
| Cadmium | 7 | 42.9% | 0.12-0.25 | 0.109 |
| Chromium | 7 | 42.9% | 0.26-0.39 | 0.186 |
| Copper | 7 | 100.0% | 1.2-2.2 | 1.66 |
| Manganese | 7 | 100.0% | 0.14-0.25 | 0.19 |
| Nickel | 7 | 14.3% | 0.34-0.34 | 0.201 |
| Silver | 7 | 14.3% | 0.15-0.15 | 0.058 |
| Vanadium | 7 | 14.3% | 0.21-0.21 | 0.101 |
| Zinc | 7 | 100.0% | 20.0-34.0 | 26.7 |
| Liver | ||||
| Aluminum | 7 | 71.4% | 3.0-9.3 | 3.77 |
| Cadmium | 7 | 100.0% | 0.1-0.67 | 0.323 |
| Chromium | 7 | 57.1% | 0.18-0.64 | 0.265 |
| Copper | 7 | 100.0% | 1.9-29.4 | 14.2 |
| Lead | 6 | 16.7% | 0.24-0.24 | 0.0775 |
| Manganese | 7 | 100.0% | 1.3-2.7 | 1.90 |
| Nickel | 7 | 28.6% | 0.42-0.84 | 0.311 |
| Selenium | 3 | 66.7% | 0.14-0.15 | 0.112 |
| Silver | 7 | 14.3% | 0.29-0.29 | 0.0793 |
| Vanadium | 7 | 14.3% | 0.19-0.19 | 0.104 |
| Zinc | 7 | 100.0% | 25.0-53.6 | 30.6 |
Source: EA Engineering 1995
* The mean was calculated using censored data (nondetects were assumed to be equal to 50% of the reported detection limit) when the frequency of detection was less than 100%.
ppm = parts per million
Table D-2.Chemical Concentrations Detected
in Tissue (Muscle and Liver) of Sambar Deer (Cervus unicolor) Collected
Off-site Andersen AFB, Guam
| Contaminant | Number of Samples | Detection Frequency | Concentration Range (ppm) | Mean* Concentration (ppm) |
| Muscle | ||||
| Aluminum | 2 | 50.0% | 2.8-2.8 | 1.68 |
| Cadmium | 2 | 50.0% | 0.14-0.14 | 0.0925 |
| Chromium | 2 | 50.0% | 0.35-0.35 | 0.218 |
| Copper | 2 | 100.0% | 1.4-75.6 | 38.5 |
| Manganese | 2 | 100.0% | 0.77-2.6 | 1.69 |
| Zinc | 2 | 100.0% | 15.2-25.5 | 20.4 |
| Liver | ||||
| Aluminum | 2 | 100.0% | 2.3-2.7 | 2.50 |
| Cadmium | 2 | 50.0% | 0.14-0.14 | 0.095 |
| Chromium | 2 | 50.0% | 0.35-0.35 | 0.225 |
| Copper | 2 | 100.0% | 1.7-16.70 | 9.20 |
| Manganese | 2 | 100.0% | 0.29-2.3 | 1.30 |
| Zinc | 2 | 100.0% | 22.3-25.4 | 23.9 |
Source: EA Engineering 1995
* The mean was calculated using censored data (nondetects were assumed to be equal to 50% of the reported detection limit) when the frequency of detection was less than 100%.
