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HEALTH CONSULTATION

Review of 1993 Public Health Assessment Recommendations

DEFENSE SUPPLY CENTER RICHMOND
[a/k/a DEFENSE GENERAL SUPPLY CENTER (DLA)]
RICHMOND, CHESTERFIELD COUNTY, VIRGINIA


STATEMENT OF ISSUE

The Agency for Toxic Substances and Disease Registry (ATSDR) completed a public healthassessment (PHA) for the U.S. Defense General Supply Center Richmond, currently known asDefense Supply Center Richmond (DSCR), Chesterfield County, Virginia (CERCLIS No.VA3971520751) on April 21, 1993 (ATSDR, 1993). The PHA concluded the site did not pose athreat to human health. It was placed in the ATSDR category of "no apparent public healthhazard." Included in the PHA document were a total of eight recommendations and a publichealth action plan listing actions undertaken, and actions planned. In May 2001, the VirginiaDepartment of Environmental Quality (VDEQ) requested that ATSDR determine if the 1993PHA recommendations were adequately addressed.


BACKGROUND

The Defense Supply Center Richmond (DSCR) is a Defense Logistics Agency (DLA) federalfacility that comprises 631 acres in Chesterfield County, Virginia, approximately 12 miles southof the city of Richmond, Virginia. The DSCR has been managing and furnishing militarygeneral supplies to the Armed Forces and several federal civilian agencies since 1942. Currentoperations at the site include the management and storage of military supplies, material handling,and storage of chemicals such as pesticides, herbicides, lubricants and petroleum products (Law,2001a). As a result of past activities, environmental contamination exists at the site. Theresponsibility for site environmental cleanup belongs to the DLA, with oversight by the UnitedStates Environmental Protection Agency (EPA) and state regulatory agencies, such as VDEQ. The site was proposed for inclusion on the U.S. EPA's Exiting ATSDR Website National Priorities List (NPL) in 1984 byEPA for contaminated groundwater and source areas. ATSDR is responsible for preparingpublic health assessments according to the Comprehensive Environmental ResponseCompensation and Liability Act (CERCLA or Superfund) section 104 (i) (6) (42 U.S.C. 9604 (i)(6). As mandated by that law, ATSDR conducts PHAs of hazardous waste sites listed orproposed for listing on the NPL. ATSDR completed it's PHA of DSCR in 1993.


DISCUSSION

This public health consultation (PHC) has been prepared to provide a status and summary of theresults of the various investigations or other public health activities undertaken to respond to theeight recommendations made in the 1993 public health assessment (PHA). Therecommendations given in that PHA presented issues to be resolved. Those issues and theirresolutions are given in the Discussion section of this consultation.

For clarity, this section repeats the recommendations of the 1993 PHA and then gives thefollow-up public health action(s) taken to resolve that particular issue. In some cases additionaldiscussion will be given to further clarify events, findings, or actions leading to the conclusion orresolution of a particular recommendation.

Recommendation 1: Identify and periodically monitor the wells of residences in theRayon Park, Kingsland Creek, and other areas that are not connected to a public water supply ifcontaminant plumes are determined to migrate in those directions. Use appropriate qualityassurance and quality control procedures to validate sampling data, and set detection limitsbelow MCLs.

Public Health Action(s) 1:

According to the Virginia Department of Health (VDH)-Chesterfield County, there are threeresidential wells in Rayon Park currently being used for drinking water. Two of these have beentested and the other resident does not want the well to be tested. One of the residents whose wellhas been tested was offered the chance to hook up to the county water system prior to discoveryof the NPL site, but turned it down at the time. This resident has not yet connected to the publicwater system. Several additional wells are used for gardening, watering lawns, washing cars,and the like. The Virginia Department of Health-Chesterfield County offers private drinkingwater well testing to anyone living within a 1/4 mile radius of DSCR.

