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PUBLIC HEALTH ASSESSMENT

HOMESTEAD AIR FORCE BASE
HOMESTEAD, DADE COUNTY, FLORIDA


TABLES

The following section 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

FIGURES

Figure 1. Homestead AFB Location Map
Figure 1. Homestead AFB Location Map

Figure 2. Homestead Air Force Base Site Plan
Figure 2. Homestead Air Force Base Site Plan

Figure 3. Homestead AFB Parcel Map
Figure 3. Homestead AFB Parcel Map

Figure 4. ATSDR's Exposure Evaluation Process
Figure 4. ATSDR's Exposure Evaluation Process




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.

Base/Neutral and Acid Extractable Compounds (BNAs)
Compounds amenable to analysis by extraction of the sample with an organic solvent. Polycyclic aromatic hydrocarbons, such as naphthalene, phenanthrene, benzo(a)pyrene, and chrysene, comprise one category of BNAs. The term BNAs is used synonymously with semi-volatile organic compounds.

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.

Polycyclic Aromatic Hydrocarbons (PAHs)
PAHs comprise one category of base/neutral acid or extractable compounds and are a group of chemicals that are formed during the burning of coal, oil, gas, wood, or other organic substance. Some PAHs are contained in asphalt used for paving roads or runways. There are more than 100 different PAH compounds and they are found throughout the environment in air, water, and soil. Most PAHs do not appear alone in the environment but, rather, in complex mixtures of many individual PAHs, which may be carcinogenic or noncarcinogenic.

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.

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 causeadverse health effects. Comparison values represent media-specific contaminant concentrationsthat are used to select contaminants for further evaluation to determine the possibility of adversepublic health effects.

Cancer Risk Evaluation Guides (CREGs)

CREGs are estimated contaminant concentrations that would be expected to cause no more thanone excess cancer in a million (10-6) persons exposed over lifetime. ATSDR's CREGs arecalculated 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 andingestion 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 levelof a contaminant in water that is delivered to the free-flowing outlet. MCLs are consideredprotective of public health over a lifetime (70 years) for people consuming two liters of water perday.

Reference Media Evaluation Guides (RMEGs)

ATSDR derives RMEGs from EPA's oral reference doses. The RMEG represents theconcentration in water or soil at which daily human exposure is unlikely to result in adversenoncarcinogenic effects.

EPA Region III Risk-Based Concentrations

EPA combines reference doses and carcinogenic potency slopes with "standard" exposurescenarios to calculate risk-based concentrations, which are chemical concentrations correspondingto fixed levels of risk (i.e., a hazard quotient of 1, or lifetime cancer risk of 10-6, whichever occursat a lower concentration) in water, air, fish tissue, and soil.


APPENDIX C: Evaluation of Estimated Exposure Doses and Health Effects from Contact with OU-18 Soil and Ingestion of Fish from the Boundary and Outfall Canals.

Deriving Exposure Doses

ATSDR estimated the human exposure doses for trespassers from dermal contact with orincidental ingestion of on-site soil at OU-18, and for nearby residents from ingestion of fish fromthe Boundary and Outfall Canals. Deriving exposure doses requires evaluating the concentrationsof the contaminants to which people may have been exposed and how often and for how longexposure to those contaminants occurred. Health effects are also related to individualcharacteristics such as age, gender, and nutritional status that influence how a chemical might beabsorbed, metabolized, and eliminated by the body. Together, these factors help influence theindividual's physiological response to chemical contaminant exposure and potential noncancer(noncarcinogenic) or cancer (carcinogenic) outcomes. In the absence of exposure-specificinformation, ATSDR applied several conservative exposure assumptions to define site-specificexposures as accurately as possible for trespassers at the OU-18 site and residents near the canals.