ppm = parts per million
Table D-3. Chemical Concentrations Detected in Tissue (Muscle
and Liver) Samples of Wild Pigs (Sus scrofa) Collected On-site Andersen
AFB, Guam
| Contaminant | Number of Samples | Detection Frequency | Concentration Range (ppm) | Mean* Concentration (ppm) |
| Muscle | ||||
| Aluminum | 8 | 100.0% | 1.7-6.8 | 3.69 |
| Cadmium | 8 | 12.5% | 0.23-0.23 | 0.0675 |
| Chromium | 8 | 87.5% | 0.18-0.72 | 0.351 |
| Copper | 8 | 100.0% | 0.31-1.1 | 0.756 |
| Manganese | 8 | 87.5% | 0.08-0.17 | 0.128 |
| Nickel | 8 | 37.5% | 0.67-0.9 | 0.413 |
| Silver | 8 | 50.0% | 0.11-0.63 | 0.154 |
| Vanadium | 8 | 37.5% | 0.3-0.66 | 0.225 |
| Zinc | 8 | 100.0% | 16.8-23.8 | 19.4 |
| DDE | 8 | 12.5% | 0.0037-0.0037 | 0.00191 |
| 4-Methylphenol | 5 | 40.0% | 0.034-0.037 | 0.113 |
| Liver | ||||
| Aluminum | 8 | 100.0% | 3.7-34.3 | 11.8 |
| Antimony | 8 | 37.5% | 0.08-0.33 | 0.0856 |
| Cadmium | 8 | 100.0% | 0.26-3.6 | 1.08 |
| Chromium | 8 | 100.0% | 0.13-0.48 | 0.298 |
| Copper | 8 | 100.0% | 2.2-4.7 | 3.14 |
| Lead | 5 | 80.0% | 0.12-0.16 | 0.112 |
| Manganese | 8 | 100.0% | 1.4-3.0 | 2.09 |
| Mercury | 8 | 62.5% | 0.1-0.27 | 0.127 |
| Nickel | 8 | 37.5% | 0.4-1.1 | 0.349 |
| Selenium | 5 | 100.0% | 0.12-0.53 | 0.292 |
| Silver | 8 | 12.5% | 0.05-0.05 | 0.0406 |
| Vanadium | 8 | 37.5% | 0.18-0.21 | 0.116 |
| Zinc | 8 | 100.0% | 25.1-83.3 | 46.1 |
| DDE | 8 | 25.0% | 0.0072-0.022 | 0.00489 |
| Endosulfan sulfate | 8 | 12.5% | 0.0045-0.0045 | 0.00201 |
| Endrin | 8 | 12.5% | 0.0065-0.0065 | 0.00226 |
| 4-Methylphenol | 5 | 80.0% | 0.14-0.38 | 0.217 |
Source: EA Engineering 1995
* The mean was calculated using censored data (nondetects were assumed to be equal to 50% of the reported detection limit) when the frequency of detection was less than 100%.
ppm = parts per million
Table D-4. Chemical Concentrations in Samples of Wild Pigs
(Sus scrofa) Collected Off-site, Andersen AFB, Guam
| Contaminant | Number of Samples | Detection Frequency | Concentration Range (ppm) | Mean* Concentration (ppm) |
| Muscle | ||||
| Aluminum | 1 | 100.0% | NA | 2.0 |
| Antimony | 1 | 100.0% | NA | 0.27 |
| Copper | 1 | 100.0% | NA | 0.58 |
| Nickel | 1 | 100.0% | NA | 0.53 |
| Zinc | 1 | 100.0% | NA | 21.4 |
| Liver | ||||
| Antimony | 1 | 100.0% | NA | 0.11 |
| Cadmium | 1 | 100.0% | NA | 0.13 |
| Copper | 1 | 100.0% | NA | 36.0 |
| Manganese | 1 | 100.0% | NA | 2.7 |
| Selenium | 1 | 100.0% | NA | 1.3 |
| Zinc | 1 | 100.0% | NA | 29.4 |
Source: EA Engineering 1995
* The mean was calculated using censored data (nondetects were assumed to be equal to 50% of the reported detection limit) when the frequency of detection was less than 100%.