Historical activities at DSCR have caused contamination of the groundwater from solvents andmetals. There are two contamination plumes extending from Area 50 eastward through theNational Guard Area. Contamination in the upper aquifer is primarily volatile organiccompounds (VOCs), as well as some semi-volatile organic compounds (SVOCs) and metals. Ingeneral, these same contaminants are also found in the lower aquifer. Area 50 is a formerlandfill suspected to be the source of the groundwater contamination (Law, 2001a). DSCRconducts periodic groundwater monitoring, and mapping of the contaminant plumes. By 1993,DSCR had established the movement of the plumes. DSCR has continued to monitor the plumessince then, but DSCR has not monitored off-site private drinking water wells.

In 1993, DSCR conducted a residential well survey. Engineering-Science, Inc. reviewed stateand county records, conducted a door-to-door survey of residential wells within 1/4 mile of theDSCR property boundary, completed survey forms for all residents contacted, and providedlocation maps of each residence/well. 108 well surveys were completed. Nine well surveyswere left in doorways and were not returned. Of those 108 completed well surveys, 16residences were using a well as a sole source of potable water. 25 additional residences wereusing a well for non-potable (other than drinking water) purposes (Engineering-Science, Inc.,1992). These wells were not tested for contamination at that time.

In 1996, the Operable Unit 9 (OU 9) groundwater pump and treat system was initiated. OU 9consists of the Interim Action System for Operable Unit 6 (OU 6). OU 6 consists of the Area50/Open Storage Area/National Guard Area Groundwater. OU 9 is a groundwater treatmentsystem that was installed to remove volatile organic compounds from groundwater via airstripping. Residual vapors are treated with activated carbon. The remedial system is in place tointercept, remove, and treat impacted groundwater from both the upper and lower aquifers on-site, prior to migrating off site and coming into contact with No Name Creek (Law, 2001a). Atthis time, DSCR also established quarterly groundwater sampling to monitor the performance ofOU9. The results of the quarterly sampling are also used in DSCR's continued mapping of thecontamination plumes. DSCR has conducted quarterly groundwater sampling consistently since1996.

In 2001, DSCR conducted an updated residential well survey. Law Engineering andEnvironmental Services (Law) reviewed state and county records and conducted a door-to-doorsurvey of residential property within 1/4 mile of the DSCR property boundary. The compileddata showed 654 well surveys were completed and 410 letters were returned from the postmasterindicating an invalid address. The compiled survey data indicated that 155 residents haveprivate wells on their property. Of these, 20 residents use their private wells for multiplepurposes (drinking, washing, and food preparation); 6 use their well for outside purposes only(washing cars and watering grass); 96 residents never use their private wells; 27 residents haveprivate wells on their property but usage is unknown; and 6 wells showed discrepancies in therecords (Law, 2001b).

The Virginia Department of Health-Chesterfield County conducted private drinking water wellsampling in Rayon Park and surrounding areas in 2001 and 2002. VDH sampled one privatewell in Rayon Park on April 27, 2001, one on May 29, 2001, three on September 12, 2001, andtwo on March 26, 2002. VDH sampled three private wells in surrounding areas on September12, 2001, three on September 24, 2001, one on October 3, 2001, two on March 14, 2002, threeon March 26, 2002, and one on May 30, 2002 (VDH, 2001). Very few compounds were foundover the detection limits. Most of the compounds that were detected were metals, which arecommon and naturally occurring. Of those compounds that were detected, only three were foundat levels over the most conservative comparison values. ATSDR uses comparison values toselect environmental contaminants for further evaluation. A comparison value is a concentrationof a given contaminant in soil, water, or air below which no adverse human health effects areexpected to occur.

Manganese was found once in one well at a concentration of 1690 ppb. The chronic ReferenceMedia Evaluation Guide (RMEG) for manganese for children is 500 ppb, and the chronic RMEGfor adults is 2000 ppb. Chloroform was found once at 30 ppb. The Cancer Risk EvaluationGuide (CREG) for chloroform is 6 ppb. Lead was found once at 17 ppb. The Action Level forlead is 15 ppb (VDH, 2001).

ATSDR estimated the human exposure doses of manganese and chloroform from ingestion anddermal absorption of private well water. The equations used to derive exposure doses can befound in Appendix B. In order to account for the inhalation route of exposure to chloroform, theingestion rate was doubled. This is a standard, conservative method for evaluating inhalationexposure doses (Andelman, et.al., 1989 and Wan, et.al., 1990). When the ingestion rate wasdoubled, the resulting chloroform exposure dose was still below the EPA's reference dose (RfD).