Evaluating Potential Health Hazards

The estimated exposure doses are used to evaluate potential noncancer and cancer effectsassociated with chemicals of concern. When evaluating noncancer effects, ATSDR uses standardhealth guidelines, including ATSDR's Minimal Risk Levels (MRLs) and EPA's Reference Doses(RfDs), to evaluate whether adverse effects may occur. The chronic MRLs and RfDs areestimates of daily human exposure to a substance that are unlikely to result in adverse noncancereffects over a specified duration. ATSDR compared estimated exposure doses associated withOU-18 soil exposure and fish ingestion scenarios to conservative health guidelines such as MRLsor RfDs for each contaminant. If the exposure dose is greater than the MRL or RfD, then apossibility exists that noncancer effects will occur. However, because comparison values do notrepresent thresholds of toxicity, exposure to chemical concentrations above comparison valuesdoes not necessarily produce health effects.

To evaluate cancer effects, ATSDR uses Cancer Potency Factors (CPFs) that define therelationship between oral exposure doses and the increased likelihood of developing cancer over alifetime. The CPFs are developed using data from animal or human studies and often requireextrapolation from high exposure doses administered in animal studies to the lower exposurelevels 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 anumber of uncertainties in the data used in the extrapolation.

ATSDR estimated the potential for cancer to occur using the following equation. The estimatedexposure doses and CPF values for the contaminants of concern are incorporated into theequation:

    Lifetime Cancer Risk = Estimated exposure dose (mg/kg/day) x CPF (mg/kg/day)-1

Although no risk of cancer is considered acceptable, it is impossible to achieve a zero cancer risk.Consequently, ATSDR often uses a range of 10-4 to 10-6 estimated lifetime cancer risk (or 1 newcase in 10,000 to 1,000,000 exposed persons), based on conservative assumptions aboutexposure, to determine whether a concern regarding cancer effects is valid. This range isconsistent with values adopted by EPA for evaluating the need for cleanup at hazardous wastesites. Some of the chemicals of concern detected in soil at the OU-18 site and in the fish from theBoundary and Outfall Canals are considered to be human carcinogens or probable human carcinogens.

OU-18: Soil

Benzo(a)pyrene Toxic Equivalents

When estimating exposure doses for carcinogenic effects of polycyclic aromatic hydrocarbons(PAHs), ATSDR uses a Toxic Equivalency Factor (TEF) approach (EPA, 1993) to account forthe fact that toxicity values are not available for all the PAHs detected in soil at the site. Thebenzo(a)pyrene toxic equivalent is a weighted concentration of carcinogenicity of PAHs in amixture that compensates for the differences in toxicity among the different PAHs. A TEF hasbeen assigned to 17 individual PAH compounds based on laboratory evidence of carcinogenicityand on their prevalence at hazardous waste sites. Although the TEF approach assumes that thecarcinogenic activity of PAH mixtures depends primarily on the carcinogenic PAHs,noncarcinogenic PAHs are included because they may increase the potency of the carcinogenicPAHs (Nisbet and LaGoy, 1992).

The relative weight is 1 for benzo(a)pyrene; 5 for dibenzo(a,h)anthracene; 0.1 forbenzo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, and indeno(1,2,3-cd)pyrene;0.001 for anthracene, benzo(g,h,i)perylene, and chrysene; and 0.0001 for acenaphthene,acenaphthylene, fluoranthene, fluorene, 2-methylnaphthalene, naphthalene, phenanthrene, andpyrene. ATSDR used the benzo(a)pyrene equivalent to evaluate the likelihood for cancer effectsto occur from contact with or incidental ingestion of soil at the OU-18 site.

ATSDR used the maximum PAH values for samples collected on site to estimate exposure dosesfor noncancer effects. The total PAH value is the sum of the concentrations of the individualnoncarcinogenic PAHs.



Table C-1:

Maximum Contaminant Concentrations in On-Site Surface Soil at OU-18
Contaminant Maximum
Concentration (mg/kg)
Comparison Value
Concentration
(mg/kg)
Reference
PAHs
Benzo(a)pyrene equivalents
2,526
438.36
no value
0.1

CREG
Arsenic1020
0.5
RMEG
CREG
Aldrin0.530.04CREG
Heptachlor Epoxide2.20.08CREG

Dermal Contact With Soil at OU-18

ATSDR used the following equation to estimate human exposure doses for dermal (skin) contactwith soil at the OU-18 site:

Estimated Exposure Dose = Conc. x CF x SA x ABS x AF x EF x ED
BW x AT



where:
Conc. = Maximum contaminant concentration in on-site soil (mg/kg)
CF = Conversion factor: 10-6 kg/mg
SA = Skin surface area available for contact (cm2/event): trespasser: 6,170 cm2 (hands, arms, legs, and feet) (EPA, 1989)
ABS = Absorption Factor (unitless) for dermal exposure
AF = Skin to soil adherence factor = 0.6 mg/cm2-event (EPA, 1992)
EF = Exposure frequency, or number of exposure events per year of exposure: trespasser = 2 days/week x 50 weeks = 100 times per year
ED = Exposure duration, or the duration over which exposure occurs: trespasser = 7 years
BW = Body weight (kg): trespasser (age 7-14) = 50 kg
AT = Averaging time, or the time period over which cumulative exposures are averaged (ED x 365 days/year for noncancer effects; 70 years x 365 days/year for cancer effects)

Assumptions for Estimating Human Exposure Dose:

  • The skin surface area (SA) available for contact per exposure event was assumed to be10% of the 95th percentile values for the whole body of a juvenile trespasser (hands, arms,legs, and feet) (EPA, 1992). Although estimates of exposed skin are fairly realistic, it islikely that less than the estimated area of exposed skin actually becomes covered with soil.
  • Assessing exposure to contaminants from dermal contact involves determining the amountof contaminant actually absorbed into the body rather than the amount that comes intocontact with the outer skin. Therefore, exposures that occur through dermal contact werecalculated as absorbed doses. A dermal absorption factor (ABS-dermal) was used toapproximate how much of the contaminant contacting the body is actually absorbed. TheABS-dermal values for the chemicals of concern represent the percentage of thecontaminant concentration contacted. The ABS-dermal factor is 10 percent for PAHs andthe benzo(a)pyrene equivalent (Ryan and Hawkins, et al., 1987), 3.2 percent for arsenic(West and Maibach, et al., 1993), and 10 percent for heptachlor epoxide (Feldman andMaibach, 1974). Because no ABS-dermal factor is known for aldrin, ATSDR assumed 100percent.
  • The amount of soil adherence to skin (the adherence factor [AF]) per exposure event wasassumed to be 0.6 mg/cm2, the midpoint of the range recommended by EPA for dermalexposure to soil (EPA, 1992). Measurements of soil adherence for workers, however,reportedly approach only 0.2 mg/cm2 for hands and approximately 0.02 mg/cm2 for otherexposed parts of the body (Kissel et al., 1995).
  • The exposure frequency (EF), or number of exposure events per year, was assumed to be100 days per year for juvenile trespassers. This assumes that a juvenile might have spenttwo days a week at OU-18 almost every week of the year (50 weeks). This site was alandfill; although nearby residents may have accessed the site, there is no indication that itwas a frequently visited site or meeting place for juveniles. ATSDR believes that thisassumption overestimates exposure.
  • The duration of exposure (ED) was assumed to have occurred over seven years for a juvenile trespasser, for instance, from the age of nine through the age of 16.
  • The averaging time (AT) for noncancer effects was assumed to be seven years for 365days/year, and 70 years for 365 days/years (or 25,550 days) for cancer effects.
  • No health guidelines for carcinogenic and noncarcinogenic effects are available for thedermal route of exposure. Therefore, the values available for the oral route of exposurewere adjusted to account for exposure occurring through the skin rather than fromingestion.
Likelihood of Health Effects for a Trespasser from Dermal Contact with On-Site Soil at OU-18
    Noncancer Effects: Estimated exposure doses for a juvenile trespasser (7 to 14 years)exposed to the maximum detected concentration of PAHs, arsenic, aldrin, or heptachlorepoxide two days per week for 50 weeks over seven years are below health guidelines andtherefore do not pose a public health hazard.

    Cancer Effects: Based on detected levels and intermittent exposures, PAHs, arsenic, aldrin, and heptachlor epoxide in soil are not likely to be associated with excess cancers.