ppm = parts per million
NA = not applicable
Table D-5. Chemical Concentrations Detected in Whole Body
(Heads Were Removed Prior to Analysis) Samples of Monitor Lizards (Varanus
indicus) Collected On-site Andersen AFB, Guam
| Contaminant | Number of Samples | Detection Frequency | Concentration Range (ppm) | Mean* Concentration (ppm) |
| Whole Body | ||||
| Aluminum | 5 | 100.0% | 23.4-332.0 | 113.0 |
| Antimony | 5 | 80.0% | 0.12-1.6 | 0.56 |
| Cadmium | 5 | 80.0% | 0.14-0.47 | 0.227 |
| Chromium | 5 | 100.0% | 0.45-2.4 | 1.11 |
| Copper** | 5 | 100.0% | 0.95-14.7 | 5.01 |
| Lead** | 4 | 100.0% | 0.23-45.6 | 14.2 |
| Manganese | 5 | 100.0% | 0.48-6.6 | 2.0 |
| Mercury | 5 | 40.0% | 0.1-0.18 | 0.081 |
| Nickel | 5 | 100.0% | 0.44-2.1 | 0.846 |
| Silver | 5 | 80.0% | 0.14-0.78 | 0.394 |
| Vanadium | 5 | 40.0% | 0.33-0.36 | 0.196 |
| Zinc | 5 | 100.0% | 23.3-55.0 | 36.8 |
| DDD | 5 | 20.0% | 0.038-0.038 | 0.00892 |
| DDE | 5 | 40.0% | 0.0044-0.1 | 0.0219 |
| DDT | 5 | 20.0% | 0.15-0.15 | 0.0313 |
Source: EA Engineering 1995
* The mean was calculated using censored data (nondetects were
assumed to be equal to 50% of the reported detection limit) when the frequency
of detection was less than 100%.
** Copper and lead values are biased since the animals were shot with copper-plated
lead pellets.
ppm = parts per million
Table D-6. Chemical Concentrations Detected in Whole Body
(Heads Were Removed Prior to Analysis) Samples of Monitor Lizards (Varanus
indicus) Collected Off-site Andersen AFB, Guam
| Contaminant | Number of Samples | Detection Frequency | Concentration Range (ppm) | Mean* Concentration (ppm) |
| Whole Body | ||||
| Aluminum | 2 | 100.0% | 38.0-104.0 | 71.0 |
| Antimony | 2 | 100.0% | 0.09-0.13 | 0.11 |
| Cadmium | 2 | 50.0% | 0.08-0.08 | 0.065 |
| Chromium | 2 | 100.0% | 0.48-0.98 | 0.73 |
| Copper** | 2 | 100.0% | 0.71-0.92 | 0.815 |
| Lead** | 2 | 100.0% | 0.11-0.16 | 0.135 |
| Manganese | 2 | 100.0% | 0.62-2.7 | 1.66 |
| Nickel | 2 | 100.0% | 0.62-0.67 | 0.645 |
| Selenium | 1 | 100.0% | 0.19-0.19 | ND |
| Silver | 2 | 100.0% | 0.12-0.47 | 0.295 |
| Vanadium | 2 | 100.0% | 0.24-0.45 | 0.345 |
| Zinc | 2 | 100.0% | 31.4-37.8 | 34.6 |
| DDE | 2 | 50.0% | 0.029-0.029 | 0.0153 |
| DDT | 2 | 50.0% | 0.0039-0.0039 | 0.00278 |
| Dieldrin | 2 | 50.0% | 0.0036-0.0036 | 0.00263 |
| Heptachlor epoxide | 2 | 50.0% | 0.0053-0.0053 | 0.00308 |
Source: EA Engineering 1995
* The mean was calculated using censored data (nondetects were
assumed to be equal to 50% of the reported detection limit) when the frequency
of detection was less than 100%.
** Copper and lead values are biased since the animals were shot with copper-plated
lead pellets.