VDH will re-test the well with chloroform to determine if the presence of chloroform was anisolated occurrence. None of the exposure doses of contaminants detected in Rayon Park andsurrounding area private wells were greater than health guidelines such as ATSDR's minimalrisk levels (MRL) or RfDs.

Deriving exposure doses requires evaluating the concentrations of the contaminants to whichpeople may have been exposed, and how often and how long exposures to those contaminantsoccurred. Together, these factors help influence the individual's physiological response tochemical contaminant exposure and the potential for non-cancer or cancer outcomes. In theabsence of exposure specific information, ATSDR applied several conservative assumptions todefine site-specific exposures as accurately as possible for people contacting contaminatedmedia.

The estimated exposure doses were used to evaluate potential non-cancer effects associated withcontaminants detected in site media. When evaluating non-cancer effects, ATSDR firstcompared the estimated exposure dose to standard toxicity values, including MRLs and RfDs, toevaluate whether adverse effects may occur. The chronic MRLs and RfDs are estimates of dailyhuman exposure to a substance that is likely to be without appreciable risk of adverse non-cancereffects over a specified duration. The chronic MRLs and RfDs are conservative values, based onthe 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 outcomefor a given route of exposure (e.g., dermal contact, ingestion). In addition, uncertainty (safety)factors are applied to NOAELs or LOAELs to account for variation in the human population anduncertainty involved in extrapolating human health effects from animal studies. Whencomparing dermal absorption exposure doses to oral health guidelines, a gastrointestinal (GI)factor is applied to the Oral RfD or Oral MRL. This accounts for the difference in absorptionthrough skin as compared to the absorption through the gastrointestinal wall. If estimatedexposure doses are greater than the MRL or RfD, ATSDR reviews the toxicological literature todetermine the likelihood of adverse effects.

ATSDR health guidelines are not available for lead, but toxicological and epidemiologicalinformation is available. The maximum lead concentration in private well water in Rayon Parkwas 17 ppb. This level was detected once in one private well. VDH informed the owner of thewell of the elevated lead level. The well is not used for drinking water, and therefore does notpose a health hazard. ATSDR determined that chronic drinking water exposure at the highestdetected concentration of lead in water (17 ppb) would not pose a public health hazard tochildren or adults. ATSDR estimated blood lead levels using the Integrated Exposure UptakeBiokinetic Model (IEUBK) for Lead (EPA, 1996). The Centers for Disease Control andPrevention (CDC) have determined that health effects are more likely to be observed if actualblood lead levels are at or above 10 micrograms per deciliter (µg/dl). Using the IEUBK model,estimated blood lead levels were found to be below 10 µg/dl for all populations. Health effectsare not expected from exposure to the levels of lead in private well water in Rayon Park andsurrounding areas.

In summary, ATSDR does not find that the drinking water from private wells in Rayon Park orsurrounding areas poses a health threat. Most residents of Rayon Park and the surrounding areasare connected to the public water supply. Contaminants were not found at levels that couldcause health effects. VDH will continue to test private drinking water wells in Rayon Park andsurrounding areas at the request of residents.

Recommendation 2: Restrict site access to non-essential personnel at the NationalGuard Area and Fire Training Area, as well as the Fuel Oil Storage Area and Buildings 202,112, and 68. For personnel who must be at those areas, provide personal protective equipmentin accordance with OSHA and NIOSH standards.