Incidental Ingestion of Soil at OU-18

Estimated Exposure Dose = Conc. x IR x CF x EF x ED
BW x AT



where:
Conc. = Maximum contaminant concentration in OU-18 site soil (mg/kg)
IR = Ingestion Rate (mg/day): 100 mg/day for trespassers.
CF = Conversion factor (10-6 kg/mg)
EF = Exposure frequency, or number of exposure events per year of exposure: trespasser = two days/week x 50 weeks.
ED = Exposure duration, or the duration over which exposure occurs: trespasser = 7 years
BW = Body weight (kg): trespasser (age 7-14) = 50 kg
AT = Averaging time, or the time period over which cumulative exposures are averaged (ED x 365 days/year for noncancer effects; 70 years x 365 days/year for cancer effects)

Assumptions for Estimating Human Exposure Dose:

  • A soil ingestion rate (IR) of 100 mg/day was based on an assumption that soil on the handsis incidentally ingested while eating or playing, and that soil adheres to the palms of thehands. A more typical value for ingestion over an entire day is probably less than 50mg/day. The soil ingestion rate also assumes that the contaminant in soil is bioavailable asthe pure chemical, whereas the actual bioavailability may be substantially less.

  • The exposure frequency (EF), or number of exposure events per year, was assumed to be100 days per year for juvenile trespassers. This assumes that a juvenile might have spenttwo days a week at OU-18 almost every week of the year (50 weeks). This site was alandfill; although nearby residents may have accessed the site, there is no indication that itwas a frequently visited site or meeting place for juveniles. ATSDR believes that thisassumption overestimates exposure.
  • The duration of exposure (ED) was assumed to have occurred over seven years for a juvenile trespasser, for instance, from the age of nine through the age of 16.
  • The averaging time (AT) for noncancer effects was assumed to be seven years for 365days/year and 70 years for 365 days/years (or 25,550 days) for cancer effects.

Likelihood of Health Effects From Incidental Ingestion of Soil at OU-18

    Noncancer Effects: The estimated exposure doses for a juvenile trespasser (7 to 14 years)who is exposed to the maximum concentration of PAHs, arsenic, aldrin, or heptachlorepoxide two days per week for 50 weeks over seven years are lower than health guidelinevalues and therefore do not pose a public health hazard.

    Cancer Effects: No increased likelihood of developing cancer is associated with incidentalexposures to soil contaminants at OU-18, even using conservative assumptions.

Boundary and Outfall Canals: Fish



Table C-2:

Summary of Contaminants that Exceeded EPA Region III Risk-Based Concentrations in FishFillet Samples from the Boundary and Outfall Canals.
Contaminant Contaminant Concentration (mg/kg) EPA Region
III Risk-Based
Concentration1
(mg/kg)
Minimum Maximum Frequency of
Detections/
Total Samples
Number of
Detections
greater thanthe EPA
Region III
Value
Polychlorinated Biphenyls (PCBs)/Pesticides
Aroclor-12600.0180.0545/2450.0016
4,4'-DDD0.0260.0673/2430.013
4,4'-DDE0.00270.1720/24140.0093
4,4'-DDT0.00620.01712/2410.0093
Metals/Inorganics
Arsenic0.050.2613/24130.0021
Mercury0.020.4624/2410.52
1 Revised April 15, 1998. Listed values are based on cancer effects.
2 The Florida Department of Health's limited ingestion advisory for mercury in fish (0.5 to 1.5 mg/kg).

Ingestion of Contaminated Fish from the Boundary and Outfall Canals

ATSDR used the following equation to estimate human exposure doses for ingestion of fish from the Boundary and Outfall Canals:

Estimated Exposure Dose = Conc. x IR x FI x EF x ED
BW x AT



where:
Conc. = Maximum contaminant concentration detected in fish (mg/kg)
IR = Ingestion rate (kg/day):
0.014 kg/day daily intake averaged over a year (EPA, 1998)
[approximately 1.5, 0.2 kg fish meals per month]
0.051 kg/day daily intake averaged over a year for Florida residents ingesting freshwater predator fish (Portier et al., 1995)
[approximately 5, 0.2 kg fish meals per month]
0.132 kg/day upper bound value of fin fish ingestion (Pao et al., 1982)
[approximately 14, 0.2 kg fish meals per month]
FI =

Fraction ingested from the canals (assumed to be 100 percent)