ppm = parts per million
ND = not detected
Table D-7. Chemical Concentrations Detected in Papaya (Carica
papaya) Collected On-base Andersen AFB, Guam
| Contaminant | Number of Samples | Detection Frequency | Concentration Range (ppm) | Mean* Concentration (ppm) |
| Edible Tissue | ||||
| Aluminum | 5 | 100.0% | 1.4-8.2 | 5.22 |
| Arsenic | 5 | 20.0% | 0.09-0.09 | 0.055 |
| Chromium | 5 | 40.0% | 0.51-0.8 | 0.318 |
| Copper | 5 | 100.0% | 0.93-8.7 | 3.07 |
| Lead | 3 | 33.3% | 0.12-0.12 | 0.0717 |
| Manganese | 5 | 100.0% | 1.3-3.9 | 2.54 |
| Nickel | 5 | 80.0% | 0.54-0.97 | 0.637 |
| Silver | 5 | 40.0% | 0.21-0.77 | 0.225 |
| Vanadium | 5 | 40.0% | 0.54-0.68 | 0.3 |
| Zinc | 5 | 100.0% | 3.0-10.1 | 5.84 |
| Di-n-butyl phthalate | 3 | 33.3% | 0.036-0.036 | 0.122 |
| Cyanide | 5 | 20.0% | 0.16-0.16 | 0.069 |
Source: EA Engineering 1995
* The mean was calculated using censored data (nondetects were assumed to be equal to 50% of the reported detection limit) when the frequency of detection was less than 100%.
ppm = parts per million
Table D-8. Chemical Concentrations Detected in Papaya (Carica papaya) Collected Off-base Andersen AFB, Guam
| Contaminant | Number of Samples | Detection Frequency | Concentration Range (ppm) | Mean* Concentration (ppm) |
| Edible Tissue | ||||
| Aluminum | 3 | 100.0% | 1.9-7.5 | 5.47 |
| Chromium | 3 | 67.7% | 0.48-0.66 | 0.413 |
| Copper | 3 | 100.0% | 0.61-1.1 | 0.937 |
| Lead | 3 | 33.3% | 0.09-0.09 | 0.0617 |
| Manganese | 3 | 100.0% | 1.0-1.3 | 1.17 |
| Nickel | 3 | 33.3% | 1.0-1.0 | 0.457 |
| Silver | 3 | 67.7% | 0.35-0.64 | 0.347 |
| Vanadium | 3 | 67.7% | 0.4-0.77 | 0.423 |
| Zinc | 3 | 100.0% | 2.7-3.0 | 2.9 |
| Di-n-butyl phthalate | 3 | 67.7% | 0.035-0.04 | 0.08 |
Source: EA Engineering 1995
* The mean was calculated using censored data (nondetects were assumed to be equal to 50% of the reported detection limit) when the frequency of detection was less than 100%.
ppm = parts per million
APPENDIX E: RESPONSE TO PUBLIC COMMENT
The Agency for Toxic Substances and Disease Registry (ATSDR) released the Andersen Air Force Base (Andersen AFB) Public Health Assessment (PHA) on September 27, 2001, for public review and comment. That public comment period ended November 30, 2001. The following documents ATSDR's response to comments and questions received during the public comment period.
Response: No data on coconut crabs were available for ATSDR's review during the preparation of this public health assessment. Despite the lack of data, ATSDR believes that people are not at risk of exposure to unhealthy levels of Andersen AFB-related contaminants when they consume coconut crabs. In making this determination, ATSDR reviewed relevant, supplemental information, including bioaccumulation data for other native biota, areas of soil contamination, and possible harvesting areas.
Both on-site and off-site wildlife data were available for Sambar deer, wild pig, snakes, and lizards. Although not specific to coconut crab, these data help us assess whether wildlife, in general, are accumulating contaminants from Andersen AFB and, if so, whether contaminants are accumulating at levels that might be harmful to the consumer. For all cases, ATSDR found no apparent health hazards associated with the wildlife as a source of food.
Several areas of soil contamination were noted at Andersen AFB, but PCBs were most often reported in soil at the Main Base. Access restrictions are enforced at sites on the Main Base, thus essentially preventing people from harvesting crabs in the areas of likely PCB contamination.
Together, this information suggests that the wildlife are not accumulating contaminants at levels of concern and the soil contamination and harvesting areas are not co-located. Still, if biota sampling is conducted in the future, ATSDR recommends as a prudent measure that the program include sampling of coconut crabs.
Response: TCE and PCE have been detected in groundwater beneath Andersen Air Force Base, but ATSDR believes that sufficient regulatory mechanisms are in place to track groundwater contamination and prevent potential harmful exposures in the future.
ATSDR believes that these collective measures will help protect the aquifer beneath Andersen AFB and safeguard the quality of drinking water for future use.