Public Health Action(s) 2:

Access to DSCR is restricted to employees. The general public must have specific permission toenter DSCR. Access to the National Guard Area, Fire Training Area, Fuel Storage Area, andBuildings 202, 112, and 68 is restricted to DSCR Engineers and Protective Services utilizingprotective equipment in most cases. All activities that involve the operable units (OUs) arereviewed by the DSCR environmental office to determine whether the OUs will be impacted. Ifthe environmental office determines that contact with contaminated soil or groundwater is likely,then projects may be modified to eliminate contact, or engineering controls may be added toprotect workers. In addition, Records of Decision (ROD) for the National Guard Area and theOpen Storage Area may require pre-construction sampling. In 1999, a No Further Action RODwas completed for the Fire Training Pit Soil, also known as OU4. Access to this site is no longerrestricted, but the groundwater beneath the site, also known as OU7, is still contaminated. Exposure to contaminated groundwater at these areas is unlikely, and exposure to soils would bethrough intermittent dermal contact. Although not directly related to the issue of site access,indoor air quality is also a concern for workers in buildings at the National Guard Area and FireTraining Area. DSCR will address inhalation exposure to VOCs through indoor air in theirRODs for OU6 and OU7.

Recommendation 3: Periodically monitor Kingsland Creek and the No-Name Creekadjoining the installation if future groundwater monitoring results indicate that concentrationscould be higher than previously detected. Use appropriate quality assurance and quality controlprocedures to validate the sampling data.

Public Health Action(s) 3:

DSCR has been monitoring Kingsland and No Name Creeks periodically since 1993. Historicalactivities at DSCR have caused contamination of the groundwater from solvents and metals. The OU6 upper aquifer groundwater flow, during periods of elevated water-table conditions, isbelieved to discharge into No Name Creek. By contrast, OU6 lower aquifer groundwater flowstoward and beneath No Name Creek. Due to the presence of a stratigraphic confining unit, thereis no apparent hydraulic connection between OU6 lower aquifer groundwater flow and No NameCreek. The primary source of flow for No Name Creek is surface water runoff from DSCR andthe area west of DSCR (Law, 2001a). The primary source of flow for Kingsland Creek issurface water runoff from the area west of DSCR.

The administrative record and information repositories contain several reports that concern creekmonitoring, including the Creek Monitoring Plan for Kingsland, No Name, and Falling CreekTributary, August 2001. Law Engineering and Environmental Services, Inc. (Law) sampledKingsland Creek on May 16, 2001. Law also sampled No Name Creek on May 14, May 16, andJuly 20, 2001. Additionally, the Virginia Department of Environmental Quality (VDEQ)sampled No Name Creek on May 14, May 21, and May 30, 2001. Appropriate quality assuranceand quality control procedures were used to validate the sampling data. The results of thesesampling efforts have been reviewed by ATSDR, and were not found to pose a human healthhazard. These results were discussed in ATSDR's Defense Supply Center Richmond HealthConsultation, dated April 4, 2002 (ATSDR, 2002).

VDEQ sampled stormwater channels in Rayon Park on March 18, 2002 following the firststormwater runoff event since summer 2001. The only three channels that contained flowingstormwater were sampled. No stations contained trichloroethylene (TCE) above the detectionlimit of 0.5 ppb. VDEQ will try to sample a larger storm event if one occurs.

Recommendation 4: Appropriately store and shelter drums and containers of chemicalsin the Open Storage Area.

Public Health Action(s) 4:

According to DSCR's Environmental Program Manager, all drums with liquid contents wereremoved from the OU 1 storage area in 1995. Drums are now stored at another location insidenew covered storage facilities. These facilities utilize concrete berms, and the drums are neatlyand compatibly organized in discrete locations according to the National Stock Numbers. TheOU 1 area stores gas cylinders ready for refurbishment.

Recommendation 5: Stock Parker Pond with fish from non-contaminated supplies.

Public Health Action(s) 5:

This recommendation was made because during August 1987, DSCR experienced a fish kill inParker Pond. This occurred during a time of dry, hot weather, and low dissolved oxygen levels. One of the fish had a total DDT concentration of 0.26 ppm. Parker Pond was restocked with fishfrom a state fish hatchery in 1988 (DGSC, 1994).

Because DDT was found in the fish in 1987, DSCR was required to perform an expanded siteinvestigation at Parker Pond. Approximately 20 fish were caught in September 1993. Severalfish were analyzed to determine if compounds would bioaccumulate in the fish. Three sampleswere prepared; one edible fillet composited from two fish, and two samples which were mixedwhole pond fish. DDT was not detected above the lower detection limit of 0.005 ppm. Nochlorinated pesticides were found above the detection limits in Parker Pond that were part of theexpanded site investigation. Since DDT was not found in either the sediment or the water at orabove the detection level of approximately 1 ppb, it was concluded that the fish that was foundto have DDT in its system in 1987 was exposed to the DDT prior to being placed in Parker Pond(DGSC, 1994). Parker Pond is not currently stocked with fish.