EF = Exposure frequency, or number of exposure events: 365 days/year
ED =

Exposure duration, or the duration over which exposure occurs: 30 years for adults, 6 years for children

BW = Body weight (kg): 70 kg for adult, 10 kg for children (aged 0-6)
AT =

Averaging time, or the time period over which cumulative exposures are averaged:
noncancer effects: ED x 365 days/year; cancer effects: 70 years x 365 days/year

Assumptions for Estimating Human Exposure Dose:

  • Tables C-3 and C-4 show estimated daily doses of contaminants using common assumptionsabout daily intake. Estimated daily intakes are heavily dependent on assumed ingestion ratesof recreationally caught fish. The fish ingestion rates that ATSDR used ranged from 1.5 to 14fish meals per month. The smallest ingestion rate scenario is based on EPA's estimation of theaverage daily intake of fish in the U.S. The mid-range scenario is based on a study evaluatingfish consumption in Florida. The largest value is used for evaluating the possible ingestion rateof subsistence fishermen. The fish ingestion rate also assumes the highest concentration of thecontaminant detected was consumed for each fish meal. These very conservative assumptionswill most likely overestimate exposure. The same ingestion rate was used for children, whotend to eat smaller serving sizes than adults. Therefore, a greater number of smaller sizedmeals would have to be consumed for each ingestion scenario.

  • The fraction ingested (FI) was conservatively assumed to be 100 percent, meaning that all fishconsumed were caught in the Boundary or Outfall Canals.
  • The duration of exposure (ED) was assumed to have occurred over 30 years for an adult and6 years for a child.
  • The averaging time (AT) was assumed to be 30 years for 365 days/year for noncancer effectsand 70 years for 365 days/years (or 25,550 days) for cancer effects.

Likelihood of Health Effects From Ingestion of Fish from the Boundary and Outfall Canals

Adult Exposure

Noncancer Effects: With few exceptions, estimated adult exposure doses, based on three differentingestion rate scenarios, are below health guidelines for PCBs, pesticides, and metals andtherefore do not pose a public health hazard. The estimated exposure doses for an adult exposedto the maximum detected concentrations of Aroclor-1260 and arsenic, however, are above healthguidelines and may therefore be a health concern.



Table C-3.

Estimated Exposure Doses for Noncancer Effects for an Adult Exposed to the Maximum DetectedConcentration in Fish Fillets over 30 Years for Three Ingestion Rate Scenarios. (Bold values indicate a dosein excess of the MRL/RfD value.)
Contaminant Dose from
approximately 1.5,
0.02 kg fish
meals/month
(mg/kg/day)
Dose from
approximately 5,
0.2 kg fish
meals/month
(mg/kg/day)
Dose from
approximately 14,
0.2 kg fish
meals/month
(mg/kg/day)
MRL/RfD
(mg/kg/day)
Aroclor-12600.0000110.0000390.00010.00002
Arsenic0.0000530.000190.000490.0003

Cancer Effects: Based on the highest detected concentration of arsenic, the cancer risk estimate isslightly elevated (3.2×10-4) for an adult ingesting 14 fish meals per month from the canal system.No increased likelihood of developing cancer is associated with ingestion of detected levels ofPCBs, pesticides, or other metals in fish, even using the most conservative ingestion rate scenario.

Child Exposure

Noncancer Effects: The bolded estimated exposure doses presented in Table C-4 for a childexposed to the maximum detected concentration of the contaminants listed are above healthguidelines and may therefore be a health concern. All other estimated exposure doses, even for themost conservative ingestion rate, are lower than health guideline values and therefore do not posea public health hazard.



Table C-4.

Estimated Exposure Doses for Noncancer Effects for a Child Exposed to the Maximum DetectedConcentration in Fish Fillets over Six Years for Three Ingestion Rate Scenarios. (Bold values indicate a dosein excess of the MRL/RfD value.)
Contaminant Dose from
approximately 1.5,
0.2 kg fish
meals/month
(mg/kg/day)
Dose from
approximately 5,
0.2 kg fish
meals/month
(mg/kg/day)
Dose from
approximately 14,
0.2 kg fish
meals/month
(mg/kg/day)
MRL/RfD
(mg/kg/day)
Aroclor-12600.0000770.000280.000710.00002
4,4'-DDD0.0000960.000340.000880.0005
4,4'-DDE0.000240.000870.002240.0005
Arsenic0.000370.001330.003430.0003
Mercury0.000660.002350.006070.002

Cancer Effects: ATSDR does not routinely evaluate cancer for children primarily because of theuncertainty stemming from limited understanding of mechanisms of carcinogenicity in children. Inaddition, CPFs are generally derived from lifetime studies (i.e., 70 years), and children haveexperienced much less than a lifetime exposure.

