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Table 1.



Total persons54,923
Total area (square miles)21.86
Persons per square mile2,512
% Male49.4
% Female50.6
% White73.0
% Black3.8
% American Indian, Eskimo, or Aleut1.1
% Asian or Pacific Islander1.7
% Other races20.4
% Hispanic origin35.6
% Under age 1018.7
% Age 65 and older12.0
            Source: Census, 1991.

Table 2.



Persons per household2.80
% Households owner-occupied58.5
% Households renter-occupied41.5
% Households mobile homes12.7
% Persons in group quarters1.6
Median value, owner-occupiedhouseholds (dollars)65,400
Median rent paid, renter-occupiedhouseholds (dollars)375
            Source: Census, 1991.


Figure 1. Location Map of MCAS Yuma and Surrounding Area

Figure 2. Station Map of MCAS Yuma

Figure 3. ATSDR's Exposure Evaluation Process

Figure 4. Marine Corps Air Station Yuma Impacted Groundwater Plumes and Downgradient Drinking Wells

Figure 5. Location of ACM at Radar Hill Disposal Area

Appendix A: Evaluation of Potential Public Health Hazards Associated With Marine Corps Air Station Yuma

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
1600 Clifton Road NE, Atlanta, Georgia 30333

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)

    Estimated contaminant concentrations that would be expected to cause no more than oneexcess cancer in a million (10-6) persons exposed over a 70-year life span. 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 andingestion rates. An EMEG is an estimate of daily human exposure to a chemical (inmg/kg/day) that is likely to be without noncarcinogenic health effects over a specified duration of exposure to include acute, intermediate, and chronic exposures.

Maximum Contaminant Level (MCL)

    The MCL is the drinking water standard established by EPA. It is the maximumpermissible level of a contaminant in water that is delivered to the free-flowing outlet.MCLs are considered protective of human health over a lifetime (70 years) for individuals consuming 2 liters of water per day.

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 inadverse noncarcinogenic effects.

Appendix C: Glossary

Asbestos-containing material (ACM)
Material, usually involved in construction, which contains asbestos, a known carcinogen.The asbestos fibers in ACM are often imbedded in the material and, therefore, exposure to ACM issometimes less of a hazard than direct exposure to asbestos fibers.

Background level
A typical or average level of a chemical in the environment. Background often refers tonaturally occurring or uncontaminated levels.

Any substance that may produce cancer.

The Comprehensive Environmental Response, Compensation, and Liability Act of 1980, also known as Superfund. This is the legislation that created ATSDR.

Comparison Values (CVs)
Estimated contaminant concentrations in specific media that are not likely to cause adversehealth effects, given a standard daily ingestion rate and standard body weight. The CVs arecalculated from the scientific literature available on exposure and health effects.

The amount of one substance dissolved or contained in a given amount of another. Forexample, sea water contains a higher concentration of salt than fresh water.

Any substance or material that enters a system (the environment, human body, food, etc.) where it is not normally found.

Referring to the skin. Dermal absorption means absorption through the skin.

The amount of substance to which a person is exposed. Dose often takes body weight intoaccount.

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).

A source of risk that does not necessarily imply potential for occurrence. A hazardproduces risk only if an exposure pathway exists and if exposures create the possibility of adverseconsequences.

Indeterminate public health hazard
The designation given to sites for which no conclusions about public health hazards can be made because data are lacking.

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 intothe blood and distributed throughout the body.

Breathing. Exposure may occur from inhaling contaminants because they can be deposited in the lungs, taken into the blood, or both.

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 tobe without an appreciable risk of adverse effects (noncancer) over a specified duration ofexposure. 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 ofexposure. 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 preliminaryassessment and site inspection to determine which locations pose immediate threat to personsliving 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.

An area of chemicals in a particular medium, such as air or groundwater, moving awayfrom its source in a long band or column. A plume can be a column of smoke from a chimney orchemicals moving with groundwater.

Public Health Assessment (PHA)
The evaluation of data and information on the release of hazardous substances into theenvironment in order to assess any current or future impact on public health, develop healthadvisories or other recommendations, and identify studies or action needed to evaluate andmitigate 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.

In risk assessment, the probability that something will cause injury, combined with the potential severity of that injury.

Volatile organic compounds (VOCs)
Substances containing carbon and different proportions of other elements such ashydrogen, oxygen, fluorine, chlorine, bromine, sulfur, or nitrogen; these substances easily becomevapors or gases. A significant number of the VOCs are commonly used as solvents (paint thinners,lacquer thinner, degreasers, and dry-cleaning fluids).

Appendix D: Responses to Public Comments

ATSDR distributed copies of the public comment release of the Marine Corps Air Station YumaPublic Health Assessment (PHA). The comment period lasted between June 8, 1998 and July 19,1998. The following are the comments received by ATSDR and ATSDR's responses.

  1. Comment: Page 5 UST Program

    Currently in the State of Arizona, MTBE in the groundwater is not a concern. There are noremedial alternatives being considered to remediate MTBE.

    Response: MTBE levels in groundwater at MCAS Yuma do not pose a public health hazardand no one has been, is currently, or likely will be in the future exposed to the MTBEplumes in the groundwater at MCAS Yuma. Therefore, ATSDR has removed references toMTBE contamination in the groundwater at MCAS Yuma.

  2. Comment: Page 13 Conclusions

    I do not agree with Conclusion #4.