Recommendation 6: If a multiple-contaminant exposure registry is initiated, DGSC,because of past exposure, should be re-evaluated to determine if persons who were exposed toVOCs in their private drinking water wells should be included in that registry.

Public Health Action(s) 6:

ATSDR has not established a multiple-contaminant exposure registry. The National ExposureRegistry (NER) is a critical, long-term effort that meets the need for collecting informationconcerning the potential impact of hazardous substances on human health. It is a listing ofpersons exposed to hazardous substances at various sites around the country. It contains sub-registries for specific substances. Currently, there are four active sub-registries-trichloroethylene (TCE), trichloroethane (TCA), benzene, and dioxin. Each sub-registry is asubstance-specific part of the NER. It is made up of self-reported health information, frompeople throughout the United States who have been exposed to one of the four listed substancesfrom the environment. The purpose of the sub-registries is to assess the long-term healthconsequences to a general population from long-term, low-level exposures to specificcontaminants in the environment. ATSDR has not yet established a substance-specific sub-registry that combines more than one contaminant. If ATSDR establishes a multiple-contaminant exposure sub-registry, community members from sites in the country that have hadexposure to the multiple contaminants in the sub-registry will be considered for inclusion,according to established criteria for that sub-registry.

Recommendation 7: Health Guidelines, such as Minimal Risk Levels, should be developed for contaminants for all exposure routes (ingestion, inhalation, and dermal contact). Guidelines lacking for specific contaminants in this public health assessment are discussed in the Toxicologic Evaluation section. Validated studies should also be either conducted or funded by EPA, ATSDR, or other appropriate agencies and organizations to determine possible health effects that may be associated with simultaneous exposure to multiple VOCs.

Public Health Action(s) 7:

Several new health guidelines have been established by ATSDR for the contaminants of concernthat were outlined in the Toxicologic Evaluation section of the 1993 public health assessment(PHA). In 1993, benzene, 1, 2-dichloroethane, and 1, 1, 1-trichloroethane did not have healthguidelines for any exposure routes. 1, 1-Dichloroethylene and tetrachloroethylene had healthguidelines for ingestion and inhalation routes, and trichloroethylene had a health guideline forthe ingestion route. Currently, 1, 2-dichloroethane, 1, 1-dichloroethylene, tetrachloroethylene,and trichloroethylene have health guidelines for ingestion and inhalation routes. Benzene and 1,1, 1-trichloroethane have health guidelines for the inhalation route of exposure. Dermal healthguidelines have not been established by ATSDR, but they can be extrapolated from the oralhealth guidelines by applying a gastrointestinal factor to account for the difference in absorptionthrough skin, versus the gastrointestinal wall. The 1993 PHA determined that because ofinfrequent exposure to low levels of VOCs in those private wells in Rayon Park, adverse healtheffects were not expected (ATSDR, 1993). Current private well data (2001) is available forRayon Park and is discussed in Public Health Action 1 of this document.

ATSDR considered interactive effects (cumulative, additive, synergistic, and antagonistic) ofchemicals following exposure to multiple chemicals to the extent of the scientific knowledge inthis area. ATSDR has reviewed the scientific literature surrounding chemical interactions andnoted that if the estimated exposure doses for individual contaminants detected at the site arebelow doses shown to cause adverse effects, No Observed Adverse Effect Level (NOAEL), thenthe combined effect of multiple chemicals is not expected to result in adverse health effects. Studies have shown that exposure to a mixture of chemicals is unlikely to produce adverse healtheffects as long as components of that mixture are detected at levels below the NOAEL forindividual compounds (Seed et al. 1995; Feron et al. 1995).