Discussion

Estimated doses from ingesting fish exceeded the MRL or RfD for a few contaminants, mostnotably PCBs (Aroclor-1260), pesticides (4,4'-DDD and 4,4'-DDE), arsenic, and mercury.Exceeding an MRL or RfD, however, does not necessarily mean that an adverse health effect willbe seen. These values are very conservative and do not represent thresholds of toxicity. Most ofthe estimated doses in this analysis exceeded the MRL or RfD only slightly.

The analysis that ATSDR performed assumed that all the fish consumed by an individual containsthe highest detected levels of a given contaminant. It is important to note, however, that all fish inthe canal do not contain the highest detected levels of all of the contaminants (see Table C-2). Forinstance, arsenic was detected in only half of the fish samples. Similarly, Aroclor-1260 wasdetected in only 5 of 24 samples, and 4,4'-DDD was detected in only 3 of 24 samples. While 4,4'-DDE was detected in 20 of the 24 samples, only 14 of those detections were at levels above theEPA Region III Risk-Based Concentration of 0.0093 mg/kg. It is highly unlikely that an individualwould be exposed to the highest concentration of a contaminant detected in every fish he or shecaught in the canal and ate.

It is very important to understand that ATSDR based this analysis on the consumption of fishmeals from the canal only. The three different fish ingestion rate scenarios are based on studiesfor the U.S. population and do not necessarily represent what residents near Homestead AFBmight catch and eat from the canals. For instance, the Statistical Analysis of Florida Per CapitaFish and Shellfish Consumption Data report (Portier et al., 1995) performed telephone surveysand determined that Floridians eat an average of 370.85 grams of freshwater predator fish (suchas the largemouth bass caught in the canal) in their home per month (this is equivalent toapproximately five fish meals). ATSDR used this number as a guideline for what residents in thearea of Homestead might consume, and extrapolated that they might eat all of those meals fromfish caught in the canals, as opposed to store-bought fish.

Estimated exposure doses for ingestion are also highly dependent on what people actually eat.People have been seen fishing along the Outfall Canal; how much fishing is done recreationallyand how much fish caught in the canals is ingested is not known. This analysis indicates that theinfrequent ingestion of fish from the canal system (for instance, one or two fish meals per month)is not likely to be associated with either cancer on noncancer effects. However, there is apossibility that ingestion of fish from the canals at a subsistence level (eating 14 fish meals permonth) may be associated with health effects. It is unknown if subsistence fishing in the canalsoccurs or whether the Boundary and Outfall Canals are even capable of providing enough fish tomake subsistence fishing possible.

ATSDR analyzed contaminant concentrations in fish fillets based on the assumption that peopleusually eat the fillet section of the fish. It should be noted, however, that the skin, fatty tissues,and organs of fish accumulate PCBs and pesticides more readily than the fillet section. Wholebody fish samples from the canals contained greater concentrations of PCBs and pesticides thanthe fillet samples. Therefore, people who consume other parts of the fish, in addition to the filletsection, will be exposed to higher quantities of contaminants. It should also be noted that all ofthe fish samples used for this analysis were taken from largemouth bass. No bottom feeding fish,such as catfish, were sampled. Bottom feeding fish tend to accumulate contaminants such asPCBs and pesticides more readily than predator fish such as largemouth bass. Therefore, ingestingcatfish or a similar type fish from the canal system may also expose individuals to higher quantitiesof contaminants.


REFERENCES

EPA. See U.S. Environmental Protection Agency.

Feldman, R.J. and H.I. Maibach. 1975. Percutaneous penetration of some pesticides andherbicides in man. Toxicol. Appl. Pharmacol. 28:126-132.