    During the OU2 Remedial Investigation, this area was sampled and did not suggest thatthere were any tear gas crystals buried in that area. In addition to the sampling, that area ishighly disturbed due to the building of the CALA. The comment that tear gas crystals wereburied in the area is questionable and if tear gas crystals were to be buried, it would havebeen done by an individual, who would have used his shovel and dug to a depth of only afew feet below ground surface.

    Response: ATSDR has further clarified statements in the PHA on the issue of the reportedtear gas disposal. Although the reports of tear gas disposal could not be verified, ATSDRstill feels that some precautionary measures should be taken for future excavations at thissite.

  3. Comment: Page 12 Past Exposure

    The area in which high levels of organic lead were found are currently used as contractorstorage yards. These yards mainly contain construction materials and some vehicles.Personnel do not work in these areas 8 hours per day, 5 days per week. Any exposure toorganic lead should not be considered as chronic exposure. This area has been used ascontractor storage yards for at least the last 10 years. Prior to that, this area was used asshops area. The area in question has not been used as a barracks area. Military personnelwho worked in that area would not have been assigned to MCAS Yuma for more than threeyears. Considering that the areas of contamination are outdoors and the personnel whoworked in the area were not assigned to the base for a significant period of time, I wouldassume that any exposure to tetraethyl lead would have been minimal and would not affect their health.

    Page 13 Conclusions

    I do not agree with ATSDR with Conclusion #6.

    ATSDR identified the presence of organic lead at three sites, CAOCs 1, 2, and 7, as aconcern. They go on to say that since these areas are isolated and paved (or covered withsealant), or have restricted access, they do not pose a current or future public health hazard.[The commentor] agrees.

    ATSDR goes on to say they do not have sufficient information to evaluate the pastexposures to organic lead, so they classify these sites as an indeterminate public healthhazard and recommend further investigation regarding the organic lead. [The commentor]does not agree with this assessment.

    Based on [the commentor's] review of historical aerial photographs and station records, theportion of CAOC 1 where the organic lead was found has always been associated with flightoperations and appears to have been always paved. Thus, past exposure to organic lead insoil at this location is minimal. Any increased exposure to organic lead, or othercontaminants, in this area were likely due to the daily maintenance operations that occurred.

    At CAOC 7, the organic lead hits were found at former Fire Training Pit (FTP) 15 locatedto the north of the CALA. This FTP was apparently used during the 1970s for fire and crashtraining. The FTP is currently covered with a sealant for dust control, and appears to havebeen covered since the early 1980s. This FTP appears to have been in use for a limitedperiod of time, and has been covered with the sealant since the early 1980s. Thus, exposureto organic lead at this location since use of this FTP was terminated is minimal. Duringoperations, exposure to the burning of flammables during fire training exercises was likelyto be more significant than the presence of organic lead in the soil.

    At CAOC 2, this site has been used for vehicle maintenance and public works from the1940s to the early 1980s. The OU2 RI investigated areas of reported spills and grounddisposal of chemicals, which reportedly occurred until the early 1980s. Of the areasinvestigated, only one hit of organic lead was detected. If this hit of organic lead was relatedto past spills and/or disposal activities, the impacted area appears small so exposure to thecontaminated soil was likely minimal. In addition, this area was used for industrial activities,so it is unlikely that any station personnel would be in this area for more than a normal workschedule. Also, the nearby base dormitories and Enlisted Dining Facilities were constructedafter the early 1980s so occupants of these buildings would have minimal exposure to pastspills or disposals. Since the area where the organic lead hit was found has been used as avehicle parking area for at least the past 5 years, it is likely that the presence of organic leadcame from parked vehicles and does not represent a significant past exposure pathway.

    Response: ATSDR has further clarified statements in the PHA on the issue of past exposure to organic lead.

    The very high levels of organic lead found at some locations, while not a current or futureconcern, do raise questions about potential exposures in the past. The current high levelsof tetraethyl lead degradation products suggest the possibility that high levels of tetraethyllead may have been present in the past. Past exposure at the Flight Line CAOC 1 (the FlightLine) was quite limited. Although, as the commentor states, past exposures at the FireSchool Area CAOC 7 (the Fire School Area) and CAOC 2 (the Shops Area) may have alsobeen quite limited, ATSDR does not have sufficient information to evaluate potential pastexposures to organic lead at these areas.

    ATSDR agrees with the commentor that exposure to organic lead in the past at CAOC 1is not a public health hazard. ATSDR still believes, however, that past exposures at CAOC7 and CAOC 2 pose an indeterminate public health hazard.

  4. Comment: Page 15 Organic Lead in Surface Soil

    I do not agree with the ATSDR recommendation that the Navy further investigate the soilcontaminated with organic lead.

    As the Public Health Assessment states, it does not present a present or future health risk.Any exposure in the past would have been incidental and would not pose a health risk. TheNavy has spent several millions of dollars in investigating soil contamination at MCASYuma. The area in question was included in CERCLA Area of Concern #2. This area wasrecommended for no further action because the threat of exposure to chemicals whichwould cause cancer was less than one in one million and the non-cancer threat was less thanone. The recommendation was agreed upon by the State of Arizona, the EnvironmentalProtection Agency, and the U.S. Navy. It does not seem practical to spend more money toverify what the Public Health Assessment and the OU2 Record of Decision state.

    Response: ATSDR's recommendations have been modified as suggested by the commentor.However, if the restricted access and use of this area changes in the future, ATSDR stillrecommends further characterization of soil contaminated by organic lead.

1. A household is an occupied housing unit, but does not include group quarters such asmilitary barracks, prisons, and college dormitories.

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