Recommendation 8: The data and information in the Public Health Assessment for theDefense General Supply Center have been evaluated for follow-up health activities by theATSDR Health Activities Recommendation Panel (HARP). The citizens living in communitiesnear DGSC need information about their potential for exposure, the extent of contamination atDGSC, and additional environmental sampling and remediation that is planned at DGSC. DGSC has held public meetings with the communities and disseminated environmental factsheets to discuss those issues. DGSC has communicated sampling results to private well owners. Currently, there are no indications that adverse health conditions are occurring or haveoccurred from past exposures to DGSC contaminants. However, if contaminants are measuredin groundwater from off-site private wells, community health education concerning exposure isindicated. Moreover, if other environmental or health outcome data become available thatindicate human exposure to hazardous substances is occurring at levels that may cause illness orinjury, ATSDR will re-evaluate the need for additional follow-up health actions.

Public Health Action(s) 8:

DSCR has worked with the community for several years. In 1992, DSCR prepared aCommunity Relations Plan. Currently, DSCR is working on another Community Relations Plan. DSCR distributes a quarterly newsletter to residents of the area detailing the site's environmentalprogram. Public meetings were held in the community on July 27, 2001 and November 1, 2001. The meetings were jointly sponsored by DSCR and Chesterfield County. Representatives fromVDEQ, VDH, EPA Region III, and ATSDR were also in attendance. As a result of aCongressional Briefing held in August 2001, an EPA Community Involvement Coordinator wasassigned to the site. The Community Involvement Coordinator will oversee DSCR's communityinvolvement program and help to ensure that information is distributed to the community. DSCR set up a Restoration Advisory Board (RAB) comprised of a center representative,community members, regulators, and representatives of other organizations that are affected byrestoration activities. The RAB meets periodically. The purpose of the RAB is to provide aforum whereby community members can review the on-going restoration activities being takenby DSCR.


CONCLUSIONS

ATSDR was asked to review the recommendations from the 1993 PHA. After a review of therecommendations and environmental activities carried out by DSCR, EPA, VDEQ and VDHsince 1993, ATSDR concludes that the recommendations were substantially met with theappropriate public health actions. Activities addressing each recommendation have been carriedout with the possible exception of Recommendation 6. ATSDR has not established a multiple-contaminant exposure registry. Resources have been focused on obtaining detailed informationto determine potential health outcomes from the sub-registries that are currently in place, such asTCE, TCA, benzene, and dioxin. If ATSDR establishes a multiple-contaminant exposure sub-registry, community members from sites in the country that have had exposure to the multiplecontaminants in the sub-registry will be considered for inclusion, according to establishedcriteria for that sub-registry. As a supplement to Recommendation 2, DSCR will addressinhalation exposure to VOCs through indoor air in buildings at the National Guard Area and theFire Training Area in their RODs for OU6 and OU7.


RECOMMENDATIONS

1. Because of concerns for DSCR employees and the potential for VOCs in underground plumesto reach the surface, DSCR should address the indoor air inhalation pathway in buildings in theNational Guard Area and Fire Training Area. This will be presented in the RODs for OU6 andOU7.


PREPARER OF REPORT

Agency for Toxic Substances and Disease Registry
Department of Health Assessment and Consultation
Federal Facilities Assessment Branch
Defense Section A

Katherine E. Hanks, Environmental Health Scientist


REFERENCES

Agency for Toxic Substances and Disease Registry (ATSDR). 1993. Public Health Assessment: U.S. Defense Supply Center. Richmond, Chesterfield County, Virginia. CERCLIS No.VA3971520751. Atlanta: U.S. Department of Health and Human Services, April 21, 1993.

Agency for Toxic Substances and Disease Registry (ATSDR). 2002. Public HealthConsultation: U.S. Defense Supply Center Richmond. Richmond, Chesterfield County, Virginia. EPA Facility ID: VA3971520751. Atlanta: U.S. Department of Health and Human Services,April 4, 2002.

Andelman, B.J., et.al., 1989. Exposure to volatile chemicals from indoor uses of water.Proceeding of Total Exposure Methodology: A New Horizon. Las Vegas, NV, November 27-30,1989.

Defense General Supply Center (DGSC). February 1994. Final Expanded Site Investigation-Parker Pond.