Kissel, J., Richter, K., Duff, R. et al. 1995. Dermal soil exposure: Investigation of soil contact andskin coverage. Office of Health and Environmental Assessment. (Review Draft). June 1995.

Nisbet, I.C., and P.K. LaGoy. 1992. Toxic equivalency factors (TEFs) for polycyclic aromatichydrocarbons (PAHs). Regul. Toxicol. Pharm. 16:290-300.

Pao, E.M., Fleming, K.H., Guether, P.M., and Mickie, S.J. 1982. Food commonly eaten byindividuals: Amounts per day and per eating occasion. U.S. Department of Agriculture.

Portier, Kenneth M., Um, Yonghwan, Degner, Robert L., Mack, Stephanie K., and Adams,Charles M. 1995. Statistical analysis of Florida per capita fish and shellfish consumption data.University of Florida, Institute of Food and Agricultural Sciences. Florida Agricultural MarketResearch Center Industry Report 95-1. December 1995.

Ryan, E., E. Hawkins, et al. 1987 Assessing risk from dermal exposure at hazardous waste sites.In: Superfund '87 Proceedings of the Eighth National Conference. Bennet, G. and J. Bennet, eds.November 16-18, 1987. Washington, D.C. The Hazardous Material Control Research Institute.

U.S. Environmental Protection Agency. 1989. Exposure Factors Handbook. EPA/600/8-89/043.

U.S. Environmental Protection Agency. 1992. Dermal Exposure Assessment: Principles andApplications. Interim Report. Office of Research and Development. EPA/600/8-91/001B.

U.S. Environmental Protection Agency. 1993. EPA, Office of Research and Development,Washington, DC. Provisional Guidance for Quantitative Risk Assessment of Polycyclic AromaticHydrocarbons. EPA/600/R-93/089.

West R., R. Maibach, et al. 1993. In vivo and in vitro percutaneous absorption and skindecontamination of arsenic from water and soil. Fundamental and AppliedToxicology.20:336-340.


APPENDIX D: Responses to Public Comments

The Homestead Air Force Base Public Health Assessment was released for public comment onJuly 6, 1998. The comment period ended on August 16, 1998.

  1. Comment: Fish Pathway: Based on the surface water and sediment results (Page 12 andTable 1, Page 31), it appears that if the Boundary and Outfall Canals contributed to thecurrent fish PCB and pesticide contamination, the levels of PCBs and pesticides shoulddecrease in the future.

    Response: Because levels of PCBs and pesticides in surface water and sediment are relativelylow, it is possible levels of PCBs and pesticides in fish that are attributable to the Boundaryand Outfall Canals may decrease in the future. See also Comment 3 below.

  2. Comment: Will ATSDR consider adding some statements that the Air Force not onlyconducted an investigation of the fish in the Boundary Canal and Outfall Canal, but sampled acanal off the installation unaffected by Air Force activities (Mowry Canal)? The point of thisaddition is that organic contamination in fish in South Florida is a regional issue. Please seethe following table:



    Range of Contaminants from OU-9 Boundary Canal Remedial Investigation (ug/kg) in Fish Tissue
    Contaminant Outfall Canal Mowry Canal (unaffected by
    Homestead AFB)
    Fillet Residual Fillet Residual
    PCB (Aroclor 1260)19-130ND-250ND51-130
    DDDND-12ND-15ND-2615-310
    DDE24-18019-40058-170340-7,795
    DDTND-2.9ND-7.2ND-17.1ND-19.5

    The above table shows that organic contamination is prevalent in the region and that any fishadvisories recommended by ATSDR or other health officials need to be put into context. Forexample, DDE contamination in fish tissue in Mowry Canal was an order of magnitude higherthan in the Outfall Canal. The risk to subsistence level fishermen from eating fish from OutfallCanal may be overshadowed by the risk fishermen face from other canals. To the best of ourknowledge, the Air Force remedial investigation of OU-9 is the only study of organics in fishtissue in South Florida. There have been other studies which address mercury contaminationin fish tissue in the area.