Engineering-Science, Inc. October 1992. Residential Well Survey. Defense Supply CenterRichmond Richmond, VA.

Feron, VJ; Jonker, D; Groten, JP; Horbach, GJMJ; Cassee, FR; Schoen, ED; Opdam, JJG. 1993. Combination Technology: From Challenge to Reality. Toxicology Tribune 14:1-3.

Law Engineering and Environmental Services, Inc. (Law). July 2001a. Draft Data Summary forOperable Unit 9 Pump and Treat System Defense Supply Center Richmond Richmond, VA;Prepared for Defense Logistics Agency U.S. Army Engineering and Support Center Huntsville.

Law Engineering and Environmental Services, Inc. (Law). April 2002b. Draft UpdatedResidential Well Survey Defense Supply Center Richmond Richmond, VA; Prepared forDefense Logistics Agency U.S. Army Engineering and Support Center Huntsville.

Seed, Jennifer; Brown, Ronald P.; Olin, Stephen S.; and Foran, Jeffrey A. 1995. ChemicalMixtures: Current Risk Assessment Methodologies and Future Directions. RegulatoryToxicology and Pharmacology 22: 76-94.

U.S.EPA. Integrated Exposure Uptake Biokinetic Model (IEUBK). Washington (DC): USEnvironmental Protection Agency; 1996.

Virginia Department of Health (VDH)-Chesterfield County. 2001. Rayon Park Private DrinkingWater Well Test Results.

Wan, Jo K., Weisel, C.P., and Lioy, J.P., 1990. Chloroform exposure and the health riskassociated with multiple uses of chlorinated tap water. Risk Analysis, 1990, v.10(4):581-5.


APPENDIX A: COMPARISON VALUES AND HEALTH GUIDELINES

Comparison Values

RMEG:
Reference Media Evaluation Guide is a concentration in air, soil, or water belowwhich non-cancer health effects are not expected to occur. RMEGs are derivedfrom the US Environmental Protection Agency's (EPA) Reference Dose orReference Concentration, and are for chronic exposure.


Action Level:
Action Levels are the estimated contaminant concentrations in water whichindicate that additional evaluation is needed to determine whether action isrequired to eliminate or reduce exposure.


CREG:
Cancer Risk Evaluation Guides are derived by ATSDR from the EPA CancerSlope Factor. They represent an estimated concentration in water, soil, or air thatwould be expected to cause no more than one excess cancer in a million personsexposed over a lifetime.


Health Guidelines

MRL:
Minimal Risk Level is an estimate, developed by ATSDR, of the daily humanexposure to a substance below which no adverse non-cancer health effects areexpected to occur.


RfD:
Reference Dose is an estimate of the daily exposure to the general public that islikely to have no measurable risk of harmful health effects during a lifetimeexposure or exposure during a limited time interval.

APPENDIX B: EXPOSURE DOSE EQUATIONS

Exhibit 1.

Water Ingestion Exposure Dose Equation
Exposure doses from incidental ingestion of water can be calculated as follows:
    ED = (C * IR * EF) / BW
Default Ingestion Water Intake Rates3
 
2 L/day - adult
1 L/day - child
 
Note:
L/day - liters per day
where,    
ED = exposure dose (mg/kg/day)
C = contaminant concentration (mg/L)
IR = intake rate of contaminated water (L/day)
EF = exposure factor (unitless)
BW = body weight (kg)

 

Exhibit 2.

Water Dermal Contact Exposure Dose Equation
Exposure doses from dermal contact with water can be calculated as follows:
    ED = (C * P * SA * ET * CF) / BW
Default Dermal Exposure Values
50th Percentile Total Body Surface Area for Males
(square centimeters [cm2])
   
Age (years) Male

6<9 9310
18-70 19400
Source: EPA 1997
where,    
ED = exposure dose (mg/kg/day)
C = contaminant concentration (mg/L)
P = permeability coefficient (cm/hr)
SA = exposed body surface area (cm2)
ET = exposure time (hours/day)
CF = conversion factor (1 L/1,000 cm3)
BW = body weight (kg)


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