    Response: ATSDR noted in the discussion of Fish under Concern: Boundary and OutfallCanals that pesticide contamination in the Outfall Canal "may be due to agriculturalprocesses, as opposed to activities at Homestead AFB." Text was added to note thatbackground samples taken in Mowry Canal during the remedial investigation also containedelevated levels of pesticides and PCBs.

  3. Comment: Page 12-15. These sections discuss surface, sediment, and fish sampling thatoccurred in the boundary canals. The fish sampling results, when evaluated for the unlikelysubsistence scenario, indicated that PCBs and arsenic were the risk drivers followed bypesticides.

    Since surface and sediment sampling results are likely to predict future chemicalconcentrations in fish, these results should be discussed further. Surface and sediment sampleswere collected and analyzed for various contaminants including PCBs, arsenic, and pesticides.

    No surface water pesticide sampling results exceeded their conservative drinking waterscreening values. In addition, the sediment samples analyzed for pesticides resulted in non-detects. This suggests that future generations of fish will not be contaminated by pesticidesfrom the boundary canals.

    Sediment sampling results for arsenic were slightly above the comparison values for humanincidental ingestion exposures (Table 1, Page 31) at 3.6 ppm to 7.5 ppm. The arsenic analysesfrom surface water sampling also indicated that arsenic was above incidental ingestion for thisroute at 0.8 ppb to 1.6 ppb.

    PCBs were either not detected in the surface water samples and/or above the comparisonvalues for drinking water (Page 12 Para 2). Sediment sampling PCB results were reported tobe slightly above ATSDR's human health comparison values based on Boundary and OutfallCanals RI results (Page 12 Para 3), but were not mentioned in Table 1, Page 31, Evaluation ofPotential Public Health Hazards (Supplemental Investigation, 1996).

    Response: In both the remedial investigation and the supplemental investigation, surfacewater sampling for the Boundary and Outfall Canals did not detect any PCBs; pesticides weredetected below comparison values. Sediment sampling detected PCBs (Aroclor-1260) abovethe comparison values once in the remedial investigation; no PCBs were detected in thesupplemental investigation. Sediment sampling detected pesticides below comparison values inboth the remedial investigation and the supplemental investigation. ATSDR made changes tothe text and tables in order to clarify this information.

    ATSDR did not evaluate past levels of PCBs and pesticides in surface water and sediment.Because levels of PCBs and pesticides in surface water and sediment are relatively low,however, levels of PCBs and pesticides in fish that are attributable to the Boundary andOutfall Canals may decrease in the future.

  4. Comment: Does subsistence fishing occur in the canals? We suggest that an objective studybe conducted of anglers and fish consumption practices at the canals at Homestead AFB to ascertain whether any fish consumers were experiencing unacceptable risk.

    Response: It is unknown whether subsistence fishing occurs in the canals or even if the fishpopulation is substantial enough to support subsistence fishing. It is beyond the scope of thisreport to perform the kind of study needed to determine the answer to this question. ATSDRspoke with various groups about the possibility of subsistence fishing in canals. Some groupsthought the canals were too isolated and did not contain enough fish to support subsistencefishing, while others thought the local residents would subsistence fish from the canals. Therefore, in order to be conservative in our approach to this public health assessment,ATSDR evaluated exposure dose estimates for subsistence fishing in the canals. No adversehealth effects are expected from occasional ingestion of contaminants in fish. It is possible(though unlikely), however, that the ingestion of large quantities of fish may be associatedwith adverse health effects.

  5. Comment: We suggest that the rewritten version of the Exposure Factors Handbook(EPA/600/P95/002Fb) be used in lieu of the 1989 version.

    Response: ATSDR revised the analysis and used an estimate for fish consumption from the1998 Final Exposure Factors Handbook. The reader is referred to Appendix C.

  6. Comment: We suggest that a Florida fish consumption survey be used rather than a nationalstudy, Statistical Analysis of Florida Per Capita Fish and Shellfish Consumption Data, FloridaAgricultural Market Research Center Industry Report 95-1 prepared by the University ofFlorida Institute of Food and Agricultural Sciences.

    Response: ATSDR revised the analysis and used an estimate for fish consumption from theabove-referenced document. This estimate was used in addition to the estimate referred to in Comment 5. The reader is referred to Appendix C.

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